diff --git a/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/2301.05308v1.pdf.txt b/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/2301.05308v1.pdf.txt new file mode 100644 index 0000000000000000000000000000000000000000..6fd427b26c0c66ab03e5e55a8e71f0a0671fb83d --- /dev/null +++ b/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/2301.05308v1.pdf.txt @@ -0,0 +1,1597 @@ +Incremental Dead State Detection in +Logarithmic Time +Caleb Stanford1 and Margus Veanes2 +1 University of California, San Diego and University of California, Davis +cdstanford@ucdavis.edu +2 Microsoft Research, Redmond margus@microsoft.com +Abstract. Identifying live and dead states in an abstract transition sys- +tem is a recurring problem in formal verification. However, state-of-the- +art graph algorithms for maintaining reachability information incremen- +tally (that is, as states are visited and before the entire state space is +explored) assume that new edges can be added from any state at any +time, whereas in many applications, outgoing edges are added from each +state as it is explored. To formalize the latter situation, we propose guided +incremental digraphs (GIDs), incremental graphs which support labeling +closed states (states which will not receive further outgoing edges). Our +main result is that dead state detection in GIDs is solvable in O(log m) +time per edge update for m edges, improving upon O(√m) per edge due +to Bender, Fineman, Gilbert, and Tarjan (BFGT) for general incremen- +tal directed graphs. +We introduce two algorithms for GIDs: one establishing the logarithmic +time bound, and a second algorithm to explore a lazy heuristics-based ap- +proach. To demonstrate applicability, we show how GIDs can be used to +lazily decide regular expression constraints in SMT applications. To en- +able an apples-to-apples experimental comparison, we implemented both +algorithms, two naive baselines, and the state-of-the-art BFGT baseline +using a common directed graph interface in Rust. Our evaluation shows +110-530x speedups over BFGT for the largest input graphs over a range +of graph classes, random graphs, and graphs arising from regular expres- +sion benchmarks. +Keywords: Dead State Detection · Graph Algorithms · Online Algo- +rithms · SMT. +1 +Introduction +Classifying states in a transition system as live or dead is a recurring problem +in formal verification. For example, given an expression, can it be simplified +to the identity? Given an input to a nondeterministic program, can it reach a +terminal state, or can it reach an infinitely looping state? Given a state in an +automaton, can it reach an accepting state? Domain-specific variations on this +problem have led to many general and specialized algorithms used by automated +arXiv:2301.05308v1 [cs.DS] 12 Jan 2023 + +2 +Caleb Stanford and Margus Veanes +verification tools. State classification is relevant in the context of satisfiability +modulo theories (SMT) [17,41,3,55,15,36], where theory-specific partial decision +procedures often work by exploring the state space to find a reachable path that +corresponds to a satisfying string or, more generally, a sequence of constructors. +In all of these cases, the core problem is live and dead state detection in a +directed graph. +Motivating application. For example, recent approaches for the SMT theory of +regular expressions [34,50] rely on regular expression derivatives to explore the +states of the finite state machine corresponding to the regex incrementally, rather +than expanding all states initially which is often prohibitively expensive. This +requires solving the incremental live and dead state detection problem in the +finite state machine (a directed graph). This is particularly important for regexes +with intersection and complement (extended regexes [12,22,19]), which have been +shown to arise natively in applications of SMT string solvers to security [2,50]). +Concretely, consider the regex (�*α�100)C ∩ (�α), where � matches any character, +∩ is regex intersection, C is regex complement, and α matches any digit (0-9). A +traditional solver would expand the left and right operands as state machines, +but the left operand (�*α�100)C is astronomically large as a DFA, causing the +solver to hang. The derivative-based technique instead constructs the derivative +regex: (�*α�100)C ∩(�100)C ∩α. At this stage we have a graph of two states and one +edge, where the states are regexes and the edge is the derivative relation. After +one more derivative operation, the regex becomes one that is clearly satisfiable +as it accepts the empty string. +In order to be efficient, a derivative-based solver needs to identify satisfiable +(live) and unsatisfiable (dead) regexes incrementally (as the graph is built), be- +cause it does not generally construct the entire space before terminating (see the +graph update inference rule Upd, p. 626 [50]). Indeed, satisfiability (nonempti- +ness) for extended regexes is non-elementary, and is still PSPACE-complete for +more restrictive fragments, strongly incentivizing the incremental approach. Be- +yond regexes, we believe that GIDs are general enough to be applicable in a +range of future applications. +Prior work. Traditionally, while live state detection can be done incrementally, +dead state detection is often done exhaustively (i.e., after the entire state space +is explored). For example, bounded and finite-state model checkers based on +translations to automata [32,48,13], as well as classical dead-state elimination +algorithms [28,7,10], generally work on a fixed state space after it has been fully +enumerated. However, exhaustive exploration is prohibitive for large (e.g., ex- +ponential or infinite) state spaces which arise in an SMT verification context. +Moreover, exhaustive exploration may simply be unnecessary if partial infor- +mation can be deduced about the states seen so far which already leads to a +satisfiable or unsatisfiable result along a given solver path. We also have good +evidence that incremental feedback can improve SMT solver performance: a +representative success story is the e-graph data structure [54,16] for congruence +closure [18,42], which maintains an equivalence relation among expressions in- + +Incremental Dead State Detection in Logarithmic Time +3 +crementally; because it applies to general expressions, it is theory-independent +and re-usable. Incremental state space exploration could lead to similar benefits +if applied to SMT procedures which still rely on exhaustive search. +However, in order to perform incremental dead state detection, we currently +lack algorithms which match offline performance. As we discuss in Section 2, +the best-known existing solutions would require maintaining strong connected +components (SCCs) incrementally. For SCC maintenance and the related sim- +pler problem of cycle detection, O(m3/2) amortized algorithms are known for m +edge additions [23,4], with some recently announced improvements [5,8]. Note +that this is in sharp contrast to O(m) for the offline variants of these problems, +which can be solved by breadth-first or depth-first search. More generally, re- +search suggests that there is a computational barrier to what can be determined +incrementally in the worst case [20,21,1]. +This paper. To improve on prior results, our key observation is that in many +applications, edges are not added adversarially, but from one state at a time as +the states are explored. As a result, we know when a state will have no further +outgoing edges; we may use this information to (i) provide information about +dead states incrementally, rather than after the whole state space is explored; +and (ii) obtain more efficient algorithms than currently exist for general graph +reachability. +We introduce guided incremental digraphs (GIDs), a variation on incremental +graphs. Like an incremental directed graph, a guided incremental digraph may be +updated by adding new edges between states, or a state may be labeled as closed, +meaning it will receive no further outgoing edges. Some states are designated as +terminal, and we say that a state is live if it can reach a terminal state and dead +if it will never reach a terminal state in any extension – i.e. if all reachable states +from it are closed. To our knowledge, the problem of detecting dead states in +such a system has not been studied by existing work in graph algorithms. Our +problem can be solved through solving SCC maintenance, but not necessarily +the other way around (see Proposition 1). We provide two new algorithms for +dead-state detection in GIDs. +First, we show that the dead-state detection problem for GIDs can be solved +in time O(m · log m) for m edge additions, within a logarithmic factor of the +O(m) cost for offline search. The worst-case performance of our algorithm thus +strictly improves on the O(m3/2) upper bound for SCC maintenance in general +incremental graphs. Our algorithm utilizes several data structures and existing +results in online algorithms: in particular, Union-Find [52] and Henzinger and +King’s Euler Tour Trees [26]. The main idea of our algorithm is that, rather than +explicitly computing the set of SCCs, for closed states we maintain a single path +to a non-closed (open) state. This turns out to reduce the problem to quickly +determining whether two states are currently assigned a path to the same open +state. On the other hand, Euler Tour Trees can solve undirected reachability for +graphs that are forests in logarithmic time; the challenge then lies in figuring +out how to reduce directed connectivity in the graph of paths to undirected +connectivity in an Euler Tour Trees forest. At the same time, we must maintain + +4 +Caleb Stanford and Margus Veanes +this structure under Union-Find state merges, in order to deal with cycles that +are found in the graph. +While as theorists we would like to believe that asymptotic complexity is +enough, the truth is that the use of complex data structures (1) can be pro- +hibitively expensive in practice due to constant-time overheads, and (2) can +make algorithms substantially more difficult to implement, leading practition- +ers to prefer simpler approaches. To address these needs, in addition to the +logarithmic-time algorithm, we provide a second lazy algorithm which avoids +the user of Euler Tour Trees, and only uses union-find. This algorithm is based +on an optimization of adding shortcut jump edges for long paths in the graph to +quickly determine reachability. This approach aims to perform well in practice +on typical graphs, and is evaluated in our evaluation along with the logarithmic +time algorithm, though we do not prove its asymptotic complexity. +Finally, we implement and empirically evaluate both of our algorithms for +GIDs against several baselines in 5.5k lines of code in Rust [37,33]. Our evaluation +focuses on the performance of the GID data structure itself, rather than its end- +to-end performance in applications. To ensure an apples-to-apples comparison +with existing approaches, we put particular focus on providing a directed graph +data structure backend shared by all algorithms, so that the cost of graph search +as well as state and edge merges is identical across algorithms. We implement +two naive baselines, as well as an implementation of the state-of-the-art solution +based on maintaining SCCs, BFGT [4] in our framework. To our knowledge, +the latter is the first implementation of BFGT for SCC maintenance. On a +collection of generated benchmark GIDs and GIDs directly pulled from the regex +application, we demonstrate a substantial improvement over BFGT for both of +our algorithms. For example, for larger GIDs (those with over 100K updates), +we observe a 110-530x speedup over BFGT. +Our primary contributions are: +– Guided incremental digraphs (GIDs), a formalization of incremental live and +dead state detection which supports labeling closed states. (Section 2) +– Two algorithms for the state classification problem in GIDs: first, an algo- +rithm that works in amortized O(log m) time per update, improving upon +the state-of-the-art amortized O(√m) per update for incremental graphs; +and second, a simpler algorithm based on lazy heuristics. (Section 3) +– An open-source implementation of GIDs in Rust3, including an implementa- +tion the BFGT baseline and supporting data structures for a fair comparison, +and an evaluation which demonstrates that our algorithm outperforms the +best known incremental SCC algorithm by two orders of magnitude for a +range of GID benchmarks. (Section 4) +Following these contributions, we expand on the application of GIDs to regex +solving in SMT (Section 5), survey related work (Section 6), and conclude (Sec- +tion 7). +3 https://github.com/cdstanford/gid + +Incremental Dead State Detection in Logarithmic Time +5 +1 +2 +3 +Fig. 1. +Guided incremental digraph consisting of the sequence of updates E(1, 2), +E(1, 3), T(2). Terminal states are denoted with double circles. After the update T(2), +states 1 and 2 are known to be live. However, for this graph state 3 is not dead, as a +future edge may cause it to be live. +2 +Guided Incremental Digraphs +2.1 +Problem Statement +An incremental digraph is a sequence of edge updates E(u, v), where the algo- +rithmic challenge in this context is to produce some output after each edge is +received (e.g., whether or not a cycle exists). If the graph also contains updates +T(u) labeling a state as terminal, then we say that a state is live if it can reach +a terminal state in the current graph. In a guided incremental digraph, we also +include updates C(u) labeling a state as closed, meaning that will not receive +any further outgoing edges. +Definition 1. Define a guided incremental digraph (GID) to be a sequence of +updates, where each update is one of the following: +(i) a new directed edge E(u, v); +(ii) a label T(u) which indicates that u is terminal; or +(iii) a label C(u) which indicates that u is closed, i.e. no further edges will be +added going out from u (or labels to u). +The guided incremental digraph is valid if the closed labels are correct: there +are no instances of E(u, v) or T(u) after an update C(u). The denotation of G is +the directed graph (V, E) where V is the set of all states u which have occurred +in any update in the sequence, and E is the set of all (u, v) such that E(u, v) +occurs in G. +An extension of a valid GID G is a valid GID G′ such that G is a prefix of +G′. In a valid GID G, we say that a state u is live if there is a path from u to +a terminal state in the denotation of G; and a state u is dead if it is not live in +any extension of G. Notice that in a GID without any C(u) updates, no states +are dead as an edge may be added in an extension which makes them live. +We provide an example of a valid GID in Figures 1 and 2 resulting from +the following sequence of updates: E(1, 2), E(1, 3), T(2), E(4, 3), E(4, 5), C(4), +C(5). The states are denoted based on whether they are marked as terminal T(u) +(double circle) or closed C(u); states that are not closed are denoted with dashed +circles. Notice that after C(4), state 4 is marked closed but can still reach 3 and +5, so it is not dead. Additionally, notice that once 1 and 2 are live (after T(2)), +further edges from them do not matter. + +6 +Caleb Stanford and Margus Veanes +1 +2 +3 +4 +5 +Fig. 2. +Guided incremental digraph consisting of the sequence of updates E(1, 2), +E(1, 3), T(2), E(4, 3), E(4, 5), C(4), C(5). Closed states (from which future edges may not +be added) are denoted with solid circles. After the update C(5) (but not earlier), state +5 is dead. +Definition 2. Given as input a valid GID, the guided incremental state clas- +sification problem is to output, in an online fashion after each update, the set +of new live and new dead states. That is, output Live(u) or Dead(u) on the +smallest prefix of updates such that u is live or dead on that prefix, respectively. +2.2 +Existing Approaches +In many applications, one might choose to classify dead states offline, after the +entire state space is enumerated. This leads to a linear-time algorithm via either +DFS or BFS, but it does not solve the state classification problem (Definition 2) +because it is not incremental. Naive application of this idea leads to an O(m) +time algorithm per update for m updates (O(m2) total), as we may have to +search the entire graph after each update. +For acyclic graphs, there exists an amortized O(1)-time per update algorithm +for the problem (Definition 2): maintain the graph as a list of forward and +backward edges at each state. When a state v is marked terminal, do a DFS +along backward edges to determine all states u that can reach v not already +marked as live, and mark them live. When a state v is marked closed, visit +all forward-edges from v; if all are dead, mark v as dead and recurse along all +backwards edges from v. As each edge is visited only when marking a state live +or dead, it is only visited a constant number of times overall (though we may +use more than O(1) time on some particular update pass). Additionally, the live +state detection part of this procedure still works for graphs containing cycles. +The challenge, therefore, lies primarily in detecting dead states in graphs +which may contain cycles. For this, the breakthrough state-of-the-art approach +from [4] enables maintaining the graph as a condensed graph which is acyclic, +where the vertices in the condensed graph represent strongly connected compo- +nents (SCCs) of states. The mapping from states to SCCs is maintained using +a Union-Find [52] data structure. Maintaining this requires O(√m) time per +update. To ensure that vertices in the condensed graph correspond to SCCs in +the original, we have to also make sure that closed and non-closed states are not +merged into the same SCC; the easiest solution to this is to withhold all edges +from each state u in the graph until u are closed, which ensures that u must +be its own SCC. Once we have the condensed graph with these modifications, + +Incremental Dead State Detection in Logarithmic Time +7 +the same algorithm as in the previous paragraph works to identify live and dead +states. Since each edge is only visited when a state is marked closed or live, each +edge is visited only once throughout the algorithm, we use only amortized O(1) +additional time to calculate live and dead states. While this SCC maintenance +algorithm ignores the fact that edges do not occur from closed states C(u), this +still proves the following result: +Proposition 1. Guided incremental state classification reduces to SCC main- +tenance. That is, suppose we have an algorithm over incremental graphs that +maintains the set of SCCs in O(f(m, n)) total time given n states and m edge +additions, where “maintains” means that (i) we can check whether two states +are in the same SCC in O(1) time, and (ii) we can iterate over all the states +in an SCC, or iterate over the forward-edges or backward-edges from an SCC +(to or from other SCCs, respectively) in O(1) time per edge. Then there exists +an algorithm to solve guided incremental state classification in O(f(m, n)) total +time. +Despite this reduction one way, there is no obvious reduction the other way – +from cycle detection or SCCs to Definition 2. This is because, while the existence +of a cycle of non-live states implies bi-reachability between all states in the cycle, +it does not necessarily imply that all of the bi-reachable states are dead. In fact, +consider a GID consisting only of E(u, v) and C(u) updates. In order to identify +dead states, rather than enumerating all cycles or SCCs, it is enough to maintain +a single path from each non-dead state to a non-closed state. This observation +forms the starting point for our approach in the following sections, improving +on the upper bound given by Proposition 1. +3 +Algorithms +This section presents Algorithm 2, which solves the state classification problem in +logarithmic time (Theorem 2); and Algorithm 3, an alternative lazy approach. +Both algorithms are optimized versions of Algorithm 1, a first-cut algorithm +which establishes the structure of our approach. We begin by establishing some +basic terminology shared by all of the algorithms (see Figure 3). +States in a GID can be usefully classified as exactly one of four statuses: live, +dead, unknown, or open, where an unknown state is one that is closed but not +yet live or dead, and an open state is one that is not closed and not live. Note +that a state may be live and neither open nor closed; this terminology keeps the +classification disjoint. Pragmatically, for live states it does not matter if they +are classified as open or closed, since edges from those states no longer have any +effect. However, all dead and unknown states are closed, and no states are both +open and closed. +Given this classification, the intuition is that for each unknown state u, we +only need one path from u to an open state to prove that it is not dead; we want +to maintain one such path for all unknown states. To maintain all of these paths +simultaneously, we maintain an acyclic directed forest structure on unknown and + +8 +Caleb Stanford and Margus Veanes +Live +Some reachable state from u is terminal. +Dead +All reachable states from u (including u itself) are closed and +not terminal. +Unknown +u is closed, but not live or dead. +Open +u is not live and not closed. +Terminal +A state u labeled by T(u). +Closed +A state u labeled by C(u). +Canonical +A state x that is the uniquely chosen representative of its +union-find equivalence class, i.e. UF.find(x) = x. +u, v, w +States in the original graph. +x, y, z +Canonical states in the condensed graph. +Successor succ(x) +For an unknown, canonical state x, a uniquely chosen state v +such that (x, v) is an edge, and following the path of successors +leads to an open state. +Fig. 3. Top: Basic classification of GID states into four disjoint categories. Bottom: +Additional terminology used in this paper. +open states where the roots are open states, and all non-root states have a single +edge to another state, called its successor. Edges other than successor edges can +be temporarily ignored, except for when marking live states; these are kept as +reserve edges. Specifically, we add every edge (u, v) as a backward-edge from v +(to allow propagating live states), but for edges not in the forest we keep (u, v) +in a reserve list from u. We store all edges, including backward-edges, in the +original order (u, v). The reserve list edge becomes relevant only when either (i) +u is marked as closed, or (ii) u’s successor is marked as dead. +In order to deal with cycles, we need to maintain the forest of unknown states +not on the original graph, but on a union-find condensed graph, similar to [52]. +When we find a cycle of unknown states, we merge all states in the cycle by +calling the union method in the union-find. We refer to a state as canonical if +it is the canonical representative of its equivalence class in the union find; the +condensed graph is a forest on canonical states. We use x, y, z to denote canonical +states (states in the condensed graph), and u, v, w to denote the original states +(not known to be canonical). +Following [52], we maintain edges as linked lists rather than sets, and using +the original states instead of canonical states; this is important as it allows +combining edge lists in O(1) time when merging states. +3.1 +First-Cut Algorithm +A first-cut algorithm based on these ideas is shown in Algorithm 1. The union- +find data structure UF provides UF.union(v1, v2), UF.find(v), and UF.iter(v): +UF.union merges v1 and v2 to refer to the same canonical state, UF.find returns +the canonical state for v, and UF.iter iterates over states equivalent to v. The +running time of each of these operations is amortized α(n) for n updates, where +α(n) ∈ o(log n) is the inverse Ackermann function. + +Incremental Dead State Detection in Logarithmic Time +9 +Algorithm 1 First-cut algorithm. +V: a type for states (integers) (variables u, v, . . .) +E: the type of edges, equal to (V, V) +UF: a union-find data structure over V +X: the set of canonical states in UF (variables x, y, z, . . .) +status: a map from X to Live, Dead, Unknown, or Open +succ: a map from X to V +res and bck: maps from X to linked lists of E +procedure OnEdge(E(u, v)) +x ← UF.find(u); y ← UF.find(v) +if status(y) = Live then +OnTerminal(T(x)) +▷ mark x and its ancestors live +else if status(x) ̸= Live then +▷ status(x) must be Open +append (u, v) to res(x) +append (u, v) to bck(y) +procedure OnTerminal(T(v)) +y ← UF.find(v) +for all x in DFS backwards (along bck) from y not already Live do +status(x) ← Live +output Live(x′) for all x′ in UF.iter(x) +procedure OnClosed(C(v)) +y ← UF.find(v) +if status(y) ̸= Open then return +▷ y is already live or closed +while res(y) is nonempty do +pop (v, w) from res(y); z ← UF.find(w) +if status(z) = Dead then continue +else if CheckCycle(y, z) then +for all z′ in cycle from z to y do z ← Merge(z, z′) +else +status(y) ← Unknown; succ(y) ← z; +return +status(y) ← Dead; output Dead(y′) for all y′ in UF.iter(y) +ToRecurse ← ∅ +for all (u, v) in bck(y) do +x ← UF.find(u) +if status(x) = Unknown and UF.find(succ(x)) = y then +status(x) ← Open +▷ temporary – marked closed on recursive call +add x to ToRecurse +for all x in ToRecurse do OnClosed(C(x)) +procedure CheckCycle(y, z) returning bool +while status(z) = Unknown do z ← UF.find(succ(z)) +▷ get root state from z +return y = z +procedure Merge(x, y) returning V +z ← UF.union(x, y) +bck(z) ← bck(x) + bck(y) +▷ O(1) linked list append +res(z) ← res(x) + res(y) +▷ O(1) linked list append +return z + +10 +Caleb Stanford and Margus Veanes +We will only merge states if they are bi-reachable from each other, and both +unknown. This implies that all states in the equivalence class of a canonical state +x have the same status. We also maintain the set of canonical states in UF as a +set X. +The edge maps res and bck are stored as maps from X to linked lists of edges. +Each edge (u, v) is always stored using its original states (i.e., edge labels are not +updated when states are merged); but we can easily obtain the corresponding +edge on canonical states via (UF.find(u), UF.find(v)). On an input edge (u, v), +the edge is immediately added to bck as a backward-edge from v (this is used +for detecting live states), but forward-edges are only added selectively to succ +when they are needed to prove unknown status, and are otherwise stored in the +reserve list res. +Invariants. In total, we maintain the following invariants. For live and dead +states, we no longer care about forward or backward edges from them, so there +are no invariants about live and dead states other than that status(x) is Live or +Dead for these states, respectively. The successor edges and no cycles invariants +are about the forest structure. The last invariant, edge representation, is about +making sure that all edges in the input GID are represented somehow in the +current graph. +– Merge equivalence: For all states u and v, if UF.find(u) = UF.find(v), then +u and v are bi-reachable and both closed. (This implies that u and v are +both live, both dead, or both unknown.) +– Status correctness: For all u, status(UF.find(u)) is equal to the status of +u. +– Successor edges: If x is unknown, then succ(x) is defined and is an unknown +or open state. If x is open, then succ(x) is not defined. +– No cycles: There are no cycles among the set of edges (x, UF.find(succ(x))), +over all unknown and open canonical states x. +– Edge representation: Lastly, for all edges (u, v) in the input GID, at least one +of the following holds: (i) (u, v) is stored in res, i.e. (u, v) ∈ res(UF.find(v)); +(ii) (u, v) is stored in succ, i.e. v = succ(UF.find(u)); (iii) u and v are +equivalent in the condensed graph, i.e. UF.find(u) = UF.find(v); (iv) u is +live; or (v) v is dead. +Proposition 2. Algorithm 1 is correct. +Proof. We need to argue that all of the invariants described above are preserved. +This implies correctness of the algorithm by the status correctness invariant, +since it implies that live and dead states are labeled (and output) correctly. +Upon receiving E(u, v) or T(u), this may cause some dead, unknown, or open +states to change status to live, but does not change the status of any other +states. As bck stores all backwards-edges (not just succ edges), live states are +marked correctly. This preserves the forest invariants because if an unknown or +open state is marked live, so are all its predecessors. This also preserves the edge +representation invariant, either by adding new edges to case (i) and case (iv) + +Incremental Dead State Detection in Logarithmic Time +11 +(for E updates) or moving edges from cases (i)-(iii) to case (iv) (for both E and +T updates). +The procedure C(u) is recursive; during the procedure and on recursive calls, +some states are temporarily marked Open, meaning they are roots in the forest +structure. During these recursive calls, we need a slightly generalized invariant: +each forest root corresponds to a pending future call to OnClosed(C(u)) (i.e., +an element of ToRecurse for some call on the stack) and is a state that needs to +either find a successor or be marked dead. This means that the status labels for +unknown- and open-labeled states are not necessarily correct during recursive +calls; we are only concerned with preserving the forest structure, so that they will +be correct after all calls complete. Note in particular that after merging cycles +of unknown states via Merge(x, y), the new root is marked Open to preserve +the generalized invariant on recursive calls. +Upon receiving C(u), without loss of generality we may assume status(u) = +Open (the opposite only occurs if the input GID has duplicate C(u) updates, or +if C(u) occurs for a live state). At the top of the while loop, there are three cases: +– If a reserve edge is available, and its target is dead, then we discard it. This +preserves edge representation because that edge still satisfies (iv). +– If a reserve edge is available and its target is not dead, then we see if adding +that edge creates a cycle by calling CheckCycle. If no, then the two trees are +distinct, so we add an edge between them. This preserves edge representation +by moving that edge from case (i) to case (ii). If yes, then we collapse the +cycle in the forest to a single state by repeated calls to Merge(x, y). This +preserves edge representation by moving the edges in the cycle from case (ii) +to case (iii). The forest structure of the succ is also preserved because if a +graph is a forest, then it remains a forest after merging adjacent states. +– Finally, if there are no reserve edges left, then because of edge representation, +and because there is no successor from u, all edges from u must lead to dead +states (case (v)) and therefore u is dead. This case splits the tree rooted at +u into one tree for each of its predecessors, preserving the forest structure. +Each of the succ edges from predecessors are deleted; this preserves edge +representation by moving those edges from case (ii) to case (v). +In any case, the generalized invariant for recursive calls is preserved, and all dead +states are labeled correctly (given the invariant), so we are done. +⊓⊔ +Complexity. The core inefficiency in Algorithm 1 lies in CheckCycle. The proce- +dure repeatedly sets z ← succ(z) to find the tree root, which in general could be +linear time in the number of edges. For example, suppose we have a line graph +where we add edges in a backwards fashion and close them: E(2, 1), C(2), E(3, +2), C(3), . . . , E(n, n-1), C(n). In such a graph, this inefficiency results in O(m2) +work. We therefore want to improve upon this step in Algorithms 2 and 3. +All other parts of the algorithm run in amortized α(m) time per update for +m updates (using vectors to represent the maps fwd, bck, and succ for O(1) +lookups). The OnTerminal calls and loop iterations only run once per edge +in the graph when the target of that edge is marked live or terminal. Likewise, + +12 +Caleb Stanford and Margus Veanes +the procedure OnClosed is called conservatively: the cost of each call can be +assigned either to the target of an edge being marked dead, or to an edge being +merged as part of a cycle. Both marking dead and merging can only happen +once for a given edge, so this is O(1) per edge. +3.2 +Logarithmic Algorithm +At its core, CheckCycle requires solving an undirected reachability problem on +a graph that is restricted to a forest. However, the forest is changed not just by +edge additions, but edge additions and deletions. While undirected reachability +and reachability in directed graphs are both difficult to solve incrementally, +reachability in dynamic forests can be solved in O(log m) time per operation. +Our algorithm uses an Euler Tour Forest data structure EF of Henzinger and +King [26], and is shown in Algorithm 2. +However, this idea does not work straightforwardly – once again because of +the presence of cycles in the original graph. We cannot simply store the forest as +a condensed graph with edges on condensed states. As we saw in Algorithm 1, +it was important to store successor edges as edges into V, rather than edges into +X – this is the only way that we can merge states in O(1), without actually +inspecting the edge lists. If we needed to update the forest edges to be in X, this +could require O(m) work to merge two O(m)-sized edge lists as each edge might +need to be relabeled in the EF graph. +To solve this challenge, we instead store the EF data structure on the original +states, rather than the condensed graph; but we ensure that each condensed state +is represented by a tree of original states in the original graph. When adding +edges between condensed graph states, we need to make sure to remember the +original state labels (u, v), so that we can later remove it using the original +labels (this happens when its target becomes dead). When an edge would create +a cycle, we instead simply ignore it in the EF graph: because a line of connected +trees forms a tree. +In summary, algorithm borrows most data and procedures from Algorithm 1, +with a few important changes: (1) we maintain the EF data structure EF, a forest +on V (2) the successor edges are stored as their original edge labels (u, v), rather +than just as a target state; (3) the procedure OnClosed is updated in several +locations to maintain the graph EF. +Invariants. We continue all invariants from Algorithm 1, with the small mod- +ification that the successor edges and no cycles invariants use the new succ +representation: that is, they are constraints on the edges (x, UF.find(v)), where +succ(x) = (u, v). In addition, we have two constraints on edges in EF, de- +pending on whether those states are equivalent in the union-find structure. We +call edges between inequivalent states inter-edges and those between equivalent +states intra-edges. +– EF inter-edges: For all states u and v not in the same canonical state, (u, v) +is in the EF graph if and only if (u, v) = succ(UF.find(u)) or (v, u) = +succ(UF.find(v)). + +Incremental Dead State Detection in Logarithmic Time +13 +Algorithm 2 Logarithmic time algorithm. +All data from Algorithm 1 +succ: a map from X to E (instead of to V) +EF: Euler Tour Trees data structure providing: EF.add, EF.remove, and EF.connected +procedure OnEdge(E(u, v)) as in Algorithm 1 +procedure Merge(x, y) returning V as in Algorithm 1 +procedure OnTerminal(T(v)) +y ← UF.find(v) +for all x in DFS backwards (along bck) from y not already Live do +if status(x) = Unknown then +▷ The following line is not strictly necessary, but simplifies the analysis +(u, v) ← succ(x); delete succ(x); EF.remove(u, v) +status(x) ← Live; output Live(x′) for all x′ in UF.iter(x) +procedure OnClosed(C(v)) +y ← UF.find(v) +if status(y) ̸= Open then return +while res(y) is nonempty do +pop (v, w) from res(y); z ← UF.find(w) +if status(z) = Dead then continue +else if CheckCycle(y, z) then +for all z′ in cycle from z to y do z ← Merge(z, z′) +else +status(x) ← Unknown; succ(x) ← (v, w) +EF.add(v, w) +▷ undirected edge; use original labels (not (x, y)) +return +status(y) ← Dead; output Dead(y′) for all y′ in UF.iter(y) +ToRecurse ← ∅ +for all (u, v) in bck(y) do +x ← UF.find(u) +if status(x) = Unknown then +(u′, v′) ← succ(x) +if UF.find(v′) = y then +EF.remove(u′, v′) +▷ undirected edge; use original labels +status(x) ← Open; delete succ(x); add x to ToRecurse +for all x in ToRecurse do OnClosed(C(x)) +procedure CheckCycle(y, z) returning bool +return EF.connected(y, z) + +14 +Caleb Stanford and Margus Veanes +– EF intra-edges: For all unknown canonical states x, the set of edges (u, v) +in the EF between states belonging to x forms a tree. +Theorem 1. Algorithm 2 is correct. +Proof. Observe that the EF inter-edges constraint implies that EF only contains +edges between unknown and open states, together with isolated trees. In the +modified OnTerminal procedure, when marking states as live we remove inter- +edges, so we preserve this invariant. +Next we argue that given the invariants about EF, for an open state y the +CheckCycle procedure returns true if and only if (y, z) would create a directed +cycle. If there is a cycle of canonical states, then because canonical states are +connected trees in EF, the cycle can be lifted to a cycle on original states, so y and +z must already be connected in this cycle without the edge (y, z). Conversely, if +y and z are connected in EF, then there is a path from y to z, and this can be +projected to a path on canonical states. However, because y is open, it is a root +in the successor forest, so any path from y along successor edges travels only +on backwards edges; hence z is an ancestor of y in the directed graph, and thus +(y, z) creates a directed cycle. +This leaves the OnClosed procedure. Other than the EF lines, the structure +is the same as in Algorithm 1, so the previous invariants are still preserved, +and it remains to check the EF invariants. When we delete the successor edge +and temporarily mark status(x) = Open for recursive calls, we also remove it +from EF, preserving the inter-edge invariant. Similarly, when we add a successor +edge to x, we add it to EF, preserving the inter-edge invariant. So it remains to +consider when the set of canonical states changes, which is when merging states +in a cycle. Here, a line of canonical states is merged into a single state, and a +line of connected trees is still a tree, so the intra-edge invariant still holds for +the new canonical state, and we are done. +⊓⊔ +Theorem 2. Algorithm 2 uses amortized logarithmic time per edge update. +Proof. By the analysis of Algorithm 1, each line of the algorithm runs amortized +O(1) time other than those in CheckCycle. For the CheckCycle, procedure +it now avoids the loop and so also runs amortized O(1) times. Each line is either +constant-time, α(m) = o(log n) time for the UF calls, or O(log n) time for the EF +calls, so in total the algorithm runs in amortized O(log n) time per update. +⊓⊔ +3.3 +Lazy Algorithm +While the asymptotic complexity of log n could be the end of the story, in prac- +tice, the cost of the EF calls could be a significant overhead. The technical details +of Euler-Tour Trees include building an AVL-tree cycle for each tree, where the +cycle contains each state of the graph and each edge in the graph twice. It turns +out that adding one edge to EF results in up to eight modifications to the AVL +tree: it needs to be split at the source, split at the target, then the edge needs to + +Incremental Dead State Detection in Logarithmic Time +15 +Algorithm 3 Lazy algorithm. +All data from Algorithm 1 +jumps: a map from X to lists of V +procedure OnEdge(E(u, v)) as in Algorithm 1 +procedure OnTerminal(T(v)) as in Algorithm 1 +procedure OnClosed(C(v)) as in Algorithm 1 +procedure CheckCycle(y, z) returning bool +return y = GetRoot(z) +procedure GetRoot(z) returning V +if status(z) = Open then return z +if jumps(z) is empty then +push succ(z) to jumps(z) +▷ set 0th jump +repeat +pop w from jumps(z); z′ = UF.find(w) +▷ remove dead jumps +until status(z′) ̸= Dead +push z′ to jumps(z) +result ← GetRoot(z′) +n ← length(jumps(z)); n′ ← length(jumps(z′)) +if n ≤ n′ then +push jumps(z′)[n − 1] to jumps(z) +▷ set nth jump +return result +procedure Merge(x, y) returning V +z ← UF.union(x, y) +bck(z) ← bck(x) + bck(y); res(z) ← res(x) + res(y) +jumps(z) ← empty +return z +be added in both directions (u, v) and (v, u) to the cycle, and then these trees +need to be glued together. Every one of these operations comes with a rebalanc- +ing operation which could do Ω(log n) tree rotations and pointer dereferences to +visit the nodes in the AVL tree. +As a result of these (constant-time) overheads, in this section, we investigate +a simpler, lazy algorithm which avoids Euler Tour Trees, and works directly by +modifying Algorithm 1. To optimize Algorithm 1, one idea in the right direction +is to store for each state a direct pointer to the root which results from repeatedly +calling succ. But there are two issues with this. First, maintaining this may be +difficult (when the root changes, potentially updating a linear number of root +pointers). Second, the root may sometimes be marked dead, in which case we +have to re-compute all the successor pointers. +Instead, we introduce a jump list from each state: intuitively, it will contain +states after calling successor once, twice, four times, eight times, and so on, and +will be updated at most once for every visit to the state. When a jump becomes +obsolete (the target dead), we just pop off the largest jump, so we do not lose all +of our work in building the list. When states are merged, we do lose our work, +discarding the jump lists, and this also means the exact power-of-two distances +are no longer preserved. We maintain the following additional information: for + +16 +Caleb Stanford and Margus Veanes +each unknown canonical state x, a nonempty list of jumps [v0, v1, v2, . . . , vk], +such that v0 is reachable from x, v1 is reachable from v0, v2 is reachable from +v1, and so on, and v1 = succ(x). The algorithm is shown in Algorithm 3. +The key procedure is GetRoot(z), which is called when adding a reserve +edge (y, z) to the graph. It finds the root in the successor forest when repeatedly +calling successor from z. It shortcuts by using the jump list, and also updates +the set of jumps to be approximately at powers of two: to do this, the nth jump +from a state z is set to the (n − 1)st jump from the (n − 1)th jump from z. +Invariants. In addition to the invariants from Algorithm 1: for each unknown +canonical state x, jumps(x) is a list of states v0, v1, v2, . . . , vk such that: +– First jump: if the jump list is nonempty, then v0 = succ(v). +– Reachability: vi+1 is reachable from vi for all i. +– Powers of two: on the path of canonical states from v0 to vi, the total number +of states (including all the states in each equivalence class) is at least 2i. +The powers of two invariant is not necessary for correctness, but is the key +to the efficiency of this algorithm: it ensures that the nth jump travels at least +2n states at once in the successor forest. It follows from this that if the jump list +is fully saturated for every state, querying GetRoot(z) will take logarithmic +time. But because the jump lists are updated lazily (and have dead states that +need to be discarded), this does not establish an asymptotic complexity for the +algorithm. +Theorem 3. Algorithm 3 is correct. +Proof. We use the invariant on the jump list mentioned: that v1 is the successor, +v2 is reachable from v1, v3 is reachable from v2, and so on, using only forward +edges added to the graph (not reserve edges). I.e., v1, v2, . . . is some sublist of +the states along the path from an unknown state to its root, potentially followed +by some dead states. We need to argue that the subprocedure GetRoot (i) +receives the same verdict as repeatedly calling succ to find a cycle in the first-cut +algorithm and (ii) preserves the jump list invariant. Popping dead states from the +jump list clearly preserves the invariant, as does adding on a state along the path +to the root, which is done when k′ ≥ k. Merging states preserves the jump list +invariant trivially because we throw the jump list away, and marking states live +preserves the jump list invariant trivially since the jump list is only maintained +and used for unknown states. Finally, marking states as closed initializes the +jump list correctly assuming that the successor is calculated correctly. +⊓⊔ +4 +Experimental Evaluation +The primary goal of our evaluation has been to experimentally validate the +performance of GIDs as a data structure in isolation, rather than their use in a +particular application. Our evaluation seeks to answer the following questions: +Q1 How does our approach (Algorithms 2 and 3) compare to the state-of-the-art +approach based on maintaining SCCs? + +Incremental Dead State Detection in Logarithmic Time +17 +Q2 How does the performance of the studied algorithms vary when the class of +input graphs changes (e.g., sparse vs. dense graphs, structured vs. random +graphs)? +Q3 Finally, how do the studied algorithms perform on GIDs taken from the +example application to regexes described in Section 5? +To answer Q1, we put substantial implementation effort into a common +framework on which a fair comparison could be made between different ap- +proaches. To this end, we implemented GIDs as a data structure in Rust which +includes a graph data structure on top of which all algorithms are built. In par- +ticular, this equalizes performance across algorithms for the following baseline +operations: state and edge addition and retrieval, DFS and BFS search, edge +iteration, and state merging. We chose Rust for our implementation for its per- +formance, and because there does not appear to be an existing publicly available +implementation of BFGT in any other language. The number of lines of code +used to implement these various structures is summarized in Figure 4. We im- +plement Algorithms 2 and 3 and compare them with the following baselines: +BFGT This algorithm is a careful implementation of the state-of-the-art ap- +proach based on SCC maintenance, using worst-case amortized O(√m) time +per update [4]. +Simple In addition to BFGT, we provide a simpler SCC-based baseline, using +a DFS instead of using the BFGT algorithm. It updates the SCCs after each +state is marked closed by searching for all cycles from that state using a +forward-DFS. This takes Θ(m2) in the worst case, but can be very efficient +when edges are added in a “forward-facing” topologically sorted manner, so +represents an important point of comparison. +Naive Finally, the naive algorithm is a greedy baseline that represents a worst- +case upper bound: it re-computes the entire set of dead states using a linear- +time DFS after each update. It is Θ(m2) for m updates. +To answer Q2, first, we compiled a range of basic graph classes which are +designed to expose edge case behavior in the algorithms, as well as randomly +generated graphs. We focus on graphs with no live states, as live states are +treated similarly by all algorithms. Most of the generated graphs come in 2×2 = +4 variants: (i) the states are either read in a forwards- or backwards- order; and +(ii) they are either dead graphs, where there are no open states at the end and +so everything gets marked dead; or unknown graphs, where there is a single +open state at the end, so most states are unknown. In the unknown case, it is +sufficient to have one open state at the end, as many open states can be reduced +to the case of a single open state where all edges point to that one. We include +GIDs from line graphs and cycle graphs (up to 100K states in multiples of 3), +as well as complete graphs, complete acyclic graphs (with only forward-edges), +and bipartite graphs (up to 1K states). These are important cases, for example, +because the reverse-order version of the line and cycle graphs is an edge case for +Simple: it often times out on these, but performs well on the forward-version of +these GIDs. + +18 +Caleb Stanford and Margus Veanes +Implementation +Component +LoC +Common Framework +1197 +Naive Algorithm +78 +Simple Algorithm +98 +BFGT Algorithm +265 +Algorithm 2 (Ours) +253 +Algorithm 3 (Ours) +283 +Euler Tour Trees +1510 +Experimental Scripts +556 +Separated Unit Tests +798 +Util +217 +Other +69 +Total +5324 +Category +Benchmark +Source +Qty +Basic +Line +24 +Cycle +24 +Complete +18 +Bipartite +14 +Total +80 +Random +Sparse +260 +Dense +130 +Total +390 +Regex +RegExLib [9,49] +2061 +37 +Handwritten [50] +70 +26 +Additional +11 +Total +74 +Fig. 4. Left: Lines of code for each algorithm and other implementation components. +Right: Benchmark GIDs used in our evaluation. Where present, the source column +indicates the quantity prior to filtering out trivially small graphs. +Time (ms) +Benchmarks Solved +0 +30 +60 +90 +1 +10 +100 +1000 +10000 +Naive +Simple +BFGT +Alg 2 +Alg 3 +Time (ms) +Benchmarks Solved +0 +100 +200 +300 +400 +1 +10 +100 +1000 +10000 +Naive +Simple +BFGT +Alg 2 +Alg 3 +Time (ms) +Benchmarks Solved +0 +20 +40 +60 +80 +1 +10 +100 +1000 +10000 +Naive +Simple +BFGT +Alg 2 +Alg 3 +Benchmark Size +Time (ms) +1 +10 +100 +1000 +10000 +100 +1000 +10000 +100000 +1000000 +Naive +Simple +BFGT +Alg 2 +Alg 3 +Benchmark Size +Average Time (ms) +1 +10 +100 +1000 +10000 +100 +1000 +10000 +100000 +1000000 +Naive +Simple +BFGT +Alg 2 +Alg 3 +Fig. 5. Evaluation results. Left: Cumulative plot showing the number of benchmarks +solved in time t or less for basic GID classes (top), randomly generated GIDs (middle), +and regex-derived GIDs (bottom). Top right: Scatter plot showing the size of each +benchmark vs time to solve. Bottom right: Average time to solve benchmarks of size +closest to s, where values of s are chosen in increments of 1/3 on a log scale. + +Incremental Dead State Detection in Logarithmic Time +19 +Second, to exhibit more dynamic behavior, we generated random graphs: +sparse graphs with a fixed out-degree from each state, which can be either 1, 2, 3, +or 10 (up to 100K states); and dense graphs with a fixed probability of each edge, +which can be .01, .02, or .03 (up to 10K states). As with the basic graphs, states +are read in some order and marked closed; at most one state is left open at the +end. Each random graph is generated using 10 different random seeds. +To answer Q3, we needed to isolate the performance of the GID data struc- +ture itself, rather than the performance of the other components of the regex +SMT solver. Prior work on regex solving integrated with Z3 [50] implements +an earlier version of GIDs, which is essentially the Simple algorithm in C++. +However, preliminary tests suggest that on some examples, GIDs are already +quite efficient and contribute only a fraction of the performance (1-10%), as +a substantial amount of time is spent manipulating and rewriting expressions +and computing derivatives. While we would expect GIDs to be the bottleneck on +larger examples where the asymptotic complexity of Simple becomes prohibitive, +this fact makes it difficult to isolate the performance of the GID data structure +itself, which is the focus of this paper. +To isolate the GID performance, we therefore instrumented the modified Z3 +solver code to export the (incremental) sequence of graph updates that would +be performed during a run of Z3 on existing regex benchmarks. For each regex +benchmark, this instrumented code produces a faithful representation of the se- +quence of graph updates that would occur in a run of the SMT solver on this +particular benchmark. It is also important to use ERE benchmarks, rather than +plain regular expressions as these are the ones for which dead state detection is +relevant (see Section 5). For each regex benchmark, we thus get a GID bench- +mark for the present paper. In our regex-derived GID examples, we include the +RegExLib benchmarks from [9,49] and the handcrafted Boolean benchmarks re- +ported in [50]. We add to these 11 additional examples designed to stress test the +GID side of a regex solver. The collection of regex SMT benchmarks is available +on GitHub4. +From both the Q2 and Q3 benchmarks, we filter out those that are too easy: +any benchmark which takes under 10 milliseconds for all of the algorithms to +solve (including Naive). We enforce a timeout of 60 seconds. The evaluation was +run on a 2020 MacBook Air running MacOS Monterey, containing an Apple M1 +processor and 8GB of memory. +Correctness. To ensure that all of our implementations our correct, we also +invested time into unit testing and checked output correctness on all of our +collected benchmarks, including several cases which exposed bugs in previous +versions of one or more algorithms. In total, all algorithms are vetted against 25 +unit tests from handwritten edge cases that exposed prior bugs, 373 unit tests +from benchmarks, and 30 module-level unit tests for specific functions. +Results. Figure 5 shows the results. Algorithm 3 shows significant improve- +ments over the state-of-the-art, solving more benchmarks in a smaller amount +4 https://github.com/cdstanford/regex-smt-benchmarks + +20 +Caleb Stanford and Margus Veanes +of time across basic GIDs, random GIDs, and regex GIDs. Algorithm 2 also +shows state-of-the-art performance, similar to BFGT on basic and regex GIDs +and significantly better on random GIDs. On the bottom right, since looking at +average time is not meaningful for benchmarks of widely varying size, we stratify +the size of benchmarks into buckets, and plot time-to-solve as a function of size. +note that as both x-axis and y-axis are on a log scale, a total running time of +O(mp) for m updates corresponds to a line with slope p. The plot shows that +Algorithm 3 exhibits up to two orders of magnitude speedup over BFGT for +larger GIDs – we see speedups of 110x to 530x for GIDs in the top five size +buckets (GIDs of size nearest to 100K, 200K, 500K, 1M, and 2M). +New implementations of existing work. Our implementation contributes, to our +knowledge, the first implementation of BFGT for SCC maintenance. In addition, +it is one of the first implementations of Euler Tour Trees (EF) for undirected +reachability in forests, including the AVL tree backing for EF which maintains +a disjoint collection of lists of state and edge identifiers, and the first implemen- +tation in Rust. +5 +Application to Extended Regular Expressions +In this section, we describe one application of GIDs in the context of deciding +regex constraints in SMT. In particular, we explain how precisely the GID state +classification problem arises in the context of derivative-based solvers [50,34]. +We first define extended regexes (regexes extended with intersection & and +complement ~) modulo a (symbolic) alphabet A that intuitively provides char- +acter classes as predicates that are closed under Boolean operations. We explain +the main idea behind (symbolic) derivatives [50] that provides the foundation +for incrementally creating a GID. Then we show, through an example, how a +solver can incrementally expand derivatives to reduce the satisfiability problem +to the GID state classification problem (Definition 2). +EREs or regexes are defined as follows where ϕ is a predicate in A. +RE ::= ϕ | ε | RE1 · RE2 | RE* | RE1 | RE2 | RE1 & RE2 | ~RE +Let Rk represent the concatenation of R k times. A regex R is nullable if it +matches the empty string. Nullability is defined inductively over the structure +of regexes with ε and R* being nullable by definition. Observe in particular that +~R is nullable iff R is not nullable, and R1 & R2 is nullable iff both R1 and R2 +are nullable. Terminal states are precisely the nullable regexes. +The false predicate ⊥ of A serves as the regex that matches nothing and is +a trivially dead state. Thus ~⊥ is equivalent to �* that matches everything and +is a trivially live state, where � is the true predicate of A. +A symbolic derivative δ(R) of a regex R is a binary tree or term t whose +leaves are regexes and internal nodes are labeled by predicates from A – the two +immediate subtrees t1 and t2 of a node with label ϕ, denoted by (ϕ ? t1 : t2), +correspond to ϕ being true in t1 and false in t2. A branch with the accumulated + +Incremental Dead State Detection in Logarithmic Time +21 +branch condition ψ from the root of t to one of its leaves R′ then defines a +transition R +ψ−→R′ – provided ψ is satisfiable in A – and the edge (R, R′) is added +to the GID where the actual predicate ψ is no longer needed because the edge +itself represents its feasibility. The number of leaves of δ(R) is the out-degree +deg+(R) of R that is independent of the actual size of the concrete alphabet. +Thus R becomes closed when deg+(R) many edges have been added from R. +The formal definition of a symbolic derivative is as follows where the op- +erations ⃝| , ⃝& , ⃝~ and ⃝· are here for the purposes of this paper and w.l.o.g. +normalizing variants of | , & , ~ and ·, by distributing the operations into if-then- +elses and build a single binary tree as a nested if-then-else as a result (see [50] +for details): +δ(ε) = δ(⊥) = ⊥ +δ(ϕ) = (ϕ ? ε : ⊥) +δ(R∗) = δ(R) ⃝· R∗ +δ(R | R′) = δ(R) ⃝| δ(R′) +δ(R & R′) = δ(R) ⃝& δ(R′) +δ(~R) = ⃝~ δ(R) +δ(R · R′) = if Nullable(R) then (δ(R) ⃝· R′) ⃝| δ(R′) else δ(R) ⃝· R′ +If c is a term of type character then δc(R) is obtained from δ(R) by instantiating +all internal nodes (conditions of the if-then-elses) ϕ by tests c ∈ ϕ. This means +that in the context of SMT, δc(R) is a term of type regex, while δ(R) represents +the lambda-term λc.δc(R) that is constructed independently of c. +Concretely, to apply Definition 1 to regexes, states will be regexes, and edges +will represent transitions to their derivatives. A live state here is thus a regex +that reaches a nullable regex via 0 or more edges. This implies that there exists +a concrete string matching it. Conversely dead states are always empty, i.e. they +match no strings, but can reach other dead states, creating strongly connected +components of closed states none of which are live. +5.1 +Reduction from Incremental Regex Emptiness to GIDs +For a solver based on derivatives of EREs, suppose we want to determine the +satisfiability of a single regex constraint s ∈ R, where s is a string variable and +R is a concrete regex. E.g., let L = ~(�*α�100) and R = L & (�α) where α is some +character predicate in A s.t. both α and ¬α are satisfiable, e.g., take α to mean +“is digit” to be concrete.5 The solver manipulates regex membership constraints +on strings by unfolding them [50]. The constraint s ∈ R, that essentially tests +nonemptiness of R with s as a witness, becomes +(s = ϵ ∧ Nullable(R)) ∨ (s ̸= ϵ ∧ s1.. ∈ δs0(R)) +where, s ̸= ϵ since R is not nullable, si.. is the suffix of s from index i, and +δ(R) = δ(L) ⃝& δ(�α) = (α ? L & ~(�100) : L) ⃝& α = (α ? L & ~(�100) & α : L & α) +Let R1 = L & ~(�100) & α and R2 = L & α. So R has two outgoing transitions +R +α−→R1 and R +¬α +−−→R2 that contribute the edges (R, R1) and (R, R2) into the +GID. Note that these edges depend only on R and not on s0. +5 Using standard notations: \d denotes all digits, and [^\d] denotes all non-digits. + +22 +Caleb Stanford and Margus Veanes +We now continue the search incrementally by checking the two branches of +the if-then-else constraint, where R1 and R2 are again both not nullable (so +s1.. ̸= ϵ): +s0 ∈ α ∧ s2.. ∈ δs1(R1) +∨ +s0 ∈ ¬α ∧ s2.. ∈ δs1(R2) +δ(R1) = (α ? L & ~(�100) & ~(�99) : L & ~(�99)) ⃝& (α ? ε : ⊥) = (α ? ε : ⊥) +δ(R2) = (α ? L & ~(�100) : L) ⃝& (α ? ε : ⊥) = (α ? ε : ⊥) +It follows that R1 +α−→ε and R2 +α−→ε, so the edges (R1, ε) and (R2, ε) are added to +the GID where ϵ is a trivial terminal state. In fact, after R1 the search already +terminates because we then have the path (R, R1)(R1, ϵ) that implies that R is +live. The associated constraints s0 ∈ α and s1 ∈ α and the final constraint that +s2.. = ϵ can be used to extract a concrete witness, e.g., s = "42". From the point +of view of deciding nonemptiness the role of the witness s is immaterial, and +can be omitted, as it poses no additional constraints on its own if s is a variable +(a.k.a., an uninterpreted constant in SMT). +Soundness of the algorithm follows from that if R is nonempty, i.e., s ∈ R +is satisfiable, then by expanding the search, we eventually arrive at a nullable +(terminal) regex, as in the example run above. To achieve completeness – and +to eliminate dead states as early as possible – we incrementally construct a +GID corresponding to the set of regexes seen so far (as above). After all the +feasible transitions from R to its derivatives in δ(R) are added to the GID as +edges (w.l.o.g. in one batch), the state R becomes closed. Crucially, due to the +symbolic form of δ(R), no derivative is missing. Therefore R is known to be +empty precisely as soon as R is detected as a dead state in the GID. We get the +following theorem that uses finiteness of the closure of symbolic derivatives [50, +Theorem 7.1]: +Theorem 4. For any regex R, (1) If R is nonempty, then the decision procedure +eventually marks R live. If n is the shortest distance from R to a terminal state, +then a concrete witness of length n can be generated. (2) If R is empty, then the +decision procedure marks R dead after a finite number of steps and terminates. +Observe that any number of simultaneous regex constraints for a string s can be +combined into single regex constraint by using the Boolean operations of ERE. +More crucially, the algorithm is independent of the size of the universe of A, +that may be very large, like the Unicode character set, or even infinite. +6 +Related Work +Online graph algorithms: Online graph algorithms are typically divided into +problems over incremental graphs (where edges are added), decremental graphs +(where edges are deleted), and dynamic graphs (where edges are both added +and deleted), with core data structures discussed in [38]. For dynamic directed +graphs, important problems include transitive closure, cycle detection, topological +ordering, and strongly connected component (SCC) maintenance. Maintaining + +Incremental Dead State Detection in Logarithmic Time +23 +a topological order of dynamic DAGs is studied in [35]. An online algorithm +for topological sorting that is experimentally shown to be preferable for sparse +graphs is discussed in [46], and in a related article [45] it is also discussed how +to extend such an algorithm to detect strongly connected components. The key +applications of such algorithms have traditionally been in pointer analysis [44]. +Topological order of incremental DAGs is studied in [24], presenting two different +algorithms, one for sparse graphs and one for dense graphs – the algorithms +are also extended to work with SCCs. The sparse algorithm was subsequently +simplified in [4] and is the basis of our implementation named BFGT in the +Evaluation section. A unified approach of several algorithms based on [4] is +presented in +[14] that uses a notion of weak topological order and a labeling +technique that estimates transitive closure size. Further extensions of [4] are +studied in [6,8] based on randomization. Transitive closure of decremental DAGs +is studied in [47] that improve upon some algorithms presented earlier in [25]. +Although we have not looked at decremental graphs in this paper, the problem +may become relevant in the context of backtracking in SMT string theory solver +during proof search in the presence of non-ground regexes, where properties such +as nullability may be theory-dependent and thus affect liveness of states. +Data structures for SMT: UnionFind [52] is a frequently used data structure +that we also rely on in our algorithm. E-graphs [54,16,18,42] are used to ensure +functional extensionality, where two expressions are equivalent if their subex- +pressions are equivalent. In both cases the maintained relation is an equivalence +relation. In contrast, maintaining live and dead states involves tracking reacha- +bility rather than equivalence. While reachability is a basic problem in many core +SMT algorithms, to the best of our knowledge, the formulation of the problem +we consider here is new. +Dead state elimination: Dead state elimination for automata, also known as +trimming [7], is a specialized version of useless symbol elimination from context- +free grammars [28, pp 88-89]. It plays an important role in minimization of +automata [31,40,30,29]. The classical minimization algorithms have been studied +extensively, e.g., in [10,7]. Brzozowski [11] observed that a DFA can be minimized +by determinizing the reversal of the determinization of the reversal of the DFA. +Regular expression matching and analysis: Decision problems for regexes are +studied in the context of Satisfiability Modulo Theories (SMT), where the first- +order objects are strings and formulas consist of string constraints such as x = yz +or x ∈ R, where R is a regex. Over such theories, the problem of nonemptiness +of a regex reduces to live state detection in the automaton (or set of derivatives) +for R. String and regex constraints have been the focus of both SMT and the +Constraint Programming (CP) solving communities, with a wide range of tools +focusing on different problem classes and applications [27]. Regexes and are now a +standard part of the SMTLIB2 format [53]. In SMT, string solvers are integrated +in the CDCL(T) architecture [43]. In the CP community, the MiniZinc format +integrates membership constraints over regular languages presented as either + +24 +Caleb Stanford and Margus Veanes +DFAs or NFAs [39]. The solvers presented in [34] and [50] are based on computing +Antimirov derivatives – a state graph of regexes is used in [50] to terminate search +from dead state regular expressions that arise in ERE constraints, which helps +the solver terminate search from goals that would otherwise not terminate. +7 +Conclusion +GIDs are a form of incremental abstract transition system in which states are +closed when they will receive no further outgoing edges; Algorithm 2 and Al- +gorithm 3 solve the incremental live and dead detection problem in GIDs. The +former runs in logarithmic worst-case time, and both algorithms achieve orders +of magnitude speedup over the state-of-the-art based on maintaining strong con- +nected components. Our implementation is open-source and publicly available6. +Acknowledgments +We would like to thank the anonymous reviewers of CAV 2021 and TACAS 2022 +for feedback leading to substantial improvements in both the paper and results. +We also extend a special thanks to Nikolaj Bjørner, for his collaboration and +involvement with the Z3 implementation, and Yu Chen, for helpful discussions +in which he proposed the idea for the first-cut algorithm. +References +1. Abboud, A., Williams, V.V.: Popular conjectures imply strong lower bounds for +dynamic problems. In: 2014 IEEE 55th Annual Symposium on Foundations of +Computer Science. pp. 434–443. IEEE (2014) +2. 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Z3: (2020), http://research.microsoft.com/projects/z3 +A +Appendix +A.1 +Extension to the Framework: Non-Reachable Updates +When GIDs are viewed as an abstract data type, other application-specific +heuristics can be incorporated. To illustrate this point, we consider another piece +of application-specific information: assertions which state that one vertex is not +(and will never be) reachable from another. We discuss how to incorporate such +updates to further improve the optimized algorithm in practice to exploit such +updates. +First, we augment the definition of guided incremental digraph to allow up- +dates of the form N(u, v), which labels that v is not reachable from u. We then +say that the graph is valid if, in addition to the previous conditions, for every +update N(u, v), v is not reachable from u via a sequence of edges in the final +digraph. Figure 6 extends the example presented in Figures 1 and 2 with a not- +reachable update. Notice that N(3, 5) does not affect the set of live and dead +states, but may be exploited for more efficient search. +To incorporate N(u, v) updates in our algorithm, when moving a reserve edge +into the graph, N(u, v) can be used to shortcut the whole procedure: if we add +an edge (v, u) in particular, then we know that this doesn’t create a cycle, and +we don’t need to repeatedly call succz at all. We store N(u, v) updates in a set +instead of a list for O(1) querying; if we need to merge them, we just discard the +set if it gets too large. Therefore, in addition what was maintained previously, +the extended algorithm tracks, for each unknown canonical state x, a set of +non-reachable edges (x, y), where each corresponds to some update N(u, v) with +x = find(u) and y = find(v) (but not necessarily vice versa); and a constant κ +which bounds the amount of work when merging non-reachable sets (additional + +28 +Caleb Stanford and Margus Veanes +1 +2 +3 +4 +5 +Fig. 6. Extension to our framework: guided incremental digraph from Figures 1 and 2, +with an added update N(3, 5) which states that 5 is not reachable from 3. In this graph, +it would be invalid to then add E(3, 4) to the graph. This does not change the set of +live or dead states, but may be exploited for more efficient search: when checking if +state 3 is live or dead, we may ignore states 4 and 5. +elements will be discarded). We modify the code for is-root(y, x) with a single +check in the beginning of the procedure: if x is in the not-reachable set from y, +return false. Otherwise, we continue as normal. Because this algorithm uses the +N(u, v) information directly and conservatively, assuming the input GID is valid, +it remains correct. +A.2 +Reachability Problems on EREs +For extended regexes X and Y , we say that Y is reachable from X if Y ∈ ∂⋆(X). +We say that X and Y are strongly connected, denoted X ⟳ Y , when both +Y ∈ ∂⋆(X) and X ∈ ∂⋆(Y ), i.e., when both Y is reachable from X and X is +reachable from Y through derivation as defined above. +We also consider the following subclasses of extended regexes: +– Regexes (REs) are EREs that do not contain complement or intersection, +that is, classical regexes. +– Semi-extended regexes (SEREs) are EREs that do not contain complement. +– Intersections of regexes (IREs) are SEREs that are equal to an intersection +of REs. +– Boolean combinations of regexes (BCREs) are EREs that are equal to a +Boolean combination (combination of intersection and complement) of REs. +Semantically, all of these capture the set of regular languages. The syntactic +relationships between these different subclasses is summarized as follows, where +all inclusions are strict: +RE ⊂ IRE ⊂ BCRE +∩ +∩ +SERE ⊂ ERE +We consider the following three decision problems. They are closely related +and in order of generality: the first is a special case of both the second and +thirds, and the second reduces to two queries of the third. For each problem, +we also consider problems on all the subclasses of EREs that we defined: REs, +SEREs, IREs, and BCREs. We summarize the complexity results in the table in +Figure 7. + +Incremental Dead State Detection in Logarithmic Time +29 +Subclass +Edge in Cycle +Strong Connectedness +Reachability +RE +Linear +Linear +Linear +IRE +PSPACE-C +PSPACE-C +PSPACE-C +BCRE +PSPACE-C +PSPACE-C +PSPACE-C +SERE +PSPACE-C +PSPACE-C +PSPACE-C +ERE +non-elementary +non-elementary +non-elementary +Fig. 7. Complexity results for reachability of various subclasses of extended regexes. +Edge in Cycle: Given X and Y such that X ∈ ∂(Y ), is Y ∈ ∂⋆(X)? +Strong Connectedness: Given X and Y , is X ⟳ Y ? +Reachability: Given X and Y , is Y ∈ ∂⋆(X)? +Theorem 5. For RE, the edge-in-cycle, strong-connectedness, and reachability +problems can be solved in linear time. +Proof. It suffices to show that reachability can be solved in linear time, since as +stated above, it is the most general of the three. We give a decision procedure for +deciding Y ∈ ∂⋆(X) by recursing on the structure of X. Prior to the procedure, +we ensure (i) that all regexes are normalized, (ii) that equal regexes are repre- +sented by the same pointer, and (iii) that concatenations are represented as lists +and precompute the length of each list, so that for any subexpression X0 of X, +whether Y = Y1·X0 can be checked in constant time. This precomputation takes +O(|X| + |Y |) time. The recursion then works as follows, on input (X, Y ). (1) If +X = ϕ, ε, or ⊥, we can check directly if Y is one of the finitely many derivatives. +(2) If X = X1 | X2, we observe that Y ∈ ∂⋆(X) if and only if Y ∈ ∂⋆(X1) or +Y ∈ ∂⋆(X2). So we recurse on (X1, Y ) and (X2, Y ). (3) If X = X∗ +1, we observe +that Y ∈ ∂⋆(X) if and only if Y = X′ +1(X∗ +1) for X′ +1 ∈ ∂⋆(X1). So we first check +if Y has the form Y1X∗ +1, then recurse on (X1, Y1). (4) Finally, if X = X1 · X2, +we observe that Y ∈ ∂⋆(X) if and only if either Y = X′ +1 · X2 for X′ +1 ∈ ∂⋆(X1), +or Y = X′ +2 for X′ +2 ∈ ∂⋆(X2). (Note that this relies on the fact that X1 is an +RE, not an ERE, so we know it is nonempty and in particular ε ∈ ∂⋆(X1).) So +we first check if Y has the form Y1 · X2, if so recursing on both (X1, Y1) and +(X2, Y ), otherwise recursing on just (X2, Y ). Since the procedure never recurses +twice on X or twice on the same subexpression of X, it takes O(|X|) time. +⊓⊔ +Theorem 6. For the classes IRE, BCRE, and SERE, the edge-in-cycle, strong- +connectedness, and reachability problems are PSPACE-complete. +Proof. It suffices to show: (1) the edge-in-cycle problem for IRE is PSPACE- +hard; (2) the reachability problem for BCRE is in PSPACE; and (3) the reach- +ability problem for SERE is in PSPACE. (1) We reduce from intersection- +nonemptiness of REs, which is known to be PSPACE-hard. Given a list of +REs R1, R2, . . . , Rk, then let b be a fresh character that does not appear in + +30 +Caleb Stanford and Margus Veanes +R1, . . . , Rk, and construct the IRE X = (bR1)∗ & (bR2)∗ & · · · & (bRk)∗. X has +only one derivative X′, which is an intersection where the ith term is Ri(bRi)∗. +Then the edge-in-cycle property for (X, X′) holds if and only if the intersection +of Ri is nonempty, because ∂b is empty for all subexpressions of Ri except ε, +so the only way to get back to X is by stepping all Ri to ε simultaneously. (2) +We first convert the BCRE X to an alternating automaton (AFA): first convert- +ing the RE subexpressions to NFAs, then using the standard constructions for +Boolean operations on AFAs. (3) For an SERE X, for any X′ ∈ ∂⋆(X) we show +that the size of X′ is bounded linearly in the size of the X. This can be seen +by induction on the structure of X; for example, elements of ∂⋆(X1 & X2) are a +pair of an element of ∂⋆(X1) and an element of ∂⋆(X2). It follows that we can +provide the following NPSPACE algorithm for reachability of (X, Y ): at each +step, pick a derivative nondeterministically of X and recurse. +⊓⊔ +Theorem 7. For ERE, the edge-in-cycle, strong-connectedness, and reachability +problems are non-elementary. +Proof. It suffices to show that the edge-in-cycle problem is non-elementary. We +reduce from the nonemptiness problem for EREs, which is known to be non- +elementary [51]. Given an ERE R, we let b be a fresh character not appearing +in R, and we let X = (bR)∗. Then X has one derivative, X′ = R(bR)∗. The +edge-in-cycle property for (X, X′) holds and only if R is nonempty, because R +is nonempty exactly when ε ∈ ∂⋆(R). +⊓⊔ + diff --git a/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/load_file.txt b/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..44a54828f8311584e8a988f952a44efdcbc8f837 --- /dev/null +++ b/-NE4T4oBgHgl3EQf3w1M/content/tmp_files/load_file.txt @@ -0,0 +1,1233 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf,len=1232 +page_content='Incremental Dead State Detection in Logarithmic Time Caleb Stanford1 and Margus Veanes2 1 University of California, San Diego and University of California, Davis cdstanford@ucdavis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='edu 2 Microsoft Research, Redmond margus@microsoft.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='com Abstract.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Identifying live and dead states in an abstract transition sys- tem is a recurring problem in formal verification.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, state-of-the- art graph algorithms for maintaining reachability information incremen- tally (that is, as states are visited and before the entire state space is explored) assume that new edges can be added from any state at any time, whereas in many applications, outgoing edges are added from each state as it is explored.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To formalize the latter situation, we propose guided incremental digraphs (GIDs), incremental graphs which support labeling closed states (states which will not receive further outgoing edges).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our main result is that dead state detection in GIDs is solvable in O(log m) time per edge update for m edges, improving upon O(√m) per edge due to Bender, Fineman, Gilbert, and Tarjan (BFGT) for general incremen- tal directed graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We introduce two algorithms for GIDs: one establishing the logarithmic time bound, and a second algorithm to explore a lazy heuristics-based ap- proach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To demonstrate applicability, we show how GIDs can be used to lazily decide regular expression constraints in SMT applications.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To en- able an apples-to-apples experimental comparison, we implemented both algorithms, two naive baselines, and the state-of-the-art BFGT baseline using a common directed graph interface in Rust.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our evaluation shows 110-530x speedups over BFGT for the largest input graphs over a range of graph classes, random graphs, and graphs arising from regular expres- sion benchmarks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Keywords: Dead State Detection · Graph Algorithms · Online Algo- rithms · SMT.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 1 Introduction Classifying states in a transition system as live or dead is a recurring problem in formal verification.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For example, given an expression, can it be simplified to the identity?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given an input to a nondeterministic program, can it reach a terminal state, or can it reach an infinitely looping state?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given a state in an automaton, can it reach an accepting state?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Domain-specific variations on this problem have led to many general and specialized algorithms used by automated arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='05308v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='DS] 12 Jan 2023 2 Caleb Stanford and Margus Veanes verification tools.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' State classification is relevant in the context of satisfiability modulo theories (SMT) [17,41,3,55,15,36], where theory-specific partial decision procedures often work by exploring the state space to find a reachable path that corresponds to a satisfying string or, more generally, a sequence of constructors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In all of these cases, the core problem is live and dead state detection in a directed graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Motivating application.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For example, recent approaches for the SMT theory of regular expressions [34,50] rely on regular expression derivatives to explore the states of the finite state machine corresponding to the regex incrementally, rather than expanding all states initially which is often prohibitively expensive.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This requires solving the incremental live and dead state detection problem in the finite state machine (a directed graph).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This is particularly important for regexes with intersection and complement (extended regexes [12,22,19]), which have been shown to arise natively in applications of SMT string solvers to security [2,50]).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Concretely, consider the regex (�*α�100)C ∩ (�α), where � matches any character, ∩ is regex intersection, C is regex complement, and α matches any digit (0-9).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A traditional solver would expand the left and right operands as state machines, but the left operand (�*α�100)C is astronomically large as a DFA, causing the solver to hang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The derivative-based technique instead constructs the derivative regex: (�*α�100)C ∩(�100)C ∩α.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' At this stage we have a graph of two states and one edge, where the states are regexes and the edge is the derivative relation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' After one more derivative operation, the regex becomes one that is clearly satisfiable as it accepts the empty string.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In order to be efficient, a derivative-based solver needs to identify satisfiable (live) and unsatisfiable (dead) regexes incrementally (as the graph is built), be- cause it does not generally construct the entire space before terminating (see the graph update inference rule Upd, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 626 [50]).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Indeed, satisfiability (nonempti- ness) for extended regexes is non-elementary, and is still PSPACE-complete for more restrictive fragments, strongly incentivizing the incremental approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Be- yond regexes, we believe that GIDs are general enough to be applicable in a range of future applications.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Prior work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Traditionally, while live state detection can be done incrementally, dead state detection is often done exhaustively (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', after the entire state space is explored).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For example, bounded and finite-state model checkers based on translations to automata [32,48,13], as well as classical dead-state elimination algorithms [28,7,10], generally work on a fixed state space after it has been fully enumerated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, exhaustive exploration is prohibitive for large (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', ex- ponential or infinite) state spaces which arise in an SMT verification context.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Moreover, exhaustive exploration may simply be unnecessary if partial infor- mation can be deduced about the states seen so far which already leads to a satisfiable or unsatisfiable result along a given solver path.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We also have good evidence that incremental feedback can improve SMT solver performance: a representative success story is the e-graph data structure [54,16] for congruence closure [18,42], which maintains an equivalence relation among expressions in- Incremental Dead State Detection in Logarithmic Time 3 crementally;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' because it applies to general expressions, it is theory-independent and re-usable.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental state space exploration could lead to similar benefits if applied to SMT procedures which still rely on exhaustive search.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, in order to perform incremental dead state detection, we currently lack algorithms which match offline performance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As we discuss in Section 2, the best-known existing solutions would require maintaining strong connected components (SCCs) incrementally.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For SCC maintenance and the related sim- pler problem of cycle detection, O(m3/2) amortized algorithms are known for m edge additions [23,4], with some recently announced improvements [5,8].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Note that this is in sharp contrast to O(m) for the offline variants of these problems, which can be solved by breadth-first or depth-first search.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' More generally, re- search suggests that there is a computational barrier to what can be determined incrementally in the worst case [20,21,1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To improve on prior results, our key observation is that in many applications, edges are not added adversarially, but from one state at a time as the states are explored.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As a result, we know when a state will have no further outgoing edges;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' we may use this information to (i) provide information about dead states incrementally, rather than after the whole state space is explored;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and (ii) obtain more efficient algorithms than currently exist for general graph reachability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We introduce guided incremental digraphs (GIDs), a variation on incremental graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Like an incremental directed graph, a guided incremental digraph may be updated by adding new edges between states, or a state may be labeled as closed, meaning it will receive no further outgoing edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Some states are designated as terminal, and we say that a state is live if it can reach a terminal state and dead if it will never reach a terminal state in any extension – i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' if all reachable states from it are closed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To our knowledge, the problem of detecting dead states in such a system has not been studied by existing work in graph algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our problem can be solved through solving SCC maintenance, but not necessarily the other way around (see Proposition 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We provide two new algorithms for dead-state detection in GIDs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' First, we show that the dead-state detection problem for GIDs can be solved in time O(m · log m) for m edge additions, within a logarithmic factor of the O(m) cost for offline search.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The worst-case performance of our algorithm thus strictly improves on the O(m3/2) upper bound for SCC maintenance in general incremental graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our algorithm utilizes several data structures and existing results in online algorithms: in particular, Union-Find [52] and Henzinger and King’s Euler Tour Trees [26].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The main idea of our algorithm is that, rather than explicitly computing the set of SCCs, for closed states we maintain a single path to a non-closed (open) state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This turns out to reduce the problem to quickly determining whether two states are currently assigned a path to the same open state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' On the other hand, Euler Tour Trees can solve undirected reachability for graphs that are forests in logarithmic time;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' the challenge then lies in figuring out how to reduce directed connectivity in the graph of paths to undirected connectivity in an Euler Tour Trees forest.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' At the same time, we must maintain 4 Caleb Stanford and Margus Veanes this structure under Union-Find state merges, in order to deal with cycles that are found in the graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' While as theorists we would like to believe that asymptotic complexity is enough, the truth is that the use of complex data structures (1) can be pro- hibitively expensive in practice due to constant-time overheads, and (2) can make algorithms substantially more difficult to implement, leading practition- ers to prefer simpler approaches.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To address these needs, in addition to the logarithmic-time algorithm, we provide a second lazy algorithm which avoids the user of Euler Tour Trees, and only uses union-find.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This algorithm is based on an optimization of adding shortcut jump edges for long paths in the graph to quickly determine reachability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This approach aims to perform well in practice on typical graphs, and is evaluated in our evaluation along with the logarithmic time algorithm, though we do not prove its asymptotic complexity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Finally, we implement and empirically evaluate both of our algorithms for GIDs against several baselines in 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='5k lines of code in Rust [37,33].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our evaluation focuses on the performance of the GID data structure itself, rather than its end- to-end performance in applications.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To ensure an apples-to-apples comparison with existing approaches, we put particular focus on providing a directed graph data structure backend shared by all algorithms, so that the cost of graph search as well as state and edge merges is identical across algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We implement two naive baselines, as well as an implementation of the state-of-the-art solution based on maintaining SCCs, BFGT [4] in our framework.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To our knowledge, the latter is the first implementation of BFGT for SCC maintenance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' On a collection of generated benchmark GIDs and GIDs directly pulled from the regex application, we demonstrate a substantial improvement over BFGT for both of our algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For example, for larger GIDs (those with over 100K updates), we observe a 110-530x speedup over BFGT.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our primary contributions are: – Guided incremental digraphs (GIDs), a formalization of incremental live and dead state detection which supports labeling closed states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (Section 2) – Two algorithms for the state classification problem in GIDs: first, an algo- rithm that works in amortized O(log m) time per update, improving upon the state-of-the-art amortized O(√m) per update for incremental graphs;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and second, a simpler algorithm based on lazy heuristics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (Section 3) – An open-source implementation of GIDs in Rust3, including an implementa- tion the BFGT baseline and supporting data structures for a fair comparison, and an evaluation which demonstrates that our algorithm outperforms the best known incremental SCC algorithm by two orders of magnitude for a range of GID benchmarks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (Section 4) Following these contributions, we expand on the application of GIDs to regex solving in SMT (Section 5), survey related work (Section 6), and conclude (Sec- tion 7).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 3 https://github.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='com/cdstanford/gid Incremental Dead State Detection in Logarithmic Time 5 1 2 3 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Guided incremental digraph consisting of the sequence of updates E(1, 2), E(1, 3), T(2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Terminal states are denoted with double circles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' After the update T(2), states 1 and 2 are known to be live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, for this graph state 3 is not dead, as a future edge may cause it to be live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 2 Guided Incremental Digraphs 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 Problem Statement An incremental digraph is a sequence of edge updates E(u, v), where the algo- rithmic challenge in this context is to produce some output after each edge is received (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', whether or not a cycle exists).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If the graph also contains updates T(u) labeling a state as terminal, then we say that a state is live if it can reach a terminal state in the current graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In a guided incremental digraph, we also include updates C(u) labeling a state as closed, meaning that will not receive any further outgoing edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Definition 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Define a guided incremental digraph (GID) to be a sequence of updates, where each update is one of the following: (i) a new directed edge E(u, v);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (ii) a label T(u) which indicates that u is terminal;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' or (iii) a label C(u) which indicates that u is closed, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' no further edges will be added going out from u (or labels to u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The guided incremental digraph is valid if the closed labels are correct: there are no instances of E(u, v) or T(u) after an update C(u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The denotation of G is the directed graph (V, E) where V is the set of all states u which have occurred in any update in the sequence, and E is the set of all (u, v) such that E(u, v) occurs in G.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' An extension of a valid GID G is a valid GID G′ such that G is a prefix of G′.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In a valid GID G, we say that a state u is live if there is a path from u to a terminal state in the denotation of G;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and a state u is dead if it is not live in any extension of G.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Notice that in a GID without any C(u) updates, no states are dead as an edge may be added in an extension which makes them live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We provide an example of a valid GID in Figures 1 and 2 resulting from the following sequence of updates: E(1, 2), E(1, 3), T(2), E(4, 3), E(4, 5), C(4), C(5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The states are denoted based on whether they are marked as terminal T(u) (double circle) or closed C(u);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' states that are not closed are denoted with dashed circles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Notice that after C(4), state 4 is marked closed but can still reach 3 and 5, so it is not dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Additionally, notice that once 1 and 2 are live (after T(2)), further edges from them do not matter.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 6 Caleb Stanford and Margus Veanes 1 2 3 4 5 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Guided incremental digraph consisting of the sequence of updates E(1, 2), E(1, 3), T(2), E(4, 3), E(4, 5), C(4), C(5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Closed states (from which future edges may not be added) are denoted with solid circles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' After the update C(5) (but not earlier), state 5 is dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Definition 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given as input a valid GID, the guided incremental state clas- sification problem is to output, in an online fashion after each update, the set of new live and new dead states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' That is, output Live(u) or Dead(u) on the smallest prefix of updates such that u is live or dead on that prefix, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='2 Existing Approaches In many applications, one might choose to classify dead states offline, after the entire state space is enumerated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This leads to a linear-time algorithm via either DFS or BFS, but it does not solve the state classification problem (Definition 2) because it is not incremental.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Naive application of this idea leads to an O(m) time algorithm per update for m updates (O(m2) total), as we may have to search the entire graph after each update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For acyclic graphs, there exists an amortized O(1)-time per update algorithm for the problem (Definition 2): maintain the graph as a list of forward and backward edges at each state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When a state v is marked terminal, do a DFS along backward edges to determine all states u that can reach v not already marked as live, and mark them live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When a state v is marked closed, visit all forward-edges from v;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' if all are dead, mark v as dead and recurse along all backwards edges from v.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As each edge is visited only when marking a state live or dead, it is only visited a constant number of times overall (though we may use more than O(1) time on some particular update pass).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Additionally, the live state detection part of this procedure still works for graphs containing cycles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The challenge, therefore, lies primarily in detecting dead states in graphs which may contain cycles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For this, the breakthrough state-of-the-art approach from [4] enables maintaining the graph as a condensed graph which is acyclic, where the vertices in the condensed graph represent strongly connected compo- nents (SCCs) of states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The mapping from states to SCCs is maintained using a Union-Find [52] data structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Maintaining this requires O(√m) time per update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To ensure that vertices in the condensed graph correspond to SCCs in the original, we have to also make sure that closed and non-closed states are not merged into the same SCC;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' the easiest solution to this is to withhold all edges from each state u in the graph until u are closed, which ensures that u must be its own SCC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Once we have the condensed graph with these modifications, Incremental Dead State Detection in Logarithmic Time 7 the same algorithm as in the previous paragraph works to identify live and dead states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Since each edge is only visited when a state is marked closed or live, each edge is visited only once throughout the algorithm, we use only amortized O(1) additional time to calculate live and dead states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' While this SCC maintenance algorithm ignores the fact that edges do not occur from closed states C(u), this still proves the following result: Proposition 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Guided incremental state classification reduces to SCC main- tenance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' That is, suppose we have an algorithm over incremental graphs that maintains the set of SCCs in O(f(m, n)) total time given n states and m edge additions, where “maintains” means that (i) we can check whether two states are in the same SCC in O(1) time, and (ii) we can iterate over all the states in an SCC, or iterate over the forward-edges or backward-edges from an SCC (to or from other SCCs, respectively) in O(1) time per edge.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Then there exists an algorithm to solve guided incremental state classification in O(f(m, n)) total time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Despite this reduction one way, there is no obvious reduction the other way – from cycle detection or SCCs to Definition 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This is because, while the existence of a cycle of non-live states implies bi-reachability between all states in the cycle, it does not necessarily imply that all of the bi-reachable states are dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In fact, consider a GID consisting only of E(u, v) and C(u) updates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In order to identify dead states, rather than enumerating all cycles or SCCs, it is enough to maintain a single path from each non-dead state to a non-closed state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This observation forms the starting point for our approach in the following sections, improving on the upper bound given by Proposition 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 3 Algorithms This section presents Algorithm 2, which solves the state classification problem in logarithmic time (Theorem 2);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and Algorithm 3, an alternative lazy approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Both algorithms are optimized versions of Algorithm 1, a first-cut algorithm which establishes the structure of our approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We begin by establishing some basic terminology shared by all of the algorithms (see Figure 3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' States in a GID can be usefully classified as exactly one of four statuses: live, dead, unknown, or open, where an unknown state is one that is closed but not yet live or dead, and an open state is one that is not closed and not live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Note that a state may be live and neither open nor closed;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' this terminology keeps the classification disjoint.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Pragmatically, for live states it does not matter if they are classified as open or closed, since edges from those states no longer have any effect.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, all dead and unknown states are closed, and no states are both open and closed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given this classification, the intuition is that for each unknown state u, we only need one path from u to an open state to prove that it is not dead;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' we want to maintain one such path for all unknown states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To maintain all of these paths simultaneously, we maintain an acyclic directed forest structure on unknown and 8 Caleb Stanford and Margus Veanes Live Some reachable state from u is terminal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Dead All reachable states from u (including u itself) are closed and not terminal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Unknown u is closed, but not live or dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Open u is not live and not closed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Terminal A state u labeled by T(u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Closed A state u labeled by C(u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Canonical A state x that is the uniquely chosen representative of its union-find equivalence class, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(x) = x.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' u, v, w States in the original graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' x, y, z Canonical states in the condensed graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Successor succ(x) For an unknown, canonical state x, a uniquely chosen state v such that (x, v) is an edge, and following the path of successors leads to an open state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Top: Basic classification of GID states into four disjoint categories.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Bottom: Additional terminology used in this paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' open states where the roots are open states, and all non-root states have a single edge to another state, called its successor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Edges other than successor edges can be temporarily ignored, except for when marking live states;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' these are kept as reserve edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Specifically, we add every edge (u, v) as a backward-edge from v (to allow propagating live states), but for edges not in the forest we keep (u, v) in a reserve list from u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We store all edges, including backward-edges, in the original order (u, v).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The reserve list edge becomes relevant only when either (i) u is marked as closed, or (ii) u’s successor is marked as dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In order to deal with cycles, we need to maintain the forest of unknown states not on the original graph, but on a union-find condensed graph, similar to [52].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When we find a cycle of unknown states, we merge all states in the cycle by calling the union method in the union-find.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We refer to a state as canonical if it is the canonical representative of its equivalence class in the union find;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' the condensed graph is a forest on canonical states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We use x, y, z to denote canonical states (states in the condensed graph), and u, v, w to denote the original states (not known to be canonical).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Following [52], we maintain edges as linked lists rather than sets, and using the original states instead of canonical states;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' this is important as it allows combining edge lists in O(1) time when merging states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 First-Cut Algorithm A first-cut algorithm based on these ideas is shown in Algorithm 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The union- find data structure UF provides UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='union(v1, v2), UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v), and UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter(v): UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='union merges v1 and v2 to refer to the same canonical state, UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find returns the canonical state for v, and UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter iterates over states equivalent to v.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The running time of each of these operations is amortized α(n) for n updates, where α(n) ∈ o(log n) is the inverse Ackermann function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental Dead State Detection in Logarithmic Time 9 Algorithm 1 First-cut algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' V: a type for states (integers) (variables u, v, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=') E: the type of edges, equal to (V, V) UF: a union-find data structure over V X: the set of canonical states in UF (variables x, y, z, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=') status: a map from X to Live, Dead, Unknown, or Open succ: a map from X to V res and bck: maps from X to linked lists of E procedure OnEdge(E(u, v)) x ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' y ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v) if status(y) = Live then OnTerminal(T(x)) ▷ mark x and its ancestors live else if status(x) ̸= Live then ▷ status(x) must be Open append (u, v) to res(x) append (u, v) to bck(y) procedure OnTerminal(T(v)) y ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v) for all x in DFS backwards (along bck) from y not already Live do status(x) ← Live output Live(x′) for all x′ in UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter(x) procedure OnClosed(C(v)) y ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v) if status(y) ̸= Open then return ▷ y is already live or closed while res(y) is nonempty do pop (v, w) from res(y);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' z ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(w) if status(z) = Dead then continue else if CheckCycle(y, z) then for all z′ in cycle from z to y do z ← Merge(z, z′) else status(y) ← Unknown;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' succ(y) ← z;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' return status(y) ← Dead;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' output Dead(y′) for all y′ in UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter(y) ToRecurse ← ∅ for all (u, v) in bck(y) do x ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u) if status(x) = Unknown and UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(succ(x)) = y then status(x) ← Open ▷ temporary – marked closed on recursive call add x to ToRecurse for all x in ToRecurse do OnClosed(C(x)) procedure CheckCycle(y, z) returning bool while status(z) = Unknown do z ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(succ(z)) ▷ get root state from z return y = z procedure Merge(x, y) returning V z ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='union(x, y) bck(z) ← bck(x) + bck(y) ▷ O(1) linked list append res(z) ← res(x) + res(y) ▷ O(1) linked list append return z 10 Caleb Stanford and Margus Veanes We will only merge states if they are bi-reachable from each other, and both unknown.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This implies that all states in the equivalence class of a canonical state x have the same status.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We also maintain the set of canonical states in UF as a set X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The edge maps res and bck are stored as maps from X to linked lists of edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Each edge (u, v) is always stored using its original states (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', edge labels are not updated when states are merged);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' but we can easily obtain the corresponding edge on canonical states via (UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u), UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' On an input edge (u, v), the edge is immediately added to bck as a backward-edge from v (this is used for detecting live states), but forward-edges are only added selectively to succ when they are needed to prove unknown status, and are otherwise stored in the reserve list res.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Invariants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In total, we maintain the following invariants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For live and dead states, we no longer care about forward or backward edges from them, so there are no invariants about live and dead states other than that status(x) is Live or Dead for these states, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The successor edges and no cycles invariants are about the forest structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The last invariant, edge representation, is about making sure that all edges in the input GID are represented somehow in the current graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Merge equivalence: For all states u and v, if UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u) = UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v), then u and v are bi-reachable and both closed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (This implies that u and v are both live, both dead, or both unknown.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=') – Status correctness: For all u, status(UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u)) is equal to the status of u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Successor edges: If x is unknown, then succ(x) is defined and is an unknown or open state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If x is open, then succ(x) is not defined.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – No cycles: There are no cycles among the set of edges (x, UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(succ(x))), over all unknown and open canonical states x.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Edge representation: Lastly, for all edges (u, v) in the input GID, at least one of the following holds: (i) (u, v) is stored in res, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (u, v) ∈ res(UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v));' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (ii) (u, v) is stored in succ, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' v = succ(UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u));' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (iii) u and v are equivalent in the condensed graph, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u) = UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (iv) u is live;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' or (v) v is dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proposition 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 1 is correct.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We need to argue that all of the invariants described above are preserved.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This implies correctness of the algorithm by the status correctness invariant, since it implies that live and dead states are labeled (and output) correctly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Upon receiving E(u, v) or T(u), this may cause some dead, unknown, or open states to change status to live, but does not change the status of any other states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As bck stores all backwards-edges (not just succ edges), live states are marked correctly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This preserves the forest invariants because if an unknown or open state is marked live, so are all its predecessors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This also preserves the edge representation invariant, either by adding new edges to case (i) and case (iv) Incremental Dead State Detection in Logarithmic Time 11 (for E updates) or moving edges from cases (i)-(iii) to case (iv) (for both E and T updates).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The procedure C(u) is recursive;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' during the procedure and on recursive calls, some states are temporarily marked Open, meaning they are roots in the forest structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' During these recursive calls, we need a slightly generalized invariant: each forest root corresponds to a pending future call to OnClosed(C(u)) (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', an element of ToRecurse for some call on the stack) and is a state that needs to either find a successor or be marked dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This means that the status labels for unknown- and open-labeled states are not necessarily correct during recursive calls;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' we are only concerned with preserving the forest structure, so that they will be correct after all calls complete.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Note in particular that after merging cycles of unknown states via Merge(x, y), the new root is marked Open to preserve the generalized invariant on recursive calls.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Upon receiving C(u), without loss of generality we may assume status(u) = Open (the opposite only occurs if the input GID has duplicate C(u) updates, or if C(u) occurs for a live state).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' At the top of the while loop, there are three cases: – If a reserve edge is available, and its target is dead, then we discard it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This preserves edge representation because that edge still satisfies (iv).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – If a reserve edge is available and its target is not dead, then we see if adding that edge creates a cycle by calling CheckCycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If no, then the two trees are distinct, so we add an edge between them.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This preserves edge representation by moving that edge from case (i) to case (ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If yes, then we collapse the cycle in the forest to a single state by repeated calls to Merge(x, y).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This preserves edge representation by moving the edges in the cycle from case (ii) to case (iii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The forest structure of the succ is also preserved because if a graph is a forest, then it remains a forest after merging adjacent states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Finally, if there are no reserve edges left, then because of edge representation, and because there is no successor from u, all edges from u must lead to dead states (case (v)) and therefore u is dead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This case splits the tree rooted at u into one tree for each of its predecessors, preserving the forest structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Each of the succ edges from predecessors are deleted;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' this preserves edge representation by moving those edges from case (ii) to case (v).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In any case, the generalized invariant for recursive calls is preserved, and all dead states are labeled correctly (given the invariant), so we are done.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ Complexity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The core inefficiency in Algorithm 1 lies in CheckCycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The proce- dure repeatedly sets z ← succ(z) to find the tree root, which in general could be linear time in the number of edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For example, suppose we have a line graph where we add edges in a backwards fashion and close them: E(2, 1), C(2), E(3, 2), C(3), .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' , E(n, n-1), C(n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In such a graph, this inefficiency results in O(m2) work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We therefore want to improve upon this step in Algorithms 2 and 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' All other parts of the algorithm run in amortized α(m) time per update for m updates (using vectors to represent the maps fwd, bck, and succ for O(1) lookups).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The OnTerminal calls and loop iterations only run once per edge in the graph when the target of that edge is marked live or terminal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Likewise, 12 Caleb Stanford and Margus Veanes the procedure OnClosed is called conservatively: the cost of each call can be assigned either to the target of an edge being marked dead, or to an edge being merged as part of a cycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Both marking dead and merging can only happen once for a given edge, so this is O(1) per edge.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='2 Logarithmic Algorithm At its core, CheckCycle requires solving an undirected reachability problem on a graph that is restricted to a forest.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, the forest is changed not just by edge additions, but edge additions and deletions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' While undirected reachability and reachability in directed graphs are both difficult to solve incrementally, reachability in dynamic forests can be solved in O(log m) time per operation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our algorithm uses an Euler Tour Forest data structure EF of Henzinger and King [26], and is shown in Algorithm 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, this idea does not work straightforwardly – once again because of the presence of cycles in the original graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We cannot simply store the forest as a condensed graph with edges on condensed states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As we saw in Algorithm 1, it was important to store successor edges as edges into V, rather than edges into X – this is the only way that we can merge states in O(1), without actually inspecting the edge lists.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If we needed to update the forest edges to be in X, this could require O(m) work to merge two O(m)-sized edge lists as each edge might need to be relabeled in the EF graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To solve this challenge, we instead store the EF data structure on the original states, rather than the condensed graph;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' but we ensure that each condensed state is represented by a tree of original states in the original graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When adding edges between condensed graph states, we need to make sure to remember the original state labels (u, v), so that we can later remove it using the original labels (this happens when its target becomes dead).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When an edge would create a cycle, we instead simply ignore it in the EF graph: because a line of connected trees forms a tree.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In summary, algorithm borrows most data and procedures from Algorithm 1, with a few important changes: (1) we maintain the EF data structure EF, a forest on V (2) the successor edges are stored as their original edge labels (u, v), rather than just as a target state;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (3) the procedure OnClosed is updated in several locations to maintain the graph EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Invariants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We continue all invariants from Algorithm 1, with the small mod- ification that the successor edges and no cycles invariants use the new succ representation: that is, they are constraints on the edges (x, UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v)), where succ(x) = (u, v).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In addition, we have two constraints on edges in EF, de- pending on whether those states are equivalent in the union-find structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We call edges between inequivalent states inter-edges and those between equivalent states intra-edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – EF inter-edges: For all states u and v not in the same canonical state, (u, v) is in the EF graph if and only if (u, v) = succ(UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u)) or (v, u) = succ(UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental Dead State Detection in Logarithmic Time 13 Algorithm 2 Logarithmic time algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' All data from Algorithm 1 succ: a map from X to E (instead of to V) EF: Euler Tour Trees data structure providing: EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='add, EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='remove, and EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='connected procedure OnEdge(E(u, v)) as in Algorithm 1 procedure Merge(x, y) returning V as in Algorithm 1 procedure OnTerminal(T(v)) y ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v) for all x in DFS backwards (along bck) from y not already Live do if status(x) = Unknown then ▷ The following line is not strictly necessary, but simplifies the analysis (u, v) ← succ(x);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' delete succ(x);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='remove(u, v) status(x) ← Live;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' output Live(x′) for all x′ in UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter(x) procedure OnClosed(C(v)) y ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v) if status(y) ̸= Open then return while res(y) is nonempty do pop (v, w) from res(y);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' z ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(w) if status(z) = Dead then continue else if CheckCycle(y, z) then for all z′ in cycle from z to y do z ← Merge(z, z′) else status(x) ← Unknown;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' succ(x) ← (v, w) EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='add(v, w) ▷ undirected edge;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' use original labels (not (x, y)) return status(y) ← Dead;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' output Dead(y′) for all y′ in UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='iter(y) ToRecurse ← ∅ for all (u, v) in bck(y) do x ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(u) if status(x) = Unknown then (u′, v′) ← succ(x) if UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(v′) = y then EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='remove(u′, v′) ▷ undirected edge;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' use original labels status(x) ← Open;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' delete succ(x);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' add x to ToRecurse for all x in ToRecurse do OnClosed(C(x)) procedure CheckCycle(y, z) returning bool return EF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='connected(y, z) 14 Caleb Stanford and Margus Veanes – EF intra-edges: For all unknown canonical states x, the set of edges (u, v) in the EF between states belonging to x forms a tree.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Theorem 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 2 is correct.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Observe that the EF inter-edges constraint implies that EF only contains edges between unknown and open states, together with isolated trees.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In the modified OnTerminal procedure, when marking states as live we remove inter- edges, so we preserve this invariant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Next we argue that given the invariants about EF, for an open state y the CheckCycle procedure returns true if and only if (y, z) would create a directed cycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If there is a cycle of canonical states, then because canonical states are connected trees in EF, the cycle can be lifted to a cycle on original states, so y and z must already be connected in this cycle without the edge (y, z).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Conversely, if y and z are connected in EF, then there is a path from y to z, and this can be projected to a path on canonical states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, because y is open, it is a root in the successor forest, so any path from y along successor edges travels only on backwards edges;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' hence z is an ancestor of y in the directed graph, and thus (y, z) creates a directed cycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This leaves the OnClosed procedure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Other than the EF lines, the structure is the same as in Algorithm 1, so the previous invariants are still preserved, and it remains to check the EF invariants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When we delete the successor edge and temporarily mark status(x) = Open for recursive calls, we also remove it from EF, preserving the inter-edge invariant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Similarly, when we add a successor edge to x, we add it to EF, preserving the inter-edge invariant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' So it remains to consider when the set of canonical states changes, which is when merging states in a cycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Here, a line of canonical states is merged into a single state, and a line of connected trees is still a tree, so the intra-edge invariant still holds for the new canonical state, and we are done.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 2 uses amortized logarithmic time per edge update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' By the analysis of Algorithm 1, each line of the algorithm runs amortized O(1) time other than those in CheckCycle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For the CheckCycle, procedure it now avoids the loop and so also runs amortized O(1) times.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Each line is either constant-time, α(m) = o(log n) time for the UF calls, or O(log n) time for the EF calls, so in total the algorithm runs in amortized O(log n) time per update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='3 Lazy Algorithm While the asymptotic complexity of log n could be the end of the story, in prac- tice, the cost of the EF calls could be a significant overhead.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The technical details of Euler-Tour Trees include building an AVL-tree cycle for each tree, where the cycle contains each state of the graph and each edge in the graph twice.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It turns out that adding one edge to EF results in up to eight modifications to the AVL tree: it needs to be split at the source, split at the target, then the edge needs to Incremental Dead State Detection in Logarithmic Time 15 Algorithm 3 Lazy algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' All data from Algorithm 1 jumps: a map from X to lists of V procedure OnEdge(E(u, v)) as in Algorithm 1 procedure OnTerminal(T(v)) as in Algorithm 1 procedure OnClosed(C(v)) as in Algorithm 1 procedure CheckCycle(y, z) returning bool return y = GetRoot(z) procedure GetRoot(z) returning V if status(z) = Open then return z if jumps(z) is empty then push succ(z) to jumps(z) ▷ set 0th jump repeat pop w from jumps(z);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' z′ = UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='find(w) ▷ remove dead jumps until status(z′) ̸= Dead push z′ to jumps(z) result ← GetRoot(z′) n ← length(jumps(z));' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' n′ ← length(jumps(z′)) if n ≤ n′ then push jumps(z′)[n − 1] to jumps(z) ▷ set nth jump return result procedure Merge(x, y) returning V z ← UF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='union(x, y) bck(z) ← bck(x) + bck(y);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' res(z) ← res(x) + res(y) jumps(z) ← empty return z be added in both directions (u, v) and (v, u) to the cycle, and then these trees need to be glued together.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Every one of these operations comes with a rebalanc- ing operation which could do Ω(log n) tree rotations and pointer dereferences to visit the nodes in the AVL tree.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As a result of these (constant-time) overheads, in this section, we investigate a simpler, lazy algorithm which avoids Euler Tour Trees, and works directly by modifying Algorithm 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To optimize Algorithm 1, one idea in the right direction is to store for each state a direct pointer to the root which results from repeatedly calling succ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' But there are two issues with this.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' First, maintaining this may be difficult (when the root changes, potentially updating a linear number of root pointers).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Second, the root may sometimes be marked dead, in which case we have to re-compute all the successor pointers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Instead, we introduce a jump list from each state: intuitively, it will contain states after calling successor once, twice, four times, eight times, and so on, and will be updated at most once for every visit to the state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When a jump becomes obsolete (the target dead), we just pop off the largest jump, so we do not lose all of our work in building the list.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' When states are merged, we do lose our work, discarding the jump lists, and this also means the exact power-of-two distances are no longer preserved.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We maintain the following additional information: for 16 Caleb Stanford and Margus Veanes each unknown canonical state x, a nonempty list of jumps [v0, v1, v2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' , vk], such that v0 is reachable from x, v1 is reachable from v0, v2 is reachable from v1, and so on, and v1 = succ(x).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The algorithm is shown in Algorithm 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The key procedure is GetRoot(z), which is called when adding a reserve edge (y, z) to the graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It finds the root in the successor forest when repeatedly calling successor from z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It shortcuts by using the jump list, and also updates the set of jumps to be approximately at powers of two: to do this, the nth jump from a state z is set to the (n − 1)st jump from the (n − 1)th jump from z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Invariants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In addition to the invariants from Algorithm 1: for each unknown canonical state x, jumps(x) is a list of states v0, v1, v2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' , vk such that: – First jump: if the jump list is nonempty, then v0 = succ(v).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Reachability: vi+1 is reachable from vi for all i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Powers of two: on the path of canonical states from v0 to vi, the total number of states (including all the states in each equivalence class) is at least 2i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The powers of two invariant is not necessary for correctness, but is the key to the efficiency of this algorithm: it ensures that the nth jump travels at least 2n states at once in the successor forest.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It follows from this that if the jump list is fully saturated for every state, querying GetRoot(z) will take logarithmic time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' But because the jump lists are updated lazily (and have dead states that need to be discarded), this does not establish an asymptotic complexity for the algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 3 is correct.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We use the invariant on the jump list mentioned: that v1 is the successor, v2 is reachable from v1, v3 is reachable from v2, and so on, using only forward edges added to the graph (not reserve edges).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', v1, v2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' is some sublist of the states along the path from an unknown state to its root, potentially followed by some dead states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We need to argue that the subprocedure GetRoot (i) receives the same verdict as repeatedly calling succ to find a cycle in the first-cut algorithm and (ii) preserves the jump list invariant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Popping dead states from the jump list clearly preserves the invariant, as does adding on a state along the path to the root, which is done when k′ ≥ k.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Merging states preserves the jump list invariant trivially because we throw the jump list away, and marking states live preserves the jump list invariant trivially since the jump list is only maintained and used for unknown states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Finally, marking states as closed initializes the jump list correctly assuming that the successor is calculated correctly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ 4 Experimental Evaluation The primary goal of our evaluation has been to experimentally validate the performance of GIDs as a data structure in isolation, rather than their use in a particular application.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our evaluation seeks to answer the following questions: Q1 How does our approach (Algorithms 2 and 3) compare to the state-of-the-art approach based on maintaining SCCs?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental Dead State Detection in Logarithmic Time 17 Q2 How does the performance of the studied algorithms vary when the class of input graphs changes (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', sparse vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' dense graphs, structured vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' random graphs)?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Q3 Finally, how do the studied algorithms perform on GIDs taken from the example application to regexes described in Section 5?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To answer Q1, we put substantial implementation effort into a common framework on which a fair comparison could be made between different ap- proaches.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To this end, we implemented GIDs as a data structure in Rust which includes a graph data structure on top of which all algorithms are built.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In par- ticular, this equalizes performance across algorithms for the following baseline operations: state and edge addition and retrieval, DFS and BFS search, edge iteration, and state merging.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We chose Rust for our implementation for its per- formance, and because there does not appear to be an existing publicly available implementation of BFGT in any other language.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The number of lines of code used to implement these various structures is summarized in Figure 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We im- plement Algorithms 2 and 3 and compare them with the following baselines: BFGT This algorithm is a careful implementation of the state-of-the-art ap- proach based on SCC maintenance, using worst-case amortized O(√m) time per update [4].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Simple In addition to BFGT, we provide a simpler SCC-based baseline, using a DFS instead of using the BFGT algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It updates the SCCs after each state is marked closed by searching for all cycles from that state using a forward-DFS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This takes Θ(m2) in the worst case, but can be very efficient when edges are added in a “forward-facing” topologically sorted manner, so represents an important point of comparison.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Naive Finally, the naive algorithm is a greedy baseline that represents a worst- case upper bound: it re-computes the entire set of dead states using a linear- time DFS after each update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It is Θ(m2) for m updates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To answer Q2, first, we compiled a range of basic graph classes which are designed to expose edge case behavior in the algorithms, as well as randomly generated graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We focus on graphs with no live states, as live states are treated similarly by all algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Most of the generated graphs come in 2×2 = 4 variants: (i) the states are either read in a forwards- or backwards- order;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and (ii) they are either dead graphs, where there are no open states at the end and so everything gets marked dead;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' or unknown graphs, where there is a single open state at the end, so most states are unknown.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In the unknown case, it is sufficient to have one open state at the end, as many open states can be reduced to the case of a single open state where all edges point to that one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We include GIDs from line graphs and cycle graphs (up to 100K states in multiples of 3), as well as complete graphs, complete acyclic graphs (with only forward-edges), and bipartite graphs (up to 1K states).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' These are important cases, for example, because the reverse-order version of the line and cycle graphs is an edge case for Simple: it often times out on these, but performs well on the forward-version of these GIDs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 18 Caleb Stanford and Margus Veanes Implementation Component LoC Common Framework 1197 Naive Algorithm 78 Simple Algorithm 98 BFGT Algorithm 265 Algorithm 2 (Ours) 253 Algorithm 3 (Ours) 283 Euler Tour Trees 1510 Experimental Scripts 556 Separated Unit Tests 798 Util 217 Other 69 Total 5324 Category Benchmark Source Qty Basic Line 24 Cycle 24 Complete 18 Bipartite 14 Total 80 Random Sparse 260 Dense 130 Total 390 Regex RegExLib [9,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='49] 2061 37 Handwritten [50] 70 26 Additional 11 Total 74 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Left: Lines of code for each algorithm and other implementation components.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Right: Benchmark GIDs used in our evaluation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Where present, the source column indicates the quantity prior to filtering out trivially small graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Time (ms) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Benchmarks Solved ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='30 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='60 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='90 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='10 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='100 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='10000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Naive ' metadata={'source': 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1000000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Naive ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Simple ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='BFGT ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Alg 2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Alg 3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Benchmark Size ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Average Time (ms) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='10 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='100 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='10000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='100 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='10000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='100000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1000000 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Naive ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Simple ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='BFGT ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Alg 2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Alg 3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Evaluation results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Left: Cumulative plot showing the number of benchmarks solved in time t or less for basic GID classes (top), randomly generated GIDs (middle), and regex-derived GIDs (bottom).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Top right: Scatter plot showing the size of each benchmark vs time to solve.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Bottom right: Average time to solve benchmarks of size closest to s, where values of s are chosen in increments of 1/3 on a log scale.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental Dead State Detection in Logarithmic Time 19 Second, to exhibit more dynamic behavior, we generated random graphs: sparse graphs with a fixed out-degree from each state, which can be either 1, 2, 3, or 10 (up to 100K states);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and dense graphs with a fixed probability of each edge, which can be .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='01, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='02, or .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='03 (up to 10K states).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' As with the basic graphs, states are read in some order and marked closed;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' at most one state is left open at the end.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Each random graph is generated using 10 different random seeds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To answer Q3, we needed to isolate the performance of the GID data struc- ture itself, rather than the performance of the other components of the regex SMT solver.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Prior work on regex solving integrated with Z3 [50] implements an earlier version of GIDs, which is essentially the Simple algorithm in C++.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' However, preliminary tests suggest that on some examples, GIDs are already quite efficient and contribute only a fraction of the performance (1-10%), as a substantial amount of time is spent manipulating and rewriting expressions and computing derivatives.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' While we would expect GIDs to be the bottleneck on larger examples where the asymptotic complexity of Simple becomes prohibitive, this fact makes it difficult to isolate the performance of the GID data structure itself, which is the focus of this paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To isolate the GID performance, we therefore instrumented the modified Z3 solver code to export the (incremental) sequence of graph updates that would be performed during a run of Z3 on existing regex benchmarks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For each regex benchmark, this instrumented code produces a faithful representation of the se- quence of graph updates that would occur in a run of the SMT solver on this particular benchmark.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It is also important to use ERE benchmarks, rather than plain regular expressions as these are the ones for which dead state detection is relevant (see Section 5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For each regex benchmark, we thus get a GID bench- mark for the present paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In our regex-derived GID examples, we include the RegExLib benchmarks from [9,49] and the handcrafted Boolean benchmarks re- ported in [50].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We add to these 11 additional examples designed to stress test the GID side of a regex solver.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The collection of regex SMT benchmarks is available on GitHub4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' From both the Q2 and Q3 benchmarks, we filter out those that are too easy: any benchmark which takes under 10 milliseconds for all of the algorithms to solve (including Naive).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We enforce a timeout of 60 seconds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The evaluation was run on a 2020 MacBook Air running MacOS Monterey, containing an Apple M1 processor and 8GB of memory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Correctness.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To ensure that all of our implementations our correct, we also invested time into unit testing and checked output correctness on all of our collected benchmarks, including several cases which exposed bugs in previous versions of one or more algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In total, all algorithms are vetted against 25 unit tests from handwritten edge cases that exposed prior bugs, 373 unit tests from benchmarks, and 30 module-level unit tests for specific functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Figure 5 shows the results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 3 shows significant improve- ments over the state-of-the-art, solving more benchmarks in a smaller amount 4 https://github.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='com/cdstanford/regex-smt-benchmarks 20 Caleb Stanford and Margus Veanes of time across basic GIDs, random GIDs, and regex GIDs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 2 also shows state-of-the-art performance, similar to BFGT on basic and regex GIDs and significantly better on random GIDs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' On the bottom right, since looking at average time is not meaningful for benchmarks of widely varying size, we stratify the size of benchmarks into buckets, and plot time-to-solve as a function of size.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' note that as both x-axis and y-axis are on a log scale, a total running time of O(mp) for m updates corresponds to a line with slope p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The plot shows that Algorithm 3 exhibits up to two orders of magnitude speedup over BFGT for larger GIDs – we see speedups of 110x to 530x for GIDs in the top five size buckets (GIDs of size nearest to 100K, 200K, 500K, 1M, and 2M).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' New implementations of existing work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our implementation contributes, to our knowledge, the first implementation of BFGT for SCC maintenance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In addition, it is one of the first implementations of Euler Tour Trees (EF) for undirected reachability in forests, including the AVL tree backing for EF which maintains a disjoint collection of lists of state and edge identifiers, and the first implemen- tation in Rust.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 5 Application to Extended Regular Expressions In this section, we describe one application of GIDs in the context of deciding regex constraints in SMT.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In particular, we explain how precisely the GID state classification problem arises in the context of derivative-based solvers [50,34].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We first define extended regexes (regexes extended with intersection & and complement ~) modulo a (symbolic) alphabet A that intuitively provides char- acter classes as predicates that are closed under Boolean operations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We explain the main idea behind (symbolic) derivatives [50] that provides the foundation for incrementally creating a GID.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Then we show, through an example, how a solver can incrementally expand derivatives to reduce the satisfiability problem to the GID state classification problem (Definition 2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' EREs or regexes are defined as follows where ϕ is a predicate in A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' RE ::= ϕ | ε | RE1 · RE2 | RE* | RE1 | RE2 | RE1 & RE2 | ~RE Let Rk represent the concatenation of R k times.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A regex R is nullable if it matches the empty string.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Nullability is defined inductively over the structure of regexes with ε and R* being nullable by definition.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Observe in particular that ~R is nullable iff R is not nullable, and R1 & R2 is nullable iff both R1 and R2 are nullable.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Terminal states are precisely the nullable regexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The false predicate ⊥ of A serves as the regex that matches nothing and is a trivially dead state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Thus ~⊥ is equivalent to �* that matches everything and is a trivially live state, where � is the true predicate of A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A symbolic derivative δ(R) of a regex R is a binary tree or term t whose leaves are regexes and internal nodes are labeled by predicates from A – the two immediate subtrees t1 and t2 of a node with label ϕ, denoted by (ϕ ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' t1 : t2), correspond to ϕ being true in t1 and false in t2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A branch with the accumulated Incremental Dead State Detection in Logarithmic Time 21 branch condition ψ from the root of t to one of its leaves R′ then defines a transition R ψ−→R′ – provided ψ is satisfiable in A – and the edge (R, R′) is added to the GID where the actual predicate ψ is no longer needed because the edge itself represents its feasibility.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The number of leaves of δ(R) is the out-degree deg+(R) of R that is independent of the actual size of the concrete alphabet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Thus R becomes closed when deg+(R) many edges have been added from R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The formal definition of a symbolic derivative is as follows where the op- erations ⃝| , ⃝& , ⃝~ and ⃝· are here for the purposes of this paper and w.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='l.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='o.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' normalizing variants of | , & , ~ and ·, by distributing the operations into if-then- elses and build a single binary tree as a nested if-then-else as a result (see [50] for details): δ(ε) = δ(⊥) = ⊥ δ(ϕ) = (ϕ ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ε : ⊥) δ(R∗) = δ(R) ⃝· R∗ δ(R | R′) = δ(R) ⃝| δ(R′) δ(R & R′) = δ(R) ⃝& δ(R′) δ(~R) = ⃝~ δ(R) δ(R · R′) = if Nullable(R) then (δ(R) ⃝· R′) ⃝| δ(R′) else δ(R) ⃝· R′ If c is a term of type character then δc(R) is obtained from δ(R) by instantiating all internal nodes (conditions of the if-then-elses) ϕ by tests c ∈ ϕ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This means that in the context of SMT, δc(R) is a term of type regex, while δ(R) represents the lambda-term λc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='δc(R) that is constructed independently of c.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Concretely, to apply Definition 1 to regexes, states will be regexes, and edges will represent transitions to their derivatives.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A live state here is thus a regex that reaches a nullable regex via 0 or more edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This implies that there exists a concrete string matching it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Conversely dead states are always empty, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' they match no strings, but can reach other dead states, creating strongly connected components of closed states none of which are live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 Reduction from Incremental Regex Emptiness to GIDs For a solver based on derivatives of EREs, suppose we want to determine the satisfiability of a single regex constraint s ∈ R, where s is a string variable and R is a concrete regex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', let L = ~(�*α�100) and R = L & (�α) where α is some character predicate in A s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' both α and ¬α are satisfiable, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', take α to mean “is digit” to be concrete.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='5 The solver manipulates regex membership constraints on strings by unfolding them [50].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The constraint s ∈ R, that essentially tests nonemptiness of R with s as a witness, becomes (s = ϵ ∧ Nullable(R)) ∨ (s ̸= ϵ ∧ s1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. ∈ δs0(R)) where, s ̸= ϵ since R is not nullable, si.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. is the suffix of s from index i, and δ(R) = δ(L) ⃝& δ(�α) = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' L & ~(�100) : L) ⃝& α = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' L & ~(�100) & α : L & α) Let R1 = L & ~(�100) & α and R2 = L & α.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' So R has two outgoing transitions R α−→R1 and R ¬α −−→R2 that contribute the edges (R, R1) and (R, R2) into the GID.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Note that these edges depend only on R and not on s0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 5 Using standard notations: \\d denotes all digits, and [^\\d] denotes all non-digits.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 22 Caleb Stanford and Margus Veanes We now continue the search incrementally by checking the two branches of the if-then-else constraint, where R1 and R2 are again both not nullable (so s1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. ̸= ϵ): s0 ∈ α ∧ s2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. ∈ δs1(R1) ∨ s0 ∈ ¬α ∧ s2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. ∈ δs1(R2) δ(R1) = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' L & ~(�100) & ~(�99) : L & ~(�99)) ⃝& (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ε : ⊥) = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ε : ⊥) δ(R2) = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' L & ~(�100) : L) ⃝& (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ε : ⊥) = (α ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ε : ⊥) It follows that R1 α−→ε and R2 α−→ε, so the edges (R1, ε) and (R2, ε) are added to the GID where ϵ is a trivial terminal state.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In fact, after R1 the search already terminates because we then have the path (R, R1)(R1, ϵ) that implies that R is live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The associated constraints s0 ∈ α and s1 ∈ α and the final constraint that s2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='. = ϵ can be used to extract a concrete witness, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', s = "42".' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' From the point of view of deciding nonemptiness the role of the witness s is immaterial, and can be omitted, as it poses no additional constraints on its own if s is a variable (a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='k.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', an uninterpreted constant in SMT).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Soundness of the algorithm follows from that if R is nonempty, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', s ∈ R is satisfiable, then by expanding the search, we eventually arrive at a nullable (terminal) regex, as in the example run above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To achieve completeness – and to eliminate dead states as early as possible – we incrementally construct a GID corresponding to the set of regexes seen so far (as above).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' After all the feasible transitions from R to its derivatives in δ(R) are added to the GID as edges (w.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='l.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='o.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' in one batch), the state R becomes closed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Crucially, due to the symbolic form of δ(R), no derivative is missing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Therefore R is known to be empty precisely as soon as R is detected as a dead state in the GID.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We get the following theorem that uses finiteness of the closure of symbolic derivatives [50, Theorem 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1]: Theorem 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For any regex R, (1) If R is nonempty, then the decision procedure eventually marks R live.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' If n is the shortest distance from R to a terminal state, then a concrete witness of length n can be generated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (2) If R is empty, then the decision procedure marks R dead after a finite number of steps and terminates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Observe that any number of simultaneous regex constraints for a string s can be combined into single regex constraint by using the Boolean operations of ERE.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' More crucially, the algorithm is independent of the size of the universe of A, that may be very large, like the Unicode character set, or even infinite.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 6 Related Work Online graph algorithms: Online graph algorithms are typically divided into problems over incremental graphs (where edges are added), decremental graphs (where edges are deleted), and dynamic graphs (where edges are both added and deleted), with core data structures discussed in [38].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For dynamic directed graphs, important problems include transitive closure, cycle detection, topological ordering, and strongly connected component (SCC) maintenance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Maintaining Incremental Dead State Detection in Logarithmic Time 23 a topological order of dynamic DAGs is studied in [35].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' An online algorithm for topological sorting that is experimentally shown to be preferable for sparse graphs is discussed in [46], and in a related article [45] it is also discussed how to extend such an algorithm to detect strongly connected components.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The key applications of such algorithms have traditionally been in pointer analysis [44].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Topological order of incremental DAGs is studied in [24], presenting two different algorithms, one for sparse graphs and one for dense graphs – the algorithms are also extended to work with SCCs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The sparse algorithm was subsequently simplified in [4] and is the basis of our implementation named BFGT in the Evaluation section.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A unified approach of several algorithms based on [4] is presented in [14] that uses a notion of weak topological order and a labeling technique that estimates transitive closure size.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Further extensions of [4] are studied in [6,8] based on randomization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Transitive closure of decremental DAGs is studied in [47] that improve upon some algorithms presented earlier in [25].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Although we have not looked at decremental graphs in this paper, the problem may become relevant in the context of backtracking in SMT string theory solver during proof search in the presence of non-ground regexes, where properties such as nullability may be theory-dependent and thus affect liveness of states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Data structures for SMT: UnionFind [52] is a frequently used data structure that we also rely on in our algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' E-graphs [54,16,18,42] are used to ensure functional extensionality, where two expressions are equivalent if their subex- pressions are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In both cases the maintained relation is an equivalence relation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In contrast, maintaining live and dead states involves tracking reacha- bility rather than equivalence.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' While reachability is a basic problem in many core SMT algorithms, to the best of our knowledge, the formulation of the problem we consider here is new.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Dead state elimination: Dead state elimination for automata, also known as trimming [7], is a specialized version of useless symbol elimination from context- free grammars [28, pp 88-89].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It plays an important role in minimization of automata [31,40,30,29].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The classical minimization algorithms have been studied extensively, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', in [10,7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Brzozowski [11] observed that a DFA can be minimized by determinizing the reversal of the determinization of the reversal of the DFA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Regular expression matching and analysis: Decision problems for regexes are studied in the context of Satisfiability Modulo Theories (SMT), where the first- order objects are strings and formulas consist of string constraints such as x = yz or x ∈ R, where R is a regex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Over such theories, the problem of nonemptiness of a regex reduces to live state detection in the automaton (or set of derivatives) for R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' String and regex constraints have been the focus of both SMT and the Constraint Programming (CP) solving communities, with a wide range of tools focusing on different problem classes and applications [27].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Regexes and are now a standard part of the SMTLIB2 format [53].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In SMT, string solvers are integrated in the CDCL(T) architecture [43].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In the CP community, the MiniZinc format integrates membership constraints over regular languages presented as either 24 Caleb Stanford and Margus Veanes DFAs or NFAs [39].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The solvers presented in [34] and [50] are based on computing Antimirov derivatives – a state graph of regexes is used in [50] to terminate search from dead state regular expressions that arise in ERE constraints, which helps the solver terminate search from goals that would otherwise not terminate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 7 Conclusion GIDs are a form of incremental abstract transition system in which states are closed when they will receive no further outgoing edges;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Algorithm 2 and Al- gorithm 3 solve the incremental live and dead detection problem in GIDs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The former runs in logarithmic worst-case time, and both algorithms achieve orders of magnitude speedup over the state-of-the-art based on maintaining strong con- nected components.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Our implementation is open-source and publicly available6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Acknowledgments We would like to thank the anonymous reviewers of CAV 2021 and TACAS 2022 for feedback leading to substantial improvements in both the paper and results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We also extend a special thanks to Nikolaj Bjørner, for his collaboration and involvement with the Z3 implementation, and Yu Chen, for helpful discussions in which he proposed the idea for the first-cut algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' References 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Abboud, A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', Williams, V.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='V.' metadata={'source': 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metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', Flatt, O.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', Tatlock, Z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', Panchekha, P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=': egg: fast and extensible equality saturation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proceedings of the ACM on Programming Languages 5(POPL), 1–29 (2021) 55.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Z3: (2020), http://research.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='microsoft.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='com/projects/z3 A Appendix A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='1 Extension to the Framework: Non-Reachable Updates When GIDs are viewed as an abstract data type, other application-specific heuristics can be incorporated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To illustrate this point, we consider another piece of application-specific information: assertions which state that one vertex is not (and will never be) reachable from another.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We discuss how to incorporate such updates to further improve the optimized algorithm in practice to exploit such updates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' First, we augment the definition of guided incremental digraph to allow up- dates of the form N(u, v), which labels that v is not reachable from u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We then say that the graph is valid if, in addition to the previous conditions, for every update N(u, v), v is not reachable from u via a sequence of edges in the final digraph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Figure 6 extends the example presented in Figures 1 and 2 with a not- reachable update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Notice that N(3, 5) does not affect the set of live and dead states, but may be exploited for more efficient search.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' To incorporate N(u, v) updates in our algorithm, when moving a reserve edge into the graph, N(u, v) can be used to shortcut the whole procedure: if we add an edge (v, u) in particular, then we know that this doesn’t create a cycle, and we don’t need to repeatedly call succz at all.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We store N(u, v) updates in a set instead of a list for O(1) querying;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' if we need to merge them, we just discard the set if it gets too large.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Therefore, in addition what was maintained previously, the extended algorithm tracks, for each unknown canonical state x, a set of non-reachable edges (x, y), where each corresponds to some update N(u, v) with x = find(u) and y = find(v) (but not necessarily vice versa);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and a constant κ which bounds the amount of work when merging non-reachable sets (additional 28 Caleb Stanford and Margus Veanes 1 2 3 4 5 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Extension to our framework: guided incremental digraph from Figures 1 and 2, with an added update N(3, 5) which states that 5 is not reachable from 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' In this graph, it would be invalid to then add E(3, 4) to the graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This does not change the set of live or dead states, but may be exploited for more efficient search: when checking if state 3 is live or dead, we may ignore states 4 and 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' elements will be discarded).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We modify the code for is-root(y, x) with a single check in the beginning of the procedure: if x is in the not-reachable set from y, return false.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Otherwise, we continue as normal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Because this algorithm uses the N(u, v) information directly and conservatively, assuming the input GID is valid, it remains correct.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='2 Reachability Problems on EREs For extended regexes X and Y , we say that Y is reachable from X if Y ∈ ∂⋆(X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We say that X and Y are strongly connected, denoted X ⟳ Y , when both Y ∈ ∂⋆(X) and X ∈ ∂⋆(Y ), i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=', when both Y is reachable from X and X is reachable from Y through derivation as defined above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We also consider the following subclasses of extended regexes: – Regexes (REs) are EREs that do not contain complement or intersection, that is, classical regexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Semi-extended regexes (SEREs) are EREs that do not contain complement.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Intersections of regexes (IREs) are SEREs that are equal to an intersection of REs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' – Boolean combinations of regexes (BCREs) are EREs that are equal to a Boolean combination (combination of intersection and complement) of REs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Semantically, all of these capture the set of regular languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The syntactic relationships between these different subclasses is summarized as follows, where all inclusions are strict: RE ⊂ IRE ⊂ BCRE ∩ ∩ SERE ⊂ ERE We consider the following three decision problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' They are closely related and in order of generality: the first is a special case of both the second and thirds, and the second reduces to two queries of the third.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For each problem, we also consider problems on all the subclasses of EREs that we defined: REs, SEREs, IREs, and BCREs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We summarize the complexity results in the table in Figure 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Incremental Dead State Detection in Logarithmic Time 29 Subclass Edge in Cycle Strong Connectedness Reachability RE Linear Linear Linear IRE PSPACE-C PSPACE-C PSPACE-C BCRE PSPACE-C PSPACE-C PSPACE-C SERE PSPACE-C PSPACE-C PSPACE-C ERE non-elementary non-elementary non-elementary Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Complexity results for reachability of various subclasses of extended regexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Edge in Cycle: Given X and Y such that X ∈ ∂(Y ), is Y ∈ ∂⋆(X)?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Strong Connectedness: Given X and Y , is X ⟳ Y ?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Reachability: Given X and Y , is Y ∈ ∂⋆(X)?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Theorem 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For RE, the edge-in-cycle, strong-connectedness, and reachability problems can be solved in linear time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It suffices to show that reachability can be solved in linear time, since as stated above, it is the most general of the three.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We give a decision procedure for deciding Y ∈ ∂⋆(X) by recursing on the structure of X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Prior to the procedure, we ensure (i) that all regexes are normalized, (ii) that equal regexes are repre- sented by the same pointer, and (iii) that concatenations are represented as lists and precompute the length of each list, so that for any subexpression X0 of X, whether Y = Y1·X0 can be checked in constant time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This precomputation takes O(|X| + |Y |) time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The recursion then works as follows, on input (X, Y ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (1) If X = ϕ, ε, or ⊥, we can check directly if Y is one of the finitely many derivatives.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (2) If X = X1 | X2, we observe that Y ∈ ∂⋆(X) if and only if Y ∈ ∂⋆(X1) or Y ∈ ∂⋆(X2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' So we recurse on (X1, Y ) and (X2, Y ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (3) If X = X∗ 1, we observe that Y ∈ ∂⋆(X) if and only if Y = X′ 1(X∗ 1) for X′ 1 ∈ ∂⋆(X1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' So we first check if Y has the form Y1X∗ 1, then recurse on (X1, Y1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (4) Finally, if X = X1 · X2, we observe that Y ∈ ∂⋆(X) if and only if either Y = X′ 1 · X2 for X′ 1 ∈ ∂⋆(X1), or Y = X′ 2 for X′ 2 ∈ ∂⋆(X2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (Note that this relies on the fact that X1 is an RE, not an ERE, so we know it is nonempty and in particular ε ∈ ∂⋆(X1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=') So we first check if Y has the form Y1 · X2, if so recursing on both (X1, Y1) and (X2, Y ), otherwise recursing on just (X2, Y ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Since the procedure never recurses twice on X or twice on the same subexpression of X, it takes O(|X|) time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ Theorem 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For the classes IRE, BCRE, and SERE, the edge-in-cycle, strong- connectedness, and reachability problems are PSPACE-complete.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It suffices to show: (1) the edge-in-cycle problem for IRE is PSPACE- hard;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (2) the reachability problem for BCRE is in PSPACE;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' and (3) the reach- ability problem for SERE is in PSPACE.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (1) We reduce from intersection- nonemptiness of REs, which is known to be PSPACE-hard.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given a list of REs R1, R2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' , Rk, then let b be a fresh character that does not appear in 30 Caleb Stanford and Margus Veanes R1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' , Rk, and construct the IRE X = (bR1)∗ & (bR2)∗ & · · · & (bRk)∗.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' X has only one derivative X′, which is an intersection where the ith term is Ri(bRi)∗.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Then the edge-in-cycle property for (X, X′) holds if and only if the intersection of Ri is nonempty, because ∂b is empty for all subexpressions of Ri except ε, so the only way to get back to X is by stepping all Ri to ε simultaneously.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (2) We first convert the BCRE X to an alternating automaton (AFA): first convert- ing the RE subexpressions to NFAs, then using the standard constructions for Boolean operations on AFAs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' (3) For an SERE X, for any X′ ∈ ∂⋆(X) we show that the size of X′ is bounded linearly in the size of the X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' This can be seen by induction on the structure of X;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' for example, elements of ∂⋆(X1 & X2) are a pair of an element of ∂⋆(X1) and an element of ∂⋆(X2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It follows that we can provide the following NPSPACE algorithm for reachability of (X, Y ): at each step, pick a derivative nondeterministically of X and recurse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔ Theorem 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' For ERE, the edge-in-cycle, strong-connectedness, and reachability problems are non-elementary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' It suffices to show that the edge-in-cycle problem is non-elementary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' We reduce from the nonemptiness problem for EREs, which is known to be non- elementary [51].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Given an ERE R, we let b be a fresh character not appearing in R, and we let X = (bR)∗.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' Then X has one derivative, X′ = R(bR)∗.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' The edge-in-cycle property for (X, X′) holds and only if R is nonempty, because R is nonempty exactly when ε ∈ ∂⋆(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} +page_content=' ⊓⊔' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-NE4T4oBgHgl3EQf3w1M/content/2301.05308v1.pdf'} diff --git a/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/2301.03092v1.pdf.txt b/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/2301.03092v1.pdf.txt new file mode 100644 index 0000000000000000000000000000000000000000..fbfb305e76de4ae48fde8db0bf032492868896d4 --- /dev/null +++ b/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/2301.03092v1.pdf.txt @@ -0,0 +1,1059 @@ +1 +Deep Injective Prior for Inverse Scattering +AmirEhsan Khorashadizadeh , Sepehr Eskandari , Vahid Khorashadi-Zadeh +and Ivan Dokmani´c +Abstract—In electromagnetic inverse scattering, we aim +to reconstruct object permittivity from scattered waves. Deep +learning is a promising alternative to traditional iterative solvers, +but it has been used mostly in a supervised framework to regress +the permittivity patterns from scattered fields or back-projections. +While such methods are fast at test-time and achieve good results +for specific data distributions, they are sensitive to the distribution +drift of the scattered fields, common in practice. If the distribu- +tion of the scattered fields changes due to changes in frequency, +the number of transmitters and receivers, or any other real-world +factor, an end-to-end neural network must be re-trained or fine- +tuned on a new dataset. In this paper, we propose a new data- +driven framework for inverse scattering based on deep generative +models. We model the target permittivities by a low-dimensional +manifold which acts as a regularizer and learned from data. +Unlike supervised methods which require both scattered fields +and target signals, we only need the target permittivities for +training; it can then be used with any experimental setup. We +show that the proposed framework significantly outperforms the +traditional iterative methods especially for strong scatterers while +having comparable reconstruction quality to state-of-the-art deep +learning methods like U-Net. +I. INTRODUCTION +E +LECTROMAGNETIC inverse scattering is the problem of +determining the electromagnetic properties of unknown +objects from how they scatter incident fields. As it is non- +destructive, it has a variety of applications in different areas, +such as early detection of breast cancer [1], mineral prospect- +ing [2], detecting defects and cracks inside objects [3], imaging +through the wall [4] and remote sensing [5]. +We consider the reconstruction of the finite number of +parameters of the object from the scattered fields. While inverse +scattering is well-posed and Lipschitz stable in theory, when +full-aperture continuous measurements are available [6], it is +Manuscript received December 29, 2022. +AmirEhsan Khorashadizadeh and Ivan Dokmani´c were supported by the +European Research Council Starting Grant 852821–SWING. +AmirEhsan Khorashadizadeh is with the Department of Mathematics and +Computer Science of the University of Basel, 4001 Basel, Switzerland (e-mail: +amir.kh@unibas.ch). +Sepehr Eskandari is with Microwave Systems, Sensors, and Imaging Lab +(MiXIL), University of Southern California, Los Angeles, CA 90089 USA +(e-mail: sepehres@usc.edu). +Vahid Khorashadi-Zadeh is with School of Electric and Computer +Engineering, University of Tehran, Tehran 14399-57131, Iran (e-mail: +v.khorashadi@ut.ac.ir). +Ivan Dokmani´c is with the Department of Mathematics and Computer +Science of the University of Basel, 4001 Basel, Switzerland, and also +with the Department of Electrical, Computer Engineering, the Univer- +sity of Illinois at Urbana-Champaign, Urbana, IL 61801 USA (e-mail: +ivan.dokmanic@unibas.ch). +Our +implementation +is +available +at +https://github.com/swing-research/ +scattering injective prior. +a severely ill-posed inverse problem for a finite number of +measurements. This means that a small perturbation in the +scattered fields may lead to a large error in the reconstructed +permittivity pattern [7]. Moreover, the forward operator from +the permittivity to the scattered fields is nonlinear, which +further complicates the inversion. The nonlinearity is due to the +multiple scattering; the problem becomes more nonlinear as the +permittivity contrast increases [7]. All these together make the +inverse scattering challenging, especially for strong scatterers +(objects with large permittivity) and noisy measurements, which +require an effective regularization to restrict the search space +and enable accurate reconstruction. +A number of optimization-based methods are proposed to +address nonlinearity and ill-posedness of the inverse scattering +including Born iterative [8], distorted Born iterative method +(DBIM) [9], contrast source inversion (CSI) [10], and subspace- +based optimization (SOM) [11]. Although these methods have +been shown to be effective for objects with small permittivity, +they do not give an accurate reconstruction for large permittivity. +All the above methods iteratively optimize a regularized +objective, with a hand-crafted regularization term. +Recently, thanks to the significant increase in computing +power and the availability of sufficient data, data-driven +approaches to inverse scattering have started receiving attention. +Most deep learning models for inverse scattering use a super- +vised learning approach, which takes the scattered fields or a +simple back-projection as input and trains a deep neural network +to produce the target permittivity pattern. The authors of [12]– +[14] used scattered fields as input. While this approach provides +good reconstructions even for objects with strong scatterers [14], +it is sensitive to the experiment configuration such as the +frequency or the number of incident waves and receivers; if +the distribution of the scattered fields in test-time slightly +changes, the quality of reconstructions remarkably degrades; +the model requires new training data which is too costly. +One strategy to tackle this issue is to use back-projections +as input instead of the raw scattered fields, thus enabling +the use of convolutional neural networks [15]–[17]. While +this approach is shown to be effective for objects with small +and moderate permittivity, the quality of the back-projections +significantly drops in large permittivity (Figure 3), which leads +to a drop in the reconstruction quality [14]. On the other hand, +supervised learning methods are also potentially vulnerable +to adversarial attacks [18], which is problematic in medical +applications [19]. Moreover, incorporating the well-known +physics of the scattering problem (forward operator), which +can strikingly improve the accuracy of the reconstructions, is +not easy in supervised learning models [20]. +arXiv:2301.03092v1 [cs.LG] 8 Jan 2023 + +2 +To tackle these issues, we propose a deep learning +approach to inverse scattering using injective generative models. +The proposed method benefits from an unsupervised learning +framework—the training phase uses only the target permittivity +patterns and the physics of scattering is fully incorporated into +the solution. Deep generative models are a class of unsupervised +learning methods that model the probability distribution of +data by using deep neural networks. Latent-variable generative +models such as generative adversarial networks (GAN) [21], +[22], variational autoencoders [23], normalizing flows [24]– +[26] and diffusion models [27] train a deep neural network to +transform the samples of a simple (Gaussian) distribution to +those of target data distribution. We expect a trained generator +produce plausible samples similar to the training data when +taking samples of a Gaussian distribution as input. +Bora et al. [28] used GANs to constrain the solution +domain to the range of the trained generator for solving +compressed sensing inverse problems. The strength of this +idea is that it requires only the target signals for training and +does not know anything about the inverse problem is going to +be solved. As soon as the generator is trained, it can be used +to solve any inverse problem with a known forward operator. +This property makes the model robust to the distribution shift +of the measurements and adversarial attack. +Several methods have tried to improve the quality of +reconstructions; Kelkar et al. [29] used the popular style- +GAN generator [30] while Hussein et al. [31] jointly optimize +the generator weights with latent codes to further reduce +the reconstructions error. However, GANs are known to be +unstable in training, and the optimization process over latent +space sticks in the local minimum which requires many +restarts [28]. Recently, normalizing flows as a generator instead +of GANs have been shown to have a stable optimization +landscape [32], [33]. Nevertheless, normalizing flows have +their own drawbacks; having a latent code with the same +dimension as data space makes them too expensive in training +and does not provide an appropriate constraint in the generator +output, leading to poor reconstruction for ill-posed inverse +problems. More recently, injective normalizing flows [34], [35] +are proposed to alleviate these issues. Injective flows are a +class of deep generative models that are well-suited for solving +ill-posed inverse problems. These models unlike GANs give us +access to the approximate likelihood of the generated samples, +which provides a likelihood-based regularization. Moreover, +injective flows unlike regular normalizing flows benefit from +a low-dimensional latent space which provides an additional +effective regularizer for ill-posed inverse problems. Injective +flows have been shown in [35] to effectively solve linear inverse +problems. +In this paper, we use injective flows as the generator +to solve full-wave inverse scattering. we will show that the +proposed method effectively solves inverse scattering even for +objects with large permittivity for which traditional methods +fail. Moreover, we use a data-driven initial guess for starting +the iterative optimization, which significantly outperforms the +simple back-projection initialization used in the traditional +Fig. 1: The setup for the inverse scattering problem, red +arrows show the incident plane waves; the green circles are +the receivers. +methods. Finally, we show that the proposed framework yields +reconstructions of comparable or better quality to highly +successful supervised methods like the U-Net [36]. +II. FORWARD AND INVERSE SCATTERING +We begin our discussion with equations governing the +2D forward and inverse scattering problem. We consider +two-dimensional transverse magnetic scattering, where the +longitudinal direction is along the z direction (TMz). As shown +in Figure 1, non-magnetic scatterers with permittivity ϵr in +a vacuum background with permittivity ϵ0 and permeability +µ0 are located in investigation domain Dinv which is a D×D +square, and are illuminated by Ni plane waves with equispaced +directions. We have Nr receivers placed uniformly on a circle S +with radius R which measure the scattered fields. The forward +scattering problem can be derived from the time-harmonic form +of Maxwell’s equations and stated as [37], +∇ × (∇ × Et(r)) − k2 +0ϵr(r)Et(r) = iωµ0J(r) +(1) +where Et is the total electric field, k0 = ω√µ0ϵ0 is the +wavenumber of the homogeneous background and J is the +contrast current density and can be calculated using equivalence +theorem [38] as J(r) = χ(r)Et(r) where χ(r) = ϵr(r)−1 and +is called the contrast. The time-dependence factor exp(iωt) +with angular working frequency ω is assumed and will be +suppressed throughout this paper. By using Dyadic Green’s +function [39], Equation (1) can be formalized by two coupled +integral equations. The first one, called Lippmann–Schwinger +equation, relates total electric fields Et in an unknown domain +to contrast current density J, +Et(r) = Ei(r) + k2 +0 +� +Dinv +g(r, r′)J(r′)dr′, +(2) + +3 +where r ∈ Dinv, and +g(r, r′) = 1 +4iH(2) +0 (k0|r − r′|), +and H(2) +0 +is the Hankel function of the second kind, denotes +2D free space Green’s function. The second equation, referred +to as the data equation, maps the contrast current density J +to the scattered electric fields Es at the receivers locations, +Es(r) = k2 +0 +� +Dinv +g(r, r′)J(r′)dr′, r ∈ S. +(3) +We discretize the investigation domain Dinv with N × N units +and rewrite Equations (2) and (3) as +Et = Ei + GdχEt +(4) +Es = GsχEt + δ +(5) +where Gd ∈ RN 2×N 2 and Gs ∈ RNr×N 2 have analytical +closed form [7]. Moreover, Et, Ei and Es respectively +correspond to total, incident and scattered electric fields +and χ is a diagonal matrix with the diagonal elements +χ(n, n) = ϵr(rn) − 1. We also consider additive noise δ to the +measurements. +We merge Equations (4) and (5) to make a single +expression for the forward equation [7], +Es = Gsχ(I − Gdχ)−1Ei + δ, +(6) +which is a nonlinear mapping χ �→ Es. It is convenient to +define a forward operator A mapping χ to Es, +y = A(x) + δ, +(7) +where A(·) is the nonlinear forward scattering operator +A(χ) = Gsχ(I − Gdχ)−1Ei, +(8) +y = Es and x = χ. The task of inverse scattering is to +reconstruct the contrast signal χ from the scattered fields Es +where we assume Gd, Gs, incident electric waves Ei and +consequently the forward operator A(·) are known. In the next +section, we briefly review deep generative models as the prior +model for inverse problems. +III. DEEP GENERATIVE MODELS +One major division in machine learning is generative and +discriminative models. In discriminative models, one aims +to learn a direct mapping from the measurements to the +target signals. Discriminative approaches have been extensively +used in solving inverse problems, specifically U-Net [36] has +shown great success in many applications such as computed +tomography (CT) [40], magnetic resonance imaging (MRI) [41], +optoacoustic tomography [42] and electromagnetic inverse +scattering [16]. The key idea of this success might be ascribed to +having a multiscale architecture [43]. Recently, the variational +version of U-Net has shown excellent performance for posterior +sampling and uncertainty quantification of inverse scattering +problem [44]. +On the other hand, the task of generative models is to learn +the probability distribution of data. Latent-variable generative +models including generative adversarial networks (GANs) [21], +[22], variational autoencoders [23] and normalizing flows [24]– +[26] are a subcategory of deep generative models (DGMs) +which train a deep neural network, called the generator, to +transform the samples of a simple and known distribution +(often Gaussian) to data distribution samples. DGMs have +many applications such as image generation [22], image-to- +image translation [45], density estimation [46] and variational +inference [47], [48]. Recently, DGMs have been used as a prior +for solving inverse problems [28], [35], [49]–[52]; consider a +DGM trained on a training set of target signals (the solutions +of a given inverse problem), one can search in the latent space +of the trained generator for the latent code yielding a solution +aligns with the given measurements. The pre-trained generator +plays the role of an effective regularizer for generating plausible +target signals. As discussed earlier, the key advantage of this +approach is that the measurements are not used in the training +phase. As a result, once the DGM is trained, it can be used +for solving any inverse problems. +However, the choice of DGM is of paramount importance +to provide stable training, high-quality sample generation, +and an effective regularizer for solving ill-posed inverse +problems. While modern GANs with the various innovations +in architectures and training protocols exhibit high-quality +samples, they suffer from training instability [53], [54] and have +shown poor reconstructions when used as a prior for solving ill- +posed inverse problems [35], [55]. Normalizing flows alleviates +many drawbacks of GAN; they are stable in training and can +produce high-quality samples. Normalizing flows comprise a +set of bijective transformations which have tractable inverse +and log det Jacobian computations. They give access to the +likelihood of the generated samples and can be trained based +on maximum likelihood. Normalizing flows as a prior were +shown to be more effective than GANs for solving inverse +problems [32], [33]. However unlike GANs, normalizing flows +are bijective mappings, having the same dimension in the +latent space and data space, consequently, the network output +is not constraint and leading to poor regularization for solving +ill-posed inverse problems [14]. +More recently, the authors of [35] showed that injective +normalizing flows are so effective for solving ill-posed inverse +problems. Injective normalizing flows are an extension of +normalizing flows which have a low-dimensional latent space. +Injective flows provide a low-dimensional representation of the +data (like GANs) which perform as a strong regularization for +solving inverse problems while giving access to the likelihood +of the generated samples (like normalizing flows) which can +be seen as the second regularization. In the next section, we +briefly review injective flows called Trumpets. +IV. INJECTIVE NORMALIZING FLOWS +Injective normalizing flows [35] map a low-dimensional +latent space to the high-dimensional data space using a set of + +4 +MOG (µz) +ACAnicbVA9SwNBEN3zM8avqJXYLAYhNuFOIloGLbQRI5gPSMKxt9kS3bvjt05MR6HjX/FxkIRW3+Fnf/GT +XKFJj4YeLw3w8w8LxRcg21/W3PzC4tLy5mV7Ora+sZmbmu7poNIUValgQhUwyOaCe6zKnAQrBEqRqQnWN0bnI/8+h1T +mgf+LQxD1pak5/MupwSM5OZ2W8DuIb6vsCFpCUj92EiHCZuLm8X7THwLHFSkcpKm7uq9UJaCSZD1QrZuOHUI7Jgo +4FSzJtiLNQkIHpMeahvpEMt2Oxy8k+MAoHdwNlCkf8Fj9PRETqfVQeqZTEujraW8k/uc1I+ietmPuhxEwn04WdSOBIc +CjPHCHK0ZBDA0hVHFzK6Z9ogFk1rWhOBMvzxLakdFp1Q8vinly2dpHBm0h/ZRATnoBJXRJaqgKqLoET2jV/RmPVkv1r +v1MWmds9KZHfQH1ucPKAKXSg= +Fig. 2: Injective normalizing flows [35] comprise two submodules, a low-dimensional bijective flow hη and an injective network +with expansive layers gγ. The MOG initialization is the mean of the Gaussian in the latent space zinit = µz (red circle). +invertible neural networks. Injective normalizing flows have +a fast inverse on the range and give access to the likelihood +of the generated samples. As shown in Figure 2, fθ(z) = +gγ(hη(z)) with weights θ = (γ, η) comprises two subnetworks: +an injective part (with expansive layers) gγ that maps a low- +dimensional space Rd to high-dimensional data space RD +where d ≪ D, and a bijective mapping hη that keeps the +dimension in low dimensional space Rd. The training of the +injective normalizing flows consists of two phases, at first, the +range of the injective generator must be adjusted to lie on the +training data by optimizing over the weights of the injective +subnetwork gγ, when we ensure the training data are close to +the range of the generator, in the second phase the likelihood +of the pre-image of the training data should be maximized +over the weights of the bijective subnetwork hη. Further details +are explained in [35]. When the network is trained, we can +generate random samples similar to the training data +xgen = f(zgen) +(9) +where zgen ∼ N(µz, σ2 +zI). Further information about the +universality of density and manifold approximation of injective +normalizing flows are studied in [56]. +Due to having a low-dimensional latent space, injec- +tive flows provide a low-dimensional manifold in the high- +dimensional data space. When they are trained, the manifold +would contain plausible samples which can be used as an +effective regularizer for solving ill-posed inverse problems. +The injective part provides a projection operator gγ(g† +γ(x)) +which maps the data samples x to the intermediate space by +z′ = g† +γ(x) and projects them back to the data space by g† +γ(z′). +The authors of [35] used the projection operator to project a +sample on the manifold to suppress the noise and artifacts, +as the learned manifold contains high-quality samples. In the +next section, we will present our method of solving inverse +scattering problems using injective normalizing flows. +V. INJECTIVE FLOWS FOR INVERSE SCATTERING +Inverse scattering is a severely ill-posed inverse problem, +which means a small perturbation in the scattered fields leads +to an exponentially large error in the contrast [7]. This makes +the inversion unstable even for a small amount of noise. As +discussed in section II, inverse scattering is a nonlinear inverse +problem whose nonlinearity heavily relies on the maximum +contrast value. For objects with large contrasts, the problem +becomes highly nonlinear, which makes the inversion extremely +difficult. In such a scenario, the significance of having a strong +regularizer to restrict the search domain is crucially important. +We consider the contrast signal χ = x ∈ X and +the scattered fields Es = y ∈ Y, described by forward +operator (7), as random vectors. While our framework admits +other distributions beyond Gaussian for the additive noise δ in +(7), in this paper we assume that δ is a random vector with +Gaussian distribution δ ∼ N(0, σ2I) yielding +Y |X ∼ N(A(X), σ2I). +(10) +One effective approach for solving ill-posed inverse problems is +computing MAP estimate, where we look for the solution x that +has the highest posterior likelihood for a given measurement +y, +xMAP = arg maxx log(pX|Y (x|y)), +(11) + +85 +where pX|Y (x|y) is the posterior distribution for the given +measurement y. Using Bayes theorem yields, +xMAP += +arg minx − log(pX|Y (x|y)) += +arg minx − log(pY |X(y|x)pX(x) +pY (y) +) += +arg minx − log(pY |X(y|x)) − log(pX(x)). +(12) +The first term can be obtained from (10), +xMAP = arg minx +1 +2∥y − A(x)∥2 +2 − λ log(pX(x)), +(13) +where the first term is the data-consistency loss while +log(pX(x)) is the prior distribution of the contrast and plays +the role of the regularization. We also have λ which is a +hyperparameter to adjust the amount of regularization term +(although it comes from the noise standard deviation which +we assume is unknown). In principle, the prior distribution +pX(x) is not available and must be estimated. For example, +traditionally pX(x) is approximated with a Gaussian distribu- +tion with zero mean leading to the Tikhonov regularization. +However, a Gaussian distribution is often too far from the true +prior distribution and leads to poor reconstructions. +In this paper, we study a new regularization family for +inverse scattering based on deep generative models. We consider +a training set of contrast signals {x(i)}N +i=1 is available, and we +train a deep generative model x = f(z) to produce high-quality +contrast samples. we expect the trained generator f to produce +high-quality contrast samples when it takes random samples +from the Gaussian distribution in the latent space z ∈ Z. +As discussed in section III, this property of deep generative +models makes them an effective regularizer for solving inverse +problems [28]. +We use injective normalizing flows as the generator of the +contrast signal since they are well-suited for solving ill-posed +inverse problems [35]. We perform an optimization in the latent +space to find the latent code that aligns with scattered fields y, +zMAP = arg max +z +1 +2∥y −A(f(z))∥2 +2 +λ log(pX(f(z))), (14) +Where an approximation to pX is also provided by the injective +flows and acts as the second regularizer. The reconstructed +contrast signal can be obtained as xMAP = f(zMAP). We +call this method latent space optimization (LSO). It is worth +mentioning that (14) has been previously proposed by [32], +[33] for solving compressed sensing inverse problems using +regular normalizing flows. +Unlike the supervised learning methods for inverse scatter- +ing [13], [15]–[17] which use a paired training set of contrast +and scattered fields {(x(i), y(i))}N +i=1, our framework benefits +from an unsupervised learning paradigm where scattered fields +are not used in the training of injective flows. This means, if the +distribution of the scattered fields changes (due to the change +in experimental configuration), the generative network is not +required to be retrained unlike the supervised methods; as soon +as the injective generator is trained over the contrast signals, we +can optimize (14) for each new scattered fields to reconstruct +Ground truth +BP (𝜖! = 1.2) +BP (𝜖! = 2) +BP (𝜖! = 4) +BA (𝜖! = 1.2) +BA (𝜖! = 2) +BA (𝜖! = 4) +Fig. 3: Performance analysis of back-propagation (BP) and +Born approximation (BA) methods for different ϵr; while BA +and BP reconstructions are visually meaningful for small ϵr, +their performance sharply drop for objects with large ϵr. +Random ellipses +MNIST +Fig. 4: Illustration of the MOG initializer in the data space +f(µz) for random ellipses and MNIST datasets +the corresponding contrast. Apart from the advantages of an +unsupervised learning paradigm, the proposed method fully +exploits the underlying physics of the scattering problem by +optimizing over the complex-valued scattered fields in (14). +Kothari et al. [57] have shown incorporating wave physics +in the neural network architecture can significantly improve +the quality of reconstructions, especially for out-of-distribution +data. +We solve the optimization problem (14) by Adam op- +timizer [58] and compute the gradients with respect to z +by automatic differentiation provided by TensorFlow [59] in +Python. We also use an alternative method for Equation (14) +proposed by [35] which performs the optimization in the data +space, +xMAP = arg min +x +1 +2∥y −A(g(g†(x)))∥2 +2 −λ log(pX(x)) (15) +where g(g†(x)) is the projection operator explained in sec- +tion IV. We call this method data space optimization (DSO). +This method is shown in [35] to be effective for solving +linear inverse problems. While in each of the LSO iterations +the reconstructed point x = f(z) is always on the learned +manifold, this is not the case for the DSO method, where the +reconstructed image might be off the manifold. Moreover, the +DSO method requires more computations than LSO as we need +to take derivatives over the reverse direction of the injective +subnetwork g†(x). +The choice of initial guess is crucially important in inverse + +0.07 +0.41 +0.08 +0.01 +0.02 +-0.33 +0.08 +0.14 +0.12 +0.00 +-0.04 +-0.156 +Ground truths +Projections on the manifold +Generated samples +Fig. 5: Performance evaluation of the trained injective normalizing flows for random ellipses dataset; ground truth contrasts, +their projections on the learned manifold and some randomly generated samples. +scattering solvers. While a poor initialization misleads the +optimization process, a good initial step helps the algorithm to +converge more accurately and faster. The authors of [9] used +Born approximation as the initialization for the distorted Born +iterative method (DBIM). A back-propagation (BP) solution +was also used in [10], [60] as an initial guess of the contrast +source inversion (CSI) method. Figure 3 shows the ground +truth, back-propagation (BP) and Born approximations (BA) +for an object with different maximum ϵr values. While BP +and BA can present fuzzy reconstructions for objects with +small permittivity, their performance sharply drops for large ϵr +(especially numerically) which makes them a poor initialization +for strong scatterers. +In order to circumvent this issue, we use a data-driven +initialization suggested in [32]; mean of the Gaussian distri- +bution (MOG) in the latent space as shown in Figure 2. The +MOG initializer zinit = µz provides a fixed initialization with +respect to the measurements (scattered fields); thereby being +independent of the maximum contrast value and the problem +configuration. This property helps (14) and (15) to converge +better even for a large ϵr. In section VI, we will show that +MOG initialization significantly improves the quality of the +reconstructions compared to BP. To our best knowledge, this +is the first time that we propose a data-driven initializer for +inverse scattering. +VI. COMPUTATIONAL EXPERIMENTS +In the following, we will evaluate the performance of DSO +and LSO for inverse scattering. We consider the MOG and BP +initializations for DSO while using just MOG initialization for +LSO. We compare the performance of our proposed methods +with a traditional iterative method DBIM [9]. While our method +is based on an unsupervised-learning paradigm; scattered fields +are not used during training, we also compare its performance +with a successful supervised learning method, U-Net [36] which +has shown great success for inverse scattering [16], to show the +effectivity of our method. U-Net takes the back-propagation +(BP) as input and returns the permittivity pattern of the object +in the output. +We use MNIST [61] with 60000 training samples in the +resolution N = 32. We also use a custom dataset of 60000 +training samples with resolution N = 64 of overlapping ellipses +used in [14] to have a more challenging task for accurate +reconstructions. +We use Ni = 12 incident plane waves and Nr = 12 +receivers, uniformly distributed on a circle with radius R = +20 cm around the object with maximum permittivity ϵr and +dimension D = 20 cm. The working frequency is 3 GHz and +we added 30 dB noise to the scattered fields. +We used the injective normalizing flows with the same +architecture described in [35]. We trained the injective subnet- +work gγ for 150 epochs to ensure the training samples (contrast +signals) are close to the range of the generator. Figure 5 shows +some test samples and their projections on the learned manifold. +Then we trained the bijective subnetwork hη for 150 epochs +to maximize the likelihood of the pre-image of the training +samples in the intermediate space. Figure 5 illustrates some +randomly generated samples which confirms that the model +can produce plausible samples to be used as an effective prior +for solving inverse scattering. +We optimize (14) and (15) by using Adam optimizer with a +learning rate of 0.05 for 300 iterations. We use λ = 0.01 for BP +and λ = 0 for MOG initialization. It is worth mentioning that +when we use MOG initializer, we start from high-likelihood +regions (mean of the Gaussian) which can be viewed as a +hidden regularizer, we thus use λ = 0 in this case. Figure 4 +shows the MOG initialization for MNIST and random ellipses +datasets. +Figures 6 and 7 show the performance of different methods +for inverse scattering for ϵr = 4 over five test samples from +random ellipses and MNIST datasets. While the traditional +iterative method (DBIM) meets with complete failure in this +challenging task (ϵr = 4 and 30 dB noise), DSO and LSO +have strikingly more accurate reconstructions, which clearly + +7 +BP +DBIM +U-Net +DSO (BP) +DSO (MOG) +LSO +Ground truth +Fig. 6: Performance comparison of different methods over random ellipses dataset in resolution 64 × 64 +BP +DBIM +U-Net +DSO (BP) +DSO (MOG) +LSO +Ground truth +Fig. 7: Performance comparison of different methods over MNIST dataset in resolution 32 × 32 + +0.5 +2.5 +3.7 +4.0 +4.0 +3.5 +3.6 +-3.5 +1.0 +1.0 +1.0 +1.0 +0.5 +5.3 +4.0 +4.0 +4.0 +4.0 +3.5 +1.0 +1.0 +1.0 +1.0 +1.0 +0.5 +4.5 +4.0 +4.0 +3.9 + 3.9 +-3.2 +1.0 +1.0 +1.0 +1.0 +1.0 +0.5 +2.9 +4.0 +4.0 +4.0 +4.0 + 4.0 +-1.8 +1.0 +1.0 +1.0 +1.0 +1.0 +0.5 +1.5 +3.9 +4.0 +4.0 +4.0 + 4.0 +0.3 +-4.5 +1.0 +1.0 +1.0 +1.0 +1.00.5 +4.0 +9.4 +4.2 +3.9 +4.0 +0.4 +0.7 +0.9 +5.7 +3.9 +4.1 +4.1 +3.9 +4.0 +5 +01 +3.3 +1.0 +0.9 +0.9 +1.0 +1.0 +0.6 +5.6 +4.0 +11.8 +6.6 +4.0 + 4.0 +-3.2 +1.0 +3.2 +-1.6 +0.9 +1.0 +0.5 +5.8 +4.0 +11.9 +7.8 +4.1 + 4.0 +-3.8 +1.0 +.1.4 +-0.8 +0.9 +1.0 +4.4 +4.0 +12.1 +4.2 +3.9 + 4.0 +0.7 +9 +1 +0.3 +2.8 +1.0 +-7.1 +0.8 +0.9 +1.08 +TABLE I: Performance of different methods for solving inverse +scattering (ϵr = 4) averaged over 25 test samples +PSNR +SSIM +MNIST +Ellipses +MNIST +Ellipses +BP +7.75 +7.00 +0.01 +0.01 +DBIM [9] +5.77 +4.67 +0.01 +0.01 +U-Net [36] +24.26 +21.94 +0.90 +0.82 +DSO (BP) +8.73 +7.89 +0.16 +0.16 +DSO (MOG) +21.50 +14.56 +0.56 +0.44 +LSO (MOG) +25.22 +20.50 +0.89 +0.85 +Fig. 8: The performance of different methods for different ϵr +over MNIST dataset; SSIM is computed over the normalized +signals between −1 and 1. +shows the significance of a data-driven regularization. Moreover, +the MOG initialization, as we expected, exhibits remarkably +better reconstructions compared to BP for this high permittivity +(ϵr = 4). Furthermore, both figures show that LSO outperforms +DSO; running optimization in the latent space results in better +reconstructions as discussed in section V. Finally, while LSO +does not use scattered fields in the training phase, it could +present the reconstructions with comparable quality (or even +better) to the highly successful supervised method U-Net. +Table I shows the numerical results in PSNR and SSIM +averaged over 25 test samples. +As discussed in section V, the maximum ϵr of the +object plays a significant role in the performance of inverse +scattering solvers; objects with large ϵr are more difficult to +be reconstructed. Figure 8 demonstrates the performance of +different methods per ϵr over the MNIST dataset. This figure +discovers that LSO with MOG initialization is effective even +for objects with large, ϵr which clearly signifies the power of +a data-driven initialization and performing the optimization in +the latent space. +VII. LIMITATIONS AND CONCLUSIONS +We proposed a learning-based framework for inverse +scattering using an injective prior. The proposed method fully +exploits the physical domain of the scattering problem while +benefiting from a data-driven initialization which makes a +powerful solver even for objects with a large contrast. The +invertible generator admits performing optimization in both +latent and data space and uses a data-driven or back-projection +as the initializer. We showed that performing optimization in +the latent space and using the mean of the Gaussian as the +initial guess significantly outperforms the traditional iterative +methods and even gives reconstructions comparable to the +successful supervised learning method, U-Net. +Limitations: The proposed framework has several limitations +and entails discussion. It requires running an iterative method +in test-time, which is slow and cannot be used for real-time +applications. To speed up the convergence, one may consider a +more accurate initial guess by exploiting the physical domain +in the data-driven initializer; a combination of traditional back- +projection (like BP) and the data-driven initializers (like MOG). +Recently, Hussein et all. [31] optimized the generator weights +with a small rate after finding the optimal latent code in +Equation (14) to further improve the reconstructions. 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Haffner, “Gradient-based learning +applied to document recognition,” Proceedings of the IEEE, vol. 86, +no. 11, pp. 2278–2324, 1998. 6 + diff --git a/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/load_file.txt b/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..3f0b0f1ce23c0e5771921347c5c5686c3305c945 --- /dev/null +++ b/-dE1T4oBgHgl3EQfUgPr/content/tmp_files/load_file.txt @@ -0,0 +1,854 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf,len=853 +page_content='1 Deep Injective Prior for Inverse Scattering AmirEhsan Khorashadizadeh , Sepehr Eskandari , Vahid Khorashadi-Zadeh and Ivan Dokmani´c Abstract—In electromagnetic inverse scattering, we aim to reconstruct object permittivity from scattered waves.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Deep learning is a promising alternative to traditional iterative solvers, but it has been used mostly in a supervised framework to regress the permittivity patterns from scattered fields or back-projections.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While such methods are fast at test-time and achieve good results for specific data distributions, they are sensitive to the distribution drift of the scattered fields, common in practice.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' If the distribu- tion of the scattered fields changes due to changes in frequency, the number of transmitters and receivers, or any other real-world factor, an end-to-end neural network must be re-trained or fine- tuned on a new dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In this paper, we propose a new data- driven framework for inverse scattering based on deep generative models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We model the target permittivities by a low-dimensional manifold which acts as a regularizer and learned from data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Unlike supervised methods which require both scattered fields and target signals, we only need the target permittivities for training;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' it can then be used with any experimental setup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We show that the proposed framework significantly outperforms the traditional iterative methods especially for strong scatterers while having comparable reconstruction quality to state-of-the-art deep learning methods like U-Net.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' INTRODUCTION E LECTROMAGNETIC inverse scattering is the problem of determining the electromagnetic properties of unknown objects from how they scatter incident fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As it is non- destructive, it has a variety of applications in different areas, such as early detection of breast cancer [1], mineral prospect- ing [2], detecting defects and cracks inside objects [3], imaging through the wall [4] and remote sensing [5].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We consider the reconstruction of the finite number of parameters of the object from the scattered fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While inverse scattering is well-posed and Lipschitz stable in theory, when full-aperture continuous measurements are available [6], it is Manuscript received December 29, 2022.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' AmirEhsan Khorashadizadeh and Ivan Dokmani´c were supported by the European Research Council Starting Grant 852821–SWING.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' AmirEhsan Khorashadizadeh is with the Department of Mathematics and Computer Science of the University of Basel, 4001 Basel, Switzerland (e-mail: amir.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='kh@unibas.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='ch).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Sepehr Eskandari is with Microwave Systems, Sensors, and Imaging Lab (MiXIL), University of Southern California, Los Angeles, CA 90089 USA (e-mail: sepehres@usc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='edu).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Vahid Khorashadi-Zadeh is with School of Electric and Computer Engineering, University of Tehran, Tehran 14399-57131, Iran (e-mail: v.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='khorashadi@ut.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='ac.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='ir).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Ivan Dokmani´c is with the Department of Mathematics and Computer Science of the University of Basel, 4001 Basel, Switzerland, and also with the Department of Electrical, Computer Engineering, the Univer- sity of Illinois at Urbana-Champaign, Urbana, IL 61801 USA (e-mail: ivan.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='dokmanic@unibas.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='ch).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Our implementation is available at https://github.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='com/swing-research/ scattering injective prior.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' a severely ill-posed inverse problem for a finite number of measurements.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This means that a small perturbation in the scattered fields may lead to a large error in the reconstructed permittivity pattern [7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, the forward operator from the permittivity to the scattered fields is nonlinear, which further complicates the inversion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The nonlinearity is due to the multiple scattering;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' the problem becomes more nonlinear as the permittivity contrast increases [7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' All these together make the inverse scattering challenging, especially for strong scatterers (objects with large permittivity) and noisy measurements, which require an effective regularization to restrict the search space and enable accurate reconstruction.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' A number of optimization-based methods are proposed to address nonlinearity and ill-posedness of the inverse scattering including Born iterative [8], distorted Born iterative method (DBIM) [9], contrast source inversion (CSI) [10], and subspace- based optimization (SOM) [11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Although these methods have been shown to be effective for objects with small permittivity, they do not give an accurate reconstruction for large permittivity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' All the above methods iteratively optimize a regularized objective, with a hand-crafted regularization term.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Recently, thanks to the significant increase in computing power and the availability of sufficient data, data-driven approaches to inverse scattering have started receiving attention.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Most deep learning models for inverse scattering use a super- vised learning approach, which takes the scattered fields or a simple back-projection as input and trains a deep neural network to produce the target permittivity pattern.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The authors of [12]– [14] used scattered fields as input.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While this approach provides good reconstructions even for objects with strong scatterers [14], it is sensitive to the experiment configuration such as the frequency or the number of incident waves and receivers;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' if the distribution of the scattered fields in test-time slightly changes, the quality of reconstructions remarkably degrades;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' the model requires new training data which is too costly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' One strategy to tackle this issue is to use back-projections as input instead of the raw scattered fields, thus enabling the use of convolutional neural networks [15]–[17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While this approach is shown to be effective for objects with small and moderate permittivity, the quality of the back-projections significantly drops in large permittivity (Figure 3), which leads to a drop in the reconstruction quality [14].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' On the other hand, supervised learning methods are also potentially vulnerable to adversarial attacks [18], which is problematic in medical applications [19].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, incorporating the well-known physics of the scattering problem (forward operator), which can strikingly improve the accuracy of the reconstructions, is not easy in supervised learning models [20].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='03092v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='LG] 8 Jan 2023 2 To tackle these issues, we propose a deep learning approach to inverse scattering using injective generative models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The proposed method benefits from an unsupervised learning framework—the training phase uses only the target permittivity patterns and the physics of scattering is fully incorporated into the solution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Deep generative models are a class of unsupervised learning methods that model the probability distribution of data by using deep neural networks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Latent-variable generative models such as generative adversarial networks (GAN) [21], [22], variational autoencoders [23], normalizing flows [24]– [26] and diffusion models [27] train a deep neural network to transform the samples of a simple (Gaussian) distribution to those of target data distribution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We expect a trained generator produce plausible samples similar to the training data when taking samples of a Gaussian distribution as input.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Bora et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' [28] used GANs to constrain the solution domain to the range of the trained generator for solving compressed sensing inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The strength of this idea is that it requires only the target signals for training and does not know anything about the inverse problem is going to be solved.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As soon as the generator is trained, it can be used to solve any inverse problem with a known forward operator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This property makes the model robust to the distribution shift of the measurements and adversarial attack.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Several methods have tried to improve the quality of reconstructions;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Kelkar et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' [29] used the popular style- GAN generator [30] while Hussein et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' [31] jointly optimize the generator weights with latent codes to further reduce the reconstructions error.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' However, GANs are known to be unstable in training, and the optimization process over latent space sticks in the local minimum which requires many restarts [28].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Recently, normalizing flows as a generator instead of GANs have been shown to have a stable optimization landscape [32], [33].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Nevertheless, normalizing flows have their own drawbacks;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' having a latent code with the same dimension as data space makes them too expensive in training and does not provide an appropriate constraint in the generator output, leading to poor reconstruction for ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' More recently, injective normalizing flows [34], [35] are proposed to alleviate these issues.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Injective flows are a class of deep generative models that are well-suited for solving ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' These models unlike GANs give us access to the approximate likelihood of the generated samples, which provides a likelihood-based regularization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, injective flows unlike regular normalizing flows benefit from a low-dimensional latent space which provides an additional effective regularizer for ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Injective flows have been shown in [35] to effectively solve linear inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In this paper, we use injective flows as the generator to solve full-wave inverse scattering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' we will show that the proposed method effectively solves inverse scattering even for objects with large permittivity for which traditional methods fail.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, we use a data-driven initial guess for starting the iterative optimization, which significantly outperforms the simple back-projection initialization used in the traditional Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 1: The setup for the inverse scattering problem, red arrows show the incident plane waves;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' the green circles are the receivers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Finally, we show that the proposed framework yields reconstructions of comparable or better quality to highly successful supervised methods like the U-Net [36].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' II.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' FORWARD AND INVERSE SCATTERING We begin our discussion with equations governing the 2D forward and inverse scattering problem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We consider two-dimensional transverse magnetic scattering, where the longitudinal direction is along the z direction (TMz).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As shown in Figure 1, non-magnetic scatterers with permittivity ϵr in a vacuum background with permittivity ϵ0 and permeability µ0 are located in investigation domain Dinv which is a D×D square, and are illuminated by Ni plane waves with equispaced directions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We have Nr receivers placed uniformly on a circle S with radius R which measure the scattered fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The forward scattering problem can be derived from the time-harmonic form of Maxwell’s equations and stated as [37], ∇ × (∇ × Et(r)) − k2 0ϵr(r)Et(r) = iωµ0J(r) (1) where Et is the total electric field, k0 = ω√µ0ϵ0 is the wavenumber of the homogeneous background and J is the contrast current density and can be calculated using equivalence theorem [38] as J(r) = χ(r)Et(r) where χ(r) = ϵr(r)−1 and is called the contrast.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The time-dependence factor exp(iωt) with angular working frequency ω is assumed and will be suppressed throughout this paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' By using Dyadic Green’s function [39], Equation (1) can be formalized by two coupled integral equations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The first one, called Lippmann–Schwinger equation, relates total electric fields Et in an unknown domain to contrast current density J, Et(r) = Ei(r) + k2 0 � Dinv g(r, r′)J(r′)dr′, (2) 3 where r ∈ Dinv, and g(r, r′) = 1 4iH(2) 0 (k0|r − r′|), and H(2) 0 is the Hankel function of the second kind, denotes 2D free space Green’s function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The second equation, referred to as the data equation, maps the contrast current density J to the scattered electric fields Es at the receivers locations, Es(r) = k2 0 � Dinv g(r, r′)J(r′)dr′, r ∈ S.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' (3) We discretize the investigation domain Dinv with N × N units and rewrite Equations (2) and (3) as Et = Ei + GdχEt (4) Es = GsχEt + δ (5) where Gd ∈ RN 2×N 2 and Gs ∈ RNr×N 2 have analytical closed form [7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, Et, Ei and Es respectively correspond to total, incident and scattered electric fields and χ is a diagonal matrix with the diagonal elements χ(n, n) = ϵr(rn) − 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We also consider additive noise δ to the measurements.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We merge Equations (4) and (5) to make a single expression for the forward equation [7], Es = Gsχ(I − Gdχ)−1Ei + δ, (6) which is a nonlinear mapping χ �→ Es.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' It is convenient to define a forward operator A mapping χ to Es, y = A(x) + δ, (7) where A(·) is the nonlinear forward scattering operator A(χ) = Gsχ(I − Gdχ)−1Ei, (8) y = Es and x = χ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The task of inverse scattering is to reconstruct the contrast signal χ from the scattered fields Es where we assume Gd, Gs, incident electric waves Ei and consequently the forward operator A(·) are known.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In the next section, we briefly review deep generative models as the prior model for inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' III.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' DEEP GENERATIVE MODELS One major division in machine learning is generative and discriminative models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In discriminative models, one aims to learn a direct mapping from the measurements to the target signals.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Discriminative approaches have been extensively used in solving inverse problems, specifically U-Net [36] has shown great success in many applications such as computed tomography (CT) [40], magnetic resonance imaging (MRI) [41], optoacoustic tomography [42] and electromagnetic inverse scattering [16].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The key idea of this success might be ascribed to having a multiscale architecture [43].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Recently, the variational version of U-Net has shown excellent performance for posterior sampling and uncertainty quantification of inverse scattering problem [44].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' On the other hand, the task of generative models is to learn the probability distribution of data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Latent-variable generative models including generative adversarial networks (GANs) [21], [22], variational autoencoders [23] and normalizing flows [24]– [26] are a subcategory of deep generative models (DGMs) which train a deep neural network, called the generator, to transform the samples of a simple and known distribution (often Gaussian) to data distribution samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' DGMs have many applications such as image generation [22], image-to- image translation [45], density estimation [46] and variational inference [47], [48].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Recently, DGMs have been used as a prior for solving inverse problems [28], [35], [49]–[52];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' consider a DGM trained on a training set of target signals (the solutions of a given inverse problem), one can search in the latent space of the trained generator for the latent code yielding a solution aligns with the given measurements.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The pre-trained generator plays the role of an effective regularizer for generating plausible target signals.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As discussed earlier, the key advantage of this approach is that the measurements are not used in the training phase.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As a result, once the DGM is trained, it can be used for solving any inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' However, the choice of DGM is of paramount importance to provide stable training, high-quality sample generation, and an effective regularizer for solving ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While modern GANs with the various innovations in architectures and training protocols exhibit high-quality samples, they suffer from training instability [53], [54] and have shown poor reconstructions when used as a prior for solving ill- posed inverse problems [35], [55].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Normalizing flows alleviates many drawbacks of GAN;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' they are stable in training and can produce high-quality samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Normalizing flows comprise a set of bijective transformations which have tractable inverse and log det Jacobian computations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' They give access to the likelihood of the generated samples and can be trained based on maximum likelihood.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Normalizing flows as a prior were shown to be more effective than GANs for solving inverse problems [32], [33].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' However unlike GANs, normalizing flows are bijective mappings, having the same dimension in the latent space and data space, consequently, the network output is not constraint and leading to poor regularization for solving ill-posed inverse problems [14].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' More recently, the authors of [35] showed that injective normalizing flows are so effective for solving ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Injective normalizing flows are an extension of normalizing flows which have a low-dimensional latent space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Injective flows provide a low-dimensional representation of the data (like GANs) which perform as a strong regularization for solving inverse problems while giving access to the likelihood of the generated samples (like normalizing flows) which can be seen as the second regularization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In the next section, we briefly review injective flows called Trumpets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' IV.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' INJECTIVE NORMALIZING FLOWS ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='Injective normalizing flows [35] map a low-dimensional ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='latent space to the high-dimensional data space using a set of ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='4 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='MOG (µz) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='ACAnicbVA9SwNBEN3zM8avqJXYLAYhNuFOIloGLbQRI5gPSMKxt9kS3bvjt05MR6HjX/FxkIRW3+Fnf/GT ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='XKFJj4YeLw3w8w8LxRcg21/W3PzC4tLy5mV7Ora+sZmbmu7poNIUValgQhUwyOaCe6zKnAQrBEqRqQnWN0bnI/8+h1T ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='mgf+LQxD1pak5/MupwSM5OZ2W8DuIb6vsCFpCUj92EiHCZuLm8X7THwLHFSkcpKm7uq9UJaCSZD1QrZuOHUI7Jgo ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='4FSzJtiLNQkIHpMeahvpEMt2Oxy8k+MAoHdwNlCkf8Fj9PRETqfVQeqZTEujraW8k/uc1I+ietmPuhxEwn04WdSOBIc ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='CjPHCHK0ZBDA0hVHFzK6Z9ogFk1rWhOBMvzxLakdFp1Q8vinly2dpHBm0h/ZRATnoBJXRJaqgKqLoET2jV/RmPVkv1r ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='v1MWmds9KZHfQH1ucPKAKXSg= ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 2: Injective normalizing flows [35] comprise two submodules, a low-dimensional bijective flow hη and an injective network with expansive layers gγ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The MOG initialization is the mean of the Gaussian in the latent space zinit = µz (red circle).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' invertible neural networks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Injective normalizing flows have a fast inverse on the range and give access to the likelihood of the generated samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As shown in Figure 2, fθ(z) = gγ(hη(z)) with weights θ = (γ, η) comprises two subnetworks: an injective part (with expansive layers) gγ that maps a low- dimensional space Rd to high-dimensional data space RD where d ≪ D, and a bijective mapping hη that keeps the dimension in low dimensional space Rd.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The training of the injective normalizing flows consists of two phases, at first, the range of the injective generator must be adjusted to lie on the training data by optimizing over the weights of the injective subnetwork gγ, when we ensure the training data are close to the range of the generator, in the second phase the likelihood of the pre-image of the training data should be maximized over the weights of the bijective subnetwork hη.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Further details are explained in [35].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' When the network is trained, we can generate random samples similar to the training data xgen = f(zgen) (9) where zgen ∼ N(µz, σ2 zI).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Further information about the universality of density and manifold approximation of injective normalizing flows are studied in [56].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Due to having a low-dimensional latent space, injec- tive flows provide a low-dimensional manifold in the high- dimensional data space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' When they are trained, the manifold would contain plausible samples which can be used as an effective regularizer for solving ill-posed inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The injective part provides a projection operator gγ(g† γ(x)) which maps the data samples x to the intermediate space by z′ = g† γ(x) and projects them back to the data space by g† γ(z′).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The authors of [35] used the projection operator to project a sample on the manifold to suppress the noise and artifacts, as the learned manifold contains high-quality samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In the next section, we will present our method of solving inverse scattering problems using injective normalizing flows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' V.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' INJECTIVE FLOWS FOR INVERSE SCATTERING Inverse scattering is a severely ill-posed inverse problem, which means a small perturbation in the scattered fields leads to an exponentially large error in the contrast [7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This makes the inversion unstable even for a small amount of noise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As discussed in section II, inverse scattering is a nonlinear inverse problem whose nonlinearity heavily relies on the maximum contrast value.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' For objects with large contrasts, the problem becomes highly nonlinear, which makes the inversion extremely difficult.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In such a scenario, the significance of having a strong regularizer to restrict the search domain is crucially important.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We consider the contrast signal χ = x ∈ X and the scattered fields Es = y ∈ Y, described by forward operator (7), as random vectors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While our framework admits other distributions beyond Gaussian for the additive noise δ in (7), in this paper we assume that δ is a random vector with Gaussian distribution δ ∼ N(0, σ2I) yielding Y |X ∼ N(A(X), σ2I).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' (10) One effective approach for solving ill-posed inverse problems is computing MAP estimate, where we look for the solution x that has the highest posterior likelihood for a given measurement y, xMAP = arg maxx log(pX|Y (x|y)), (11) 85 where pX|Y (x|y) is the posterior distribution for the given measurement y.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Using Bayes theorem yields, xMAP = arg minx − log(pX|Y (x|y)) = arg minx − log(pY |X(y|x)pX(x) pY (y) ) = arg minx − log(pY |X(y|x)) − log(pX(x)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' (12) The first term can be obtained from (10), xMAP = arg minx 1 2∥y − A(x)∥2 2 − λ log(pX(x)), (13) where the first term is the data-consistency loss while log(pX(x)) is the prior distribution of the contrast and plays the role of the regularization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We also have λ which is a hyperparameter to adjust the amount of regularization term (although it comes from the noise standard deviation which we assume is unknown).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In principle, the prior distribution pX(x) is not available and must be estimated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' For example, traditionally pX(x) is approximated with a Gaussian distribu- tion with zero mean leading to the Tikhonov regularization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' However, a Gaussian distribution is often too far from the true prior distribution and leads to poor reconstructions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In this paper, we study a new regularization family for inverse scattering based on deep generative models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We consider a training set of contrast signals {x(i)}N i=1 is available, and we train a deep generative model x = f(z) to produce high-quality contrast samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' we expect the trained generator f to produce high-quality contrast samples when it takes random samples from the Gaussian distribution in the latent space z ∈ Z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As discussed in section III, this property of deep generative models makes them an effective regularizer for solving inverse problems [28].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We use injective normalizing flows as the generator of the contrast signal since they are well-suited for solving ill-posed inverse problems [35].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We perform an optimization in the latent space to find the latent code that aligns with scattered fields y, zMAP = arg max z 1 2∥y −A(f(z))∥2 2 +λ log(pX(f(z))), (14) Where an approximation to pX is also provided by the injective flows and acts as the second regularizer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The reconstructed contrast signal can be obtained as xMAP = f(zMAP).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We call this method latent space optimization (LSO).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' It is worth mentioning that (14) has been previously proposed by [32], [33] for solving compressed sensing inverse problems using regular normalizing flows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Unlike the supervised learning methods for inverse scatter- ing [13], [15]–[17] which use a paired training set of contrast and scattered fields {(x(i), y(i))}N i=1, our framework benefits from an unsupervised learning paradigm where scattered fields are not used in the training of injective flows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This means, if the distribution of the scattered fields changes (due to the change in experimental configuration), the generative network is not required to be retrained unlike the supervised methods;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' as soon as the injective generator is trained over the contrast signals, we can optimize (14) for each new scattered fields to reconstruct Ground truth BP (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='2) BP (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 2) BP (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 4) BA (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='2) BA (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 2) BA (𝜖!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' = 4) Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 3: Performance analysis of back-propagation (BP) and Born approximation (BA) methods for different ϵr;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' while BA and BP reconstructions are visually meaningful for small ϵr, their performance sharply drop for objects with large ϵr.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Random ellipses MNIST Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 4: Illustration of the MOG initializer in the data space f(µz) for random ellipses and MNIST datasets the corresponding contrast.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Apart from the advantages of an unsupervised learning paradigm, the proposed method fully exploits the underlying physics of the scattering problem by optimizing over the complex-valued scattered fields in (14).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Kothari et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' [57] have shown incorporating wave physics in the neural network architecture can significantly improve the quality of reconstructions, especially for out-of-distribution data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We solve the optimization problem (14) by Adam op- timizer [58] and compute the gradients with respect to z by automatic differentiation provided by TensorFlow [59] in Python.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We also use an alternative method for Equation (14) proposed by [35] which performs the optimization in the data space, xMAP = arg min x 1 2∥y −A(g(g†(x)))∥2 2 −λ log(pX(x)) (15) where g(g†(x)) is the projection operator explained in sec- tion IV.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We call this method data space optimization (DSO).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This method is shown in [35] to be effective for solving linear inverse problems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While in each of the LSO iterations the reconstructed point x = f(z) is always on the learned manifold, this is not the case for the DSO method, where the reconstructed image might be off the manifold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, the DSO method requires more computations than LSO as we need to take derivatives over the reverse direction of the injective subnetwork g†(x).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The choice of initial guess is crucially important in inverse 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='07 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='41 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='08 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='02 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='33 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='08 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='14 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='12 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='00 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='04 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='156 Ground truths Projections on the manifold Generated samples Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 5: Performance evaluation of the trained injective normalizing flows for random ellipses dataset;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' ground truth contrasts, their projections on the learned manifold and some randomly generated samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' scattering solvers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While a poor initialization misleads the optimization process, a good initial step helps the algorithm to converge more accurately and faster.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The authors of [9] used Born approximation as the initialization for the distorted Born iterative method (DBIM).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' A back-propagation (BP) solution was also used in [10], [60] as an initial guess of the contrast source inversion (CSI) method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figure 3 shows the ground truth, back-propagation (BP) and Born approximations (BA) for an object with different maximum ϵr values.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While BP and BA can present fuzzy reconstructions for objects with small permittivity, their performance sharply drops for large ϵr (especially numerically) which makes them a poor initialization for strong scatterers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In order to circumvent this issue, we use a data-driven initialization suggested in [32];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' mean of the Gaussian distri- bution (MOG) in the latent space as shown in Figure 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The MOG initializer zinit = µz provides a fixed initialization with respect to the measurements (scattered fields);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' thereby being independent of the maximum contrast value and the problem configuration.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This property helps (14) and (15) to converge better even for a large ϵr.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' In section VI, we will show that MOG initialization significantly improves the quality of the reconstructions compared to BP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' To our best knowledge, this is the first time that we propose a data-driven initializer for inverse scattering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' VI.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' COMPUTATIONAL EXPERIMENTS In the following, we will evaluate the performance of DSO and LSO for inverse scattering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We consider the MOG and BP initializations for DSO while using just MOG initialization for LSO.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We compare the performance of our proposed methods with a traditional iterative method DBIM [9].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While our method is based on an unsupervised-learning paradigm;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' scattered fields are not used during training, we also compare its performance with a successful supervised learning method, U-Net [36] which has shown great success for inverse scattering [16], to show the effectivity of our method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' U-Net takes the back-propagation (BP) as input and returns the permittivity pattern of the object in the output.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We use MNIST [61] with 60000 training samples in the resolution N = 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We also use a custom dataset of 60000 training samples with resolution N = 64 of overlapping ellipses used in [14] to have a more challenging task for accurate reconstructions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We use Ni = 12 incident plane waves and Nr = 12 receivers, uniformly distributed on a circle with radius R = 20 cm around the object with maximum permittivity ϵr and dimension D = 20 cm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The working frequency is 3 GHz and we added 30 dB noise to the scattered fields.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We used the injective normalizing flows with the same architecture described in [35].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We trained the injective subnet- work gγ for 150 epochs to ensure the training samples (contrast signals) are close to the range of the generator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figure 5 shows some test samples and their projections on the learned manifold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Then we trained the bijective subnetwork hη for 150 epochs to maximize the likelihood of the pre-image of the training samples in the intermediate space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figure 5 illustrates some randomly generated samples which confirms that the model can produce plausible samples to be used as an effective prior for solving inverse scattering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We optimize (14) and (15) by using Adam optimizer with a learning rate of 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='05 for 300 iterations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We use λ = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 for BP and λ = 0 for MOG initialization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' It is worth mentioning that when we use MOG initializer, we start from high-likelihood regions (mean of the Gaussian) which can be viewed as a hidden regularizer, we thus use λ = 0 in this case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figure 4 shows the MOG initialization for MNIST and random ellipses datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figures 6 and 7 show the performance of different methods for inverse scattering for ϵr = 4 over five test samples from random ellipses and MNIST datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' While the traditional iterative method (DBIM) meets with complete failure in this challenging task (ϵr = 4 and 30 dB noise), DSO and LSO have strikingly more accurate reconstructions, which clearly 7 BP DBIM U-Net DSO (BP) DSO (MOG) LSO Ground truth Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 6: Performance comparison of different methods over random ellipses dataset in resolution 64 × 64 BP DBIM U-Net DSO (BP) DSO (MOG) LSO Ground truth Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 7: Performance comparison of different methods over MNIST dataset in resolution 32 × 32 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='5 2.' metadata={'source': 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='1 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='2 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='9 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='7 9 1 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='3 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='8 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='0 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='1 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='9 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='08 TABLE I: Performance of different methods for solving inverse scattering (ϵr = 4) averaged over 25 test samples PSNR SSIM MNIST Ellipses MNIST Ellipses BP 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='75 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='00 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 DBIM [9] 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='77 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='67 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='01 U-Net [36] 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='26 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='94 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='90 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='82 DSO (BP) 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='73 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='89 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='16 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='16 DSO (MOG) 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='50 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='56 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='56 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='44 LSO (MOG) 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='22 20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='50 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='89 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content='85 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' 8: The performance of different methods for different ϵr over MNIST dataset;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' SSIM is computed over the normalized signals between −1 and 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' shows the significance of a data-driven regularization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Moreover, the MOG initialization, as we expected, exhibits remarkably better reconstructions compared to BP for this high permittivity (ϵr = 4).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Furthermore, both figures show that LSO outperforms DSO;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' running optimization in the latent space results in better reconstructions as discussed in section V.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Finally, while LSO does not use scattered fields in the training phase, it could present the reconstructions with comparable quality (or even better) to the highly successful supervised method U-Net.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Table I shows the numerical results in PSNR and SSIM averaged over 25 test samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' As discussed in section V, the maximum ϵr of the object plays a significant role in the performance of inverse scattering solvers;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' objects with large ϵr are more difficult to be reconstructed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Figure 8 demonstrates the performance of different methods per ϵr over the MNIST dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' This figure discovers that LSO with MOG initialization is effective even for objects with large, ϵr which clearly signifies the power of a data-driven initialization and performing the optimization in the latent space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' VII.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' LIMITATIONS AND CONCLUSIONS We proposed a learning-based framework for inverse scattering using an injective prior.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The proposed method fully exploits the physical domain of the scattering problem while benefiting from a data-driven initialization which makes a powerful solver even for objects with a large contrast.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' The invertible generator admits performing optimization in both latent and data space and uses a data-driven or back-projection as the initializer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' We showed that performing optimization in the latent space and using the mean of the Gaussian as the initial guess significantly outperforms the traditional iterative methods and even gives reconstructions comparable to the successful supervised learning method, U-Net.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Limitations: The proposed framework has several limitations and entails discussion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' It requires running an iterative method in test-time, which is slow and cannot be used for real-time applications.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' To speed up the convergence, one may consider a more accurate initial guess by exploiting the physical domain in the data-driven initializer;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' a combination of traditional back- projection (like BP) and the data-driven initializers (like MOG).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' Recently, Hussein et all.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/-dE1T4oBgHgl3EQfUgPr/content/2301.03092v1.pdf'} +page_content=' [31] optimized the generator weights with a small rate after 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ALMOST-PERIODICITY CRITERION +PHILIPPE CIEUTAT +Abstract. We give an extension of Bochner’s criterion for the almost periodic func- +tions. By using our main result, we extend two results of A. Haraux. The first is a +generalization of Bochner’s criterion which is useful for periodic dynamical systems. The +second is a characterization of periodic functions in term of Bochner’s criterion. +2020 Mathematic Subject Classification: 35B10, 35B40, 42A75, 47H20. +Keywords: Bochner almost periodicity, periodic function, almost periodic function, +asymptotically almost periodic function, nonlinear semigroup, periodic dynamical sys- +tem. +1. Introduction +The almost periodic functions in the sense of Bohr have been characterized by Bochner +by means of a compactness criterion in the space of the bounded and continuous functions +[2, 3]. The Bochner’s criterion plays an essential role in the theory and in applications. +We give a new almost-periodicity criterion for functions with values in a given complete +metric space which is useful to study the almost periodicity of solutions of dynamical +systems governed by a family of operators with a positive parameter. This criterion is an +extension of Bochner’s criterion. Then Haraux gave a generalization of Bochner’s criterion +[9, Theorem 1], called a simple almost-periodicity criterion which is useful for periodic +dynamical systems. From our result, we deduce an extension of this criterion. We also +obtain an extension of an other result of Haraux which characterizes the periodic functions +in terms of the Bochner’s criterion [8]. In the same spirit, we treat the asymptotically +almost periodic case. +We give a description of this article, the precise definitions will be given in Section 2. +Throughout this section (X, d) is a complete metric space. An almost periodic function +u : R → X in the sense of Bohr is characterized by the Bochner’s criterion which is the +following: u is bounded and continuous, and from any real sequence of real numbers (τn)n, +there exists a subsequence (τφ(n))n such that the sequence of functions (u(t + τφ(n)))n is +uniformly convergent on R. In Section 3, we give two extensions of Bochner’s criterion. +First u : R → X is an almost periodic if and if only if in the Bochner’s criterion, we impose +that the terms of the sequence of real numbers (τn)n are all positive. Second u : R → X +is an almost periodic if and if only if in the Bochner’s criterion, the convergence of the +subsequence of functions (u(t + τφ(n)))n is uniform only on [0, +∞). These improvements +are useful to study the almost periodicity of solutions of an evolution equation governed by +a family of operators with a positive parameter, in particular for a C0-semigroup of linear +operators or more generally, for an autonomous dynamical system (nonlinear semigroup). +Universit´e Paris-Saclay, UVSQ, CNRS, Laboratoire de math´ematiques de Versailles, 78000, Versailles, +France. E-mail address: philippe.cieutat@uvsq.fr +1 + +2 +P. Cieutat +From our extension of Bochner’s criterion, we give new proofs which are direct and simpler +on known results on the almost periodicity of solutions of autonomous dynamic systems. +Haraux gave a generalization of Bochner’s criterion the called a simple almost-periodicity +criterion [9, Theorem 1]. This criterion makes it possible to choose in the Bochner’s cri- +terion, the sequence of real numbers (τn)n in a set of the type ωZ which is very useful +for periodic dynamical systems. From our extension of Bochner’s criterion, in Section +4, we deduce an improvement of this result. An asymptotically almost periodic function +u : R+ → X is a perturbation of almost periodic. A such function is characterized by a +property of the type of the Bochner’s criterion. In the same spirit, we extend this char- +acterization of asymptotically almost periodic functions. Then we apply these results to +study the almost periodicity of solutions of periodic dynamical systems. +Bochner’s criterion can also be expressed in terms of the relative compactness of the +set {u(· + τ); τ ∈ R} in a suitable set of continuous functions. A periodic function is a +special case of almost periodic function. A direct consequence of [8, Proposition 2] given +by Haraux characterizes a periodic function in terms of the Bochner’s criterion. This +characterization is the following: u : R → X is continuous is periodic if and if only if the +set {u(· + τ); τ ∈ R} is compact. In Section 5, By using our improvement of Bochner’s +criterion, we give an extension of the Haraux’s characterization of periodic functions. We +will also give a result on asymptotically periodic functions of the type of Haraux result +described above. Then we apply these results to study the periodicity of solutions of +autonomous dynamical systems. +2. Notation +Let us now give some notations, definitions and properties which will be used. +Throughout this section (X, d) is a complete metric space. +R, Z and N stand re- +spectively for the real numbers, the integers and the natural integers. +We denote by +R+ := {t ∈ R; t ≥ 0}. +Let E be a topological space. +We denote by C(E, X) the +space of all continuous functions from E into X. +When J = R or J = R+, we de- +note by BC(J, X) the space of all bounded and continuous functions from J into X +equipped with the sup-distance, denoted by d∞(u, v) := sup +t∈R +d(u(t), v(t)) when J = R and +d∞,+(u, v) := sup +t≥0 +d(u(t), v(t))) when J = R+ for u, v ∈ BC(J, X). The metric spaces +(BC(R, X), d∞) and (BC(R+, X), d∞,+)) are complete. +We now give some definitions and properties on almost periodic, asymptotically almost +periodic functions with values in a given complete metric space. +A subset D of R (respectively of R+) is said to be relatively dense if there exists ℓ > 0 +such that D ∩ [α, α + ℓ] ̸= ∅ for all α ∈ R (respectively α ≥ 0). A continuous function +u : R → X is said to be almost periodic (in the sense of Bohr) if for each ε > 0, +the set of ε-almost periods: P(u, ε) = +� +τ ∈ R ; sup +t∈R +d(u(t + τ), u(t)) ≤ ε +� +is relatively +dense in R. An almost periodic function u has its range u(R) relatively compact, that +is its closure denoted by cl (u(R)) is a compact set of (X, d). We denote the space of +all such functions by AP(R, X). It is a closed metric subspace of (BC(R, X), d∞). An +almost periodic function u is uniformly recurrent, that is there exists a sequence of real + +On Bochner’s almost-periodicity criterion +3 +numbers (τn)n such that +lim +n→+∞ sup +t∈R +d(u(t + τn), u(t)) = 0 and +lim +n→+∞ τn = +∞. To see +that consider the Bohr’s definition of u ∈ AP(R, X), then the set of +1 +n-almost periods +satisfies P(u, 1 +n)∩[n, +∞) ̸= ∅, for each integer n > 0. A useful characterization of almost +periodic functions was given by Bochner. The Bochner’s criterion which may be found in +[12, Bochner’s theorem, p. 4] in the context of metric spaces. Before to cite this criterion, +we need to introduce the translation mapping of a function of BC(R, X). For τ ∈ R and +u ∈ BC(R, X), we define the translation mapping Tτu ∈ BC(R, X) by Tτu(t) = u(t + τ) +for t ∈ R. +Theorem 2.1 (Bochner’s criterion). For u ∈ BC(R, X), the following statements are +equivalent. +i) u ∈ AP(R, X). +ii) The set {Tτu; τ ∈ R} is relatively compact in (BC(R, X), d∞). +Haraux gave a generalization of Bochner’ criterion the called a simple almost-periodicity +criterion [9, Theorem 1] which is useful for periodic dynamical systems. +Theorem 2.2 (Haraux’s criterion). Let D be a relatively dense subset of R. The following +statements are equivalent for u ∈ BC(R, X). +i) u ∈ AP(R, X). +ii) The set {Tτu; τ ∈ D} is relatively compact in (BC(R, X), d∞). +Periodic functions, which are a special case of almost periodic functions, are also char- +acterized in terms of Bochner’s criterion. This criterion is a direct consequence of a result +of Haraux. +Theorem 2.3. [8, Consequence of Proposition 2] The following statements are equivalent +for u ∈ BC(R, X). +i) u is periodic. +ii) The set {Tτu; τ ∈ R} is a compact set of (BC(R, X), d∞). +For some preliminary results on almost periodic functions with values in a given com- +plete metric space, we refer to the book of Levitan-Zhikov [12] and in the special case of +Banach spaces to the book of Amerio-Prouse [1]. +The notion of asymptotic almost periodicity was first introduced by Fr´echet [6] in 1941 +in the case where X = C. A continuous function u : R+ → X is said to be asymp- +totically almost periodic if there exists v ∈ AP(R, X) such that lim +t→∞ d(u(t), v(t)) = 0. +An asymptotic almost periodic function u has its range u(R+) relatively compact. We +denote the space of all such functions by AAP(R+, X). It is a closed metric subspace +of (BC(R+, X), d∞,+). An asymptotic almost periodicity function u : R+ → X is char- +acterized by u ∈ APP(R+, X) if and only if u ∈ C(R+, X) and for each ε > 0, there +exists M ≥ 0 such that the +� +τ ≥ 0 ; sup +t≥M +d(u(t + τ), u(t)) ≤ ε +� +is relatively dense in R+ +[15, Theorems 1.3]. In the context of metric spaces, Ruess and Summers give a charac- +terization of asymptotically almost periodic functions in the spirit of Bochner’s criterion. + +4 +P. Cieutat +To prove this characterization, Ruess and Summers use results from the paper [16] by +the same authors. For τ ≥ 0 and u ∈ BC(R+, X), we define the translation mapping +T + +τ u ∈ BC(R+, X) by T + +τ u(t) = u(t + τ) for t ≥ 0. +Theorem 2.4. [15, a part of Theorems 1.2 & 1.3] Let (X, d) be a complete metric space. +For u ∈ BC(R+, X), the following statements are equivalent. +i) u ∈ AAP(R+, X). +ii) The set {T + +τ u; τ ≥ 0} is relatively compact in (BC(R+, X), d∞,+). +For some preliminary results on asymptotically almost periodic functions, we refer to +the book of Yoshizawa [17] in the case where X is a finite dimensional space, to the book +of Zaidman [18] where X is a Babach space and to Ruess and Summers [14, 15, 16] in the +general case: X is a complete metric space. +3. An improvement of Bochner’s criterion +An almost periodic function is characterized by the Bochner’s criterion, recalled in Sec- +tion 2. Our main result is an extension of Bochner’s criterion. Then we deduce new proofs +which are direct and simpler on known results on the solutions of autonomous dynamic +systems. Before to state our extension of Bochner’s criterion, we need to introduce the +restriction operator R : BC(R, X) → BC(R+, X) defined by R(u)(t) := u(t) for t ≥ 0 +and u ∈ BC(R, X). +Theorem 3.1. Let (X, d) be a complete metric space. For u ∈ BC(R, X) the following +statements are equivalent. +i) u ∈ AP(R, X). +ii) The set {Tτu; τ ≥ 0} is relatively compact in (BC(R, X), d∞). +iii) The set {R(Tτu); τ ∈ R} is relatively compact in (BC(R+, X), d∞,+). +In our results, the compactness and the relative compactness of a set often intervene. +To prove them, we will often use the following result whose proof is obvious. Recall that +a set A of a metric space (E, d) is relatively compact if its closure denoted by cl (A) is a +compact set of (E, d). +Lemma 3.2. Let E be a set, (G1, d1) and (G2, d2) be two metric spaces. Let u : E → G1 +and v : E → G2 be two functions. Assume there exists M > 0 such that +∀x1, x2 ∈ E, +d1(u(x1), u(x2)) ≤ Md2(v(x1), v(x2)). +Then the following statements hold. +i) If the metric space (G1, d1) is complete and v(E) is relatively compact in (G2, d2), +then u(E) is relatively compact in (G1, d1). +ii) If v(E) is a compact set of (G2, d2), then u(E) is a compact set of (G1, d1). +Proof of Theorem 3.1. i) =⇒ iii). It is obvious by using the Bochner’s criterion and the +continuity of the restriction operator R. +iii) =⇒ ii). The set u(R) = {R(Tτu)(0); τ ∈ R} is relatively compact in X as the +range of {R(Tτu); τ ∈ R} by the continuous evaluation map at 0 from BC(R+, X) into +X. By assumption, H := cl ({R(Ttu) ; t ∈ R}) is a compact set of (BC(R+, X), d∞,+). + +On Bochner’s almost-periodicity criterion +5 +For all τ ≥ 0, we define φτ : H → X by φτ(h) = h(τ). The functions φτ are 1-Lipschitz +continuous and for each t ∈ R, the set {φτ(R(Ttu)) = u(τ + t) ; τ ≥ 0} is included in the +relatively compact set u(R). By density of {R(Ttu) ; t ∈ R} in H and the continuity of +φτ, it follows that {φτ(h) ; τ ≥ 0} is relatively compact in X for each h ∈ H. According +to Arzel`a-Ascoli’s theorem [11, Theorem 3.1, p. 57], the set {φτ ; τ ≥ 0} is relatively +compact in C(H, X) equipped with the sup-norm denoted by dC. +From the density +of {R(Ttu) ; t ∈ R} in H and the continuity of φτ, we deduce that for τ1 and τ2 ≥ 0, +sup +h∈H +d(φτ1(h), φτ2(h)) = sup +t∈R +d (φτ1(R(Ttu)), φτ2(R(Ttu))) = sup +t∈R +d (u(τ1 + t), u(τ2 + t)) = +sup +t∈R +d (Tτ1u(t), Tτ2u(t)), then dC(φτ1, φτ2) = d∞ (Tτ1u, Tτ2u). From Lemma 3.2, it follows +that {Tτu; τ ≥ 0} is relatively compact in the complete metric space (BC(R, X), d∞) +since {φτ ; τ ≥ 0} is also one in (C(H, X), dC). +ii) =⇒ i). For τ1, τ2 ≥ 0, d∞(Tτ1u, Tτ2u) := sup +t∈R +d(u(τ1 + t), u(τ2 + t)). Replacing t +by t − τ1 − τ2 in the upper bound, we get d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u). Then the +set {Tτu; τ ≤ 0} = {T−τu; τ ≥ 0} is relatively compact in BC(R, X) since {Tτu; τ ≥ 0} +is also one. Therefore the set {Tτu; τ ∈ R} is relatively compact in BC(R, X) as the +union of two relatively compact sets in BC(R, X). +According to Bochner’s criterion, +u ∈ AP(R, X). +□ +The connection between the almost periodicity of a solution of a dynamical system and +its stability is well known (see the monograph by Nemytskii & Stepanov [13, Ch. 5]. This +weakened form of Bochner’s criterion: Theorem 3.1 makes it possible to obtain direct and +simpler proofs on these questions. Let us start by recalling some definitions on dynamical +systems. +A dynamical system or nonlinear semigroup on a complete metric space (X, d) is a one +parameter family (S(t))t≥0 of maps from X into itself such that i) S(t) ∈ C(X, X) for all +t ≥ 0, ii) S(0)x = x for all x ∈ X, iii) S(t + s) = S(t) ◦ S(s) for all s, t ≥ 0 and iv) the +mapping S(·)x ∈ C([0, +∞), X) for all x ∈ X. +For each x ∈ X, the positive trajectory of x is the map S(·)x : R+ → X. A function +u : R → X is called a complete trajectory if we have u(t + τ) = S(τ)u(t), for all t ∈ R +and τ ≥ 0. +We will need a notion of Lagrange-type stability to ensure that a solution with a +relatively compact range is almost periodic. Recall that (S(t))t≥0 is equicontinuous on a +compact set K of X, if forall ε > 0, there exists δ > 0, such that +∀x1, x2 ∈ K, d(x1, x2) ≤ δ =⇒ sup +t≥0 +d(x1, x2) ≤ ε. +Using Theorem 3.1, we give a new proof which is direct and simpler of the following +result which can be found in [10, Theorem 4.3.2, p. 51] or partly in [12, Markov’s theorem, +p. 10]. +Corollary 3.3. Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d) +and u be a complete trajectory such that u(R) is relatively compact. Then u is almost +periodic if and only if (S(t))t≥0 is equicontinuous on cl (u(R)) the closure of u(R). +Proof. Let us denote the compact set K := cl (u(R)). It follows by density of u(R) in +K and the continuity of S(t), that {S(t)x; t ≥ 0} ⊂ K for each x ∈ K. +According + +6 +P. Cieutat +to Arzel`a-Ascoli’s theorem, (S(t))t≥0 is equicontinuous on K if and only if (S(t))t≥0 is +relatively compact in C(K, X). From Theorem 3.1, we have u ∈ AP(R, X) if and only if +{Tτu; τ ≥ 0} is relatively compact in BC(R, X). Then it remains to prove that (S(t))t≥0 +is relatively compact in C(K, X) equipped with the sup-norm if and only if {Tτu; τ ≥ 0} +is relatively compact in (BC(R, X), d∞). This results from the following equalities, for τ1 +and τ2 ≥ 0, sup +t∈R +d (Tτ1u(t), Tτ2u(t)) = sup +t∈R +d (S(τ1)u(t), S(τ2)u(t)) = sup +x∈K +d (S(τ1)x, S(τ2)x) +and Lemma 3.2. +□ +Remark 3.4. a) The condition of equicontinuity required by Corollary 3.3 is satisfied by +a bounded dynamical system : d (S(t)x1, S(t)x2) ≤ Md (x1, x2) for some M ≥ 1 and +in particular for a C0 semigroup of contractions. In this case, the almost periodicity of +a complete trajectory u having a relatively compact range results from Corollary 3.3. +We can also obtain this result with the implication iii) =⇒ i) of Theorem 3.1 and the +inequality sup +t≥0 +d(R(Tτ1u)(t), R(Tτ2u)(t)) = sup +t≥0 +d (S(t)u(τ1), S(t)u(τ2) ≤ Md(u(τ1), u(τ2)) +for τ1, τ2 ∈ R. +b) For a bounded C0-semigroup (S(t))t≥0, the main result of Zaidman [19] asserts +that a positive trajectory u with relatively compact range satisfies a condition called the +generalized normality property in Bochner’s sense, without concluding that u is almost +periodic. This condition is nothing but hypothesis iii) of Theorem 3.1, so u is almost +periodic. +Using Theorem 2.4, we give a new proof which is direct and simpler of the following +result which can be found in [15, Theorem 2.2, p. 149]. +Corollary 3.5. Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d) and +u be a positive trajectory such that u(R+) is relatively compact. Then u is asymptotically +almost periodic if and only if (S(t))t≥0 is equicontinuous on cl (u(R+)). +Proof. The proof is analogous to that of Corollary 3.3, using Corollary 2.4 instead of +Theorem 3.1 and by replacing R by R+ and AP(R, X) by AAP(R+, X). +□ +4. An improvement of Haraux’s criterion +Haraux gave a generalization of Bochner’scriterion [9, Theorem 1], the called a simple +almost-periodicity criterion which is useful for periodic dynamical systems. +From our +main result, Theorem 3.1, we deduce an extension of the Haraux’s criterion, recalled in +Section 2. In the same spirit, we extend the well-known characterization of asymptotically +almost periodic functions. To end this section, we give an exemple of application on a +periodic dynamical system. +We give an extension of the Haraux’s criterion (see Theorem 2.2). Recall that we denote +by R the restriction operator R : BC(R, X) → BC(R+, X) defined by R(u)(t) := u(t) for +t ≥ 0 and u ∈ BC(R, X). +Corollary 4.1. Let (X, d) be a complete metric space. For u ∈ BC(R, X) the following +statements are equivalent. +i) u ∈ AP(R, X). +ii) The set {Tτu; τ ∈ D} is relatively compact in (BC(R, X), d∞) where D be a relatively +dense subset of R+. + +On Bochner’s almost-periodicity criterion +7 +iii) The set {R(Tτu); τ ∈ D} is relatively compact in (BC(R+, X), d∞,+) where D be a +relatively dense subset of R. +Remark 4.2. Our main result, Theorem 3.1 is obviously a particular case of Corollary 4.1. +But to present our results, it was easier to start with Theorem 3.1. To prove Corollary +4.1, we use Haraux’s criterion and Theorem 3.1. +Proof of Corollary 4.1. i) =⇒ iii). It is a consequence of Theorem 3.1. +iii) =⇒ ii). To establish this implication, using Theorem 3.1, it suffices to show that +assertion iii) implies that {R(Tτu); τ ∈ R} is relatively compact in BC(R+, X). The proof +of this last implication is a slight adaptation of those of those of the Haraux’s criterion +given in [9, Theorem 1]. A similar proof will be detailed in the following result as there +will be technical issues. To demonstrate that {R(Tτu); τ ∈ R} is relatively compact, it +suffices in the proof of ii) =⇒ i) of Corollary 4.3 to take ℓ = 0 and replace {T + +τ u; τ ∈ D} +by {R(Tτu); τ ∈ D}. +ii) =⇒ i). For τ1, τ2 ≥ 0, d∞(Tτ1u, Tτ2u) = sup +t∈R +d(u(τ1 + t), u(τ2 + t)). Replacing t by +t − τ1 − τ2 in the upper bound, we get d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u). Then the set +{Tτu; τ ∈ −D} = {T−τu; τ ∈ D} is relatively compact in BC(R, X) since {Tτu; τ ∈ D} +is also one. Therefore the set {Tτu; τ ∈ D ∪ (−D)} is relatively compact in BC(R, X). +Moreover D ∪(−D) is a relatively dense subset of R. According to Haraux’s criterion, we +have u ∈ AP(R, X). +□ +We extend Theorem 2.4, the well-known characterization of asymptotically almost pe- +riodic functions. For τ ∈ R+ and u ∈ BC(R+, X), we define the translation mapping +T + +τ u ∈ BC(R+, X) by T + +τ u(t) = u(t + τ) for t ≥ 0. +Corollary 4.3. Let (X, d) be a complete metric space and let D be a relatively dense +subset of R+. For u ∈ BC(R+, X) the following statements are equivalent. +i) u ∈ AAP(R+, X). +ii) The set {T + +τ u; τ ∈ D} is relatively compact in (BC(R+, X), d∞,+). +Remark 4.4. To establish implication ii) =⇒ i), by using Theorem 2.4, it suffices to prove +that assertion ii) implies that {T + +τ u; τ ≥ 0} is relatively compact in (BC(R+, X), d∞,+). +The proof of this last implication is an adaptation of those of the Haraux’s criterion. But +contrary to the proof of implication iii) =⇒ ii) in Corollary 4.1, there are technical issues. +These technical difficulties come from the fact that when D is a relatively dense subset +in R+, the sets D and [t − ℓ, t] can be disjoint for some 0 ≤ t ≤ ℓ. For this reason we give +the complete proof of this implication. +Proof of Corollary 4.3. i) =⇒ ii). It is a consequence of Theorem 2.4. +ii) =⇒ i). We will prove that assumption ii) implies {T + +τ u; τ ≥ 0} is relatively compact +in BC(R+, X), then we conclude by using Theorem 2.4. The subset D being relatively +dense in R+, there exists ℓ > 0 such that D ∩ [α, α + ℓ] ̸= ∅ for all α ≥ 0. +• We prove that u is uniformly continuous on [ℓ, +∞). Let us fix ε > 0. By assump- +tion the set {T + +τ u; τ ∈ D} is in particular relatively compact in C([0, 2ℓ], X), then it is +uniformly equicontinuous on [0, 2ℓ], that is there exists δ > 0 such that +s1, s2 ∈ [0, 2l], +|s1 − s2| ≤ δ =⇒ sup +τ∈D +d(u(s1 + τ), u(s2 + τ)) ≤ ε. +(4.1) + +8 +P. Cieutat +Let t1, t2 be two real numbers such that t1, t2 ≥ ℓ and |t1 − t2| ≤ δ. We can assume +without loss of generality that ℓ ≤ t1 ≤ t2 ≤ t1 + ℓ. We have D ∩ [t1 − ℓ, t1] ̸= ∅ since +t1 − ℓ ≥ 0, then there exists τ ∈ D such that 0 ≤ t1 − τ ≤ t2 − τ ≤ 2l. Taking account +(4.1), we deduce that d(u(t1), u(t2)) = d(u((t1 − τ) + τ), u((t2 − τ) + τ)) ≤ ε. Hence u is +uniformly continuous on [ℓ, +∞). +• We prove that {T + +τ u; τ ≥ ℓ} is relatively compact in BC(R+, X) . Let (tn)n be a +sequence of real numbers such that tn ≥ ℓ. We have D ∩ [tn − ℓ, tn] ̸= ∅ for each n ∈ N, +since tn − ℓ ≥ 0, then there exist τn ∈ D and σn ∈ [0, l] such that tn = τn + σn. By +compactness of the sequences (σn)n in [0, ℓ] and (T + +τnu)n in BC(R+, X), it follows that +lim +n→+∞ σn = σ and +lim +n→+∞ sup +t≥0 +d(u(t + τn), v(t)) = 0 (up to a subsequence). +From the +following inequality +sup +t≥0 +d(u(tn + t), v(σ + t)) ≤ sup +t≥0 +d(u(τn + σn + t), u(τn + σ + t) + sup +t≥0 +d(u(τn + t), v(t)) +and the uniform continuity of u, we deduce that lim +n→+∞ sup +t≥0 +d(u(tn +t), v(σ +t)) = 0. Then +{T + +τ u; τ ≥ ℓ} is relatively compact in BC(R+, X). +• We prove that u ∈ AAP(R+, X). The function u is uniformly continuous on R+, +since u is continuous on [0, ℓ] and uniformly continuous on [ℓ, +∞). Then the map ˆu : +R+ → BC(R+, X) defined by ˆu(τ) = T + +τ u for τ ≥ 0 is continuous, consequently the +set {T + +τ u; 0 ≤ τ ≤ ℓ} is relatively compact in BC(R+, X). The set {T + +τ u; τ ≥ 0} is +relatively compact in BC(R+, X) as the union of two relatively compact sets. According +to Theorem 2.4, u ∈ AAP(R, X). +□ +Using corollaries 4.1 and 4.3, we give a proof which is direct and simpler of the following +result which can be found in [7, 9, 10]. Before we recall some definitions on process. +A process on a complete metric space (X, d) according to Dafermos [4] is a two pa- +rameter family U(t, τ) of maps from X into itself defined for (t, τ) ∈ R × R+ and such +that i) U(t, 0)x = x for all (t, x) ∈ R × X, ii) U(t, σ + τ) = U(t + σ, τ) ◦ U(t, σ) for all +(t, σ, τ) ∈ R×R+×R+ and iii) the mapping U(t, ·)x ∈ C([0, +∞), X) for all (t, x) ∈ R×X. +For each x ∈ X, the positive trajectory starting of x is the map U(0, ·)x : R+ → X. A +function u : R → X is called a complete trajectory if we have u(t + τ) = U(t, τ)u(t) for +all (t, τ) ∈ R × R+. +A process U is said ω-periodic (ω > 0) if U(t + ω, τ) = U(t, τ) for all (t, τ) ∈ R × R+. +A process U is said bounded if we have for some M ≥ 1 for all (τ, x1, x2) ∈ R+ ×X ×X +d (U(0, τ)x1, U(0, τ)x2) ≤ Md (x1, x2). +Corollary 4.5. [7, 9], [10, Th´eor`eme 6.4.6, p. 84] Let U be a ω-periodic process on a +complete metric space (X, d). If U is bounded, then the following statements hold. +i) If u is a complete trajectory of U such that u(−ωN) is relatively compact, then u is +almost periodic. +ii) If u is a positive trajectory of U such that u(ωN) is relatively compact, then u is +asymptotically almost periodic. +Proof. i) The process U is ω-periodic, then we have u(nω) = U(−mω, (n+m)ω)u(−mω) = +U(0, (n + m)ω)u(−mω) for all n, m ∈ N. From the boundedness assumption on U, we + +On Bochner’s almost-periodicity criterion +9 +deduce that d (u(nω), u(mω)) ≤ Md (u(−mω), u(−nω)), then u(ωN) is relatively compact +since u(−ωN) is also one, therefore u(ωZ) is relatively compact. From assumptions on +the process U, it follows that for all n, m ∈ Z, +sup +τ≥0 +d (u(τ + nω), u(τ + mω)) ≤ Md (u(nω), u(mω)) . +(4.2) +From Lemma 3.2, {R(Tnωu); n ∈ Z} is relatively compact in (BC(R+, X), d∞,+) since +u(ωZ) is also one in (X, d). We conclude with Corollary 4.1 by setting D = ωZ. +ii) For all n, m ∈ N, (4.2) holds on the positive trajectory u, then from Lemma 3.2, +{T + +nωu; n ∈ N} is relatively compact in (BC(R+, X), d∞,+) since u(ωN) is also one in +(X, d). We conclude with Corollary 4.3 by setting D = ωN. +□ +5. Bochner’s criterion in the periodic case +Periodic functions are a special case of almost periodic functions. Haraux gave a charac- +terization of periodic functions in terms of Bochner’s criterion which is recalled in Section +2. +This criterion is a direct consequence of [8, Proposition 2]. +Haraux established a +general result [8, Th´eor`eme 1] implying as a special case a characterization of periodic +functions and the fact that any compact trajectory of a one-parameter continuous group +is automatically periodic. +In this section, we give an extension of this characterization of periodic functions in the +spirit of the main result of this article. We also treat the asymptotically periodic case. +Then we apply these results to study the periodicity of solutions of dynamical systems. +Recall that we denote by R the restriction operator R : BC(R, X) → BC(R+, X) +defined by R(u)(t) := u(t) for t ≥ 0 and u ∈ BC(R, X). +Corollary 5.1. Let (X, d) be a complete metric space. For u ∈ BC(R, X) the following +statements are equivalent. +i) The function u is ω-periodic (ω > 0). +ii) The set {Tτu; τ ≥ 0} is a compact set of (BC(R, X), d∞). +iii) The set {R(Tτu); τ ∈ R} is a compact set of (BC(R+, X), d∞,+). +Proof. i) =⇒ ii). From assumption, it follows that the function τ → Tτu from R into +BC(R, X) is continuous and ω-periodic. Then the {Tτu; τ ≥ 0} = {Tτu; 0 ≤ τ ≤ ω} is a +compact set of (BC(R, X), d∞) as the range of a compact set by a continuous map. +ii) =⇒ i). +For τ1, τ2 ∈ R, d∞(Tτ1u, Tτ2u) := sup +t∈R +d(u(τ1 + t), u(τ2 + t)), we get +d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u). +Then the set {Tτu; τ ≤ 0} = {T−τu; τ ≥ 0} is +compact in BC(R, X) since {Tτu; τ ≥ 0} is also one. Therefore the set {Tτu; τ ∈ R} is a +compact set of BC(R, X) as the union of two compact sets in BC(R, X). According to +Theorem 2.3, u is periodic. +i) =⇒ iii). It is obvious by using Theorem 2.3 and the continuity of the restriction +operator R. +iii) =⇒ i). By using Theorem 2.3, we have to prove that K := {Tτu; τ ∈ R} is a +compact set of (BC(R, X), d∞). As consequence of Theorem 3.1 and Bohner’s criterion, +the set K is relatively compact in (BC(R, X), d∞) and the function u is almost periodic. + +10 +P. Cieutat +It remains to prove that K is closed in (BC(R, X), d∞). Let (τn)n be a sequence of real +numbers such that +lim +n→+∞ d∞(Tτnu, v) = 0. Let us prove that v = Tτu for some τ ∈ R. By +continuity of the operator R, we have lim +n→+∞ d∞,+(R(Tτnu), R(v)) = 0. By assumption, the +set {R(Tτu); τ ∈ R} is in particular closed in (BC(R+, X), d∞,+), then R(v) = R(Tτu) +for some τ ∈ R, that is +∀t ≥ 0, +v(t) = Tτu(t). +(5.1) +We have to prove that (5.1) holds on the whole real line. The function Tτu is almost +periodic as translation of an almost periodic function and v is also one as uniform limit +on R of almost periodic functions. Let us denote by φ : R → R the function defined by +φ(t) := d(Tτu(t), v(t)). The function φ is almost periodic [12, Property 4, p. 3 & 7, p.6]. +An almost periodic function is uniformly recurrent, then there exists a sequence of real +numbers such that +lim +n→+∞ τn = +∞ and +lim +n→+∞ φ(t+ τn) = φ(t) for all t ∈ R. From (5.1), it +follows φ(t) = 0 for all t ≥ 0, so we deduce that φ(t) = +lim +n→+∞ φ(t + τn) = 0 for all t ∈ R. +Then v(t) = Tτu(t) for all t ∈ R. This ends the proof. +□ +According Theorem 2.4, if the set {T + +τ u; τ ≥ 0} is relatively compact in BC(R+, X), +then the function u is asymptotically almost periodic. We now give an answer to the +question what can be said about the function u when {T + +τ u; τ ≥ 0} is a compact set of +BC(R+, X). For u ∈ BC(R+, X), we say that u is ω-periodic (ω > 0) on [t0, +∞) for +some t0 ≥ 0 if u(t + ω) = u(t) for all t ≥ t0. +Corollary 5.2. Let (X, d) be a complete metric space. For u ∈ BC(R+, X) the following +statements are equivalent. +i) There exists t0 ≥ 0 such that u is ω-periodic on [t0, +∞). +ii) The set {T + +τ u; τ ≥ 0} is a compact set of (BC(R+, X), d∞,+). +Remark 5.3. Let u be a function which satisfies condition i) of Corollary 5.2. +i) Let us denote by v ∈ C(R, X) the ω-periodic function satisfying u(t) = v(t) for +t ≥ t0. A such function v exists and is unique, v is defined by v(t) = u(t − [ t−t0 +ω ]ω) where +[ t−t0 +ω ] denotes the integer part of t−t0 +ω . +ii) The function u is a special case of asymptotic almost periodic function where the +almost periodic function v is periodic and d(u(t), v(t)) = 0 for t ≥ t0. +Proof of Corollary 5.2. i) =⇒ ii). Let us denote by v the function defined in Remark 5.3. +By Corollary 5.1 and the periodicity of v, we have {R(Tτv); τ ≥ t0} = {R(Tτv); τ ∈ R} is +a compact set of (BC(R+, X), d∞,+). +First, we have T + +τ u = R(Tτv) for τ ≥ t0, then {T + +τ u; τ ≥ t0} is a compact set. +Second, the function u is uniformly continuous on R+, then the function from R+ to +BC(R+, X) defined by τ → T + +τ u is continuous. +Then the set {T + +τ u; 0 ≤ τ ≤ t0} is +compact. +Therefore the set {T + +τ u; τ ≥ 0} is a compact set of BC(R+, X) as the union of two +compact set. +ii) =⇒ i). As consequence of Theorem 2.4, the function u is asymptotically almost +periodic, that is lim +t→∞ d(u(t), v(t)) = 0 for some v ∈ AP(R, X). +An almost periodic + +On Bochner’s almost-periodicity criterion +11 +function is uniformly recurrent, then there exists a sequence of real numbers (tn)n such +that +lim +n→+∞ tn = +∞ and +lim +n→+∞ v(t + tn) = v(t) for all t ∈ R. We deduce that +∀t ∈ R, +lim +n→+∞ u(t + tn) = v(t). +(5.2) +First we prove that v is periodic. For t ∈ R, τ1, τ2 ≥ 0, we have for n enough large +d(u(t + tn + τ1), u(t + tn + τ2)) ≤ sup +s≥0 +d(u(s + τ1), u(s + τ2)). From (5.2), it follows that +sup +t∈R +d(v(t+τ1), v(t+τ2)) ≤ sup +s≥0 +d(u(s+τ1), u(s+τ2)) for each τ1 and τ2 ≥ 0. According to +Lemma 3.2, {Tτv ; τ ≥ 0} is a compact set of (BC(R, X), d∞) since {T + +τ u ; τ ≥ 0} is also +one in (BC(R+, X), d∞,+). As consequence of Corollary 5.1, the function v is periodic. +Second we prove that: ∃t0 ≥ 0 such that ∀t ≥ 0, v(t) = u(t + t0). By compactness of +{T + +τ u; τ ≥ 0}, there exists a subsequence (T + +tφ(n)u)n such that lim +n→+∞ d∞,+(T + +tφ(n)u, T + +t0 u) = 0 +for some t0 ≥ 0. From (5.2) we deduce that R(v) = T + +t0 u, that is v(t) = u(t + t0) for all +t ≥ 0. +Then u(t) = v(t − t0) for each t ≥ t0 where the function v(· − t0) is periodic on R. +□ +Now we give an example of application on dynamical systems of Corollary of 5.1 and +Corollary of 5.2. For the definition of a dynamical system, see above Corollary 3.3 in +Section 3. +Corollary 5.4. Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d). +i) If u is a positive trajectory, then u is periodic on [t0, +∞) for some t0 ≥ 0 if and +only if u(R+) is a compact set and (S(t))t≥0 is equicontinuous on u(R+). +ii) If u is a complete trajectory, then u is periodic if and only if u(R) is a compact set +and (S(t))t≥0 is equicontinuous on u(R). +iii) There exists a complete trajectory which is periodic if and only if there exists a +positive trajectory u such that u(R+) is a compact set and (S(t))t≥0 is equicontinuous on +u(R+). +Remark 5.5. Thus under the assumption of equicontinuity, a complete trajectory of a +dynamical system with a compact range is necessarily periodic, although there are almost +periodic functions with a compact range, which are not periodic. An example of such +function is given by Haraux in [8]. +Proof of Corollary 5.4. i) Remark that if u is a positive trajectory which is periodic on +[t0, +∞) for some t0 ≥ 0, then first u(R+) is compact and second u ∈ AAP(R+, X) +(see Remark 5.3). As consequence of Corollary 3.5, the set (S(t))t≥0 is equicontinuous on +u(R+). Reciprocally assume the positive trajectory u is such that (S(t))t≥0 is equicontinu- +ous on the compact set u(R+). It remains to prove that the positive trajectory u is periodic +on [t0, +∞) for some t0 ≥ 0. For each x ∈ u(R+), the map S(·)x is continuous and satisfies +S(t)x ∈ u(R+) for each t ≥ 0. Then the map S(·)x is bounded and continuous , so the map +Φ : u(R+) → BC(R+, X) with Φ(x) = S(·)x is well-defined. The continuity of Φ results +of the equicontinuity of (S(t))t≥0 on u(R+). Then the set Φ(u(R+)) = {Φ(u(τ)) ; τ ≥ 0} +is a compact of BC(R+, X). Moreover Φ(u(τ))(t) = S(t)u(τ) = u(t + τ) for t and τ ≥ 0, + +12 +P. Cieutat +then Φ(u(τ)) = T + +τ u, so {T + +τ u ; τ ≥ 0} is a compact set of BC(R+, X). According to +Corollary 5.2, the function u is periodic on [t0, +∞) for some t0 ≥ 0. +ii) The proof of ii) is similar to that of i) by using Corollary 3.3 instead of 3.5, Corollary +5.1 instead of Corollary 5.2 and by replacing the map Φ : u(R+) → BC(R+, X) with +Φ(x) = S(·)x by the map Φ : u(R) → BC(R+, X). This permits to prove that the set +{Φ(u(τ)) = R(Tτu); τ ∈ R} is a compact set of (BC(R+, X), d∞,+). +iii) If v is a complete trajectory which is periodic, then v(R) is compact and according +to ii), (S(t))t≥0 is equicontinuous on v(R). So the restriction u of v on R+ is a posi- +tive trajectory such that u(R+) = v(R+) = v(R) since v is periodic, then (S(t))t≥0 is +equicontinuous on the compact set u(R+). Reciprocally, assume that u is a positive tra- +jectory such that (S(t))t≥0 is equicontinuous on the compact set u(R+). According to +i), u is ω-periodic on [t0, +∞) for some t0 ≥ 0. Let us denote by v the function defined +in Remark 5.3. For t ≥ s, there exists n0 ∈ N such that s + n0ω ≥ t0. The function +v is ω-periodic and u is a positive trajectory satisfying u(τ) = v(τ) for τ ≥ t0, then +v(t) = v(t + n0ω) = u(t + n0ω) = T(t − s)u(s + n0ω) = T(t − s)v(s + n0ω) = T(t − s)v(s) +for t ∈ R and n enough large. Then v is a periodic complete trajectory. +□ +Remark 5.6. Under i) of Corollary 5.4, one can have t0 > 0, that is the positive trajectory +u is not the restriction of a periodic complete trajectory. +For example, consider the +bounded dynamical system (S(t))t≥0 on L1(0, 1) defined by +(S(t)x)(s) = + + + +x(s − t) +if +t < s < 1 +0 +if +0 < s < t +for x ∈ L1(0, 1) and 0 < t < 1. For t ≥ 1, we set S(t) = 0. Then all positive trajectories +have a compact range and the alone complete trajectory is the null function. Thus all +positive trajectories are not the restriction of a periodic complete trajectory except the +null function. +Not all dynamical systems have this pathology, some systems are such that if two +positive trajectories have the same value at the same time, then they are equal. If we +consider such systems, we get more refined results from Corollary 5.4. +A dynamical system (S(t))t≥0 has the backward uniqueness property if any two positive +trajectories having the same value at t = t0 ≥ 0 coincide for any other t ≥ 0. This +property is equivalent to S(t) ∈ C(X, X) is injective for each t ≥ 0. We say that a +positive trajectory u is extendable to a periodic complete trajectory, if there exists a periodic +complete trajectory such that its restriction on R+ is u. +Corollary 5.7. Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d). +Assume that (S(t))t≥0 has the backward uniqueness property. +i) If u is a positive trajectory, then u is periodic on R+ if and only if u(R+) is a +compact set and (S(t))t≥0 is equicontinuous on u(R+). In this case the positive trajectory +u is extendable to a periodic complete trajectory v. +ii) If v is a complete trajectory, then v is periodic if and only if v(R+) is a compact set +and (S(t))t≥0 is equicontinuous on v(R+). + +On Bochner’s almost-periodicity criterion +13 +Proof. i) The direct implication results of i) of Corollary 5.4. For the reciprocal implica- +tion we use i) of Corollary 5.4. Then the positive trajectory u is ω-periodic on [t0, +∞) for +some t0 ≥ 0. Let us denote by v ∈ C(R, X) the ω-periodic function satisfying u(t) = v(t) +for t ≥ t0 (see Remark 5.3). The restriction of v on R+ and u are two positive trajectories +having the same value at t = t0 (t0 ≥ 0). From the backward uniqueness property, we +have u(t) = v(t) for t ≥ 0, then u is periodic on R+. By build, v is periodic and as in the +proof of iii) of Corollary 5.4, we deduce that v is a complete trajectory. +ii) The direct implication results of ii) Corollary 5.4, since v(R+) = v(R). For the +reciprocal implication, we consider v a complete trajectory such that v(R+) is a compact +set and (S(t))t≥0 is equicontinuous on v(R+). Then the restriction u of the complete +trajectory v on R+ is a positive trajectory such that u(R+) is compact and (S(t))t≥0 +is equicontinuous on u(R+). According to i), u is ω-periodic on R+. Let us denote by +w ∈ C(R, X) the ω-periodic function satisfying u(t) = w(t) for t ≥ 0. As in proof of iii) +Corollary 5.4, we deduce that w is a complete trajectory. Fix T > 0. The two maps ˜v +and ˜w : R+ → X defined by ˜v = v(·, −T) and ˜w = w(·, −T) are two positive trajectories +having the same value at t = T. From the backward uniqueness property, we have ˜v = ˜w, +that is v(t) = w(t) for t ≥ −T. Since T is arbitrary, then v(t) = w(t) for each t ∈ R +where w is a periodic complete trajectory. +This proves that v is a periodic complete +trajectory. +□ +References +[1] L. Amerio, G. Prouse, Almost periodic functions and functional equations, Van Nostrand Reinhold +Comp., New York, 1971. +[2] S. Bochner, A new approach to almost periodicity, Proc. Natl. Acad. Sci. USA 48 (1962) 2039-2043. +[3] S. Bochner, Continuous mappings of almost automorphic and almost periodic functions, Proc. Natl. +Acad. Sci. USA 52 (1964) 907-910. +[4] C. M. Dafermos, Almost periodic processes and almost periodic solutions of evolution equations. Dy- +namical systems (Proc. Internat. Sympos., Univ. Florida, Gainesville, Fla., 1976), pp. 43-57. Academic +Press, New York, 1977. +[5] A. M. Fink, Almost periodic differential equations, Lecture Notes in Math., vol. 377, Springer-Verlag, +Berlin-New York, 1974. +[6] M. Fr´echet, Les fonctions asymptotiquement presque-p´eriodiques continues, C.R. Math. Acad. Sci. +Paris 213 (1941), pp. 520-522 (in French). +[7] A. Haraux, Asymptotic behavior of trajectories for some nonautonomous, almost periodic processes, +J. Differential Equations 49 (1983), 473-483. +[8] A. Haraux, Sur les trajectoires compactes de syst`emes dynamiques autonomes. [On the compact tra- +jectories of autonomous dynamical systems], Portugal. Math. 44 (1987), 253-259 (in French). +[9] A. Haraux, A simple almost-periodicity criterion and applications, J. Differential Equations 66 (1987), +51-61. +[10] A. Haraux, Syst`emes dynamiques dissipatifs et applications. [Dissipative dynamical systems and ap- +plications], Recherches en Math´ematiques Appliqu´ees [Research in Applied Mathematics], 17, Masson, +Paris, 1991 (in French). +[11] S. Lang Real and functional analysis, Third edition, Springer-Verlag, New York, 1993. +[12] B. M. Levitan, V. V. Zhikov, Almost periodic functions and differential equations,Translated from +the Russian by L. W. Longdon. Cambridge University Press, Cambridge-New York, 1982. +[13] V. Nemytskii and V. Stepanov, Qualitative theory of differential equations, Princeton University +Press, Princeton, New Jersey, 1960. +[14] W. M. Ruess, W. H. Summers, Asymptotic almost periodicity and motions of semigroups of operators, +Proceedings of the symposium on operator theory (Athens, 1985). Linear Algebra Appl. 84 (1986), +335-351. + +14 +P. Cieutat +[15] W. M. Ruess, W. H. Summers, Minimal sets of almost periodic motions Math. Ann. 276 (1986), +145-158. +[16] W. M. Ruess, W. H. Summers, Compactness in spaces of vector valued continuous functions and +asymptotic almost periodicity, Math. Nachr. 135 (1988), 7-33. +[17] T. Yoshizawa, Stability theory and the existence of periodic solutions and almost periodic solutions, +Springer, New-york, 1975. +[18] S. Zaidman, Almost-periodic functions in abstract spaces, Research Notes in Mathematics, 126, +Boston, 1985. +[19] S. Zaidman, On relatively compact trajectories of semigroups of class C0, Applicable Anal. 21 (1986), +9-12. + diff --git a/0dAyT4oBgHgl3EQfbfdc/content/tmp_files/load_file.txt b/0dAyT4oBgHgl3EQfbfdc/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..f420d7af444b11ae615c6a98c8877b240ed4c2bf --- /dev/null +++ b/0dAyT4oBgHgl3EQfbfdc/content/tmp_files/load_file.txt @@ -0,0 +1,694 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf,len=693 +page_content='arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='00263v1 [math.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='CA] 31 Dec 2022 ON BOCHNER’S ALMOST-PERIODICITY CRITERION PHILIPPE CIEUTAT Abstract.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We give an extension of Bochner’s criterion for the almost periodic func- tions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By using our main result, we extend two results of A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Haraux.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The first is a generalization of Bochner’s criterion which is useful for periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The second is a characterization of periodic functions in term of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 2020 Mathematic Subject Classification: 35B10, 35B40, 42A75, 47H20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Keywords: Bochner almost periodicity, periodic function, almost periodic function, asymptotically almost periodic function, nonlinear semigroup, periodic dynamical sys- tem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Introduction The almost periodic functions in the sense of Bohr have been characterized by Bochner by means of a compactness criterion in the space of the bounded and continuous functions [2, 3].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The Bochner’s criterion plays an essential role in the theory and in applications.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We give a new almost-periodicity criterion for functions with values in a given complete metric space which is useful to study the almost periodicity of solutions of dynamical systems governed by a family of operators with a positive parameter.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This criterion is an extension of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then Haraux gave a generalization of Bochner’s criterion [9, Theorem 1], called a simple almost-periodicity criterion which is useful for periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From our result, we deduce an extension of this criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We also obtain an extension of an other result of Haraux which characterizes the periodic functions in terms of the Bochner’s criterion [8].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In the same spirit, we treat the asymptotically almost periodic case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We give a description of this article, the precise definitions will be given in Section 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Throughout this section (X, d) is a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An almost periodic function u : R → X in the sense of Bohr is characterized by the Bochner’s criterion which is the following: u is bounded and continuous, and from any real sequence of real numbers (τn)n, there exists a subsequence (τφ(n))n such that the sequence of functions (u(t + τφ(n)))n is uniformly convergent on R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In Section 3, we give two extensions of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' First u : R → X is an almost periodic if and if only if in the Bochner’s criterion, we impose that the terms of the sequence of real numbers (τn)n are all positive.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Second u : R → X is an almost periodic if and if only if in the Bochner’s criterion, the convergence of the subsequence of functions (u(t + τφ(n)))n is uniform only on [0, +∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' These improvements are useful to study the almost periodicity of solutions of an evolution equation governed by a family of operators with a positive parameter, in particular for a C0-semigroup of linear operators or more generally, for an autonomous dynamical system (nonlinear semigroup).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Universit´e Paris-Saclay, UVSQ, CNRS, Laboratoire de math´ematiques de Versailles, 78000, Versailles, France.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' E-mail address: philippe.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='cieutat@uvsq.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='fr 1 2 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat From our extension of Bochner’s criterion, we give new proofs which are direct and simpler on known results on the almost periodicity of solutions of autonomous dynamic systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Haraux gave a generalization of Bochner’s criterion the called a simple almost-periodicity criterion [9, Theorem 1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This criterion makes it possible to choose in the Bochner’s cri- terion, the sequence of real numbers (τn)n in a set of the type ωZ which is very useful for periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From our extension of Bochner’s criterion, in Section 4, we deduce an improvement of this result.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An asymptotically almost periodic function u : R+ → X is a perturbation of almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A such function is characterized by a property of the type of the Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In the same spirit, we extend this char- acterization of asymptotically almost periodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then we apply these results to study the almost periodicity of solutions of periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Bochner’s criterion can also be expressed in terms of the relative compactness of the set {u(· + τ);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} in a suitable set of continuous functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A periodic function is a special case of almost periodic function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A direct consequence of [8, Proposition 2] given by Haraux characterizes a periodic function in terms of the Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This characterization is the following: u : R → X is continuous is periodic if and if only if the set {u(· + τ);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In Section 5, By using our improvement of Bochner’s criterion, we give an extension of the Haraux’s characterization of periodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We will also give a result on asymptotically periodic functions of the type of Haraux result described above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then we apply these results to study the periodicity of solutions of autonomous dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Notation Let us now give some notations, definitions and properties which will be used.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Throughout this section (X, d) is a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' R, Z and N stand re- spectively for the real numbers, the integers and the natural integers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We denote by R+ := {t ∈ R;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' t ≥ 0}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let E be a topological space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We denote by C(E, X) the space of all continuous functions from E into X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' When J = R or J = R+, we de- note by BC(J, X) the space of all bounded and continuous functions from J into X equipped with the sup-distance, denoted by d∞(u, v) := sup t∈R d(u(t), v(t)) when J = R and d∞,+(u, v) := sup t≥0 d(u(t), v(t))) when J = R+ for u, v ∈ BC(J, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The metric spaces (BC(R, X), d∞) and (BC(R+, X), d∞,+)) are complete.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We now give some definitions and properties on almost periodic, asymptotically almost periodic functions with values in a given complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A subset D of R (respectively of R+) is said to be relatively dense if there exists ℓ > 0 such that D ∩ [α, α + ℓ] ̸= ∅ for all α ∈ R (respectively α ≥ 0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A continuous function u : R → X is said to be almost periodic (in the sense of Bohr) if for each ε > 0, the set of ε-almost periods: P(u, ε) = � τ ∈ R ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' sup t∈R d(u(t + τ), u(t)) ≤ ε � is relatively dense in R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An almost periodic function u has its range u(R) relatively compact, that is its closure denoted by cl (u(R)) is a compact set of (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We denote the space of all such functions by AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is a closed metric subspace of (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An almost periodic function u is uniformly recurrent, that is there exists a sequence of real On Bochner’s almost-periodicity criterion 3 numbers (τn)n such that lim n→+∞ sup t∈R d(u(t + τn), u(t)) = 0 and lim n→+∞ τn = +∞.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To see that consider the Bohr’s definition of u ∈ AP(R, X), then the set of 1 n-almost periods satisfies P(u, 1 n)∩[n, +∞) ̸= ∅, for each integer n > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A useful characterization of almost periodic functions was given by Bochner.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The Bochner’s criterion which may be found in [12, Bochner’s theorem, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 4] in the context of metric spaces.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Before to cite this criterion, we need to introduce the translation mapping of a function of BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ ∈ R and u ∈ BC(R, X), we define the translation mapping Tτu ∈ BC(R, X) by Tτu(t) = u(t + τ) for t ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 (Bochner’s criterion).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R, X), the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact in (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Haraux gave a generalization of Bochner’ criterion the called a simple almost-periodicity criterion [9, Theorem 1] which is useful for periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2 (Haraux’s criterion).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let D be a relatively dense subset of R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The following statements are equivalent for u ∈ BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is relatively compact in (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Periodic functions, which are a special case of almost periodic functions, are also char- acterized in terms of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This criterion is a direct consequence of a result of Haraux.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' [8, Consequence of Proposition 2] The following statements are equivalent for u ∈ BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u is periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For some preliminary results on almost periodic functions with values in a given com- plete metric space, we refer to the book of Levitan-Zhikov [12] and in the special case of Banach spaces to the book of Amerio-Prouse [1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The notion of asymptotic almost periodicity was first introduced by Fr´echet [6] in 1941 in the case where X = C.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A continuous function u : R+ → X is said to be asymp- totically almost periodic if there exists v ∈ AP(R, X) such that lim t→∞ d(u(t), v(t)) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An asymptotic almost periodic function u has its range u(R+) relatively compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We denote the space of all such functions by AAP(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is a closed metric subspace of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An asymptotic almost periodicity function u : R+ → X is char- acterized by u ∈ APP(R+, X) if and only if u ∈ C(R+, X) and for each ε > 0, there exists M ≥ 0 such that the � τ ≥ 0 ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' sup t≥M d(u(t + τ), u(t)) ≤ ε � is relatively dense in R+ [15, Theorems 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In the context of metric spaces, Ruess and Summers give a charac- terization of asymptotically almost periodic functions in the spirit of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 4 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat To prove this characterization, Ruess and Summers use results from the paper [16] by the same authors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ ≥ 0 and u ∈ BC(R+, X), we define the translation mapping T + τ u ∈ BC(R+, X) by T + τ u(t) = u(t + τ) for t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' [15, a part of Theorems 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2 & 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3] Let (X, d) be a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R+, X), the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AAP(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For some preliminary results on asymptotically almost periodic functions, we refer to the book of Yoshizawa [17] in the case where X is a finite dimensional space, to the book of Zaidman [18] where X is a Babach space and to Ruess and Summers [14, 15, 16] in the general case: X is a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An improvement of Bochner’s criterion An almost periodic function is characterized by the Bochner’s criterion, recalled in Sec- tion 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Our main result is an extension of Bochner’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then we deduce new proofs which are direct and simpler on known results on the solutions of autonomous dynamic systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Before to state our extension of Bochner’s criterion, we need to introduce the restriction operator R : BC(R, X) → BC(R+, X) defined by R(u)(t) := u(t) for t ≥ 0 and u ∈ BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (X, d) be a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R, X) the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) The set {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact in (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In our results, the compactness and the relative compactness of a set often intervene.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To prove them, we will often use the following result whose proof is obvious.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Recall that a set A of a metric space (E, d) is relatively compact if its closure denoted by cl (A) is a compact set of (E, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let E be a set, (G1, d1) and (G2, d2) be two metric spaces.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let u : E → G1 and v : E → G2 be two functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Assume there exists M > 0 such that ∀x1, x2 ∈ E, d1(u(x1), u(x2)) ≤ Md2(v(x1), v(x2)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the following statements hold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) If the metric space (G1, d1) is complete and v(E) is relatively compact in (G2, d2), then u(E) is relatively compact in (G1, d1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) If v(E) is a compact set of (G2, d2), then u(E) is a compact set of (G1, d1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ iii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is obvious by using the Bochner’s criterion and the continuity of the restriction operator R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) =⇒ ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The set u(R) = {R(Tτu)(0);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact in X as the range of {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} by the continuous evaluation map at 0 from BC(R+, X) into X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By assumption, H := cl ({R(Ttu) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' t ∈ R}) is a compact set of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' On Bochner’s almost-periodicity criterion 5 For all τ ≥ 0, we define φτ : H → X by φτ(h) = h(τ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The functions φτ are 1-Lipschitz continuous and for each t ∈ R, the set {φτ(R(Ttu)) = u(τ + t) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is included in the relatively compact set u(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By density of {R(Ttu) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' t ∈ R} in H and the continuity of φτ, it follows that {φτ(h) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in X for each h ∈ H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Arzel`a-Ascoli’s theorem [11, Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 57], the set {φτ ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in C(H, X) equipped with the sup-norm denoted by dC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From the density of {R(Ttu) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' t ∈ R} in H and the continuity of φτ, we deduce that for τ1 and τ2 ≥ 0, sup h∈H d(φτ1(h), φτ2(h)) = sup t∈R d (φτ1(R(Ttu)), φτ2(R(Ttu))) = sup t∈R d (u(τ1 + t), u(τ2 + t)) = sup t∈R d (Tτ1u(t), Tτ2u(t)), then dC(φτ1, φτ2) = d∞ (Tτ1u, Tτ2u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, it follows that {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in the complete metric space (BC(R, X), d∞) since {φτ ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is also one in (C(H, X), dC).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ1, τ2 ≥ 0, d∞(Tτ1u, Tτ2u) := sup t∈R d(u(τ1 + t), u(τ2 + t)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Replacing t by t − τ1 − τ2 in the upper bound, we get d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≤ 0} = {T−τu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in BC(R, X) since {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is also one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Therefore the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact in BC(R, X) as the union of two relatively compact sets in BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Bochner’s criterion, u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ The connection between the almost periodicity of a solution of a dynamical system and its stability is well known (see the monograph by Nemytskii & Stepanov [13, Ch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 5].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This weakened form of Bochner’s criterion: Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 makes it possible to obtain direct and simpler proofs on these questions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us start by recalling some definitions on dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A dynamical system or nonlinear semigroup on a complete metric space (X, d) is a one parameter family (S(t))t≥0 of maps from X into itself such that i) S(t) ∈ C(X, X) for all t ≥ 0, ii) S(0)x = x for all x ∈ X, iii) S(t + s) = S(t) ◦ S(s) for all s, t ≥ 0 and iv) the mapping S(·)x ∈ C([0, +∞), X) for all x ∈ X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For each x ∈ X, the positive trajectory of x is the map S(·)x : R+ → X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A function u : R → X is called a complete trajectory if we have u(t + τ) = S(τ)u(t), for all t ∈ R and τ ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We will need a notion of Lagrange-type stability to ensure that a solution with a relatively compact range is almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Recall that (S(t))t≥0 is equicontinuous on a compact set K of X, if forall ε > 0, there exists δ > 0, such that ∀x1, x2 ∈ K, d(x1, x2) ≤ δ =⇒ sup t≥0 d(x1, x2) ≤ ε.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Using Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, we give a new proof which is direct and simpler of the following result which can be found in [10, Theorem 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 51] or partly in [12, Markov’s theorem, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d) and u be a complete trajectory such that u(R) is relatively compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then u is almost periodic if and only if (S(t))t≥0 is equicontinuous on cl (u(R)) the closure of u(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote the compact set K := cl (u(R)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It follows by density of u(R) in K and the continuity of S(t), that {S(t)x;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' t ≥ 0} ⊂ K for each x ∈ K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According 6 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat to Arzel`a-Ascoli’s theorem, (S(t))t≥0 is equicontinuous on K if and only if (S(t))t≥0 is relatively compact in C(K, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, we have u ∈ AP(R, X) if and only if {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then it remains to prove that (S(t))t≥0 is relatively compact in C(K, X) equipped with the sup-norm if and only if {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This results from the following equalities, for τ1 and τ2 ≥ 0, sup t∈R d (Tτ1u(t), Tτ2u(t)) = sup t∈R d (S(τ1)u(t), S(τ2)u(t)) = sup x∈K d (S(τ1)x, S(τ2)x) and Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ Remark 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' a) The condition of equicontinuity required by Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 is satisfied by a bounded dynamical system : d (S(t)x1, S(t)x2) ≤ Md (x1, x2) for some M ≥ 1 and in particular for a C0 semigroup of contractions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In this case, the almost periodicity of a complete trajectory u having a relatively compact range results from Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We can also obtain this result with the implication iii) =⇒ i) of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and the inequality sup t≥0 d(R(Tτ1u)(t), R(Tτ2u)(t)) = sup t≥0 d (S(t)u(τ1), S(t)u(τ2) ≤ Md(u(τ1), u(τ2)) for τ1, τ2 ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' b) For a bounded C0-semigroup (S(t))t≥0, the main result of Zaidman [19] asserts that a positive trajectory u with relatively compact range satisfies a condition called the generalized normality property in Bochner’s sense, without concluding that u is almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This condition is nothing but hypothesis iii) of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, so u is almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Using Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, we give a new proof which is direct and simpler of the following result which can be found in [15, Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 149].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d) and u be a positive trajectory such that u(R+) is relatively compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then u is asymptotically almost periodic if and only if (S(t))t≥0 is equicontinuous on cl (u(R+)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The proof is analogous to that of Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3, using Corollary 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4 instead of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and by replacing R by R+ and AP(R, X) by AAP(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An improvement of Haraux’s criterion Haraux gave a generalization of Bochner’scriterion [9, Theorem 1], the called a simple almost-periodicity criterion which is useful for periodic dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From our main result, Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, we deduce an extension of the Haraux’s criterion, recalled in Section 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In the same spirit, we extend the well-known characterization of asymptotically almost periodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To end this section, we give an exemple of application on a periodic dynamical system.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We give an extension of the Haraux’s criterion (see Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Recall that we denote by R the restriction operator R : BC(R, X) → BC(R+, X) defined by R(u)(t) := u(t) for t ≥ 0 and u ∈ BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (X, d) be a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R, X) the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is relatively compact in (BC(R, X), d∞) where D be a relatively dense subset of R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' On Bochner’s almost-periodicity criterion 7 iii) The set {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is relatively compact in (BC(R+, X), d∞,+) where D be a relatively dense subset of R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Remark 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Our main result, Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 is obviously a particular case of Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' But to present our results, it was easier to start with Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To prove Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, we use Haraux’s criterion and Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof of Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ iii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is a consequence of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) =⇒ ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To establish this implication, using Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, it suffices to show that assertion iii) implies that {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact in BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The proof of this last implication is a slight adaptation of those of those of the Haraux’s criterion given in [9, Theorem 1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A similar proof will be detailed in the following result as there will be technical issues.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To demonstrate that {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is relatively compact, it suffices in the proof of ii) =⇒ i) of Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 to take ℓ = 0 and replace {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} by {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ1, τ2 ≥ 0, d∞(Tτ1u, Tτ2u) = sup t∈R d(u(τ1 + t), u(τ2 + t)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Replacing t by t − τ1 − τ2 in the upper bound, we get d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ −D} = {T−τu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is relatively compact in BC(R, X) since {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is also one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Therefore the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D ∪ (−D)} is relatively compact in BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Moreover D ∪(−D) is a relatively dense subset of R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Haraux’s criterion, we have u ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ We extend Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, the well-known characterization of asymptotically almost pe- riodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ ∈ R+ and u ∈ BC(R+, X), we define the translation mapping T + τ u ∈ BC(R+, X) by T + τ u(t) = u(t + τ) for t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (X, d) be a complete metric space and let D be a relatively dense subset of R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R+, X) the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) u ∈ AAP(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is relatively compact in (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Remark 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' To establish implication ii) =⇒ i), by using Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, it suffices to prove that assertion ii) implies that {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The proof of this last implication is an adaptation of those of the Haraux’s criterion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' But contrary to the proof of implication iii) =⇒ ii) in Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, there are technical issues.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' These technical difficulties come from the fact that when D is a relatively dense subset in R+, the sets D and [t − ℓ, t] can be disjoint for some 0 ≤ t ≤ ℓ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For this reason we give the complete proof of this implication.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof of Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is a consequence of Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We will prove that assumption ii) implies {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in BC(R+, X), then we conclude by using Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The subset D being relatively dense in R+, there exists ℓ > 0 such that D ∩ [α, α + ℓ] ̸= ∅ for all α ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We prove that u is uniformly continuous on [ℓ, +∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us fix ε > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By assump- tion the set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ D} is in particular relatively compact in C([0, 2ℓ], X), then it is uniformly equicontinuous on [0, 2ℓ], that is there exists δ > 0 such that s1, s2 ∈ [0, 2l], |s1 − s2| ≤ δ =⇒ sup τ∈D d(u(s1 + τ), u(s2 + τ)) ≤ ε.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' (4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1) 8 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat Let t1, t2 be two real numbers such that t1, t2 ≥ ℓ and |t1 − t2| ≤ δ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We can assume without loss of generality that ℓ ≤ t1 ≤ t2 ≤ t1 + ℓ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We have D ∩ [t1 − ℓ, t1] ̸= ∅ since t1 − ℓ ≥ 0, then there exists τ ∈ D such that 0 ≤ t1 − τ ≤ t2 − τ ≤ 2l.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Taking account (4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1), we deduce that d(u(t1), u(t2)) = d(u((t1 − τ) + τ), u((t2 − τ) + τ)) ≤ ε.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Hence u is uniformly continuous on [ℓ, +∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We prove that {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ ℓ} is relatively compact in BC(R+, X) .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (tn)n be a sequence of real numbers such that tn ≥ ℓ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We have D ∩ [tn − ℓ, tn] ̸= ∅ for each n ∈ N, since tn − ℓ ≥ 0, then there exist τn ∈ D and σn ∈ [0, l] such that tn = τn + σn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By compactness of the sequences (σn)n in [0, ℓ] and (T + τnu)n in BC(R+, X), it follows that lim n→+∞ σn = σ and lim n→+∞ sup t≥0 d(u(t + τn), v(t)) = 0 (up to a subsequence).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From the following inequality sup t≥0 d(u(tn + t), v(σ + t)) ≤ sup t≥0 d(u(τn + σn + t), u(τn + σ + t) + sup t≥0 d(u(τn + t), v(t)) and the uniform continuity of u, we deduce that lim n→+∞ sup t≥0 d(u(tn +t), v(σ +t)) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ ℓ} is relatively compact in BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We prove that u ∈ AAP(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The function u is uniformly continuous on R+, since u is continuous on [0, ℓ] and uniformly continuous on [ℓ, +∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the map ˆu : R+ → BC(R+, X) defined by ˆu(τ) = T + τ u for τ ≥ 0 is continuous, consequently the set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 0 ≤ τ ≤ ℓ} is relatively compact in BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in BC(R+, X) as the union of two relatively compact sets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, u ∈ AAP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ Using corollaries 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3, we give a proof which is direct and simpler of the following result which can be found in [7, 9, 10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Before we recall some definitions on process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A process on a complete metric space (X, d) according to Dafermos [4] is a two pa- rameter family U(t, τ) of maps from X into itself defined for (t, τ) ∈ R × R+ and such that i) U(t, 0)x = x for all (t, x) ∈ R × X, ii) U(t, σ + τ) = U(t + σ, τ) ◦ U(t, σ) for all (t, σ, τ) ∈ R×R+×R+ and iii) the mapping U(t, ·)x ∈ C([0, +∞), X) for all (t, x) ∈ R×X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For each x ∈ X, the positive trajectory starting of x is the map U(0, ·)x : R+ → X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A function u : R → X is called a complete trajectory if we have u(t + τ) = U(t, τ)u(t) for all (t, τ) ∈ R × R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A process U is said ω-periodic (ω > 0) if U(t + ω, τ) = U(t, τ) for all (t, τ) ∈ R × R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A process U is said bounded if we have for some M ≥ 1 for all (τ, x1, x2) ∈ R+ ×X ×X d (U(0, τ)x1, U(0, τ)x2) ≤ Md (x1, x2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' [7, 9], [10, Th´eor`eme 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='6, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 84] Let U be a ω-periodic process on a complete metric space (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' If U is bounded, then the following statements hold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) If u is a complete trajectory of U such that u(−ωN) is relatively compact, then u is almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) If u is a positive trajectory of U such that u(ωN) is relatively compact, then u is asymptotically almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) The process U is ω-periodic, then we have u(nω) = U(−mω, (n+m)ω)u(−mω) = U(0, (n + m)ω)u(−mω) for all n, m ∈ N.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From the boundedness assumption on U, we On Bochner’s almost-periodicity criterion 9 deduce that d (u(nω), u(mω)) ≤ Md (u(−mω), u(−nω)), then u(ωN) is relatively compact since u(−ωN) is also one, therefore u(ωZ) is relatively compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From assumptions on the process U, it follows that for all n, m ∈ Z, sup τ≥0 d (u(τ + nω), u(τ + mω)) ≤ Md (u(nω), u(mω)) .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' (4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2) From Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, {R(Tnωu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' n ∈ Z} is relatively compact in (BC(R+, X), d∞,+) since u(ωZ) is also one in (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We conclude with Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 by setting D = ωZ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) For all n, m ∈ N, (4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2) holds on the positive trajectory u, then from Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, {T + nωu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' n ∈ N} is relatively compact in (BC(R+, X), d∞,+) since u(ωN) is also one in (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We conclude with Corollary 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 by setting D = ωN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Bochner’s criterion in the periodic case Periodic functions are a special case of almost periodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Haraux gave a charac- terization of periodic functions in terms of Bochner’s criterion which is recalled in Section 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This criterion is a direct consequence of [8, Proposition 2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Haraux established a general result [8, Th´eor`eme 1] implying as a special case a characterization of periodic functions and the fact that any compact trajectory of a one-parameter continuous group is automatically periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In this section, we give an extension of this characterization of periodic functions in the spirit of the main result of this article.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We also treat the asymptotically periodic case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then we apply these results to study the periodicity of solutions of dynamical systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Recall that we denote by R the restriction operator R : BC(R, X) → BC(R+, X) defined by R(u)(t) := u(t) for t ≥ 0 and u ∈ BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (X, d) be a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R, X) the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) The function u is ω-periodic (ω > 0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) The set {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From assumption, it follows that the function τ → Tτu from R into BC(R, X) is continuous and ω-periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} = {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 0 ≤ τ ≤ ω} is a compact set of (BC(R, X), d∞) as the range of a compact set by a continuous map.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For τ1, τ2 ∈ R, d∞(Tτ1u, Tτ2u) := sup t∈R d(u(τ1 + t), u(τ2 + t)), we get d∞(Tτ1u, Tτ2u) = d∞(T−τ1u, T−τ2u).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≤ 0} = {T−τu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is compact in BC(R, X) since {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is also one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Therefore the set {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of BC(R, X) as the union of two compact sets in BC(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3, u is periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ iii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It is obvious by using Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 and the continuity of the restriction operator R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By using Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3, we have to prove that K := {Tτu;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' As consequence of Theorem 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and Bohner’s criterion, the set K is relatively compact in (BC(R, X), d∞) and the function u is almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 10 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat It remains to prove that K is closed in (BC(R, X), d∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (τn)n be a sequence of real numbers such that lim n→+∞ d∞(Tτnu, v) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us prove that v = Tτu for some τ ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By continuity of the operator R, we have lim n→+∞ d∞,+(R(Tτnu), R(v)) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By assumption, the set {R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is in particular closed in (BC(R+, X), d∞,+), then R(v) = R(Tτu) for some τ ∈ R, that is ∀t ≥ 0, v(t) = Tτu(t).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1) We have to prove that (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1) holds on the whole real line.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The function Tτu is almost periodic as translation of an almost periodic function and v is also one as uniform limit on R of almost periodic functions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote by φ : R → R the function defined by φ(t) := d(Tτu(t), v(t)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The function φ is almost periodic [12, Property 4, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 3 & 7, p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='6].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An almost periodic function is uniformly recurrent, then there exists a sequence of real numbers such that lim n→+∞ τn = +∞ and lim n→+∞ φ(t+ τn) = φ(t) for all t ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1), it follows φ(t) = 0 for all t ≥ 0, so we deduce that φ(t) = lim n→+∞ φ(t + τn) = 0 for all t ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then v(t) = Tτu(t) for all t ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This ends the proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ According Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, if the set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is relatively compact in BC(R+, X), then the function u is asymptotically almost periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We now give an answer to the question what can be said about the function u when {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R+, X), we say that u is ω-periodic (ω > 0) on [t0, +∞) for some t0 ≥ 0 if u(t + ω) = u(t) for all t ≥ t0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (X, d) be a complete metric space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For u ∈ BC(R+, X) the following statements are equivalent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) There exists t0 ≥ 0 such that u is ω-periodic on [t0, +∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let u be a function which satisfies condition i) of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) Let us denote by v ∈ C(R, X) the ω-periodic function satisfying u(t) = v(t) for t ≥ t0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A such function v exists and is unique, v is defined by v(t) = u(t − [ t−t0 ω ]ω) where [ t−t0 ω ] denotes the integer part of t−t0 ω .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The function u is a special case of asymptotic almost periodic function where the almost periodic function v is periodic and d(u(t), v(t)) = 0 for t ≥ t0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) =⇒ ii).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote by v the function defined in Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and the periodicity of v, we have {R(Tτv);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ t0} = {R(Tτv);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' First, we have T + τ u = R(Tτv) for τ ≥ t0, then {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ t0} is a compact set.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Second, the function u is uniformly continuous on R+, then the function from R+ to BC(R+, X) defined by τ → T + τ u is continuous.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' 0 ≤ τ ≤ t0} is compact.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Therefore the set {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of BC(R+, X) as the union of two compact set.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) =⇒ i).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' As consequence of Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, the function u is asymptotically almost periodic, that is lim t→∞ d(u(t), v(t)) = 0 for some v ∈ AP(R, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An almost periodic On Bochner’s almost-periodicity criterion 11 function is uniformly recurrent, then there exists a sequence of real numbers (tn)n such that lim n→+∞ tn = +∞ and lim n→+∞ v(t + tn) = v(t) for all t ∈ R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We deduce that ∀t ∈ R, lim n→+∞ u(t + tn) = v(t).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2) First we prove that v is periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For t ∈ R, τ1, τ2 ≥ 0, we have for n enough large d(u(t + tn + τ1), u(t + tn + τ2)) ≤ sup s≥0 d(u(s + τ1), u(s + τ2)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2), it follows that sup t∈R d(v(t+τ1), v(t+τ2)) ≤ sup s≥0 d(u(s+τ1), u(s+τ2)) for each τ1 and τ2 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, {Tτv ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of (BC(R, X), d∞) since {T + τ u ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is also one in (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' As consequence of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1, the function v is periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Second we prove that: ∃t0 ≥ 0 such that ∀t ≥ 0, v(t) = u(t + t0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By compactness of {T + τ u;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0}, there exists a subsequence (T + tφ(n)u)n such that lim n→+∞ d∞,+(T + tφ(n)u, T + t0 u) = 0 for some t0 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From (5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2) we deduce that R(v) = T + t0 u, that is v(t) = u(t + t0) for all t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then u(t) = v(t − t0) for each t ≥ t0 where the function v(· − t0) is periodic on R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ Now we give an example of application on dynamical systems of Corollary of 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 and Corollary of 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For the definition of a dynamical system, see above Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 in Section 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) If u is a positive trajectory, then u is periodic on [t0, +∞) for some t0 ≥ 0 if and only if u(R+) is a compact set and (S(t))t≥0 is equicontinuous on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) If u is a complete trajectory, then u is periodic if and only if u(R) is a compact set and (S(t))t≥0 is equicontinuous on u(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) There exists a complete trajectory which is periodic if and only if there exists a positive trajectory u such that u(R+) is a compact set and (S(t))t≥0 is equicontinuous on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Thus under the assumption of equicontinuity, a complete trajectory of a dynamical system with a compact range is necessarily periodic, although there are almost periodic functions with a compact range, which are not periodic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' An example of such function is given by Haraux in [8].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Proof of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) Remark that if u is a positive trajectory which is periodic on [t0, +∞) for some t0 ≥ 0, then first u(R+) is compact and second u ∈ AAP(R+, X) (see Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' As consequence of Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='5, the set (S(t))t≥0 is equicontinuous on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Reciprocally assume the positive trajectory u is such that (S(t))t≥0 is equicontinu- ous on the compact set u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' It remains to prove that the positive trajectory u is periodic on [t0, +∞) for some t0 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For each x ∈ u(R+), the map S(·)x is continuous and satisfies S(t)x ∈ u(R+) for each t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the map S(·)x is bounded and continuous , so the map Φ : u(R+) → BC(R+, X) with Φ(x) = S(·)x is well-defined.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The continuity of Φ results of the equicontinuity of (S(t))t≥0 on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the set Φ(u(R+)) = {Φ(u(τ)) ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact of BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Moreover Φ(u(τ))(t) = S(t)u(τ) = u(t + τ) for t and τ ≥ 0, 12 P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Cieutat then Φ(u(τ)) = T + τ u, so {T + τ u ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ≥ 0} is a compact set of BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2, the function u is periodic on [t0, +∞) for some t0 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The proof of ii) is similar to that of i) by using Corollary 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3 instead of 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='5, Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='1 instead of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='2 and by replacing the map Φ : u(R+) → BC(R+, X) with Φ(x) = S(·)x by the map Φ : u(R) → BC(R+, X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This permits to prove that the set {Φ(u(τ)) = R(Tτu);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' τ ∈ R} is a compact set of (BC(R+, X), d∞,+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' iii) If v is a complete trajectory which is periodic, then v(R) is compact and according to ii), (S(t))t≥0 is equicontinuous on v(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' So the restriction u of v on R+ is a posi- tive trajectory such that u(R+) = v(R+) = v(R) since v is periodic, then (S(t))t≥0 is equicontinuous on the compact set u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Reciprocally, assume that u is a positive tra- jectory such that (S(t))t≥0 is equicontinuous on the compact set u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to i), u is ω-periodic on [t0, +∞) for some t0 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote by v the function defined in Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For t ≥ s, there exists n0 ∈ N such that s + n0ω ≥ t0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The function v is ω-periodic and u is a positive trajectory satisfying u(τ) = v(τ) for τ ≥ t0, then v(t) = v(t + n0ω) = u(t + n0ω) = T(t − s)u(s + n0ω) = T(t − s)v(s + n0ω) = T(t − s)v(s) for t ∈ R and n enough large.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then v is a periodic complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Under i) of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, one can have t0 > 0, that is the positive trajectory u is not the restriction of a periodic complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For example, consider the bounded dynamical system (S(t))t≥0 on L1(0, 1) defined by (S(t)x)(s) = \uf8f1 \uf8f2 \uf8f3 x(s − t) if t < s < 1 0 if 0 < s < t for x ∈ L1(0, 1) and 0 < t < 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For t ≥ 1, we set S(t) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then all positive trajectories have a compact range and the alone complete trajectory is the null function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Thus all positive trajectories are not the restriction of a periodic complete trajectory except the null function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Not all dynamical systems have this pathology, some systems are such that if two positive trajectories have the same value at the same time, then they are equal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' If we consider such systems, we get more refined results from Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' A dynamical system (S(t))t≥0 has the backward uniqueness property if any two positive trajectories having the same value at t = t0 ≥ 0 coincide for any other t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This property is equivalent to S(t) ∈ C(X, X) is injective for each t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' We say that a positive trajectory u is extendable to a periodic complete trajectory, if there exists a periodic complete trajectory such that its restriction on R+ is u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let (S(t))t≥0 be a dynamical system on a complete metric space (X, d).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Assume that (S(t))t≥0 has the backward uniqueness property.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) If u is a positive trajectory, then u is periodic on R+ if and only if u(R+) is a compact set and (S(t))t≥0 is equicontinuous on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' In this case the positive trajectory u is extendable to a periodic complete trajectory v.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) If v is a complete trajectory, then v is periodic if and only if v(R+) is a compact set and (S(t))t≥0 is equicontinuous on v(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' On Bochner’s almost-periodicity criterion 13 Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' i) The direct implication results of i) of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For the reciprocal implica- tion we use i) of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the positive trajectory u is ω-periodic on [t0, +∞) for some t0 ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote by v ∈ C(R, X) the ω-periodic function satisfying u(t) = v(t) for t ≥ t0 (see Remark 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The restriction of v on R+ and u are two positive trajectories having the same value at t = t0 (t0 ≥ 0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From the backward uniqueness property, we have u(t) = v(t) for t ≥ 0, then u is periodic on R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' By build, v is periodic and as in the proof of iii) of Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, we deduce that v is a complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' ii) The direct implication results of ii) Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, since v(R+) = v(R).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' For the reciprocal implication, we consider v a complete trajectory such that v(R+) is a compact set and (S(t))t≥0 is equicontinuous on v(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Then the restriction u of the complete trajectory v on R+ is a positive trajectory such that u(R+) is compact and (S(t))t≥0 is equicontinuous on u(R+).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' According to i), u is ω-periodic on R+.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Let us denote by w ∈ C(R, X) the ω-periodic function satisfying u(t) = w(t) for t ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' As in proof of iii) Corollary 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content='4, we deduce that w is a complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Fix T > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' The two maps ˜v and ˜w : R+ → X defined by ˜v = v(·, −T) and ˜w = w(·, −T) are two positive trajectories having the same value at t = T.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' From the backward uniqueness property, we have ˜v = ˜w, that is v(t) = w(t) for t ≥ −T.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Since T is arbitrary, then v(t) = w(t) for each t ∈ R where w is a periodic complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' This proves that v is a periodic complete trajectory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' □ References [1] L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/0dAyT4oBgHgl3EQfbfdc/content/2301.00263v1.pdf'} +page_content=' Amerio, G.' metadata={'source': 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mode 100644 index 0000000000000000000000000000000000000000..f15f3a2788ecebc21a0192bbf283513f6099945b --- /dev/null +++ b/1dAzT4oBgHgl3EQfRfuL/content/tmp_files/2301.01217v1.pdf.txt @@ -0,0 +1,1312 @@ +Unlearnable Clusters: Towards Label-agnostic Unlearnable Examples +Jiaming Zhang1 Xingjun Ma2* Qi Yi1 Jitao Sang1,4∗ Yugang Jiang2 Yaowei Wang4 Changsheng Xu3,4 +1Beijing Jiaotong University 2Fudan University 3Chinese Academy of Sciences 4Peng Cheng Lab +Abstract +There is a growing interest in developing unlearnable +examples (UEs) against visual privacy leaks on the Internet. +UEs are training samples added with invisible but unlearn- +able noise, which have been found can prevent unauthorized +training of machine learning models. UEs typically are gen- +erated via a bilevel optimization framework with a surrogate +model to remove (minimize) errors from the original samples, +and then applied to protect the data against unknown target +models. However, existing UE generation methods all rely +on an ideal assumption called label-consistency, where the +hackers and protectors are assumed to hold the same label +for a given sample. In this work, we propose and promote +a more practical label-agnostic setting, where the hackers +may exploit the protected data quite differently from the +protectors. E.g., a m-class unlearnable dataset held by the +protector may be exploited by the hacker as a n-class dataset. +Existing UE generation methods are rendered ineffective in +this challenging setting. To tackle this challenge, we present +a novel technique called Unlearnable Clusters (UCs) to gen- +erate label-agnostic unlearnable examples with cluster-wise +perturbations. Furthermore, we propose to leverage Vision- +and-Language Pre-trained Models (VLPMs) like CLIP as the +surrogate model to improve the transferability of the crafted +UCs to diverse domains. We empirically verify the effective- +ness of our proposed approach under a variety of settings +with different datasets, target models, and even commercial +platforms Microsoft Azure and Baidu PaddlePaddle. +1. Introduction +While the huge amount of “free” data available on the +Internet has been key to the success of deep learning and +computer vision, this has also raised public concerns on the +unauthorized exploitation of personal data uploaded to the +Internet to train commercial or even malicious models [16]. +For example, a company named Clearview AI has been +found to have scraped billions of personal images from Face- +book, YouTube, Venmo and millions of other websites to +construct a commercial facial recognition application [44]. +*Corresponding authors +Unconscious and unauthorized collection for training +Label-consistency +Label-agnostic +Original images ������������ +Unlearnable image ������������′ +Hacker +Protector +������������-class surrogate +model ������������������������������������ += +car, dog, cat, +airplane, etc. +... +������������-class target +model ������������������������ +������������ +car, dog, cat, +airplane, etc. += +������������-class target +model ������������������������ +������������ += +animal, +vehicle, etc. +... +Hacker +Figure 1. An illustration of two different data protection assump- +tions: label-consistency vs. label-agnostic, where the hacker ex- +ploits the protected data in different manners. +This has motivated the proposal of Unlearnable Examples +(UEs) [17] to make data unlearnable (or unusable) to ma- +chine learning models/services. Similar techniques are also +known as availability attacks [2,41] or indiscriminate poi- +soning attacks [14] in the literature. These techniques allow +users to actively adding protective noise into their private +data to avoid unauthorized exploitation, rather than putting +our trust into the hands of large corporations. +The original UE generation method generates error- +minimizing noise via a bilevel min-min optimization frame- +work with a surrogate model [17]. The noise can then be +added to samples in a training set in either a sample-wise +or class-wise manner to make the entire dataset unlearnable +to different DNNs. It has been found that this method can- +not survive adversarial training, which has been addressed +by a recent method [11]. In this work, we identify one +common assumption made by existing UE methods: label- +consistency, where the hackers will exploit the protected +dataset in the same way as the protector including the labels. +This means that, for the same image, the hacker and protec- +tor hold the same label. We argue that this assumption is +too ideal, and it is possible that the hackers will collect the +protected (unlearnable) samples into a dataset for a different +task and label the dataset into different number of classes. +As illustrated in Figure 1, an image can be labelled with +1 +arXiv:2301.01217v1 [cs.CR] 31 Dec 2022 + +盒盒000000different annotated labels (cat or animal), showing that a m- +class (e.g., 10-class) unlearnable dataset may be exploited +by the hacker as a n-class (e.g., 5-class or 20-class) dataset +depending on its actual needs. We term this more generic +assumption as label-agnostic and propose a novel method +Unlearnable Clusters (UCs) to generate more effective and +transferable unlearnable examples under this harsh setting. +In Figure 2 (a), we show that this more generic label- +agnostic setting poses a unique transferability challenge +for the noise generated by existing methods like Error- +Minimizing Noise (EMinN) [17], Adversarial Poisoning +(AdvPoison) [10], Synthetic Perturbations (SynPer) [41] and +DeepConfuse [9]. This indicates that the protective noise +generated by these methods are label-dependent and are ren- +dered ineffective when presented with different number of +classes. As such, we need more fundamental approaches +to make a dataset unlearnable regardless of the annotations. +To this end, we start by analyzing the working mechanism +of UEs generated by EMinN, AdvPoison as they are very +representative under the label-consistency setting. Through +a set of visual analyses, we find that the main reason why +they could break supervised learners is that the generated +noise tends to disrupts the distributional uniformity and dis- +crepancy in the deep representation space. Uniformity refers +to the property that the manifold of UEs in the deep rep- +resentation space does not deviate much from that of the +clean examples, while discrepancy refers to the property +that examples belonging to the same class are richly diverse +in the representation space. Inspired by the above obser- +vation, we propose a novel approach called Unlearnable +Clusters (UCs) to generate label-agnostic UEs using cluster- +wise (rather than class-wise) perturbations. This allows us +to achieve a simultaneous disruption of the uniformity and +discrepancy without knowing the label information. +Arguably, the choose of a proper surrogate model also +plays an important role in generating effective UEs. Previ- +ous methods generate UEs by directly attacking a surrogate +model and then transfer the generated UEs to fight against +a diverse set of target models [10,17]. This may be easily +achievable under the label-consistency setting, but may fail +badly under the label-agnostic setting. However, even un- +der the label-consistency setting, few works have studied +the impact of the surrogate model to the final unlearnable +performance. To generate effective, and more importantly, +transferable UEs under the label-agnostic setting, we need +to explore more generic surrogate model selection strategies, +especially those that can be tailored to a wider range of un- +known target models. Intuitively, the surrogate model should +be a classification DNN that contains as many classes as +possible so as to facilitate the recognition and protection of +billions of images on the Internet. In this paper, we propose +to leverage the large-scale Vision-and-Language Pre-trained +Models (VLPMs) [22,23,30] like CLIP [30] as the surrogate +model. Pre-trained on over 400 million text-to-image pairs, +CLIP has the power to extract the representation of extremely +diverse semantics. Meanwhile, VLPMs are pre-trained with +a textual description rather than a one-hot label to align with +the image, making them less overfit to the actual class “la- +bels”. In this work, we leverage the image encoder of CLIP +to extract the embeddings of the input images and then use +the embeddings to generate more transferable UCs. +We evaluate our UC approach with different backbones +and datasets, all in a black-box setting (the protector does +not know the attacker’s network architecture or the class +labels). Cluster-wise unlearnable noise can also prevent un- +supervised exploitation against contrastive learning to certain +extent, proving its superiority to existing UEs. We also com- +pare UC with existing UE methods against two commercial +machine learning platforms: Microsoft Azure1 and Baidu +PaddlePaddle2. To the best of our knowledge, this is the +first physical-world attack to commercial APIs in this line of +work. +Our main contributions are summarized as follows: +• We promote a more generic data protection assumption +called label-agnostic, which allows the hackers to ex- +ploit the protected dataset differently (in terms of the +annotated class labels) as the protector. This opens up +a more practical and challenging setting against unau- +thorized training of machine learning models. +• We reveal the working mechanism of existing UE gener- +ation methods: they all disrupt the distributional unifor- +mity and discrepancy in the deep representation space. +• We propose a novel approach called Unlearnable Clus- +ters (UCs) to generate label-agnostic UEs with cluster- +wise perturbations without knowing the label informa- +tion. We also leverage VLPMs like CLIP as the surro- +gate model to craft more transferable UCs. +• We empirically verify the effectiveness of our proposed +approach with different backbones on different datasets. +We also show its effectiveness in protecting private data +against commercial machine learning platforms Azure +and PaddlePaddle. +2. Related Work +Unlearnable examples (UEs) can be viewed as one special +type of data poisoning attacks [1,2] that aim to make model +training fail completely on the poisoned (protected) dataset. +UEs should be differentiated from the other two well-known +attacks to deep learning models: backdoor attacks [5, 13, +24] and adversarial attacks [12, 37]. Backdoor attacks are +the other special type of data poisoning attacks that do not +1https://portal.azure.com/ +2https://www.paddlepaddle.org.cn/en/ +2 + +impact the model’s performance on clean data, which is in +sharp contrast to UEs. Adversarial attacks are one type of +test-time attacks that evade the model’s prediction by adding +small imperceptible adversarial noise to the inputs. +UEs can be generated via a min-min bilevel optimiza- +tion framework with a surrogate model [17], similar to +the generation of strong data poisons via bilevel optimiza- +tion [18, 34, 36, 45]. The generated noise is termed Error- +Minimizing Noise (EMinN) as it progressively eliminates +errors from the training data to trick the target model to be- +lieve there is nothing to learn [17]. We use EMinN to denote +the original UE generation method. In addition to EMinN, +there are also UE generation methods that utilize adversarial +noise, such as Error-Maximizing Noise (EMaxN) [19], Deep- +Confuse [9] and Adversarial Poisoning (AdvPoison) [10]. +Recently, Yu et al. [41] unveil a linear-separability property +of unlearnable noise and propose the Synthetic Perturbations +(SynPer) method to directly synthesize linearly-separable +perturbations as effective unlearnable noise. +The original UE method EMinN has a few limitations. +First, the generated unlearnable noise can be removed to a +large extent by adversarial training [26], although this will +also decrease the model’s performance by a considerable +amount [17]. This was later on solved by a recent work +published at ICLR 2022 [11]. The idea is to optimize the +adversarial training loss in place of the standard training loss +to produce more robust error-minimizing noise. The other +limitation is its transferability to different training schemes, +target models (the models to protect against) or datasets. +For example, it has been found that unlearnable noise gen- +erated in a supervised manner fails to protect the dataset +from unsupervised contrastive learning [14]. A unsupervised +UE generation method was then proposed to craft UEs un- +learnable to unsupervised contrastive learning. However, a +very recent work by Ren et al. [32] demonstrates that, sur- +prisingly, unsupervised UEs cannot protect the dataset from +supervised exploitation. All above UE methods all rely on +the ideal label-consistency assumption, i.e., the same (or +no) labels for the protected data will be used by both the +protectors and hackers. In this paper, we promote a more +practical label-agnostic setting where different labels could +be used by the hackers for their own purposes. +Besides UEs, strong adversarial attacks have also been +proposed to protect personal data from malicious face recog- +nition systems, such as LowKey [6] and APF [44]. They +differ from UEs by making a normally trained model unable +to recognize the protected images, rather than preventing +the proper training of any machine learning models on the +protected images. In this work, we focus on UEs rather than +other data protection techniques which we believe are of +independent interest. +3. Proposed Method +Threat Model. +We introduce two parties: the protector +and the hacker. The protectors leverage a surrogate model +to generate UEs for its private data before publishing it on +the Internet. For example, online social network companies +(or users) could convert their photos to their UE versions be- +fore posting them online. These “protected” images are then +collected, without the protectors’ consent, by a hacker into a +dataset to train a commercial or malicious model. The pro- +tectors’ goal is to make the collected dataset unlearnable, i.e., +cannot be used for model training, while the hackers’ goal +is to train accurate models on the unlearnable (protected) +dataset. Following prior works [11,17,25], we assume the +released dataset is 100% protected, i.e., all the samples are +perturbed to be unlearnable. While this assumption appears +to be ideal, if the protection technique is reliable, there is no +reason not to employ it to gain more protection and privacy. +Therefore, in this work we choose to focus on the unlearn- +able technique itself rather than changing the setting of the +protectors. Following our label-agnostic setting, we also as- +sume the hackers could exploit the unlearnable dataset with +different labels. E.g., a m-class dataset could be exploited +by the hacker as a n-class dataset. +Here, we give an example of such label-agnostic scenario +with a online social media company who strives to protect +the contents created by all of its users. The company could +leverage unlearnable techniques to develop systematic pro- +tection scheme against unauthorized data explorers. In this +case, we can assume all the images uploaded by the users are +protected (by the company). Potential hackers like Clearview +AI may crawl the images from the online platform without +the users’ content into one or a set of datasets for its own +purposes. Thus, the collected datasets cannot be guaranteed +to have the same labels as their original versions. The pro- +tector thus needs to craft more powerful and transferable +unlearnable examples to make data unexploitable against +different labeling strategies. +3.1. Problem Formulation +We focus on image classification tasks in this paper. +Given a clean m-class training dataset Dm +c = {(xi, yi)}k +i=1 +consisting of k clean training images x ∈ X ⊂ Rd and their +labels y ∈ Y, in a standard unlearnable setting [17], the +protector trains an m-class surrogate model f m +s on Dm +c . The +protector can then generate an unlearnable version of the +dataset as Dm +u = {(x′ +i, y′ +i)}k +i=1, based on the clean dataset +Dm +c and the surrogate model f m +s . The unlearnable images +are denoted as x′ = x + δ (x ∈ Dm +c ) with the same labels +y ∈ Y as their original versions and δ ∈ ∆ ⊂ Rd are the +generated unlearnable noise which is often regularized to be +imperceptible. The unlearnable dataset Dm +u is assumed to be +the dataset collected by the hackers, and will be exploited +to train a commercial or malicious m-class target model f m +t +3 + +EMinN +AdvPoison +SynPer +DeepConfuse +0 +25 +50 +75 +100 +Accuracy (%) +19.93 +6.25 +13.54 +28.77 +93.77 +93.6 +93 +93.31 +Label-consistency +Label-agnostic +(a) +Clean +EMinN +AdvPoison +(b) +Figure 2. (a) Current UE methods become ineffective in the label- +agnostic setting, even though they exhibit high effectiveness in the +label-consistency setting (under noise constraint ϵ = 8/255). (b) +A 3D feature visualization of clean CIFAR-10 examples and the +UEs derived by EMinN and AdvPoison. Points in the same color +denote samples of the same class. +without the protectors’ consent. +Label-consistency vs. Label-agnostic. +The above formu- +lation follows the standard label-consistency assumption of +previous works [11,17], where the hackers collect, annotate +and exploit the unlearnable dataset Dm +u exactly the same +as it was initially released by the protectors. Under a more +general and practical label-agnostic assumption, the hackers +could annotate the collected dataset Dm +u differently, e.g., as- +signing it with different number of classes. In this case, the +hackers may exploit the dataset as a n-class (n ̸= m) classi- +fication dataset Dn +c = {(x′ +i, y′ +i)}k +i=1 to train a n-class target +model f n +t . Note that the protectors have no knowledge of the +target class number n nor the target labels y′ +i. Arguably, the +hackers may even exploit the dataset as an object detection +dataset rather than a classification dataset. We will explore +such a more challenging task-agnostic assumption in our +future work and focus on the label-agnostic in this work. +3.2. The Label-agnostic Challenge +Existing methods are not robust to label-agnostic ex- +ploitation. +We test the effectiveness of existing unlearn- +able methods developed under the label-consistency set- +ting against label-agnostic hackers. Here we consider cur- +rent unlearnable method including Error-Minimizing Noise +(EMinN) [17], Adversarial Poisoning (AdvPoison) [10], Syn- +thetic Perturbations (SynPer) [41] and DeepConfuse [9], on +the CIFAR-10 dataset [21]. The ResNet-18 [15] models are +used for both the surrogate and target models. As shown +in Figure 2 (a), these methods are extremely effective in +preventing the training of machine learning models on the +unlearnable dataset with the same labels. However, if the un- +learnable dataset is crafted using ImageNet surrogate model +with the predicted ImageNet labels (i.e., labels predicted by +the surrogate model), it fails to prevent the model training +with the original CIFAR-10 labels. This indicates one unique +challenge of the label-agnostic setting: unlearnable noises +generated to prevent one set of labels are not transferable to +preventing other labeling strategies. +The working mechanism of existing UEs under the label- +consistency setting. +Here, we investigate the representa- +tions learned by the target model on clean vs. unlearnable +examples, aiming to gain more understanding of the un- +learnable mechanism. In Figure 2 (b), we visualize the +3-dimensional PCA [39] projections of the original represen- +tations learned by the ResNet-18 target model for a) clean +CIFAR-10 training samples, b) unlearnable CIFAR-10 ex- +amples crafted by EMinN method, and 3) unlearnable (poi- +soned) CIFAR-10 examples crafted by AdvPoison. The rep- +resentations are extracted at the last convolutional layer and +projected using PCA from 512 to 3 dimensions. It shows in +Figure 2 (b) that the unlearnable examples crafted by EMinN +and AdvPoison tend to significantly reduce the variance at +certain dimensions. There are also classes that collapse into +smaller clusters, like the green class. This indicates that the +noise disrupts the distributional discrepancy in the repre- +sentation space to make the data “unlearnable”. The other +key observation is that the noise greatly shifts the points +away from the normal data manifold, causing an unneces- +sary spread over a certain direction. This indicates that the +noise also breaks the distributional uniformity of the data. +Overall, it is evident the unlearnable noise crafted by EMinN +and AdvPoison cripples the learning process by distorting +both the discrepancy and uniformity of the data distribution +in the deep representation space. +Unlearnable examples can overfit to the labels. +A closer +look at the visualizations in Figure 2 (b), one may notice +that the unlearning effects occur only within the classes. I.e., +the UEs have overfitted to the class labels. This is somewhat +not surprising as the unlearnable noises are generated via +a supervised loss function (i.e., cross-entropy) defined by +the labels. The noise are thus optimized to thwart the most +predictive information to the class labels. However, this +causes the overfitting problem and fails to work if the labels +are changed. Intuitively, if we could remove the dependency +on the class labels and turn to exploit the clusters that natu- +rally arise during the learning process, we could make the +unlearnable noise more robust to different annotations. +3.3. Unlearnable Clusters (UCs) +Overview. +Motivated by the above observations, in this +work we propose to generate UEs by exploiting the clus- +ters learned by a surrogate model and making the clusters +unlearnable instead of the labeled classes. We term this +approach as Unlearnable Clusters (UCs) and illustrate its +working follow in Figure 3. The key components of UC are +one generator model G and one surrogate model fs. At a +high level, UC first employs a surrogate model fs to extract +the representations E of all samples in the clean dataset Dc. +It then utilizes the K-means [35] clustering method to derive +p clusters from the representations E. Subsequently, for +4 + +10.0 +7.5 +5.0 +2.5 +0.0 +2.5 +5.0 +7.5 +2兴 +10.0 +7.5 +5.0 +2.5 +0.0 +2.5 +5.0 +7.510.0 +7.5 +5.0 +2.5 +0.0 +2.5 +5.0 +7.5 +2 +2 +2Generator ������������(�; ������������������������) +Uniform +Noise +������������ +Cluster-wise +Perturbation +������������������������ +Unlearnable +Image +������������′ +Surrogate Model ������������������������ +Origianl +Image +������������ +������������1 +������������2 +������������3 +Feature Space +������������1 +′ +Update ������������������������ +Feature Space +K-means Initial +Minimize ������������DDU +×: clustering center ������������������������������������ +×: clustering center ������������������������������������ +������������2 +′ +������������3 +′ +Figure 3. The Unlearnable Clusters pipeline. The entire dataset is divided into p clusters via K-means clustering, where each cluster +corresponds to a certain generator with parameters θi and a cluster-wise perturbation δi. +each cluster, it generates a cluster-wise perturbation δi using +the generator G. The noise will be generated and applied to +craft the UE for each sample in Dc, with samples belonging +to the same cluster are added with the same cluster-wise +noise δi. UEs crafted in this manner can prevent the target +model from learning meaningful clusters rather than class +predictions, thus is more general to different types of label +exploitations. Next, we will introduce the details of UCs. +Cluster-wise Perturbations. +In our UC framework, one +encoder-decoder [29] generator network is used to gener- +ate the cluster-wise perturbations, with each generator will +be reinitialized for one cluster. As such, we need to ex- +tract the clusters first. Here, we leverage the most classic +clustering method K-means [35] to detect clusters from the +deep representations. Particularly, the clean dataset Dc is +fed into the surrogate model fs to extract the representation +matrix before the classification layer E = [e1, · · · , ek]. K- +means clustering is then applied on the representation matrix +to detect p number of clusters C = {C1, · · · , Cp}, where +Ci = {xij}τ(i) +j=1 = {xi1, · · · , xiτ(i)} and �p +i=1 τ(i) = +k. The corresponding centers for the clusters are µC = +{µC1, · · · , µCp}. +With the detected clusters C, we can now propose the +following method to generate the unlearnable noise for each +cluster. Intuitively, for cluster Ci, we hope the unlearnable +noise δi could move all samples in the cluster to a wrong +cluster center, so as to force the model to forget the cor- +rect clusters. This is done via the following minimization +framework: +θi = arg min +θi +LDDU(Ci, g(µCi), θi) += arg min +θi +� +xij∈Ci +d(fs(xij + G(σ; θi)), g(µCi)), +(1) +where, LDDU is our proposed Disrupting Discrepancy and +Uniformity (DDU) loss that defines the distance (d(·)) of +samples in Ci to a permuted (wrong) cluster center by a per- +mutation function g(µCi); θi are the parameters of generator +network G; G(σ; θi)) generates the unlearnable noise for all +samples in Ci (i.e., xij ∈ Ci). Please note that the above +problem needs to be solved for p times to obtain the cluster- +wise unlearnable noise for all p clusters, and for each cluster, +the generator G is reinitialized with new parameters θi. The +complete procedure is described in Algorithm 1. +Algorithm 1 Unlearnable Cluster Generation +1: Input: surrogate model fs, distance metric d, uniform +noise σ, number of clusters p, random permutation g, +L∞-norm restriction ϵ, clean images x ∈ Dc, initialized +generator G with parameters θ +2: Output: cluster-wise perturbations δ = {δ1, · · · , δp} +3: feature matrix E = fs(x) +4: clusters and cluster centers {C, µC} = K-means(E, p) +5: for i in 1 · · · p do +6: +Initialize θi +7: +δi = G(σ; θi) +8: +δi = Clamp(δi, −ϵ, ϵ) +9: +for xij in Ci do +10: +x′ +ij = Clamp(xij + δi, 0, 1) +11: +θi ← Optimize(x′ +ij, fs, g(µCi), d) +12: +end for +13: +δi = G(σ; θi) +14: +δi = Clamp(δi, −ϵ, ϵ) +15: end for +CLIP Surrogate Model. +How to choose a surrogate +model remains to be an independent challenge for gener- +5 + +X +Xating effective cluster-wise unlearnable noise. As shown in +prior works, it plays a central role in facilitating the trans- +ferability of the generated UEs to different datasets or target +models [17]. In the traditional label-consistency setting, the +surrogate model can be a model that directly trained on the +original (unprotected) dataset, which may of a different (and +plausibly a better or more complex) model architecture. It +could also be a model that trained on a larger dataset with +more classes, e.g., ImageNet-trained models [10,17]. We +thus adopt an ImageNet-pretrained ResNet-50 as the default +surrogate model of our UC. +Analogous to the classification surrogate models used +for generating the traditional UEs, the ideal surrogate mod- +els for unlearnable clusters could be those powerful fea- +ture extractors that could lead to accurate detection of clus- +ters from an image dataset. We thus propose to also lever- +age one large-scale vision-and-language pre-trained model +(VLPM) [22, 23] CLIP [30] as our surrogate model. Pre- +trained on over 400 million text-to-image pairs, CLIP has +the power to extract the representation of extremely diverse +semantics. Moreover, CLIP was pre-trained with a textual de- +scription rather than a one-hot label to align with the image, +thus overfitting less to the actual class labels. Concretely, +we employ the image encoder of CLIP to extract the feature +matrix for the clean dataset, which is then used to compute +the clusters and cluster centers. We denote the version of +UC equipped with the CLIP surrogate model as UC-CLIP. +4. Experiments +In this section, we evaluate our UCs methods on different +datasets against different target models, which is to simulate +as many unknown cases as possible. We also examine the ro- +bustness of UCs against several advanced defenses. Finally, +we demonstrate its effectiveness in attacking commercial +machine learning platforms Azure and PaddlePaddle. +4.1. Experimental Settings +Datasets and Models. +We conduct our study on 6 high- +resolution and industrial-scale vision datasets to simulate +as diverse real-world applications as possible, including +Pets [28], Cars [20], Flowers [27], Food [3], SUN397 [40] +and ImageNet [33]. For ImageNet, we only use its first +100 classes which is denoted as ImageNet⋆. For surrogate +models, we consider ResNet-50 trained on ImageNet-1k as +the default, unless otherwise explicitly stated. For target +models, we employ randomly initialized ResNet-18 [15], +EfficientNet-B1 [38] and RegNetX-1.6GF [31]. We train +the target models with data augmentations (resizing, ran- +dom crop, random horizontal flip and normalization) for 90 +epochs, using SGD with initial learning rate 0.1, Cosine +annealing, momentum 0.9, and batch size 256. +For generator G, we repeated p times to train the generator +G for 10 epochs using SGD with initial learning rate 0.1, +10 +20 +30 +Number of class +0 +20 +40 +60 +Accuracy (%) +UC +UC-CLIP +random guess +clean +(a) Different labelings +Clean +SynPer +EMaxN +EMinN +AdvPoison +DeepConfuse +UC-CLIP +UC +0 +10 +20 +30 +40 +50 +Accuracy (%) +48.3 46.8845.1948.1647.02 +24.37 26.11 +17.83 +(b) Unsupervised exploitation +Figure 4. (a) The accuracy of ResNet-18 target models trained on +the unlearnable Pets dataset but with its labels were re-labeled by +the hacker into 5 to 35 classes. (b) Comparison of our approach +with the baselines on Pets dataset against ResNet-18 target model +trained via self-supervised SimCLR. +Cosine annealing, momentum 0.9, and batch size 256, and +10 epochs for ImageNet⋆ and 50 epochs for other datasets. +For random permutation g(·), we simply chose i → i + 1 to +build a closed loop. We consider L∞-norm restriction in this +work, i.e., ∥δ∥∞ < ϵ = 16/255. The number of clusters p +is set to 10, with an analysis is provided in Section 4.5. +Baselines. +We compare our UC and UC-CLIP with 5 base- +line methods including DeepConfuse [9], Synthetic Perturba- +tions (SynPer) [41], Error-minimizing Noise (EMinN) [17], +Error-maximizing Noise(EMaxN) [19], and Adversarial Poi- +soning (AdvPoison) [10]. We use their official implementa- +tions and follow the suggested settings in the original papers +to generate the UEs or poisons. +Label-agnostic Setup. +Please note that we conduct all of +our experiments under the proposed label-agnostic setting. +The UCs (and the UEs they serve) are all generated with the +predicted labels by the surrogate models. The predicted la- +bels may overlap with the ground truth labels to some extent, +but are highly inconsistent with the original labels as the sur- +rogate models are not trained on the particular datasets. The +hackers train all target models on the unlearnable datasets +with their ground truth labels. We report the test accuracy of +the target models on the respective clean test sets. +4.2. Main Results +Effectiveness against different target models. +We first +compare our UC and UC-CLIP with the 5 baselines against +different target models. Table 1 shows the results against +ResNet-18, EfficientNet-B1, and RegNetX-1.6GF. We have +the following main findings: (1) Our methods outperform +the baselines by a huge margin consistently across different +datasets and target models. This demonstrates the superi- +ority of our methods over the baselines. (2) Our UC-CLIP +achieves a better performance than UC, and in most of the +cases, by a considerable margin. This proves the great poten- +tial of using CLIP as the surrogate model to protect person +data from unauthorized exploitations. +6 + +Table 1. The test accuracy (%) of different target models trained on the unlearnable datasets generated by our UC/UC-CLIP and the 5 +baseline methods, under the label-agnostic setting. The top-2 best results are highlighted in bold. +RESNET-18 +EFFICIENTNET-B1 +REGNETX-1.6GF +METHODS +PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ +CLEAN +62.31 67.18 +67.18 +78.97 +43.08 +77.76 +48.68 72.33 +52.46 +80.29 +42.84 +78.04 +44.86 63.84 +52.69 +84.02 +43.27 +80.78 +SYNPER +52.60 53.50 +52.74 +74.80 +38.26 +74.69 +28.02 58.34 +42.93 +74.99 +35.92 +72.94 +34.51 45.54 +47.16 +77.65 +37.78 +60.38 +EMAXN +54.70 52.95 +51.70 +73.77 +37.57 +73.82 +33.71 55.64 +42.66 +74.40 +37.30 +73.72 +34.26 43.40 +46.25 +78.76 +37.82 +76.72 +EMINN +52.96 54.43 +50.58 +75.47 +38.48 +74.20 +36.88 54.23 +44.06 +75.54 +37.20 +72.20 +37.04 39.67 +47.34 +79.43 +36.82 +74.86 +ADVPOISON +50.86 51.91 +50.64 +75.07 +38.51 +73.76 +37.99 50.08 +41.65 +74.88 +36.44 +72.54 +34.29 46.06 +47.41 +78.64 +36.42 +76.32 +DEEPCONFUSE +53.72 51.11 +50.94 +73.13 +34.41 +55.12 +35.54 47.15 +43.28 +72.91 +35.22 +45.74 +33.71 41.15 +46.01 +77.26 +33.52 +49.88 +UC (OURS) +12.21 33.57 +35.55 +55.29 20.38 +54.80 +17.06 13.92 +42.28 +53.45 22.97 +32.30 +4.28 29.46 +33.79 +64.48 22.28 +56.10 +UC-CLIP (OURS) 4.69 +4.74 +10.07 +19.07 +3.89 +39.78 +6.49 15.33 +14.13 +17.44 12.95 +31.82 +3.87 +4.18 +8.12 +26.76 +6.04 +41.66 +Effectiveness Against Different Labelings. +An even +more challenging label-agnostic setting is that the hacker +may exploit the unlearnable dataset using different labeling +strategies instead of one. So, a natural question is that what +if the number of labeled classes of the unlearnable dataset +is less than our cluster number p = 10? Here, we take the +37-class Pets dataset as an example and explore the impact +if the hacker re-labels the unlearnable version of the dataset +as a 5 to 36 class dataset. One possible labeling strategy is +that the hacker first extracts the embeddings of the original +text labels using the BERT model [8], and then clusters the +embeddings into 5-37 classes using K-means, so as to con- +struct a mapping from the old labels to the new labels. As +shown in Figure 4 (a), both our UC and UC-CLIP can bring +the test accuracy of the target model down to a level that is +close the random guess (the black curve). This verifies that +our methods can craft more generic UEs against the most +severe label-agnostic exploitations. +Robustness to Unsupervised Exploitation. +We also com- +pare our methods with the baselines under an unsupervised +contrastive learning setting against SimCLR [4]. Although +our UC methods are not specifically designed for this un- +supervised setting, Figure 4 (b) shows that cluster-wise un- +learnable noise can also prevent unsupervised exploitation +against SimCLR. +4.3. Preventing Commercial Platforms +Here, we apply our UC methods to prevent two com- +mercial machine learning platforms: Microsoft Azure and +Baidu PaddlePaddle. On both platforms, the training +details are agnostic to us, including the model architecture, +learning rate, batch size, epoch, data augmentation, splitting +of the validation set, etc. Considering that ViT may be used +on commercial platforms due to its recent popularity, we +upgrade our UC-CLIP method by replacing the ResNet-50 +(RN50) surrogate model by a ViT-B-32 (ViTB32) surrogate +model. The results are reported in Table 2, which are consis- +Table 2. The test accuracy (%) of models trained by Azure and +PaddlePaddle platforms on unlearnable Cars dataset crafted by +different methods. The training configuration on the platform was +set to “fastest training”. +METHODS +Azure +PaddlePaddle +CLEAN +48.45 +83.74 +SYNPER +42.38 +47.59 +EMAXN +42.83 +42.99 +EMINN +44.06 +44.40 +ADVPOISON +43.97 +43.38 +DEEPCONFUSE +39.47 +41.88 +UC (RN50) +36.40 +30.96 +UC-CLIP (RN50) +26.97 +25.79 +UC-CLIP (VITB32) +22.47 +11.49 +tent with that in Table 1. I.e., both of our methods can protect +the data uploaded to the two platforms against their training +algorithms. Unsurprisingly, the ViTB32-powered UC-CLIP +method achieves the best protection performance by causing +the lowest test accuracy. This suggests the effectiveness of +our methods even against commercial platforms. +4.4. Resistance to Potential Defenses +In this section, we test the robustness of our UC +methods to several augmentation based defenses, includ- +ing Mixup [43], Gaussian smoothing, Cutmix [42] and +Cutout [7]. We did not consider adversarial training here is +that the images involved in this paper are generally large in +size, number and resolution, making adversarial training ex- +tremely hard to converge without losing considerable clean +accuracy on most of the datasets [26]. Compared with ad- +versarial training, we believe that a more practical defense +should be very efficient, such as image denoising or the con- +sidered augmentation techniques. As can be observed in +Table 3, the 4 data augmentation defenses have minimum +impact on our UC and UC-CLIP methods. Particularly, Gaus- +sian smoothing appears to be the most effective defense, but +the accuracy is still below 25%. +7 + +Table 3. The test accuracy (%) of ResNet-18 trained using different +defenses against our methods on Pets dataset. +METHODS +NO DEFENSE +MIXUP +GAUSSIAN +CUTMIX +CUTOUT +UC +12.21 +14.34 +24.26 +14.50 +12.35 +UC-CLIP +4.69 +11.96 +18.59 +6.21 +12.29 +4.5. Ablation Study +5 +10 15 20 25 30 35 40 +Number of clusters +0 +5 +10 +15 +Accuracy (%) +16.08 +12.21 +4.42 3.82 3.46 2.75 +4.51 3.92 +(a) Effect of p on UC +5 +10 15 20 25 30 35 40 +Number of clusters +0 +5 +10 +15 +Accuracy (%) +6.38 +4.69 +3.11 3.33 3.33 2.73 +4.09 +2.67 +(b) Effect of p on UC-CLIP +Figure 5. Analyzing the effect of cluster number p on Pets dataset. +Here, we analyze the sensitivity of our methods to the +number of clusters p, which has been set to p = 10 as a +default. We take the 37-class Pets dataset as an example +and evaluate our UC and UC-CLIP method under different +values of p ∈ [5, 40]. As shown in Figure 5, our methods are +quite stable to varying hyperparameter p for p ≥ 10. This +indicates that, as long as the clusters can cover most of the +concepts in a dataset, the generated unlearnable noise can +effectively prevent the model from learning the real content +from the dataset. As the number of clusters increases, the +noise tends to become more effective, although there is a +slight variation at 35. Note that, even in the worst case at +p = 5, our methods still outperform the baselines. +4.6. Mixture of Clean and Unlearnable Data +0 +5 +10 15 20 25 30 35 +Number of classes +0 +10 +20 +30 +40 +50 +60 +Accuracy (%) +clean-only +mixture +(a) Mixture vs. Clean-only +0 +25 +50 +75 100 125 150 +Epoch +0 +20 +40 +60 +80 +100 +Accuracy (%) +training (unlearnable) +test (clean) +test (unlearnable) +(b) Accuracy trends +Figure 6. +(a) The test accuracy (%) of ResNet-18 trained on +unlearnable-clean mixed vs. clean-only data; and (b) the accu- +racy trends on clean vs. unlearnable examples. The unlearnable +examples are crafted using our UC method on Pets dataset. +All the above experiments are conducted under the as- +sumption that all samples in the dataset are protected, a +commonly adopted assumption in the literature [10,17,41]. +This setting is reasonable when the protectors have the access +to the entire dataset, e.g., an online social media company +adopts the technique to protect the contents created by all +of its users. A more general case is that only a certain pro- +portion of the users protect their data while others do not. +This results in mixed dataset with both clean and unlearnable +samples. Here we test our UC method under this setting +and show the change in test accuracy with the number of +clean classes in Figure 6 (a). I.e., for the mixture dataset, +the rest of the classes are made unlearnable by UC. It can be +inferred that the unlearnable classes almost do not contribute +to the model training, a similar conclusion as in previous +works [10,17,41]. This implies that only those who adopt +the technique will get protected. +4.7. More Understanding +Why our UCs are more powerful than standard UEs +against label-agnostic exploitation? As we explained in +Section 3.1, the idea of UCs is inspired by the effectiveness +of disrupting the uniformity and discrepancy in preventing +the model from learning useful information. However, this +also raises another question: what exactly does the target +model learn? To answer these two questions, here we ana- +lyze the learning curves of the target model on the clean vs. +unlearnable examples separately. As shown in Figure 6 (b), +as the training progresses, the training accuracy on the un- +learnable training samples steadily improves until it reaches +100%. But there is almost no improvement in the clean test +accuracy on the clean test samples. This is consistent with +the the above experimental results that the target model has +not learned the capability to perceive normal samples. Sur- +prisingly, however, the model’s accuracy on the perturbed +test samples is fairly high (> 60%), considering that the +normally trained ResNet-18 only achieves a test accuracy of +62.31% on clean Pets dataset. This implies that the unlearn- +able noise distribution contained in the UCs has effectively +concealed the real data distribution. +5. Conclusion +Unlearnable examples (UEs) have shown great potential +in preventing hackers from using users’ private data to train +commercial or malicious models. A number of methods +have been proposed to improve UEs’ transferability and ro- +bustness to different datasets, target models and training +paradigms. In this work, we identified one limitation of ex- +isting UE methods, i.e., their label-consistency assumption. +To overcome this limitation, we proposed a more general +setting where the hackers could exploit the protected data +with different sets of labels. We termed this more challeng- +ing setting as label-agnostic, and proposed an Unlearnable +Clusters (UCs) technique with conditioned generator models, +K-means clustering, and large-scale vision-and-language pre- +training model CLIP, to craft effective UEs against a wide +range of datasets and target models. 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PMLR, +2019. 3 +10 + diff --git a/1dAzT4oBgHgl3EQfRfuL/content/tmp_files/load_file.txt b/1dAzT4oBgHgl3EQfRfuL/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..665846d9d909143b504021c8e5ac83f7e4af29be --- /dev/null +++ b/1dAzT4oBgHgl3EQfRfuL/content/tmp_files/load_file.txt @@ -0,0 +1,790 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf,len=789 +page_content='Unlearnable Clusters: Towards Label-agnostic Unlearnable Examples Jiaming Zhang1 Xingjun Ma2* Qi Yi1 Jitao Sang1,4∗ Yugang Jiang2 Yaowei Wang4 Changsheng Xu3,4 1Beijing Jiaotong University 2Fudan University 3Chinese Academy of Sciences 4Peng Cheng Lab Abstract There is a growing interest in developing unlearnable examples (UEs) against visual privacy leaks on the Internet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' UEs are training samples added with invisible but unlearn- able noise, which have been found can prevent unauthorized training of machine learning models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' UEs typically are gen- erated via a bilevel optimization framework with a surrogate model to remove (minimize) errors from the original samples, and then applied to protect the data against unknown target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, existing UE generation methods all rely on an ideal assumption called label-consistency, where the hackers and protectors are assumed to hold the same label for a given sample.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this work, we propose and promote a more practical label-agnostic setting, where the hackers may exploit the protected data quite differently from the protectors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', a m-class unlearnable dataset held by the protector may be exploited by the hacker as a n-class dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Existing UE generation methods are rendered ineffective in this challenging setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To tackle this challenge, we present a novel technique called Unlearnable Clusters (UCs) to gen- erate label-agnostic unlearnable examples with cluster-wise perturbations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Furthermore, we propose to leverage Vision- and-Language Pre-trained Models (VLPMs) like CLIP as the surrogate model to improve the transferability of the crafted UCs to diverse domains.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We empirically verify the effective- ness of our proposed approach under a variety of settings with different datasets, target models, and even commercial platforms Microsoft Azure and Baidu PaddlePaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Introduction While the huge amount of “free” data available on the Internet has been key to the success of deep learning and computer vision, this has also raised public concerns on the unauthorized exploitation of personal data uploaded to the Internet to train commercial or even malicious models [16].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For example, a company named Clearview AI has been found to have scraped billions of personal images from Face- book, YouTube, Venmo and millions of other websites to construct a commercial facial recognition application [44].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Corresponding authors Unconscious and unauthorized collection for training Label-consistency Label-agnostic Original images ������������ Unlearnable image ������������′ Hacker Protector ������������-class surrogate model ������������������������������������ = car, dog, cat, airplane, etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' ������������-class target model ������������������������ ������������ car, dog, cat, airplane, etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' = ������������-class target model ������������������������ ������������ = animal, vehicle, etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Hacker Figure 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' An illustration of two different data protection assump- tions: label-consistency vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' label-agnostic, where the hacker ex- ploits the protected data in different manners.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This has motivated the proposal of Unlearnable Examples (UEs) [17] to make data unlearnable (or unusable) to ma- chine learning models/services.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Similar techniques are also known as availability attacks [2,41] or indiscriminate poi- soning attacks [14] in the literature.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' These techniques allow users to actively adding protective noise into their private data to avoid unauthorized exploitation, rather than putting our trust into the hands of large corporations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The original UE generation method generates error- minimizing noise via a bilevel min-min optimization frame- work with a surrogate model [17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The noise can then be added to samples in a training set in either a sample-wise or class-wise manner to make the entire dataset unlearnable to different DNNs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' It has been found that this method can- not survive adversarial training, which has been addressed by a recent method [11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this work, we identify one common assumption made by existing UE methods: label- consistency, where the hackers will exploit the protected dataset in the same way as the protector including the labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This means that, for the same image, the hacker and protec- tor hold the same label.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We argue that this assumption is too ideal, and it is possible that the hackers will collect the protected (unlearnable) samples into a dataset for a different task and label the dataset into different number of classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As illustrated in Figure 1, an image can be labelled with 1 arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='01217v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='CR] 31 Dec 2022 盒盒000000different annotated labels (cat or animal), showing that a m- class (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', 10-class) unlearnable dataset may be exploited by the hacker as a n-class (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', 5-class or 20-class) dataset depending on its actual needs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We term this more generic assumption as label-agnostic and propose a novel method Unlearnable Clusters (UCs) to generate more effective and transferable unlearnable examples under this harsh setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In Figure 2 (a), we show that this more generic label- agnostic setting poses a unique transferability challenge for the noise generated by existing methods like Error- Minimizing Noise (EMinN) [17], Adversarial Poisoning (AdvPoison) [10], Synthetic Perturbations (SynPer) [41] and DeepConfuse [9].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This indicates that the protective noise generated by these methods are label-dependent and are ren- dered ineffective when presented with different number of classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As such, we need more fundamental approaches to make a dataset unlearnable regardless of the annotations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To this end, we start by analyzing the working mechanism of UEs generated by EMinN, AdvPoison as they are very representative under the label-consistency setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Through a set of visual analyses, we find that the main reason why they could break supervised learners is that the generated noise tends to disrupts the distributional uniformity and dis- crepancy in the deep representation space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Uniformity refers to the property that the manifold of UEs in the deep rep- resentation space does not deviate much from that of the clean examples, while discrepancy refers to the property that examples belonging to the same class are richly diverse in the representation space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Inspired by the above obser- vation, we propose a novel approach called Unlearnable Clusters (UCs) to generate label-agnostic UEs using cluster- wise (rather than class-wise) perturbations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This allows us to achieve a simultaneous disruption of the uniformity and discrepancy without knowing the label information.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Arguably, the choose of a proper surrogate model also plays an important role in generating effective UEs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Previ- ous methods generate UEs by directly attacking a surrogate model and then transfer the generated UEs to fight against a diverse set of target models [10,17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This may be easily achievable under the label-consistency setting, but may fail badly under the label-agnostic setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, even un- der the label-consistency setting, few works have studied the impact of the surrogate model to the final unlearnable performance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To generate effective, and more importantly, transferable UEs under the label-agnostic setting, we need to explore more generic surrogate model selection strategies, especially those that can be tailored to a wider range of un- known target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Intuitively, the surrogate model should be a classification DNN that contains as many classes as possible so as to facilitate the recognition and protection of billions of images on the Internet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this paper, we propose to leverage the large-scale Vision-and-Language Pre-trained Models (VLPMs) [22,23,30] like CLIP [30] as the surrogate model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Pre-trained on over 400 million text-to-image pairs, CLIP has the power to extract the representation of extremely diverse semantics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Meanwhile, VLPMs are pre-trained with a textual description rather than a one-hot label to align with the image, making them less overfit to the actual class “la- bels”.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this work, we leverage the image encoder of CLIP to extract the embeddings of the input images and then use the embeddings to generate more transferable UCs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We evaluate our UC approach with different backbones and datasets, all in a black-box setting (the protector does not know the attacker’s network architecture or the class labels).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Cluster-wise unlearnable noise can also prevent un- supervised exploitation against contrastive learning to certain extent, proving its superiority to existing UEs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also com- pare UC with existing UE methods against two commercial machine learning platforms: Microsoft Azure1 and Baidu PaddlePaddle2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To the best of our knowledge, this is the first physical-world attack to commercial APIs in this line of work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Our main contributions are summarized as follows: We promote a more generic data protection assumption called label-agnostic, which allows the hackers to ex- ploit the protected dataset differently (in terms of the annotated class labels) as the protector.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This opens up a more practical and challenging setting against unau- thorized training of machine learning models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We reveal the working mechanism of existing UE gener- ation methods: they all disrupt the distributional unifor- mity and discrepancy in the deep representation space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We propose a novel approach called Unlearnable Clus- ters (UCs) to generate label-agnostic UEs with cluster- wise perturbations without knowing the label informa- tion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also leverage VLPMs like CLIP as the surro- gate model to craft more transferable UCs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We empirically verify the effectiveness of our proposed approach with different backbones on different datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also show its effectiveness in protecting private data against commercial machine learning platforms Azure and PaddlePaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Related Work Unlearnable examples (UEs) can be viewed as one special type of data poisoning attacks [1,2] that aim to make model training fail completely on the poisoned (protected) dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' UEs should be differentiated from the other two well-known attacks to deep learning models: backdoor attacks [5, 13, 24] and adversarial attacks [12, 37].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Backdoor attacks are the other special type of data poisoning attacks that do not 1https://portal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='azure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='com/ 2https://www.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='paddlepaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='org.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='cn/en/ 2 impact the model’s performance on clean data, which is in sharp contrast to UEs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Adversarial attacks are one type of test-time attacks that evade the model’s prediction by adding small imperceptible adversarial noise to the inputs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' UEs can be generated via a min-min bilevel optimiza- tion framework with a surrogate model [17], similar to the generation of strong data poisons via bilevel optimiza- tion [18, 34, 36, 45].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The generated noise is termed Error- Minimizing Noise (EMinN) as it progressively eliminates errors from the training data to trick the target model to be- lieve there is nothing to learn [17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We use EMinN to denote the original UE generation method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In addition to EMinN, there are also UE generation methods that utilize adversarial noise, such as Error-Maximizing Noise (EMaxN) [19], Deep- Confuse [9] and Adversarial Poisoning (AdvPoison) [10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Recently, Yu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' [41] unveil a linear-separability property of unlearnable noise and propose the Synthetic Perturbations (SynPer) method to directly synthesize linearly-separable perturbations as effective unlearnable noise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The original UE method EMinN has a few limitations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' First, the generated unlearnable noise can be removed to a large extent by adversarial training [26], although this will also decrease the model’s performance by a considerable amount [17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This was later on solved by a recent work published at ICLR 2022 [11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The idea is to optimize the adversarial training loss in place of the standard training loss to produce more robust error-minimizing noise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The other limitation is its transferability to different training schemes, target models (the models to protect against) or datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For example, it has been found that unlearnable noise gen- erated in a supervised manner fails to protect the dataset from unsupervised contrastive learning [14].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' A unsupervised UE generation method was then proposed to craft UEs un- learnable to unsupervised contrastive learning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, a very recent work by Ren et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' [32] demonstrates that, sur- prisingly, unsupervised UEs cannot protect the dataset from supervised exploitation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' All above UE methods all rely on the ideal label-consistency assumption, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', the same (or no) labels for the protected data will be used by both the protectors and hackers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this paper, we promote a more practical label-agnostic setting where different labels could be used by the hackers for their own purposes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Besides UEs, strong adversarial attacks have also been proposed to protect personal data from malicious face recog- nition systems, such as LowKey [6] and APF [44].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' They differ from UEs by making a normally trained model unable to recognize the protected images, rather than preventing the proper training of any machine learning models on the protected images.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this work, we focus on UEs rather than other data protection techniques which we believe are of independent interest.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Proposed Method Threat Model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We introduce two parties: the protector and the hacker.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The protectors leverage a surrogate model to generate UEs for its private data before publishing it on the Internet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For example, online social network companies (or users) could convert their photos to their UE versions be- fore posting them online.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' These “protected” images are then collected, without the protectors’ consent, by a hacker into a dataset to train a commercial or malicious model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The pro- tectors’ goal is to make the collected dataset unlearnable, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', cannot be used for model training, while the hackers’ goal is to train accurate models on the unlearnable (protected) dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Following prior works [11,17,25], we assume the released dataset is 100% protected, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', all the samples are perturbed to be unlearnable.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' While this assumption appears to be ideal, if the protection technique is reliable, there is no reason not to employ it to gain more protection and privacy.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Therefore, in this work we choose to focus on the unlearn- able technique itself rather than changing the setting of the protectors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Following our label-agnostic setting, we also as- sume the hackers could exploit the unlearnable dataset with different labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', a m-class dataset could be exploited by the hacker as a n-class dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here, we give an example of such label-agnostic scenario with a online social media company who strives to protect the contents created by all of its users.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The company could leverage unlearnable techniques to develop systematic pro- tection scheme against unauthorized data explorers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this case, we can assume all the images uploaded by the users are protected (by the company).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Potential hackers like Clearview AI may crawl the images from the online platform without the users’ content into one or a set of datasets for its own purposes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Thus, the collected datasets cannot be guaranteed to have the same labels as their original versions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The pro- tector thus needs to craft more powerful and transferable unlearnable examples to make data unexploitable against different labeling strategies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Problem Formulation We focus on image classification tasks in this paper.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Given a clean m-class training dataset Dm c = {(xi, yi)}k i=1 consisting of k clean training images x ∈ X ⊂ Rd and their labels y ∈ Y, in a standard unlearnable setting [17], the protector trains an m-class surrogate model f m s on Dm c .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The protector can then generate an unlearnable version of the dataset as Dm u = {(x′ i, y′ i)}k i=1, based on the clean dataset Dm c and the surrogate model f m s .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The unlearnable images are denoted as x′ = x + δ (x ∈ Dm c ) with the same labels y ∈ Y as their original versions and δ ∈ ∆ ⊂ Rd are the generated unlearnable noise which is often regularized to be imperceptible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The unlearnable dataset Dm u is assumed to be the dataset collected by the hackers, and will be exploited to train a commercial or malicious m-class target model f m t 3 EMinN AdvPoison SynPer DeepConfuse 0 25 50 75 100 Accuracy (%) 19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='93 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='25 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='54 28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='77 93.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='77 93.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='6 93 93.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='31 Label-consistency Label-agnostic (a) Clean EMinN AdvPoison (b) Figure 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (a) Current UE methods become ineffective in the label- agnostic setting, even though they exhibit high effectiveness in the label-consistency setting (under noise constraint ϵ = 8/255).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (b) A 3D feature visualization of clean CIFAR-10 examples and the UEs derived by EMinN and AdvPoison.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Points in the same color denote samples of the same class.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' without the protectors’ consent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Label-consistency vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Label-agnostic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The above formu- lation follows the standard label-consistency assumption of previous works [11,17], where the hackers collect, annotate and exploit the unlearnable dataset Dm u exactly the same as it was initially released by the protectors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Under a more general and practical label-agnostic assumption, the hackers could annotate the collected dataset Dm u differently, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', as- signing it with different number of classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this case, the hackers may exploit the dataset as a n-class (n ̸= m) classi- fication dataset Dn c = {(x′ i, y′ i)}k i=1 to train a n-class target model f n t .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Note that the protectors have no knowledge of the target class number n nor the target labels y′ i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Arguably, the hackers may even exploit the dataset as an object detection dataset rather than a classification dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We will explore such a more challenging task-agnostic assumption in our future work and focus on the label-agnostic in this work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The Label-agnostic Challenge Existing methods are not robust to label-agnostic ex- ploitation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We test the effectiveness of existing unlearn- able methods developed under the label-consistency set- ting against label-agnostic hackers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here we consider cur- rent unlearnable method including Error-Minimizing Noise (EMinN) [17], Adversarial Poisoning (AdvPoison) [10], Syn- thetic Perturbations (SynPer) [41] and DeepConfuse [9], on the CIFAR-10 dataset [21].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The ResNet-18 [15] models are used for both the surrogate and target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As shown in Figure 2 (a), these methods are extremely effective in preventing the training of machine learning models on the unlearnable dataset with the same labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, if the un- learnable dataset is crafted using ImageNet surrogate model with the predicted ImageNet labels (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', labels predicted by the surrogate model), it fails to prevent the model training with the original CIFAR-10 labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This indicates one unique challenge of the label-agnostic setting: unlearnable noises generated to prevent one set of labels are not transferable to preventing other labeling strategies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The working mechanism of existing UEs under the label- consistency setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here, we investigate the representa- tions learned by the target model on clean vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' unlearnable examples, aiming to gain more understanding of the un- learnable mechanism.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In Figure 2 (b), we visualize the 3-dimensional PCA [39] projections of the original represen- tations learned by the ResNet-18 target model for a) clean CIFAR-10 training samples, b) unlearnable CIFAR-10 ex- amples crafted by EMinN method, and 3) unlearnable (poi- soned) CIFAR-10 examples crafted by AdvPoison.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The rep- resentations are extracted at the last convolutional layer and projected using PCA from 512 to 3 dimensions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' It shows in Figure 2 (b) that the unlearnable examples crafted by EMinN and AdvPoison tend to significantly reduce the variance at certain dimensions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' There are also classes that collapse into smaller clusters, like the green class.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This indicates that the noise disrupts the distributional discrepancy in the repre- sentation space to make the data “unlearnable”.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The other key observation is that the noise greatly shifts the points away from the normal data manifold, causing an unneces- sary spread over a certain direction.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This indicates that the noise also breaks the distributional uniformity of the data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Overall, it is evident the unlearnable noise crafted by EMinN and AdvPoison cripples the learning process by distorting both the discrepancy and uniformity of the data distribution in the deep representation space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Unlearnable examples can overfit to the labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' A closer look at the visualizations in Figure 2 (b), one may notice that the unlearning effects occur only within the classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', the UEs have overfitted to the class labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This is somewhat not surprising as the unlearnable noises are generated via a supervised loss function (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', cross-entropy) defined by the labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The noise are thus optimized to thwart the most predictive information to the class labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, this causes the overfitting problem and fails to work if the labels are changed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Intuitively, if we could remove the dependency on the class labels and turn to exploit the clusters that natu- rally arise during the learning process, we could make the unlearnable noise more robust to different annotations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Unlearnable Clusters (UCs) Overview.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Motivated by the above observations, in this work we propose to generate UEs by exploiting the clus- ters learned by a surrogate model and making the clusters unlearnable instead of the labeled classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We term this approach as Unlearnable Clusters (UCs) and illustrate its working follow in Figure 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The key components of UC are one generator model G and one surrogate model fs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' At a high level, UC first employs a surrogate model fs to extract the representations E of all samples in the clean dataset Dc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' It then utilizes the K-means [35] clustering method to derive p clusters from the representations E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Subsequently, for 4 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 2.' metadata={'source': 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='510.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='0 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5 2 2 2Generator ������������(�;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' ������������������������) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Uniform ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Noise ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Cluster-wise ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Perturbation ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Unlearnable ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Image ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Surrogate Model ������������������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Origianl ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Image ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Feature Space ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Update ������������������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Feature Space ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='K-means Initial ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Minimize ������������DDU ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='×: clustering center ������������������������������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='×: clustering center ������������������������������������ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='������������3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='Figure 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The Unlearnable Clusters pipeline.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The entire dataset is divided into p clusters via K-means clustering, where each cluster corresponds to a certain generator with parameters θi and a cluster-wise perturbation δi.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' each cluster, it generates a cluster-wise perturbation δi using the generator G.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The noise will be generated and applied to craft the UE for each sample in Dc, with samples belonging to the same cluster are added with the same cluster-wise noise δi.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' UEs crafted in this manner can prevent the target model from learning meaningful clusters rather than class predictions, thus is more general to different types of label exploitations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Next, we will introduce the details of UCs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Cluster-wise Perturbations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In our UC framework, one encoder-decoder [29] generator network is used to gener- ate the cluster-wise perturbations, with each generator will be reinitialized for one cluster.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As such, we need to ex- tract the clusters first.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here, we leverage the most classic clustering method K-means [35] to detect clusters from the deep representations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Particularly, the clean dataset Dc is fed into the surrogate model fs to extract the representation matrix before the classification layer E = [e1, · · · , ek].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' K- means clustering is then applied on the representation matrix to detect p number of clusters C = {C1, · · · , Cp}, where Ci = {xij}τ(i) j=1 = {xi1, · · · , xiτ(i)} and �p i=1 τ(i) = k.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The corresponding centers for the clusters are µC = {µC1, · · · , µCp}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' With the detected clusters C, we can now propose the following method to generate the unlearnable noise for each cluster.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Intuitively, for cluster Ci, we hope the unlearnable noise δi could move all samples in the cluster to a wrong cluster center, so as to force the model to forget the cor- rect clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This is done via the following minimization framework: θi = arg min θi LDDU(Ci, g(µCi), θi) = arg min θi � xij∈Ci d(fs(xij + G(σ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' θi)), g(µCi)), (1) where, LDDU is our proposed Disrupting Discrepancy and Uniformity (DDU) loss that defines the distance (d(·)) of samples in Ci to a permuted (wrong) cluster center by a per- mutation function g(µCi);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' θi are the parameters of generator network G;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' G(σ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' θi)) generates the unlearnable noise for all samples in Ci (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', xij ∈ Ci).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Please note that the above problem needs to be solved for p times to obtain the cluster- wise unlearnable noise for all p clusters, and for each cluster, the generator G is reinitialized with new parameters θi.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The complete procedure is described in Algorithm 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Algorithm 1 Unlearnable Cluster Generation 1: Input: surrogate model fs, distance metric d, uniform noise σ, number of clusters p, random permutation g, L∞-norm restriction ϵ, clean images x ∈ Dc, initialized generator G with parameters θ 2: Output: cluster-wise perturbations δ = {δ1, · · · , δp} 3: feature matrix E = fs(x) 4: clusters and cluster centers {C, µC} = K-means(E, p) 5: for i in 1 · · · p do 6: Initialize θi 7: δi = G(σ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' θi) 8: δi = Clamp(δi, −ϵ, ϵ) 9: for xij in Ci do 10: x′ ij = Clamp(xij + δi, 0, 1) 11: θi ← Optimize(x′ ij, fs, g(µCi), d) 12: end for 13: δi = G(σ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' θi) 14: δi = Clamp(δi, −ϵ, ϵ) 15: end for CLIP Surrogate Model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' How to choose a surrogate model remains to be an independent challenge for gener- 5 X Xating effective cluster-wise unlearnable noise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As shown in prior works, it plays a central role in facilitating the trans- ferability of the generated UEs to different datasets or target models [17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In the traditional label-consistency setting, the surrogate model can be a model that directly trained on the original (unprotected) dataset, which may of a different (and plausibly a better or more complex) model architecture.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' It could also be a model that trained on a larger dataset with more classes, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', ImageNet-trained models [10,17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We thus adopt an ImageNet-pretrained ResNet-50 as the default surrogate model of our UC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Analogous to the classification surrogate models used for generating the traditional UEs, the ideal surrogate mod- els for unlearnable clusters could be those powerful fea- ture extractors that could lead to accurate detection of clus- ters from an image dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We thus propose to also lever- age one large-scale vision-and-language pre-trained model (VLPM) [22, 23] CLIP [30] as our surrogate model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Pre- trained on over 400 million text-to-image pairs, CLIP has the power to extract the representation of extremely diverse semantics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Moreover, CLIP was pre-trained with a textual de- scription rather than a one-hot label to align with the image, thus overfitting less to the actual class labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Concretely, we employ the image encoder of CLIP to extract the feature matrix for the clean dataset, which is then used to compute the clusters and cluster centers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We denote the version of UC equipped with the CLIP surrogate model as UC-CLIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Experiments In this section, we evaluate our UCs methods on different datasets against different target models, which is to simulate as many unknown cases as possible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also examine the ro- bustness of UCs against several advanced defenses.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Finally, we demonstrate its effectiveness in attacking commercial machine learning platforms Azure and PaddlePaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Experimental Settings Datasets and Models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We conduct our study on 6 high- resolution and industrial-scale vision datasets to simulate as diverse real-world applications as possible, including Pets [28], Cars [20], Flowers [27], Food [3], SUN397 [40] and ImageNet [33].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For ImageNet, we only use its first 100 classes which is denoted as ImageNet⋆.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For surrogate models, we consider ResNet-50 trained on ImageNet-1k as the default, unless otherwise explicitly stated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For target models, we employ randomly initialized ResNet-18 [15], EfficientNet-B1 [38] and RegNetX-1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='6GF [31].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We train the target models with data augmentations (resizing, ran- dom crop, random horizontal flip and normalization) for 90 epochs, using SGD with initial learning rate 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1, Cosine annealing, momentum 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='9, and batch size 256.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For generator G, we repeated p times to train the generator G for 10 epochs using SGD with initial learning rate 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1, 10 20 30 Number of class 0 20 40 60 Accuracy (%) UC UC-CLIP random guess clean (a) Different labelings Clean SynPer EMaxN EMinN AdvPoison DeepConfuse UC-CLIP UC 0 10 20 30 40 50 Accuracy (%) 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='3 46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='8845.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1948.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1647.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='02 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='37 26.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='11 17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='83 (b) Unsupervised exploitation Figure 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (a) The accuracy of ResNet-18 target models trained on the unlearnable Pets dataset but with its labels were re-labeled by the hacker into 5 to 35 classes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (b) Comparison of our approach with the baselines on Pets dataset against ResNet-18 target model trained via self-supervised SimCLR.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Cosine annealing, momentum 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='9, and batch size 256, and 10 epochs for ImageNet⋆ and 50 epochs for other datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' For random permutation g(·), we simply chose i → i + 1 to build a closed loop.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We consider L∞-norm restriction in this work, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', ∥δ∥∞ < ϵ = 16/255.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The number of clusters p is set to 10, with an analysis is provided in Section 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Baselines.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We compare our UC and UC-CLIP with 5 base- line methods including DeepConfuse [9], Synthetic Perturba- tions (SynPer) [41], Error-minimizing Noise (EMinN) [17], Error-maximizing Noise(EMaxN) [19], and Adversarial Poi- soning (AdvPoison) [10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We use their official implementa- tions and follow the suggested settings in the original papers to generate the UEs or poisons.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Label-agnostic Setup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Please note that we conduct all of our experiments under the proposed label-agnostic setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The UCs (and the UEs they serve) are all generated with the predicted labels by the surrogate models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The predicted la- bels may overlap with the ground truth labels to some extent, but are highly inconsistent with the original labels as the sur- rogate models are not trained on the particular datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The hackers train all target models on the unlearnable datasets with their ground truth labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We report the test accuracy of the target models on the respective clean test sets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Main Results Effectiveness against different target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We first compare our UC and UC-CLIP with the 5 baselines against different target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Table 1 shows the results against ResNet-18, EfficientNet-B1, and RegNetX-1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='6GF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We have the following main findings: (1) Our methods outperform the baselines by a huge margin consistently across different datasets and target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This demonstrates the superi- ority of our methods over the baselines.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (2) Our UC-CLIP achieves a better performance than UC, and in most of the cases, by a considerable margin.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This proves the great poten- tial of using CLIP as the surrogate model to protect person data from unauthorized exploitations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 6 Table 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The test accuracy (%) of different target models trained on the unlearnable datasets generated by our UC/UC-CLIP and the 5 baseline methods, under the label-agnostic setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The top-2 best results are highlighted in bold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' RESNET-18 EFFICIENTNET-B1 REGNETX-1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='6GF METHODS PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ PETS CARS FLOWERS FOOD SUN397 IMAGENET⋆ CLEAN 62.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='31 67.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='18 67.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='18 78.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='97 43.' 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='89 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='78 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='49 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='33 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='13 17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='44 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='95 31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='82 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='87 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='18 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='12 26.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='76 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='04 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='66 Effectiveness Against Different Labelings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' An even more challenging label-agnostic setting is that the hacker may exploit the unlearnable dataset using different labeling strategies instead of one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' So, a natural question is that what if the number of labeled classes of the unlearnable dataset is less than our cluster number p = 10?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here, we take the 37-class Pets dataset as an example and explore the impact if the hacker re-labels the unlearnable version of the dataset as a 5 to 36 class dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' One possible labeling strategy is that the hacker first extracts the embeddings of the original text labels using the BERT model [8], and then clusters the embeddings into 5-37 classes using K-means, so as to con- struct a mapping from the old labels to the new labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As shown in Figure 4 (a), both our UC and UC-CLIP can bring the test accuracy of the target model down to a level that is close the random guess (the black curve).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This verifies that our methods can craft more generic UEs against the most severe label-agnostic exploitations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Robustness to Unsupervised Exploitation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also com- pare our methods with the baselines under an unsupervised contrastive learning setting against SimCLR [4].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Although our UC methods are not specifically designed for this un- supervised setting, Figure 4 (b) shows that cluster-wise un- learnable noise can also prevent unsupervised exploitation against SimCLR.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Preventing Commercial Platforms Here, we apply our UC methods to prevent two com- mercial machine learning platforms: Microsoft Azure and Baidu PaddlePaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' On both platforms, the training details are agnostic to us, including the model architecture, learning rate, batch size, epoch, data augmentation, splitting of the validation set, etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Considering that ViT may be used on commercial platforms due to its recent popularity, we upgrade our UC-CLIP method by replacing the ResNet-50 (RN50) surrogate model by a ViT-B-32 (ViTB32) surrogate model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The results are reported in Table 2, which are consis- Table 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The test accuracy (%) of models trained by Azure and PaddlePaddle platforms on unlearnable Cars dataset crafted by different methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The training configuration on the platform was set to “fastest training”.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' METHODS Azure PaddlePaddle CLEAN 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='45 83.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='74 SYNPER 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='38 47.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='59 EMAXN 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='83 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='99 EMINN 44.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='06 44.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='40 ADVPOISON 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='97 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='38 DEEPCONFUSE 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='47 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='88 UC (RN50) 36.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='40 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='96 UC-CLIP (RN50) 26.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='97 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='79 UC-CLIP (VITB32) 22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='47 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='49 tent with that in Table 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', both of our methods can protect the data uploaded to the two platforms against their training algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Unsurprisingly, the ViTB32-powered UC-CLIP method achieves the best protection performance by causing the lowest test accuracy.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This suggests the effectiveness of our methods even against commercial platforms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Resistance to Potential Defenses In this section, we test the robustness of our UC methods to several augmentation based defenses, includ- ing Mixup [43], Gaussian smoothing, Cutmix [42] and Cutout [7].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We did not consider adversarial training here is that the images involved in this paper are generally large in size, number and resolution, making adversarial training ex- tremely hard to converge without losing considerable clean accuracy on most of the datasets [26].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Compared with ad- versarial training, we believe that a more practical defense should be very efficient, such as image denoising or the con- sidered augmentation techniques.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As can be observed in Table 3, the 4 data augmentation defenses have minimum impact on our UC and UC-CLIP methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Particularly, Gaus- sian smoothing appears to be the most effective defense, but the accuracy is still below 25%.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 7 Table 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The test accuracy (%) of ResNet-18 trained using different defenses against our methods on Pets dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' METHODS NO DEFENSE MIXUP GAUSSIAN CUTMIX CUTOUT UC 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='21 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='34 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='26 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='50 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='35 UC-CLIP 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='69 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='96 18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='59 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='21 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='29 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Ablation Study 5 10 15 20 25 30 35 40 Number of clusters 0 5 10 15 Accuracy (%) 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='08 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='21 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='42 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='82 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='46 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='75 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='51 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='92 (a) Effect of p on UC 5 10 15 20 25 30 35 40 Number of clusters 0 5 10 15 Accuracy (%) 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='38 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='69 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='11 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='33 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='33 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='73 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='09 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='67 (b) Effect of p on UC-CLIP Figure 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Analyzing the effect of cluster number p on Pets dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here, we analyze the sensitivity of our methods to the number of clusters p, which has been set to p = 10 as a default.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We take the 37-class Pets dataset as an example and evaluate our UC and UC-CLIP method under different values of p ∈ [5, 40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As shown in Figure 5, our methods are quite stable to varying hyperparameter p for p ≥ 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This indicates that, as long as the clusters can cover most of the concepts in a dataset, the generated unlearnable noise can effectively prevent the model from learning the real content from the dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As the number of clusters increases, the noise tends to become more effective, although there is a slight variation at 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Note that, even in the worst case at p = 5, our methods still outperform the baselines.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Mixture of Clean and Unlearnable Data 0 5 10 15 20 25 30 35 Number of classes 0 10 20 30 40 50 60 Accuracy (%) clean-only mixture (a) Mixture vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Clean-only 0 25 50 75 100 125 150 Epoch 0 20 40 60 80 100 Accuracy (%) training (unlearnable) test (clean) test (unlearnable) (b) Accuracy trends Figure 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' (a) The test accuracy (%) of ResNet-18 trained on unlearnable-clean mixed vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' clean-only data;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' and (b) the accu- racy trends on clean vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' unlearnable examples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' The unlearnable examples are crafted using our UC method on Pets dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' All the above experiments are conducted under the as- sumption that all samples in the dataset are protected, a commonly adopted assumption in the literature [10,17,41].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This setting is reasonable when the protectors have the access to the entire dataset, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', an online social media company adopts the technique to protect the contents created by all of its users.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' A more general case is that only a certain pro- portion of the users protect their data while others do not.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This results in mixed dataset with both clean and unlearnable samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Here we test our UC method under this setting and show the change in test accuracy with the number of clean classes in Figure 6 (a).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', for the mixture dataset, the rest of the classes are made unlearnable by UC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' It can be inferred that the unlearnable classes almost do not contribute to the model training, a similar conclusion as in previous works [10,17,41].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This implies that only those who adopt the technique will get protected.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' More Understanding Why our UCs are more powerful than standard UEs against label-agnostic exploitation?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As we explained in Section 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='1, the idea of UCs is inspired by the effectiveness of disrupting the uniformity and discrepancy in preventing the model from learning useful information.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' However, this also raises another question: what exactly does the target model learn?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To answer these two questions, here we ana- lyze the learning curves of the target model on the clean vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' unlearnable examples separately.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' As shown in Figure 6 (b), as the training progresses, the training accuracy on the un- learnable training samples steadily improves until it reaches 100%.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' But there is almost no improvement in the clean test accuracy on the clean test samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This is consistent with the the above experimental results that the target model has not learned the capability to perceive normal samples.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Sur- prisingly, however, the model’s accuracy on the perturbed test samples is fairly high (> 60%), considering that the normally trained ResNet-18 only achieves a test accuracy of 62.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='31% on clean Pets dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' This implies that the unlearn- able noise distribution contained in the UCs has effectively concealed the real data distribution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' Conclusion Unlearnable examples (UEs) have shown great potential in preventing hackers from using users’ private data to train commercial or malicious models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' A number of methods have been proposed to improve UEs’ transferability and ro- bustness to different datasets, target models and training paradigms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' In this work, we identified one limitation of ex- isting UE methods, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=', their label-consistency assumption.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' To overcome this limitation, we proposed a more general setting where the hackers could exploit the protected data with different sets of labels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We termed this more challeng- ing setting as label-agnostic, and proposed an Unlearnable Clusters (UCs) technique with conditioned generator models, K-means clustering, and large-scale vision-and-language pre- training model CLIP, to craft effective UEs against a wide range of datasets and target models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' We also demonstrate its effectiveness against commercial platforms Microsoft Azure and Baidu PaddlePaddle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/1dAzT4oBgHgl3EQfRfuL/content/2301.01217v1.pdf'} +page_content=' 8 References [1] Battista Biggio, Blaine Nelson, and Pavel Laskov.' metadata={'source': 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s.dutta2@mimuw.edu.pl +4Universit´e Cˆote d’Azur, INRIA, Sophia Antipolis, France. email: +siddharth.pritam@inria.fr +Abstract +The strong collapse of a simplicial complex, proposed by Barmak and Minian [6], is a +combinatorial collapse of a complex onto its sub-complex. Recently, it has received attention +from computational topology researchers [22, 7, 8], owing to its empirically observed useful- +ness in simplification and size-reduction of the size of simplicial complexes while preserving +the homotopy class. We consider the strong collapse process on random simplicial complexes. +For the Erd˝os-R´enyi random clique complex X(n, c/n) on n vertices with edge probability +c/n with c > 1, we show that after any maximal sequence of strong collapses the remaining +subcomplex, or core must have (1 − γ)(1 − cγ)n + o(n) vertices asymptotically almost surely +(a.a.s.), where γ is the least non-negative fixed point of the function f(x) = exp (−c(1 − x)) +in the range (0, 1). These are the first theoretical results proved for strong collapses on +random (or non-random) simplicial complexes. +1 +Introduction +Motivation +Simple collapse is a combinatorial notion which simplifies a simplicial complex +without changing its topology. It can be expressed as a series of elementary moves of removals of +pair of simplices σ and τ, such that σ is uniquely contained in τ. The notion of simple collapse +was introduced by J.H.C Whitehead [21] to study homotopy types of cell complexes. Since then +it has found usage in many different areas of topology, especially in computational topology. +Recently new variants of simple collapses have been introduced, called strong collapses and more +generally d-collapses [6, 8, 5]. In such collapses one removes special vertices (more generally +d-simplices) called dominated vertices (simplices) whose link is a simplicial cone. It’s again +expressed as a series of elementary moves of removals of dominated vertices (simplices). They +have been shown to be very powerful tools to solve many problems in computational topology. +In particular, the recent works of Pritam et. al. [9, 8, 23] has shown that strong collapses and +edge collapses (d-collapse for d = 1) can be used for efficient computation of one parameter and +∗J.-D. Boissonnat and S. Pritam received funding from the European Research Council (ERC) under the +European Union’s Seventh Framework Programme (FP/2007- 2013) / ERC Grant Agreement No. 339025 GUDHI +(Algorithmic Foundations of Geometry Understanding in Higher Dimensions). +†K. Dutta and S. Dutta received funding from the Polish NCN SONATA Grant no. 2019/35/D/ST6/04525. +1 +arXiv:2301.03514v1 [cs.CG] 9 Jan 2023 + +multi-parameter persistence. Efficient computation of persistent homology is one of the central +topic of research in topological data analysis. +The computation of persistent homology involves computing homology groups of a nested +sequence of simplicial complexes called filtrations. And to compute persistent homology requires +O(n3) time and O(n2) space, here n is the total number of simplices in the filtration. The +general technique developed in [9, 7, 8, 12, 23] is to reduce a filtration to a smaller filtration +using strong or edge collapse such that the persistent homology is preserved. In [9, 7, 8, 12, 23], +it has been established through experiments that in practice the reduced filtrations are very +small and thereafter computation of persistent homology is extremely fast. The gain in efficiency +is quite dramatic in the case of flag (clique) complexes, where the strong collapse and edge +collapse can be computed using only the graph (1-skeleton) of the given complex [7, 12, 23]. +As mentioned above the efficiency reported in [9, 7, 12, 23] are through experiments and +there is no theoretical guarantee over the reduction size. This is due to the fact that in general +the amount of reduction depends on the individual complex and its combinatorial structure. In +fact, the reduction is dependent even on the order of the collapses and a different order can +result in a different core, except in the case of strong collapse. Which is even harder when we +want study the reduction size in a filtered simplicial complexes. This motivates us to consider +the case of random simplicial complexes and study the average reduction size by collapses. +In this article, we study the problem of reduction size achieved by the strong collapses of a +clique complex defined over an Erd˝os-R´enyi random graph. +Previous +The study of random simplicial complexes was initiated in the seminal paper of +Linial and Meshulam [16]. Later Meshulam and Wallach [19] generalized the model of random +complexes to obtain the Linial-Meshulam (LM) model of d-dimensional random complexes. +Since then a large body of work from several authors has emerged on many different models +of random simplicial complexes, studying various topological and geometric properties of such +complexes [14]. The study of simple collapses for random simplicial complexes has also been of +interest to researchers and there have been numerous works in this direction. In the d-dimensional +LM model, Kozlov [15] proved bounds on the threshold for vanishing of the d-th homology. +Simple collapses on random complexes were first studied by Aronshtam, Linial, �Luczak and +Meshulam [4], who improved Kozlov’s bound to get a tight bound on the threshold and also gave +a bound on the threshold for collapsibility in the d-dimensional LM model. Later Aronshtam +and Linial [2, 3] extended this line of work, obtaining first the threshold for the vanishing of +the d-th homology in [2] and then the threshold for non-collapsibility of the d-dimensional LM +complex [3]. In [17] Linial and Peled obtained precise asymptotic bounds on the size of the core +of such complexes. Very recently, Malen [18] has shown that the ER clique complex X(n, p) is +(k + 1)-collapsible with high probability for p = n−α when α > 1/(k + 1). +Thus, to the best of our knowledge, work on collapses in random complexes has so far +considered only simple collapses. +Throughout this paper, we shall use the notation asymptotically almost surely (a.a.s.) for a +series of events (En)n≥1, when the probability of occurence of En goes to 1 as n → ∞. +Models of Random Simplicial Complexes +In this paper we shall consider two models of +random simplicial complexes, which are described below. For a graph G, let cl(G) denotes the +clique (flag) complex on G, i.e. the simplicial complex where each complete subgraph of G +on d vertices is a d − 1-simplex in cl(G). The Erd˝os-R´enyi (ER) model X(n, p) on n vertices +with probability parameter p ∈ [0, 1] is given by connecting each possible pair of elements of an +n-element set by an edge randomly and independently with probability p to get the random +graph G = G(n, p). Let X(n, p) := cl(G(n, p)). +2 + +Our Contribution +We give bounds on the size of the core (i.e. the smallest sub complex +without any dominated vertex) of a random simplicial complex after strong (vertex) collapses. +Whereas previous works focused on computing the threshold for the appearance and disappearance +of the k-th homology class for different k, here we are more interested in computing the size of +the core. We show that for n-vertex ER clique complexes, the size of the core after a maximal +series of strong collapses is a.a.s. a constant fraction of n, with the constant depending only on +the edge probability, and bounded away from 1. Further, we also find a precise expression for +the constant, as a fixed point of an implicit equation. Our first theorem is stated below. +Let K be a simplicial complex. For i ≥ 1, we use fi(K) to denote the set of i−simplices of +the complex. By a slight abuse of notation, we let f0(K) denote the set of non-isolated vertices +of the complex and ˜f0(K) denote the set of non-isolated vertices of the complex. (A vertex +v ∈ K is isolated the if v is not a face of any edge in K.) In a pruning phase run on K, all +dominated (strong-collapsible) vertices of K are simultaneously collapsed. Let Rt(K) denote +a complex obtained by running t pruning phases over K. Lastly, R∞(K) denotes a complex +obtained from K after running a maximal series of strong collapses on K. i.e. the core of K. +Theorem 1. Let c > 1 and X ∼ X(n, c/n). Then there exists a constant γ ≡ γ(c) given by +the least non-negative fixed point of the function f(x) = exp (−c(1 − x)), x ∈ (0, 1), such that +0 < γ < 1/c < 1 and a.a.s. the following holds +|f0(R∞(X))| = (1 − γ)(1 − cγ)n + o(n). + 0 + 5000 + 10000 + 15000 + 20000 + 25000 + 0 + 10000 + 20000 + 30000 + 40000 + 50000 + 60000 + 70000 + 80000 + 90000 + 100000 +size of the CORE +n +experimental value for c=1.5 +theoretical value for c=1.5 +Figure 1: We ran experiments on ER complexes and plotted the size of the core (strong collapse) +with n ∈ [0, 105] and c = 1.5. These experiments clearly validates our theoretical results. +3 + + 0 + 1000 + 2000 + 3000 + 4000 + 5000 + 6000 + 7000 + 8000 + 9000 + 10000 + 1 + 1.5 + 2 + 2.5 + 3 + 3.5 + 4 + 4.5 + 5 +size of the CORE +c +experimental value for n=10000 +theoretical value for n=10000 +Figure 2: In a different set of experiments over ER complexes, we varied the constant c ∈ [1, 5] +keeping the number of vertices fixes to n = 104. +We then address a question of algorithmic interest: given an ε ∈ (0, 1), how many rounds +do we need in the first epoch to get within an εn gap from the actual size of the core? The +following theorem gives a bound on the number of rounds t as a function of ε. +Theorem 2. Let X ∼ X(n, c/n) and ε > 0 (sufficiently small) be given. Then there exists +t ∈ Z+ such that +(c − cγ)ec +1 − ce−c (ce−c)t ≤ ϵ ≤ (c + 1)ec +1 − cγ (cγ)t, +and |f0(Rt(X))| − |f0(R∞(X))| ≤ ϵn + o(n) a.a.s. +1.1 +Overview of Proofs and Outline of Sections +While our analysis shares the general flow of the analysis of the simple collapsibility of LM +complexes in e.g. [4, 2, 3], there are several differences and difficulties. Firstly, in both cases +(strong collapse of ER clique complex and simple collapse of LM model) our goal is to find the +size of the core, rather than whether the complex is collapsible or not. Secondly, in the case of +the random ER clique complex our analysis needs to take into account the non-homogeneity of +the complex. That is, maximal simplices in this model can have different sizes. Further, unlike +in the LM model, the existence of a maximal simplex is not independent of the existence of all +other possible maximal simplices. Finally perhaps the most interesting difference of the random +ER clique complex model in our context, is that the effect of removing a vertex is not necessarily +localized – a fact which requires a fair bit of innovation to handle (in several places), especially +in proving the concentration bounds in Section 6, and in the later stages of the analysis, in +Section 7. We present a more detailed overview of the proof strategy used in our concentration +bound, in the beginning of Section 6. +With the above caveats in mind, we first briefly review the main ideas of the proof of +Aronshtam and Linial [3]. The analysis was split into two epochs, each of which were further +divided into several rounds (phases). In the first epoch, in each round, every simple-collapsible +simplex was simultaneously collapsed, and this procedure was repeated for a constant number +of rounds. Aronshtam and Linial [3] used a tree-like model of a random simplicial complex to +approximate the local structure of the random LM complex and showed that the total number +of collapsed simplices over all such rounds tended to a constant fraction of the number of initial +4 + +simplices, as the number of rounds increased. Moreover, this limit constant could be expressed +as a fixed point of an implicit equation involving only the distribution parameter c. +In the analysis of the second epoch, a simplex would be chosen randomly from the set of +(non-neighbouring) simple-collapsible simplices, and collapsed in each round. The aim was to +show that in this epoch, the number of simplices collapsed would be asymptotically negligible +compared to the inital number of simplices present. Thus in summary, the final number of +deleted simplices is determined by the first epoch itself, and the second epoch serves to show the +tightness of this bound. +Our proofs also split the analysis into two epochs. Similar to [3], we show that a certain tree- +like model of random simplicial complexes provides a good approximation of local neighbourhoods, +which is done in Section 3. This is followed by the analysis of the first epoch, in Section 4. The +main theorem of this section gives an expression for the expected number of vertices remaining +after t rounds (or pruning phases) of the first epoch. Bounds on t as a function of ε, γ and +c, are given in Theorem 2, which is proved in Section 5. Before beginning the analysis of the +second epoch however, we need bounds on the concentration of the size of the core itself, as well +as several other random variables. These are proved in Section 6, where we use the notions of +critical and precritical (sub)complexes – described in more detail in the beginning of Section 6. +With these concentration bounds in place, we move to the analysis of the second epoch in +Section 7. +2 +Preliminaries +In this section we briefly introduce some topological and probabilistic notions. Readers can refer +to [13] for a comprehensive introduction to topics related to topology and [10] for topics related +to probability theory and random structures. +Simplicial complex. +An abstract simplicial complex K is a collection of subsets of a +non-empty finite set X, such that for every subset A in K, all the subsets of A are in K. An +element of K is called a simplex. An element of cardinality d + 1 is called a d-simplex and d +is called its dimension. Given a simplicial complex K, we denote its geometric realization as +|K|. A simplex is called maximal if it is not a proper subset of any other simplex in K. A +sub-collection L of K is called a subcomplex if it is a simplicial complex itself. A subcomplex +K′ of K is called a d-skeleton of K if it contains all the simplices of K of dimension at most d. +Erdos Renyi Graph Definition. +This is the probability space G(n, p) consisting of +all the graphs on n vertices. Probability of occurrence of a graph with m edges is pm(1 − +p)(n)(n−1)/2−m. In other words, it is a random graph on n vertices where each edge can occur +independently with probability p. +Clique complex and Neighborhood. +A complex K is a clique or a flag complex if, +when a subset of its vertices form a clique (i.e. any pair of vertices is joined by an edge), they +span a simplex. For a vertex v in G, the open neighborhood NG(v) of v in G is defined as +NG(v) := {u ∈ G | [uv] ∈ E}, here E is the set of edges of G. The closed neighborhood +NG[v] is NG[v] := NG(v) ∪ {v}. Similarly we define the closed and open neighborhood of an +edge [xy] ∈ G, NG[xy] and NG(xy) as NG[xy] := N[x] ∩ N[y] and NG(xy) := N(x) ∩ N(y), +respectively. The above definitions can be extended to any k-clique σ = [v1, v2, ..., vk] of G; +NG[σ] := � +vi∈σ N[vi] and NG(σ) := � +vi∈σ N(vi). +Star, Link and Simplicial Cone. +Let σ be a simplex of a simplicial complex K, the +closed star of σ in K, stK(σ) is a subcomplex of K which is defined as follows, stK(σ) := {τ ∈ +5 + +K| τ ∪ σ ∈ K}. The link of σ in K, lkK(σ) is defined as the set of simplices in stK(σ) which +do not intersect with σ, lkK(σ) := {τ ∈ stK(σ)|τ ∩ σ = ∅}. The open star of σ in K, sto +K(σ) is +defined as the set stK(σ) \ lkK(σ). Usually sto +K(σ) is not a subcomplex of K. +Let L be a simplicial complex and let a be a vertex not in L. Then the set aL defined as +aL := {a, τ | τ ∈ L or τ = σ ∪ a; where σ ∈ L} is called a simplicial cone. +Simple collapse. +Given a complex K, a simplex σ ∈ K is called a free simplex if σ has +a unique coface τ ∈ K. The pair {σ, τ} is called a free pair. The action of removing a free +pair: K → K \ {σ, τ} is called an elementary simple collapse. A series of such elementary +simple collapses is called a simple collapse. We denote it as K ↘ L. A subcomplex Kec of K +is called an elementary core of K if K↘Kec and Kec has no free pair. +Removal of a simplex. +We denote by K \ σ the subcomplex of K obtained by removing +σ, i.e. the complex that has all the simplices of K except the simplex σ and the cofaces of σ. +Dominated simplex. +A simplex σ in K is called a dominated simplex if the link lkK(σ) +of σ in K is a simplicial cone, i.e. if there exists a vertex v′ /∈ σ and a subcomplex L of K, such +that lkK(σ) = v′L. We say that the vertex v′ is dominating σ and that σ is dominated by v′, +which we denote as σ ≺ v′. +σ-algebra +The reader can refer to [10] for the definition of σ-algebra. +d-collapse. +Given a complex K, the action of removing a dominated k-simplex σ from K is +called an elementary d-collapse, denoted as K↘↘d{K \σ}. A series of elementary d-collapses +is called a d-collapse, denoted as K ↘↘k L. We further call a complex K d-collapse minimal +if it does not have any dominated d simplices. A subcomplex Kk of K is called a d-core if K +↘↘k Kd and Kd is d-collapse minimal. A 0-core of a complex K is unique, however it is not +true in general for k ≥ 1. Like simple collapses, d-collapses preserve the homotopy type of a +simplicial complex. +A 0-collapse is a strong collapse as introduced in [6] and 1-collapse is called an edge +collapse [8]. The following lemma from [8] characterizes the domination of a simplex in the +special case of a flag complex in terms of neighborhood. +Lemma 3. Let σ be a simplex of a flag complex K. Then σ will be dominated by a vertex v′ if +and only if NG[σ] ⊆ NG[v′]. +In this article, our main focus will be the case d = 0, i.e. when σ is a vertex. The next +lemma from [7], though elementary, is of crucial significance. +Lemma 4. Let K be a flag complex and let L be any subcomplex of K obtained by strong +collapses. Then L is also a flag complex. +Both lemmas (Lemma 3 and Lemma 4) show that strong collapse is well-suited to flag +complexes. In the next sections we will investigate the reduction capabilities of strong of a clique +complex of an Erd˝os-R´enyi random graph. +3 +Tree process +In this section, we describe the tree process which is used to simulate the collapse process in the +first epoch of the (strong) collapse. A one-dimensional tree is built recursively as follows: +1. Start with a single node(root). +6 + +2. In the nth iteration, add children to all the leaves at distance n − 1 from the root from +Poisson distribution with parameter c(> 1). +Let Tn denote the set of all possible trees after nth iteration for n > 1 and T0 being the root +itself. Let T := � +n∈N +Tn. +Let γt be the probability that a tree T ∈ Tt is pruned to the root in no more than t − 1 steps. +Clearly, γ1 = e−c. Set γ0 = 0. Also, we have the following recursive relation which is true in +general: +γt+1 = e−c(1−γt). +Note that, in this process we never prune the root itself even if its degree is 1. We call such +a process root collapsing. Let γk +t denote the probability that a tree T ∈ Tt has degree k after +t − 1 root collapsing steps. Then, +γk +t = (c(1 − γt−1))k +k! +e−c(1−γt−1) +Observe that γk +1 gives the initial degree distribution. Also, let γ≥2 +t +denote the probability that a +vertex has degree atleast 2 after t − 1 root collapsing steps. Then we have +γ≥2 +t += +∞ +� +k=2 +γk +t = 1 − γt(1 + c(1 − γt−1)). +Define βt := 1 − γt+1. Thus, βt is the probability that atleast t + 1 root collapsing steps are +needed to isolate the root of a tree T ∈ Tt. +Define f(x) := e−c(1−x) on the interval [0, 1]. We shall assume c > 1 for the rest of these +paper unless specified otherwise. Note that f([0, 1]) ⊆ [0, 1], f′(x) = cf(x) and f(x) is strictly +increasing on the interval [0, 1]. Let ft(x) denoted the function obtained by composing f t times. +Then ft is also strictly increasing on [0, 1] for all t ≥ 1. As, γ1 > γ0, applying ft−1 on both sides, +we get γt > γt−1 for all t ≥ 1. +Also define γ to be the left most zero of the function g(x) := e−c(1−x) − x defined on the +range [0, ∞). Note that 0 < γ ≤ 1 as g(1) = 0. +Lemma 5. For c > 1 and γ = γ(c) defined as earlier we have cγ < 1. +Proof of Lemma 5. Let g(x) be defined as above. So g(γ−) > 0 and g(γ) = 0. Thus, from +the differentiability of g(x), cγ − 1 = g′(γ) ≤ 0. Now, if cγ − 1 = 0 then ce1−c = 1, which is +impossible for c > 1. Thus cγ − 1 < 0. +Now observe that, x ≤ γ =⇒ f(x) ≤ f(γ) = γ. Thus, by the fact that f′(x) = cf(x), f(x) +restricted on [0, γ] becomes a contraction mapping. So, by Banach Fixed Point theorem, f|[0,γ] +has an unique fixed point which, in our case, is γ. +To summarize the above arguments we get the following remark. +Remark 1. γt converges to 0 < γ < 1/c as an increasing sequence and βt converges to +1 − 1/c < β < 1 as a decreasing sequence. +4 +First Epoch +In this section, we present the analysis of the first epoch of the collapse. The first epoch is executed +in phases and in each phase we remove a maximal set of dominated vertices simultaneously. +Our goal, in this section, is to prove the following theorem. +7 + +Theorem 6. Let X ∼ X(n, c/n). Let E(|f0(Rt(X))|) denote the expected number of non-isolated +vertices in X after t strong collapse phases and γt be as defined in the last section. Then, +E(|f0(Rt(X))|) = (1 − γt+1 − cγt + cγ2 +t )n. +We start by proving some important lemmas about the local structure of the complex. For +X ∼ X(n, c +n), let us define the following event, +D := {deg(v) ≤ log n ∀v ∈ ˜f0(X)}. +Then, the following lemma can be proved using standard Chernoff bounds. +Lemma 7. Pr{D} = 1 − on(1). +Proof of Lemma 7. Note That for any v ∈ ˜f0(X), deg(v) ∼ Bin(n − 1, c/n). Let Dv be the +event that deg(v) ≤ log(n). Then by the Chernoff Bound on Binomial Distribution +Pr{¬Dv} = Pr{deg(v) > log(n)} +≤ (ec(n − 1) +n log(n) )log(n) +≤ ( +ec +log(n))log(n) += n− log(log(n/ec)) +Thus by the union bound Pr{� +v∈f0(X) ¬Dv} ≤ n1−log(log(n/ec)). Hence, +Pr{D} = Pr{ +� +v∈f0(X) +Dv} = 1 − Pr{ +� +v∈f0(X) +¬Dv} ≥ 1 − n1−log(log(n/ec)) = 1 − on(1) +By Cl(S) we denote the simplicial closure of the set S. Fix v ∈ ˜f0(X). Define N0 := Cl(v) +and N−1 := ∅. Also define Ni+1 := Cl({s ∈ X|∃u ∈ ˜f0(Ni)\ ˜f0(Ni−1)|u ⊂ s})∪Ni. Equivalently, +this can also be defined in terms of the 1-skeleton of the complex. +Define the event At = {Nt ∈ T }. +Lemma 8. Let X ∼ X(n, p) and fix v ∈ ˜f0(X). Then Pr{At ∩ D} = 1 − o(1) . +Proof. If X ∈ D then ˜f0(Nt) = O(logt+1n) and we want to avoid O(log2t+2n) edges to make Nt +a one dimensional tree. Probability of that happening is +(1 − c/n)O(log2t+2n) = 1 − o(1) +Now the the degree of a node of this tree comes from Bin(n − 1, c/n). For large n this +distribution can be approximated by Po(c). +Proof of Theorem 6. Recall that for a simplicial complex X, Rt(X) denotes a complex obtained +after t phases and f0(X) denotes the set of non-isolated vertices (0−simplices) of the complex. +Note that if a vertex v ∈ f0(X) survived t pruning steps then it must have had degree deg(v) ≥ 2 +after t − 1 pruning steps. Thus, Pr{v ∈ f0(Rt(X))} ≤ γ≥2 +t += 1 − γt(1 + c(1 − γt−1)). This event +counts both the isolated vertices and degree one, (i.e., collapsible) vertices. Thus this gives a +slight over estimate. To get more precise estimate we observe that, in the spirit of [3], that a +vertex v ∈ f0(X) survives t pruning steps if it is neither collapsed nor isolated after t pruning +steps. Probability of such an event is 1 − γt+1 + cγt − cγ2 +t . The previous lemma asserts that it is +indeed the survival probability of a vertex of the simplicial complex. +8 + +5 +Rate of Convergence +In this section, we prove Theorem 2 thus giving bounds on the rate of convergence of the variable +γt. +Lemma 9. Let c, γt be as defined earlier. Then +cγt ≤ γt+1 − γt +γt − γt−1 +≤ cγt+1 +Proof. Let f(x) and g(x) be as defined in section 3. Clearly, +γt+1 − γt +γt − γt−1 += +g(γt) +g(γt−1) += g(γt−1 + (γt − γt−1)) +g(γt−1) += g(γt−1) + g′(s)(γt − γt−1) +g(γt−1) +(for some s ∈ [γt−1, γt]) += f′(s) = cf(s) +(as γt − γt−1 = γt−1) +As f(x) is an increasing function the result follows. +In particular, ce−c ≤ γt+1−γt +γt−γt−1 ≤ cγ for all t ≥ 1. +Let δ(t) = (1 − γt+1 − cγt + cγ2 +t ) − (1 − γt+2 − cγt+1 + cγ2 +t+1), as defined in section 7. It can +be shown that +δ(t) = (1 − γt+1 − cγt + cγ2 +t ) − (1 − γt+2 − cγt+1 + cγ2 +t+1) += (γt+2 − γt+1) + c(γt+1 − γt) + c(γt + γt+1)(γt − γt+1) += (γt+2 − γt+1 +γt+1 − γt ++ c − c(γt+1 + γt))(γt+1 − γt) +Hence, +(c − cγ)ec(ce−c)t ≤ δ(t) ≤ (c + 1)ec(cγ)t +Now define ϵ ≡ ϵ(t) := (1 − γt+1 − cγt + cγ2 +t ) − (1 − γ − cγ + cγ2) so that E[|f0(Rt(X))|] − +(1 − γ)(1 − cγ] = ϵn. Consequently, +ϵ(t) = (1 − γt+1 − cγt + cγ2 +t ) − (1 − γ − cγ + cγ2) += (γ − γt+1) + c(γ − γt) + c(γt + γ)(γt − γ) += (γ − γt+1) + (c − c(γt + γ))(γ − γt) +So, +(c − cγ)ec +1 − ce−c (ce−c)t ≤ ϵ(t) ≤ (c + 1)ec +1 − cγ (cγ)t. +Thus we get the following corollary. +Corollary 10. for any t ≥ 1 +ec(ce−c)t ≤ γt+1 − γt ≤ ec(cγ)t +and +ec +1 − ce−c (ce−c)t ≤ γ − γt ≤ +ec +1 − cγ (cγ)t. +From the above corollary, we get the Theorem 2. +9 + +6 +Concentration of Size of the Complex after the First Epoch +In this section, we shall prove a concentration bound on the size of the core. Unlike in the case +of simple collapses in d-dimensional LM complexes [2, 3], concentration bounds in our case are +less straightforward. Observe firstly, that deleting a single vertex v could potentially change +the domination status of an arbitrary number of vertices, as for example when v dominates the +entire complex. Thus the influence of a vertex can be n in the worst case. Therefore we shall +need to use an edge exposure martingale inequality, in the form of a variant of an inequality of +Freedman [11], given by Warnke [20], which allows us to consider the path variance of the effect +of a single edge, rather than the worst case effect. +In order to bound the path variance, we shall show that if the influence of a variable is large, +there is a specific class of subcomplexes, which we call Critical Complexes, one of which must +occur in the 1-skeleton of the complex. It is not hard to show (and we do) that the probability +of occurence of these subgraphs is vanishingly low in the original random complex. However, the +variance needs to be controlled at all steps in the edge exposure martingale, i.e. when we are +computing expectations over arbitrarily small subcomplexes of the original complex. To handle +this, we need to define a superset of critical complexes, which we call Precritical Complexes, +and show that their probability of occurence will still be vanishingly small throughout the edge +exposure process. We can then define a stopped martingale which stops if at any step of the edge +exposure process, a precritical complex occurs, and prove concentration bounds using Warnke’s +inequality for this martingale. The final concentration bound is then the bound obtained for +the stopped martingale, together with the probability that the martingale ever encounters a +precritical complex. +Fix p = c +n and m = n(n−1) +2 +. For 1 ≤ i ≤ m, ei ∼ Bernoulli(p) be i.i.d. random variables +corresponding to existance of edges. Clearly X(n, p) = e1 × · · · × em as probability spaces. +Now we can define a filtration of σ-algebras {Fi}m +i=0 on X(n, p) by setting Fi to the σ-algebra +corresponding to e1, · · · , ei. +Let X ∼ X(n, p). Now we construct an edge exposure martingale (see e.g. [1] for a definition +of the edge exposure martingale) as follows: Clearly, Ym = |f0(Rt(X))| and Y0 = E(|f0(Rt(X))|). +This section is devoted to prove the following concentration result, which says that the size +of the complex after t pruning rounds of the first epoch is close to its expected value with high +probability. +Theorem 11. (Main Theorem) Let X ∼ X(n, p). Let |f0(Rt(X))| be number of vertices after t +strong collapsing phases and Y0 = E(|f0(Rt(X))|) be its expected value. Then for any s ≥ 0 we +have, +Pr{||f0(Rt(X))| − Y0| ≥ s · n +2 +3 } +≤ +2 exp +� +− +s2 · n +1 +3 +(c4t+1 + (2/3)sn−1/32t+1) + O(1/n) +� ++ O(1/n) += +on(1). +To prove this we begin by observing some combinatorial results. In the following lemmas, we +show that the influence of deleting one vertex is bounded, with high probability. +Lemma 12. Pr{deleting a vertex b gives birth to k newly generated dominated vertices} ≤ +O( +1 +n3k−4 ). +Proof of Lemma 12. We first claim that deleting a vertex b gives birth to k newly generated +dominated vertices then b atleast have k neighbors one of which is the dominating vertex of +b. In the following diagram, the solid arrow denotes domination and the white arrow denotes +10 + +future domination in the next phase only after deleting vertex b. The pointy head of the arrow is +towards the dominated vertex. Vertices a, b, c may be connected to other vertices. The following +diagrams exhibits some of the potential arrangements. +a +b +c +a +b +c +a +b +c1 +ci +cj +. . . +A careful inspection will show that these kind of arrangements are impossible. Indeed if +it happens that will imply that the would-be-dominated vertices are already dominated. This +is because we are only deleting b which is a common neighbor of all the would-be-dominated- +dominating pairs. Thus neighbors of b can not have white arrows between themselves. +Thus fig:1 gives the necessary minimal arrangements for the birth of k newly generated +dominated vertices. In the following diagram, all the ci’s and their corresponding d’s are assumed +to be connected to some non-neighbor of a which lies in the set {e1, · · · , el′}. We claim that in +such case f1 − f0 ≥ (k − 2) + (k − 1) + (k − 1) ≥ 3k − 4. We shall prove our claim by induction +on k ≥ 2. The case k = 2 is evident from the following diagram. +a +b +c1 +d +e +We now prove the induction step. Consider the following figure again. +a +b +c1 +ck−2 ck−1 +{d1, · · · , dl} +{e1, · · · , el′} +. . . +Now assume that the claim holds for k − 1. Now just adding the kth vertex ck−1 increases +f1 − f0 by 1. Also the corresponding d and e increases f1 − f0 by 1 each. This ends the +induction step. So in the all the possible minimal arrangements f1 − f0 ≥ 3k − 4. Thus expected +number of such arrangements is +� n +f0 +� +· (c/n)f1 = O( +1 +n3k−4 ). Thus the result follows from Markov’s +inequality. +Corollary 13. Pr{deleting a vertex b gives birth to 3 newly generated dominated vertices} +≤ O( 1 +n5 ). +Corollary 14. Let X ∼ X(n, p) and e ∈ f1(X), then +Pr{|f0(Rt(X)) \ f0(Rt(X \ {e}))| ≥ 2t+1} ≤ O( 1 +n5 ). +11 + +Proof. If such an event happens then there must be a dominated vertex in the process whose +deletion creates atleast 3 new dominating vertices. Thus the result follows from the previous +corollary. +Let Critical Complexes denote the minimal simplicial complexes corresponding to k = 3 (see +the following diagrams). Let Precritical complexes be any of the Critical Complex without any +four of the edges.. Let N denote the set of complexes from X(n, p) that contains a Critical +Complex and N′ denote the set of complexes contains a Precritical Complex. . Clearly, N′ ⊇ N. +a +b +c1 +c2 +d +e +a +b +c1 +c2 +d1 +d2 +e +a +b +c1 +c2 +d +e1 +e2 +a +b +c1 +c2 +d1 +d2 +e1 +e2 +The following result is immediate. +Lemma 15. Let X ∼ X(n, p). Then, +Pr{X ∈ N} ≤ O( 1 +n5 ), +and +Pr{X ∈ N′} ≤ O( 1 +n). +Now define stopping time τ on {Fi}m +i=0 such that τ = t if t = min(s≤t){Fs ∈ N′}. Define a +stopped martingale with respect to {Fi}m +i=0 by Mi := Yi∧τ. +We first prove the following theorem. +Theorem 16. (Stopped Martingale inequality) Let {Mi}m +i=0 be the stopped martingale defined +as above. Then for any s ≥ 0 we have, +Pr{|Mm − M0| ≥ s · n2/3} ≤ 2 exp +� +− +s2 · n1/3 +(c4t+1 + (2/3)sn−1/32t+1) + O(1/n) +� +. +In order to prove the above theorem, we shall use the following lemma from Warnke [20]. +Assume that {FK}0≤k≤N is an increasing sequence of σ-algebras, and {MK}0≤k≤N is an +{FK}0≤k≤N-adapted bounded martingale. +Lemma 17. (2-sided version of Bounded Variance martingale Inequality) Let Uk be a Fk−1 +variable satisfying |Mk − Mk−1| ≤ Uk. Set Ck = maxi∈[k] Uk and Vk = � +i∈[k] V (Mi−Mi−1|Fi−1). +Let φ(x) = (1 + x) log(1 + x) − x. For every s ≥ 0 and V, C > 0 we have +Pr{|MK − M0| ≥ s, Vk ≤ V, Ck ≤ C for some k ∈ [N]} ≤ 2e−s2/(2V +2Cs/3) +Theorem 11 essentially follows from Theorem 16 and Lemma 15. +12 + +Proof. Proof of Theorem 16 +Let X ∈ X(n, p). We shall first try to calculate Pr{X ∈ N|ei, · · · , e1} where (e1, · · · , ei) +does not form any precritical complex. Let M ⊂ N be the set of complexes that contains +some critical complex not involving any of the edges from {ei, · · · , e1} and M′ ⊂ N be the set +of complexes where all the critical complexes involves some edges from {ei, · · · , e1}. Clearly, +N = M ⊔ M′. Thus, +Pr{X ∈ N|ei, · · · , e1} = Pr{X ∈ M ⊔ M′|ei, · · · , e1} += Pr{X ∈ M|ei, · · · , e1} + Pr{X ∈ M′|ei, · · · , e1} += Pr{X ∈ M} + Pr{X ∈ M′|ei, · · · , e1} +Pr{X ∈ M} is the probability that {ei+1, · · · , em} contains a critical complex. By reasoning +similar to the proof of Lemma 12. We get Pr{X ∈ M} = O(1/n5). On the other hand, note +that as (ei, · · · , e1) does not contain any precrtitical complex, atleast 5 more edges is needed +for X to form a critical complex involving some edges {ei, · · · , e1}. Suppose, depending on +(e1, · · · , ei), k more edges are needed to complete a critical complex. Clearly 5 ≤ k ≤ 13. Also +note that, in a critical complex, there are atmost 2 vertices of degree two and rests have degree +atleat 3. Thus even in the worst case one need to choose 3 vertices and construct 5 particular +edges. Thus Pr{X ∈ M′|ei, · · · , e1} = O(1/n2). Hence, Pr{X ∈ N|ei, · · · , e1} = O(1/n2) given +(e1, · · · , ei) does not form any precritical complex. In particular, +Pr{|f0(Rt(X)) \ f0(Rt(X \ {ei+1}))| ≥ 2t+1|ei, · · · , e1} ≤ O( 1 +n2 ) +under the same assumption. +Thus +E(|f0(Rt(X)) \ f0(Rt(X \ {ei+1}))||ei, · · · , e1) ≤ 2t+1 + n · O(1/n2) ≤ 2t+1 + O(1/n) +whenever (ei, · · · , e1) does not contain any precrtitical complex. +We now claim that |Mi+1 − Mi| ≤ 2t+1 + O(1/n). If (ei, · · · , e1) contains a precritical +complex then the martingale stops and the claim holds. Now suppose (ei, · · · , e1) does not +contain any precritical complex. Then +|[Mi+1 − Mi](1, ei, · · · , e1)| = |Mi+1(1, ei, · · · , e1) − Eei+1[Mi+1]| += |Mi+1(1, ei, · · · , e1) − p · (Mi+1(1, ei, · · · , e1)) − (1 − p) · (Mi+1(0, ei, · · · , e1))| += |(1 − p) · (Mi+1(1, ei, · · · , e1) − Mi+1(0, ei, · · · , e1))| +≤ (1 − p)(2t+1 + O(1/n)) +Similarly, +|[Mi+1 − Mi](0, ei, · · · , e1)| = |Mi+1(0, ei, · · · , e1) − Eei+1[Mi+1]| += |Mi+1(0, ei, · · · , e1) − p · (Mi+1(1, ei, · · · , e1)) − (1 − p) · (Mi+1(0, ei, · · · , e1))| += |p · (Mi+1(0, ei, · · · , e1) − Mi+1(1, ei, · · · , e1))| +≤ p(2t+1 + O(1/n)) +Hence the claim follows. +Next we claim that V ar(Mi+1 − Mi|Fi) = V ar(Mi+1|Fi) ≤ (c/n)(4t+1 + O(1/n)) ≤ O(1/n). +Indeed if (ei, · · · , e1) contains a precritical complex then the martingale stops and the variance +is zero. Otherwise +13 + +V ar(Mi+1 − Mi|ei, · · · , e1) = p · ([Mi+1 − Mi](1, ei, · · · , e1))2 + (1 − p) · ([Mi+1 − Mi](0, ei, · · · , e1))2 +≤ p(1 − p)2(2t+1 + O(1/n))2 + (1 − p)p2(2t+1 + O(1/n))2 +≤ p(1 − p)(4t+1 + O(1/n)) +≤ (c/n)(4t+1 + O(1/n)) +Thus by Lemma 17, +Pr{|Mm − M0| ≥ s · n +2 +3 } ≤ 2 exp(− +s2 · n +4 +3 +(n2 − n) · (c/n)(4t+1 + O(1/n)) + 2/3 · (2t+1 + O(1/n)) · s · n) +≤ 2 exp(− +s2 · n +4 +3 +(n − 1)c4t+1 + (2/3)sn2/32t+1 + O(1)) +≤ 2 exp(− +s2 · n +4 +3 +nc4t+1 + (2/3)sn2/32t+1 + O(1)) +≤ 2 exp(− +s2 · n +4 +3 +n(c4t+1 + (2/3)sn−1/32t+1) + O(1)) +≤ 2 exp(− +s2 · n +1 +3 +(c4t+1 + (2/3)sn−1/32t+1) + O(1/n)) +Proof. Proof of Theorem 11 Theorem 11 follows from Theorem 16 and Lemma 15 via the +following inequalities. +Pr{|Ym − Y0| ≥ s} = Pr{|Ym − Y0| ≥ s and ¬N′} + Pr{|Ym − Y0| ≥ s and N′} +≤ Pr{|Mm − M0| ≥ s} + Pr{N′} +Thus +Pr{|Ym − Y0| ≥ s · n +2 +3 } ≤ 2 exp +� +− +s2 · n +1 +3 +(c4t+1 + (2/3)sn−1/32t+1) + O(1/n) +� ++ O(1/n) = on(1). +Now set X′ +0 := |f0(Rt(X))| − |f0(Rt+1(X))|. +Lemma 18. For any s > 0, Pr{|X′ +0 − E[X′ +0]| > sn +2 +3 } < on(1). +Proof of Lemma 18. Observe that +|X′ +0 − E[X′ +0]| > t =⇒ |(|f0(Rt−1(X))| − |f0(Rt(X))|) − (E[|f0(Rt−1(X))|] − E[|f0(Rt(X))|])| > t +=⇒ ||f0(Rt(X)| − E[|f0(Rt(X))|]| + ||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > t +=⇒ ||f0(Rt(X)| − E[|f0(Rt(X))|]| > t/2 +or +||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > t/2 +Hence, by union bound, +Pr{|X′ +0 − E[X′ +0]| > sn +2 +3 } +≤ Pr{||f0(Rt(X)| − E[|f0(Rt(X))|]| > (s/2)n +2 +3 }+Pr{||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > (s/2)n +2 +3 } ≤ on(1) +Let X0 be the random variable that denotes the number of dominated vertices at the end +of the first epoch. Clearly 0 ≤ X0 ≤ |f0(Rt(X))| − |f0(Rt+1(X))| = X′ +0. As X′ +0 ≤ E[X′ +0] + o(n) +a.a.s. we get that 0 ≤ X0 ≤ E[|f0(Rt(X))|] − E[|f0(Rt+1(X))|] + o(n) a.a.s. +14 + +7 +Second Epoch +The second epoch will be a slower version of the first epoch. Here a dominated vertex is chosen +uniformly randomly and is removed. The process continues until there is no more dominated +vertices. Similar to the proof of [3], our strategy shall be to show that when a dominated vertex +is deleted, the expected number of newly created dominated vertices is strictly less than 1, so +that within o(n) steps, the strong collapse process comes to a halt. Thus the size of the core will +be – up to a o(n)-factor – the number of vertices remaining after the first epoch. +Let after t pruning phases the first epoch ends and the second epoch begins. Also, Let Yi be +the random variable that denotes number of newly generated dominated vertices solely by the +deletion of the dominated vertex at the i-th step of the second epoch. Note that Yi ∈ {0, · · · , n}. +First we try to calculate Pr{Yi = 1}. +Lemma 19. For any i ≤ 1 +12n(1 − γ)(1 − cγ),we have E[Yi] ≤ 1 − 3 +4(1 − cγ) + on(1) < 1 + on(1). +Proof of Lemma 19. We shall say that a vertex is affected by ith collapse in the second epoch if +its degree is changed by that collapsing step. Define Qi be the subset of the event {Yi = 1} that +the newly generated vertex by the ith collapse is affected for the first time. Clearly the event +{{Yi = 1} ∩ Qi} represents the fact that only one vertex, say v, is newly generated by the ith +collapse (of vertex u) and v is affected for the first time. Thus that particular vertex retains the +local structure since the first epoch. The idea here is that the edge {u, v} can be attached to +any of the possible places after the first epoch ends. We are only calculating the probability +that is is attached to a suitable vertex of Rt(X) \ {{u, v}, {u}}. To calculate Pr{{Yi = 1} ∩ Qi} +we shall further partition it into two events. To this end, define P be the event that deg(v) = 2 +after i − 1 steps. Thus the probability Pr{{Yi = 1} ∩ Qi ∩ P} is the ratio of the numbers of +degree one vertex in Rt(X) \ {{u, v}, {u}} to the number of non-isolated vertices after t − 1 +phase of the first epoch, as done in eq. 8 of [3]. It can be shown, by using similar arguments like +section 6, that both these quantities are concentrated around their mean. These two quantities +are, respectively, equal to c(1 − γt)γt+1n + o(n) and (1 − γt)n + o(n) a.a.s. +For the event {Yi = 1} ∩ Qi ∩ P to occur v must be a part of a 2-simplex. Now we shall +bound the number of 2-simplices remaining after the first epoch. Observe that during the +collapsing phases number of 2-simplices can only decrease. Let us define the random variables +T := |f2(X)| and T ′ := |f2(Rt(X))| for X ∼ X(n, c/n). Clearly T ′ ≤ T. From Markov’s +inequality we get that Pr{T > log(n)} ≤ O(1/ log(n)). Thus, Pr{T ′ > log(n)} ≤ O(1/ log(n)). +So Pr{{Yi = 1} ∩ Qi ∩ P} ≤ O(log(n))/(1 − γt)n a.a.s. Thus, a.a.s. Pr{{Yi = 1} ∩ Qi} ≤ +c(1−γt)γt+1n +(1−γt)n ++ O(log(n))/(1 − γt)n ≤ c(1−γt)γt+1 +(1−γt) ++ on(1). +Now we need to calculate Pr{{Yi = 1} ∩ Qi}. To do this we shall again partition this event +into two disjoint events. Let Ai denote the number of affected vertices at ith step of the second +epoch. Now define the event Bi := �i +j=1{Aj ≤ 3}. So, Pr{{Yi = 1} ∩ Qi ∩ Bi−1} ≤ +3(i−1) +n(1−γt). +To calculate Pr{{Yi = 1} ∩ Qi ∩ Bi−1} first observe that Pr{{Yi = 1} ∩ Qi ∩ Bi−1} ≤ +Pr{Bi−1} ≤ Σi−1 +j=1{Aj ≥ 4} . But for {Ai ≥ 4} to happen the corresponding dominated vertex u +must be a part of the following arrangement. +a +u +ck +ci +cj +Let S and S′ denote the number of such arrangements in X and Rt(X), respectively, for +X ∼ X(n, c/n). Clearly, S′ ≤ S. From Markov’s inequality we get Pr{S ≥ 1} ≤ O(1/n2). Thus, +Pr{S′ ≥ 1} ≤ O(1/n2). Hence, a.a.s. {Bi} never happens. +15 + +Similar argument combined with lemma 12 gives that Pr{Yi ∈ {2, · · · , n}} ≤ O(1/n2). +By collecting all the terms we have the following inequality. +E[Yi] = Σn +j=0j · Pr{Yi = j} +≤ Pr{Yi = 1} + n · O(1/n2) +≤ Pr{{Yi = 1} ∩ Qi} + Pr{{Yi = 1} ∩ Qi} + n · O(1/n2) +≤ Pr{{Yi = 1} ∩ Qi} + Pr{{Yi = 1} ∩ Qi ∩ Bi−1} + Pr{{Yi = 1} ∩ Qi ∩ Bi−1} + n · O(1/n2) +≤ c(1 − γt)γt+1 +1 − γt ++ 3(i − 1) +n(1 − γt) + O(1/n) + on(1) +≤ cγt+1 + 3(i − 1) +n(1 − γ) + on(1) +≤ cγ + ϵi + on(1) +≤ cγ + 1 +4(1 − cγ) + on(1) +≤ 1 − 3 +4(1 − cγ) + on(1) < 1 + on(1), by lemma 5. +Note that for any fixed i, ϵi = on(1) and for c > 1 we have cγ < 1. +Let Xi be the number of dominated vertices at the end of the ith step of the second epoch. +Then we have +Xi = Xi−1 − 1 + Yi = X0 − n + Σn +i=1Yi +Untill the second epoch ends. If the second epoch stops at i′th step then Xj = 0 +∀j > i′. +Thus we have +E[X0] ≤ E[|f0(Rt(X))|] − E[|f0(Rt+1(X))|] += (1 − γt+1 − cγt + cγ2 +t )n − (1 − γt+2 − cγt+1 + cγ2 +t+1)n +and, +E[Xi] = E[Xi−1] − 1 + Yi = E[X0] − n + Σn +i=1Yi +as long as the second epoch continues. +Now let us define δ ≡ δ(t) := (1 − γt+1 − cγt + cγ2 +t ) − (1 − γt+2 − cγt+1 + cγ2 +t+1) so that +E[X0] ≤ nδ. +Now we present the main lemmas of this section. The first lemma below shows that with +high probability, for any sufficiently small ε > 0, we can choose a sufficiently large t, such that +the number of vertices deleted in the second epoch is less than εn. The proof is by modelling +the number of remaining dominated vertices after i steps of the epoch, as a biased random walk. +Lemma 20. ∀0 < ϵ < min{ 1 +12(1 − γ)(1 − cγ), +5 +192(1 − γ)(1 − cγ)2} +∃T such that ∀t > T a.a.s. +at most ϵn vertices will be deleted from Rt(X) before algorithm reaches the core. +Proof of Lemma 20. Choose t such that δ ≡ δ(t) < 1 +8ϵ(1 − cγ). This can be done because as t +increases γt − γt+1 and γt+1 − γt+2 approaches zero. +Now suppose that the second epoch runs for ρ = ϵn steps. We shall show that E[Xρ] = 0 +a.a.s., i.e., there is no more dominated vertex left to be deleted. To this end we define a sequence +of new random variable {Zi} as follows: +Z0 := X0 +16 + +and, +Zi := Zi−1 − 1 + Yi = Z0 − n + Σn +i=1Yi +Note that Xi ≤ Zi and Zi ≤ 0 =⇒ Xi = 0. +As ρ = ϵn ≤ 1 +4n(1 − γ)(1 − cγ), at the end of the ρ steps number of dominated vertices +remaining is +E[Xρ] ≤ E[Zρ] = E[Z0] − Σρ +i 1 + Σρ +i E[Yi] +≤ nδ − 3 +4ρ(1 − cγ) +by lemma 19 +≤ 1 +8nϵ(1 − cγ) − 3 +4nϵ(1 − cγ) +≤ − 5 +96(1 − γ)(1 − cγ)2n ≤ 0 +Hence E[Xρ] = 0. +Now we shall proving the concentration. Let us define l := +5 +96(1 − γ)(1 − cγ)2. Next we +proceed to show +Pr{Zρ > 0} ≤ Pr{Zρ − E[Zρ] > l · n} < on(1) +Write Zρ as Zρ ≡ Z0 + Z′ +ρ(Y1, · · · , Yρ). First observe that, from lemma 18, Pr{Z0 − E[Z0] > +(l/2)n} ≤ Pr{|Z0 − E[Z0]| > (l/2)n} ≤ on(1) for any s > 0. +From the main geometric lemma we get +E[et(Yi−E[Yi])] ≤ E[etYi] ≤ 1 + et + O(e2t +n2 · 1 − (et/n3)n−1 +1 − et/n3 +) +Fix t > 0. Then, +Pr{Z′ +ρ − E[Z′ +ρ] > (l/2) · n} = Pr{Σρ +i Yi − Σρ +i E[Yi] > (l/2) · n} += Pr{et(Σρ +i Yi−Σρ +i E[Yi]) > etn(l/2)} +≤ et(Σρ +i Yi−Σρ +i E[Yi])/etn(l/2) +≤ +(1 + et + O( e2t +n2 · 1−(et/n3)n−1 +1−et/n3 +))ρ +etn(l/2) +setting t = log(n) we get +Pr{Z′ +ρ − E[Z′ +ρ] > (l/2) · n} ≤ +(1 + n + O( 1−(1/n2)n−1 +1−1/n2 +))ρ +nn(l/2) +≤ +(1 + n + O( +1 +1−1/n2 ))ϵn +nn(l/2) +≤ ((O(1) + n)ϵ)n +(n(l/2))n +≤ ((O(1) + n)ϵ +n(l/2) +)n ≤ on(1) +As ϵ < l/2 ,the quantity approaches zero as n increases, thus the last inequality follows. So, +Pr{Zρ − E[Zρ] > l · n} ≤ Pr{Z0 − E[Z0] > (l/2) · n} + Pr{Z′ +ρ − E[Z′ +ρ] > (l/2) · n} ≤ on(1) +17 + +The next lemma follows from properties of γt and the concentration bounds presented in +Section 6. +Lemma 21. ∀0 < δ +∃T such that ∀t > T a.a.s. +(1 − γ)(1 − cγ)n + o(n) ≤ |f0(Rt(X))| ≤ (1 − γ)(1 − cγ)n + δn + o(n). +Proof of Lemma 21. From theorem 6 and theorem 11 it can the shown that a.a.s. +|f0(Rt(X))| = (1 − γt+1 − cγt + cγ2 +t )n + o(n) +Define h(x) := 1 − e−c(1−x) − cx(1 − x) on the interval (0, 1). It can be checked that on this +interval h′(x) < 0, i.e., h(x) is strictly decreasing. Thus we have that (1−γt+2 −cγt+1 +cγ2 +t+1) ≤ +(1 − γt+1 − cγt + cγ2 +t ). Hence the left inequality follows. +Note that {γt}t is a monotonically increasing sequence that converges to γ. Therefore, +{(1−γt+1−cγt+cγ2 +t )}t is a monotonically decreasing sequence that converges to (1−γ−cγ+cγ2). +Thus, by choosing sufficiently large T, we can restrict {(1 − γt+1 − cγt + cγ2 +t )}t>T inside a δ-ball +round (1 − γ − cγ + cγ2) for any δ > 0. Hence the right inequality follows. +Using above two lemmas we have the proof of our first main result Theorem 1 about the size +of the core (after strong collapse) of a ER complex. +Proof of Theorem 1. By Lemma 20 and Lemma 21. +8 +End Range Phase Transition +Let P(X) denote the number all possible dominated-dominating pairs. It can be shown that +for X ∼ X(n, p), E[P(X)] = (n(n − 1)/2)p(1 − p(1 − p))n−2. For p = λ log(n) +n +, where λ > 1, +E[P(X)] = O( n log(n) +nλ +) = on(1). Thus, by Markov’s inequality, a.a.s. there is no dominated +vertex to start the collapsing procedure. +Now we shall focus on the behavior of X ∼ X(n, p) where p = 1 − λ log(n) +n +. For λ > 2, +E[P(X)] = O( n2 +nλ ) = on(1). Thus a.a.s. there is no dominated vertex to start the collapsing +procedure. But the situation is quite opposite when λ < 1 as the following lemma claims. +Lemma 22. For X ∼ X(X, 1 − λ log n +n +) and λ < 1, a.a.s. X is collapsible. +Proof of Lemma 22. We shall show that, in this range, a.a.s. there exits a vertex adjacent to +every other vertices. Let us define the random variable V ∈ {0, · · · , n} that counts the number +vertices that are adjacent to all other vertices. Clearly E[V ] = npn−1 = n(1− λ log(n) +n +)n−1 = Θ( n +nλ ). +Now we shall calculate V ar(V ). Let Ii denote the indicator random variable that vi is adjacent +to all other vertices. Then, +V ar(V ) = nV ar(I1) + n(n − 1)cov(I1, I2) += npn−1(1 − pn−1) + n(n − 1)(p2n−3 − p2n−2) +Thus, +Pr{V = 0} ≤ V ar(V ) +(E[V ])2 +≤ npn−1(1 − pn−1) + n(n − 1)(p2n−3 − p2n−2) +n2p2n−2 +≤ 1/(npn−1) + (1/p − 1) +≤ Θ(nλ +n ) + +λ log(n) +n − λ log(n) = on(1) +18 + +Thus V ≥ 1 a.a.s. +References +[1] N. Alon and J. Spencer. The Probabilistic Method. Wiley, New York, 3rd edition, 2008. +[2] Lior Aronshtam and Nathan Linial. When does the top homology of a random simplicial +complex vanish? Random Struct. Algorithms, 46(1):26–35, 2015. doi:10.1002/rsa.20495. +[3] Lior Aronshtam and Nathan Linial. The threshold for d-collapsibility in random complexes. +Random Struct. Algorithms, 48(2):260–269, 2016. doi:10.1002/rsa.20585. +[4] Lior Aronshtam, Nathan Linial, Tomasz Luczak, and Roy Meshulam. Collapsibility and +vanishing of top homology in random simplicial complexes. +Discret. Comput. Geom., +49(2):317–334, 2013. doi:10.1007/s00454-012-9483-8. +[5] Dominique Attali, Andr´e Lieutier, and David Salinas. Vietoris-rips complexes also provide +topologically correct reconstructions of sampled shapes. Computational Geometry, 46(4):448– +465, 2013. +[6] J. A. Barmak and E. G. Minian. Strong homotopy types, nerves and collapses. Discrete +and Computational Geometry, 47:301–328, 2012. +[7] J-D. Boissonnat and S. Pritam. Computing persistent homology of flag complexes via strong +collapses. International Symposium on Computational Geometry (SoCG), 2019. +[8] J-D. Boissonnat and S. Pritam. Edge collapse and persistence of flag complexes. International +Symposium on Computational Geometry (SoCG), 2020. +[9] J-D. Boissonnat, S.Pritam, and D. Pareek. Strong Collapse for Persistence. In 26th Annual +European Symposium on Algorithms (ESA 2018), volume 112, 2018. +[10] B´ela Bollob´as. Random graphs. Number 73 in Cambridge studies in advanced mathematics. +Cambridge University Press, 2 edition, 2001. +[11] David A. Freedman. On Tail Probabilities for Martingales. The Annals of Probability, +3(1):100 – 118, 1975. +[12] Marc Glisse and Siddharth Pritam. Swap, Shift and Trim to Edge Collapse a Filtration. +In 38th International Symposium on Computational Geometry (SoCG 2022), volume 224, +pages 44:1–44:15, 2022. +[13] A. Hatcher. Algebraic Topology. Univ. Press Cambridge, 2001. +[14] Matthew Kahle. Random simplicial complexes, 2016. arXiv:1607.07069. +[15] DMITRY N. KOZLOV. The threshold function for vanishing of the top homology group of +random d-complexes. Proceedings of the American Mathematical Society, 138(12):4517–4527, +2010. URL: http://www.jstor.org/stable/41059187. +[16] Nathan Linial and Roy Meshulam. +Homological connectivity of random 2-complexes. +Comb., 26(4):475–487, 2006. URL: https://doi.org/10.1007/s00493-006-0027-9, doi: +10.1007/s00493-006-0027-9. +[17] Nathan Linial and Yuval Peled. Random simplicial complexes: around the phase transition. +A Journey Through Discrete Mathematics, pages 543–570, 2017. +19 + +[18] Greg Malen. +Collapsibility of random clique complexes. +Discrete Mathematics, +346(3):113267, 2023. +URL: https://www.sciencedirect.com/science/article/pii/ +S0012365X22004733, doi:https://doi.org/10.1016/j.disc.2022.113267. +[19] Roy Meshulam and N. Wallach. Homological connectivity of random k-dimensional com- +plexes. Random Struct. Algorithms, 34(3):408–417, 2009. URL: https://doi.org/10. +1002/rsa.20238, doi:10.1002/rsa.20238. +[20] LUTZ WARNKE. On the method of typical bounded differences. Combinatorics, Probability +and Computing, 25(2):269–299, 2016. doi:10.1017/S0963548315000103. +[21] J. H. C Whitehead. Simplicial spaces nuclei and m-groups. Proc. London Math. Soc, +45:243–327, 1939. +[22] A. C. Wilkerson, H. Chintakunta, and H. Krim. Computing persistent features in big data: +A distributed dimension reduction approach. In International Conference on Acoustics, +Speech, and Signal Processing (ICASSP), pages 11–15, 2014. +[23] Siddharth Pritam ´Angel Javier Alonso, Michael Kerber. Filtration-Domination in Bifiltered +Graphs. In SIAM Symposium on Algorithm Engineering and Experiments (ALENEX23), +2023. +20 + diff --git a/29E1T4oBgHgl3EQf5wUG/content/tmp_files/load_file.txt b/29E1T4oBgHgl3EQf5wUG/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..f6f265ffae84ac6c9ed39db5d0e35aea0b45232e --- /dev/null +++ b/29E1T4oBgHgl3EQf5wUG/content/tmp_files/load_file.txt @@ -0,0 +1,782 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf,len=781 +page_content='Strong Collapse of Random Simplicial Complexes Jean-Daniel Boissonnat ∗ 1, Kunal Dutta † 2, Soumik Dutta † 3, and Siddharth Pritam ∗ 4 1Universit´e Cˆote d’Azur, INRIA, Sophia Antipolis, France.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' email: Jean-Daniel.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='Boissonnat@inria.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='fr 2Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Poland.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' email: K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='dutta@mimuw.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='pl 3Faculty of Mathematics, Informatics, and Mechanics, University of Warsaw, Poland.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' email: s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='dutta2@mimuw.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='pl 4Universit´e Cˆote d’Azur, INRIA, Sophia Antipolis, France.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' email: siddharth.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='pritam@inria.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='fr Abstract The strong collapse of a simplicial complex, proposed by Barmak and Minian [6], is a combinatorial collapse of a complex onto its sub-complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Recently, it has received attention from computational topology researchers [22, 7, 8], owing to its empirically observed useful- ness in simplification and size-reduction of the size of simplicial complexes while preserving the homotopy class.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We consider the strong collapse process on random simplicial complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For the Erd˝os-R´enyi random clique complex X(n, c/n) on n vertices with edge probability c/n with c > 1, we show that after any maximal sequence of strong collapses the remaining subcomplex, or core must have (1 − γ)(1 − cγ)n + o(n) vertices asymptotically almost surely (a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ), where γ is the least non-negative fixed point of the function f(x) = exp (−c(1 − x)) in the range (0, 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' These are the first theoretical results proved for strong collapses on random (or non-random) simplicial complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 1 Introduction Motivation Simple collapse is a combinatorial notion which simplifies a simplicial complex without changing its topology.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It can be expressed as a series of elementary moves of removals of pair of simplices σ and τ, such that σ is uniquely contained in τ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The notion of simple collapse was introduced by J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='C Whitehead [21] to study homotopy types of cell complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Since then it has found usage in many different areas of topology, especially in computational topology.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Recently new variants of simple collapses have been introduced, called strong collapses and more generally d-collapses [6, 8, 5].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In such collapses one removes special vertices (more generally d-simplices) called dominated vertices (simplices) whose link is a simplicial cone.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It’s again expressed as a series of elementary moves of removals of dominated vertices (simplices).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' They have been shown to be very powerful tools to solve many problems in computational topology.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In particular, the recent works of Pritam et.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' [9, 8, 23] has shown that strong collapses and edge collapses (d-collapse for d = 1) can be used for efficient computation of one parameter and ∗J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='-D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Boissonnat and S.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pritam received funding from the European Research Council (ERC) under the European Union’s Seventh Framework Programme (FP/2007- 2013) / ERC Grant Agreement No.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 339025 GUDHI (Algorithmic Foundations of Geometry Understanding in Higher Dimensions).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' †K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Dutta and S.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Dutta received funding from the Polish NCN SONATA Grant no.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 2019/35/D/ST6/04525.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 1 arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='03514v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='CG] 9 Jan 2023 multi-parameter persistence.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Efficient computation of persistent homology is one of the central topic of research in topological data analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The computation of persistent homology involves computing homology groups of a nested sequence of simplicial complexes called filtrations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' And to compute persistent homology requires O(n3) time and O(n2) space, here n is the total number of simplices in the filtration.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The general technique developed in [9, 7, 8, 12, 23] is to reduce a filtration to a smaller filtration using strong or edge collapse such that the persistent homology is preserved.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In [9, 7, 8, 12, 23], it has been established through experiments that in practice the reduced filtrations are very small and thereafter computation of persistent homology is extremely fast.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The gain in efficiency is quite dramatic in the case of flag (clique) complexes, where the strong collapse and edge collapse can be computed using only the graph (1-skeleton) of the given complex [7, 12, 23].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' As mentioned above the efficiency reported in [9, 7, 12, 23] are through experiments and there is no theoretical guarantee over the reduction size.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This is due to the fact that in general the amount of reduction depends on the individual complex and its combinatorial structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In fact, the reduction is dependent even on the order of the collapses and a different order can result in a different core, except in the case of strong collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Which is even harder when we want study the reduction size in a filtered simplicial complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This motivates us to consider the case of random simplicial complexes and study the average reduction size by collapses.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In this article, we study the problem of reduction size achieved by the strong collapses of a clique complex defined over an Erd˝os-R´enyi random graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Previous The study of random simplicial complexes was initiated in the seminal paper of Linial and Meshulam [16].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Later Meshulam and Wallach [19] generalized the model of random complexes to obtain the Linial-Meshulam (LM) model of d-dimensional random complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Since then a large body of work from several authors has emerged on many different models of random simplicial complexes, studying various topological and geometric properties of such complexes [14].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The study of simple collapses for random simplicial complexes has also been of interest to researchers and there have been numerous works in this direction.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the d-dimensional LM model, Kozlov [15] proved bounds on the threshold for vanishing of the d-th homology.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Simple collapses on random complexes were first studied by Aronshtam, Linial, �Luczak and Meshulam [4], who improved Kozlov’s bound to get a tight bound on the threshold and also gave a bound on the threshold for collapsibility in the d-dimensional LM model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Later Aronshtam and Linial [2, 3] extended this line of work, obtaining first the threshold for the vanishing of the d-th homology in [2] and then the threshold for non-collapsibility of the d-dimensional LM complex [3].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In [17] Linial and Peled obtained precise asymptotic bounds on the size of the core of such complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Very recently, Malen [18] has shown that the ER clique complex X(n, p) is (k + 1)-collapsible with high probability for p = n−α when α > 1/(k + 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, to the best of our knowledge, work on collapses in random complexes has so far considered only simple collapses.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Throughout this paper, we shall use the notation asymptotically almost surely (a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=') for a series of events (En)n≥1, when the probability of occurence of En goes to 1 as n → ∞.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Models of Random Simplicial Complexes In this paper we shall consider two models of random simplicial complexes, which are described below.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For a graph G, let cl(G) denotes the clique (flag) complex on G, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' the simplicial complex where each complete subgraph of G on d vertices is a d − 1-simplex in cl(G).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The Erd˝os-R´enyi (ER) model X(n, p) on n vertices with probability parameter p ∈ [0, 1] is given by connecting each possible pair of elements of an n-element set by an edge randomly and independently with probability p to get the random graph G = G(n, p).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X(n, p) := cl(G(n, p)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 2 Our Contribution We give bounds on the size of the core (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' the smallest sub complex without any dominated vertex) of a random simplicial complex after strong (vertex) collapses.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Whereas previous works focused on computing the threshold for the appearance and disappearance of the k-th homology class for different k, here we are more interested in computing the size of the core.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We show that for n-vertex ER clique complexes, the size of the core after a maximal series of strong collapses is a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a constant fraction of n, with the constant depending only on the edge probability, and bounded away from 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Further, we also find a precise expression for the constant, as a fixed point of an implicit equation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Our first theorem is stated below.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let K be a simplicial complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For i ≥ 1, we use fi(K) to denote the set of i−simplices of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' By a slight abuse of notation, we let f0(K) denote the set of non-isolated vertices of the complex and ˜f0(K) denote the set of non-isolated vertices of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' (A vertex v ∈ K is isolated the if v is not a face of any edge in K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=') In a pruning phase run on K, all dominated (strong-collapsible) vertices of K are simultaneously collapsed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Rt(K) denote a complex obtained by running t pruning phases over K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lastly, R∞(K) denotes a complex obtained from K after running a maximal series of strong collapses on K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' the core of K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Theorem 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let c > 1 and X ∼ X(n, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then there exists a constant γ ≡ γ(c) given by the least non-negative fixed point of the function f(x) = exp (−c(1 − x)), x ∈ (0, 1), such that 0 < γ < 1/c < 1 and a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' the following holds |f0(R∞(X))| = (1 − γ)(1 − cγ)n + o(n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 0 5000 10000 15000 20000 25000 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 size of the CORE n experimental value for c=1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 theoretical value for c=1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 Figure 1: We ran experiments on ER complexes and plotted the size of the core (strong collapse) with n ∈ [0, 105] and c = 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' These experiments clearly validates our theoretical results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 3 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 1 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 2 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 3 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 4 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='5 5 size of the CORE c experimental value for n=10000 theoretical value for n=10000 Figure 2: In a different set of experiments over ER complexes, we varied the constant c ∈ [1, 5] keeping the number of vertices fixes to n = 104.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We then address a question of algorithmic interest: given an ε ∈ (0, 1), how many rounds do we need in the first epoch to get within an εn gap from the actual size of the core?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The following theorem gives a bound on the number of rounds t as a function of ε.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, c/n) and ε > 0 (sufficiently small) be given.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then there exists t ∈ Z+ such that (c − cγ)ec 1 − ce−c (ce−c)t ≤ ϵ ≤ (c + 1)ec 1 − cγ (cγ)t, and |f0(Rt(X))| − |f0(R∞(X))| ≤ ϵn + o(n) a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='1 Overview of Proofs and Outline of Sections While our analysis shares the general flow of the analysis of the simple collapsibility of LM complexes in e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' [4, 2, 3], there are several differences and difficulties.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Firstly, in both cases (strong collapse of ER clique complex and simple collapse of LM model) our goal is to find the size of the core, rather than whether the complex is collapsible or not.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Secondly, in the case of the random ER clique complex our analysis needs to take into account the non-homogeneity of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' That is, maximal simplices in this model can have different sizes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Further, unlike in the LM model, the existence of a maximal simplex is not independent of the existence of all other possible maximal simplices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Finally perhaps the most interesting difference of the random ER clique complex model in our context, is that the effect of removing a vertex is not necessarily localized – a fact which requires a fair bit of innovation to handle (in several places), especially in proving the concentration bounds in Section 6, and in the later stages of the analysis, in Section 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We present a more detailed overview of the proof strategy used in our concentration bound, in the beginning of Section 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' With the above caveats in mind, we first briefly review the main ideas of the proof of Aronshtam and Linial [3].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The analysis was split into two epochs, each of which were further divided into several rounds (phases).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the first epoch, in each round, every simple-collapsible simplex was simultaneously collapsed, and this procedure was repeated for a constant number of rounds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Aronshtam and Linial [3] used a tree-like model of a random simplicial complex to approximate the local structure of the random LM complex and showed that the total number of collapsed simplices over all such rounds tended to a constant fraction of the number of initial 4 simplices, as the number of rounds increased.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Moreover, this limit constant could be expressed as a fixed point of an implicit equation involving only the distribution parameter c.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the analysis of the second epoch, a simplex would be chosen randomly from the set of (non-neighbouring) simple-collapsible simplices, and collapsed in each round.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The aim was to show that in this epoch, the number of simplices collapsed would be asymptotically negligible compared to the inital number of simplices present.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus in summary, the final number of deleted simplices is determined by the first epoch itself, and the second epoch serves to show the tightness of this bound.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Our proofs also split the analysis into two epochs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Similar to [3], we show that a certain tree- like model of random simplicial complexes provides a good approximation of local neighbourhoods, which is done in Section 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This is followed by the analysis of the first epoch, in Section 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The main theorem of this section gives an expression for the expected number of vertices remaining after t rounds (or pruning phases) of the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Bounds on t as a function of ε, γ and c, are given in Theorem 2, which is proved in Section 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Before beginning the analysis of the second epoch however, we need bounds on the concentration of the size of the core itself, as well as several other random variables.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' These are proved in Section 6, where we use the notions of critical and precritical (sub)complexes – described in more detail in the beginning of Section 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' With these concentration bounds in place, we move to the analysis of the second epoch in Section 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 2 Preliminaries In this section we briefly introduce some topological and probabilistic notions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Readers can refer to [13] for a comprehensive introduction to topics related to topology and [10] for topics related to probability theory and random structures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Simplicial complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' An abstract simplicial complex K is a collection of subsets of a non-empty finite set X, such that for every subset A in K, all the subsets of A are in K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' An element of K is called a simplex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' An element of cardinality d + 1 is called a d-simplex and d is called its dimension.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Given a simplicial complex K, we denote its geometric realization as |K|.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A simplex is called maximal if it is not a proper subset of any other simplex in K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A sub-collection L of K is called a subcomplex if it is a simplicial complex itself.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A subcomplex K′ of K is called a d-skeleton of K if it contains all the simplices of K of dimension at most d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Erdos Renyi Graph Definition.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This is the probability space G(n, p) consisting of all the graphs on n vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Probability of occurrence of a graph with m edges is pm(1 − p)(n)(n−1)/2−m.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In other words, it is a random graph on n vertices where each edge can occur independently with probability p.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clique complex and Neighborhood.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A complex K is a clique or a flag complex if, when a subset of its vertices form a clique (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' any pair of vertices is joined by an edge), they span a simplex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For a vertex v in G, the open neighborhood NG(v) of v in G is defined as NG(v) := {u ∈ G | [uv] ∈ E}, here E is the set of edges of G.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The closed neighborhood NG[v] is NG[v] := NG(v) ∪ {v}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Similarly we define the closed and open neighborhood of an edge [xy] ∈ G, NG[xy] and NG(xy) as NG[xy] := N[x] ∩ N[y] and NG(xy) := N(x) ∩ N(y), respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The above definitions can be extended to any k-clique σ = [v1, v2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=', vk] of G;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' NG[σ] := � vi∈σ N[vi] and NG(σ) := � vi∈σ N(vi).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Star, Link and Simplicial Cone.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let σ be a simplex of a simplicial complex K, the closed star of σ in K, stK(σ) is a subcomplex of K which is defined as follows, stK(σ) := {τ ∈ 5 K| τ ∪ σ ∈ K}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The link of σ in K, lkK(σ) is defined as the set of simplices in stK(σ) which do not intersect with σ, lkK(σ) := {τ ∈ stK(σ)|τ ∩ σ = ∅}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The open star of σ in K, sto K(σ) is defined as the set stK(σ) \\ lkK(σ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Usually sto K(σ) is not a subcomplex of K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let L be a simplicial complex and let a be a vertex not in L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then the set aL defined as aL := {a, τ | τ ∈ L or τ = σ ∪ a;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' where σ ∈ L} is called a simplicial cone.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Simple collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Given a complex K, a simplex σ ∈ K is called a free simplex if σ has a unique coface τ ∈ K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The pair {σ, τ} is called a free pair.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The action of removing a free pair: K → K \\ {σ, τ} is called an elementary simple collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A series of such elementary simple collapses is called a simple collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We denote it as K ↘ L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A subcomplex Kec of K is called an elementary core of K if K↘Kec and Kec has no free pair.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Removal of a simplex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We denote by K \\ σ the subcomplex of K obtained by removing σ, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' the complex that has all the simplices of K except the simplex σ and the cofaces of σ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Dominated simplex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A simplex σ in K is called a dominated simplex if the link lkK(σ) of σ in K is a simplicial cone, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' if there exists a vertex v′ /∈ σ and a subcomplex L of K, such that lkK(σ) = v′L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We say that the vertex v′ is dominating σ and that σ is dominated by v′, which we denote as σ ≺ v′.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' σ-algebra The reader can refer to [10] for the definition of σ-algebra.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' d-collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Given a complex K, the action of removing a dominated k-simplex σ from K is called an elementary d-collapse, denoted as K↘↘d{K \\σ}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A series of elementary d-collapses is called a d-collapse, denoted as K ↘↘k L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We further call a complex K d-collapse minimal if it does not have any dominated d simplices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A subcomplex Kk of K is called a d-core if K ↘↘k Kd and Kd is d-collapse minimal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A 0-core of a complex K is unique, however it is not true in general for k ≥ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Like simple collapses, d-collapses preserve the homotopy type of a simplicial complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A 0-collapse is a strong collapse as introduced in [6] and 1-collapse is called an edge collapse [8].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The following lemma from [8] characterizes the domination of a simplex in the special case of a flag complex in terms of neighborhood.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let σ be a simplex of a flag complex K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then σ will be dominated by a vertex v′ if and only if NG[σ] ⊆ NG[v′].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In this article, our main focus will be the case d = 0, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' when σ is a vertex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The next lemma from [7], though elementary, is of crucial significance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let K be a flag complex and let L be any subcomplex of K obtained by strong collapses.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then L is also a flag complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Both lemmas (Lemma 3 and Lemma 4) show that strong collapse is well-suited to flag complexes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the next sections we will investigate the reduction capabilities of strong of a clique complex of an Erd˝os-R´enyi random graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 3 Tree process In this section, we describe the tree process which is used to simulate the collapse process in the first epoch of the (strong) collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A one-dimensional tree is built recursively as follows: 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Start with a single node(root).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 6 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the nth iteration, add children to all the leaves at distance n − 1 from the root from Poisson distribution with parameter c(> 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Tn denote the set of all possible trees after nth iteration for n > 1 and T0 being the root itself.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let T := � n∈N Tn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let γt be the probability that a tree T ∈ Tt is pruned to the root in no more than t − 1 steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly, γ1 = e−c.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Set γ0 = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also, we have the following recursive relation which is true in general: γt+1 = e−c(1−γt).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that, in this process we never prune the root itself even if its degree is 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We call such a process root collapsing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let γk t denote the probability that a tree T ∈ Tt has degree k after t − 1 root collapsing steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then, γk t = (c(1 − γt−1))k k!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e−c(1−γt−1) Observe that γk 1 gives the initial degree distribution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also, let γ≥2 t denote the probability that a vertex has degree atleast 2 after t − 1 root collapsing steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then we have γ≥2 t = ∞ � k=2 γk t = 1 − γt(1 + c(1 − γt−1)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define βt := 1 − γt+1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, βt is the probability that atleast t + 1 root collapsing steps are needed to isolate the root of a tree T ∈ Tt.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define f(x) := e−c(1−x) on the interval [0, 1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall assume c > 1 for the rest of these paper unless specified otherwise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that f([0, 1]) ⊆ [0, 1], f′(x) = cf(x) and f(x) is strictly increasing on the interval [0, 1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let ft(x) denoted the function obtained by composing f t times.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then ft is also strictly increasing on [0, 1] for all t ≥ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' As, γ1 > γ0, applying ft−1 on both sides, we get γt > γt−1 for all t ≥ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also define γ to be the left most zero of the function g(x) := e−c(1−x) − x defined on the range [0, ∞).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that 0 < γ ≤ 1 as g(1) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For c > 1 and γ = γ(c) defined as earlier we have cγ < 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let g(x) be defined as above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So g(γ−) > 0 and g(γ) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, from the differentiability of g(x), cγ − 1 = g′(γ) ≤ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now, if cγ − 1 = 0 then ce1−c = 1, which is impossible for c > 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus cγ − 1 < 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now observe that, x ≤ γ =⇒ f(x) ≤ f(γ) = γ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, by the fact that f′(x) = cf(x), f(x) restricted on [0, γ] becomes a contraction mapping.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So, by Banach Fixed Point theorem, f|[0,γ] has an unique fixed point which, in our case, is γ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To summarize the above arguments we get the following remark.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Remark 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' γt converges to 0 < γ < 1/c as an increasing sequence and βt converges to 1 − 1/c < β < 1 as a decreasing sequence.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 4 First Epoch In this section, we present the analysis of the first epoch of the collapse.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The first epoch is executed in phases and in each phase we remove a maximal set of dominated vertices simultaneously.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Our goal, in this section, is to prove the following theorem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 7 Theorem 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let E(|f0(Rt(X))|) denote the expected number of non-isolated vertices in X after t strong collapse phases and γt be as defined in the last section.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then, E(|f0(Rt(X))|) = (1 − γt+1 − cγt + cγ2 t )n.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We start by proving some important lemmas about the local structure of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For X ∼ X(n, c n), let us define the following event, D := {deg(v) ≤ log n ∀v ∈ ˜f0(X)}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then, the following lemma can be proved using standard Chernoff bounds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{D} = 1 − on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note That for any v ∈ ˜f0(X), deg(v) ∼ Bin(n − 1, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Dv be the event that deg(v) ≤ log(n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then by the Chernoff Bound on Binomial Distribution Pr{¬Dv} = Pr{deg(v) > log(n)} ≤ (ec(n − 1) n log(n) )log(n) ≤ ( ec log(n))log(n) = n− log(log(n/ec)) Thus by the union bound Pr{� v∈f0(X) ¬Dv} ≤ n1−log(log(n/ec)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Hence, Pr{D} = Pr{ � v∈f0(X) Dv} = 1 − Pr{ � v∈f0(X) ¬Dv} ≥ 1 − n1−log(log(n/ec)) = 1 − on(1) By Cl(S) we denote the simplicial closure of the set S.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Fix v ∈ ˜f0(X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define N0 := Cl(v) and N−1 := ∅.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also define Ni+1 := Cl({s ∈ X|∃u ∈ ˜f0(Ni)\\ ˜f0(Ni−1)|u ⊂ s})∪Ni.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Equivalently, this can also be defined in terms of the 1-skeleton of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define the event At = {Nt ∈ T }.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, p) and fix v ∈ ˜f0(X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then Pr{At ∩ D} = 1 − o(1) .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' If X ∈ D then ˜f0(Nt) = O(logt+1n) and we want to avoid O(log2t+2n) edges to make Nt a one dimensional tree.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Probability of that happening is (1 − c/n)O(log2t+2n) = 1 − o(1) Now the the degree of a node of this tree comes from Bin(n − 1, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For large n this distribution can be approximated by Po(c).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Theorem 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Recall that for a simplicial complex X, Rt(X) denotes a complex obtained after t phases and f0(X) denotes the set of non-isolated vertices (0−simplices) of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that if a vertex v ∈ f0(X) survived t pruning steps then it must have had degree deg(v) ≥ 2 after t − 1 pruning steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, Pr{v ∈ f0(Rt(X))} ≤ γ≥2 t = 1 − γt(1 + c(1 − γt−1)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This event counts both the isolated vertices and degree one, (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=', collapsible) vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus this gives a slight over estimate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To get more precise estimate we observe that, in the spirit of [3], that a vertex v ∈ f0(X) survives t pruning steps if it is neither collapsed nor isolated after t pruning steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Probability of such an event is 1 − γt+1 + cγt − cγ2 t .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The previous lemma asserts that it is indeed the survival probability of a vertex of the simplicial complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 8 5 Rate of Convergence In this section, we prove Theorem 2 thus giving bounds on the rate of convergence of the variable γt.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let c, γt be as defined earlier.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then cγt ≤ γt+1 − γt γt − γt−1 ≤ cγt+1 Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let f(x) and g(x) be as defined in section 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly, γt+1 − γt γt − γt−1 = g(γt) g(γt−1) = g(γt−1 + (γt − γt−1)) g(γt−1) = g(γt−1) + g′(s)(γt − γt−1) g(γt−1) (for some s ∈ [γt−1, γt]) = f′(s) = cf(s) (as γt − γt−1 = γt−1) As f(x) is an increasing function the result follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In particular, ce−c ≤ γt+1−γt γt−γt−1 ≤ cγ for all t ≥ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let δ(t) = (1 − γt+1 − cγt + cγ2 t ) − (1 − γt+2 − cγt+1 + cγ2 t+1), as defined in section 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It can be shown that δ(t) = (1 − γt+1 − cγt + cγ2 t ) − (1 − γt+2 − cγt+1 + cγ2 t+1) = (γt+2 − γt+1) + c(γt+1 − γt) + c(γt + γt+1)(γt − γt+1) = (γt+2 − γt+1 γt+1 − γt + c − c(γt+1 + γt))(γt+1 − γt) Hence, (c − cγ)ec(ce−c)t ≤ δ(t) ≤ (c + 1)ec(cγ)t Now define ϵ ≡ ϵ(t) := (1 − γt+1 − cγt + cγ2 t ) − (1 − γ − cγ + cγ2) so that E[|f0(Rt(X))|] − (1 − γ)(1 − cγ] = ϵn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Consequently, ϵ(t) = (1 − γt+1 − cγt + cγ2 t ) − (1 − γ − cγ + cγ2) = (γ − γt+1) + c(γ − γt) + c(γt + γ)(γt − γ) = (γ − γt+1) + (c − c(γt + γ))(γ − γt) So, (c − cγ)ec 1 − ce−c (ce−c)t ≤ ϵ(t) ≤ (c + 1)ec 1 − cγ (cγ)t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus we get the following corollary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Corollary 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' for any t ≥ 1 ec(ce−c)t ≤ γt+1 − γt ≤ ec(cγ)t and ec 1 − ce−c (ce−c)t ≤ γ − γt ≤ ec 1 − cγ (cγ)t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' From the above corollary, we get the Theorem 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 9 6 Concentration of Size of the Complex after the First Epoch In this section, we shall prove a concentration bound on the size of the core.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Unlike in the case of simple collapses in d-dimensional LM complexes [2, 3], concentration bounds in our case are less straightforward.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Observe firstly, that deleting a single vertex v could potentially change the domination status of an arbitrary number of vertices, as for example when v dominates the entire complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus the influence of a vertex can be n in the worst case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Therefore we shall need to use an edge exposure martingale inequality, in the form of a variant of an inequality of Freedman [11], given by Warnke [20], which allows us to consider the path variance of the effect of a single edge, rather than the worst case effect.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In order to bound the path variance, we shall show that if the influence of a variable is large, there is a specific class of subcomplexes, which we call Critical Complexes, one of which must occur in the 1-skeleton of the complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It is not hard to show (and we do) that the probability of occurence of these subgraphs is vanishingly low in the original random complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' However, the variance needs to be controlled at all steps in the edge exposure martingale, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' when we are computing expectations over arbitrarily small subcomplexes of the original complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To handle this, we need to define a superset of critical complexes, which we call Precritical Complexes, and show that their probability of occurence will still be vanishingly small throughout the edge exposure process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We can then define a stopped martingale which stops if at any step of the edge exposure process, a precritical complex occurs, and prove concentration bounds using Warnke’s inequality for this martingale.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The final concentration bound is then the bound obtained for the stopped martingale, together with the probability that the martingale ever encounters a precritical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Fix p = c n and m = n(n−1) 2 .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For 1 ≤ i ≤ m, ei ∼ Bernoulli(p) be i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' random variables corresponding to existance of edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly X(n, p) = e1 × · · · × em as probability spaces.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we can define a filtration of σ-algebras {Fi}m i=0 on X(n, p) by setting Fi to the σ-algebra corresponding to e1, · · · , ei.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, p).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we construct an edge exposure martingale (see e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' [1] for a definition of the edge exposure martingale) as follows: Clearly, Ym = |f0(Rt(X))| and Y0 = E(|f0(Rt(X))|).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This section is devoted to prove the following concentration result, which says that the size of the complex after t pruning rounds of the first epoch is close to its expected value with high probability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Theorem 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' (Main Theorem) Let X ∼ X(n, p).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let |f0(Rt(X))| be number of vertices after t strong collapsing phases and Y0 = E(|f0(Rt(X))|) be its expected value.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then for any s ≥ 0 we have, Pr{||f0(Rt(X))| − Y0| ≥ s · n 2 3 } ≤ 2 exp � − s2 · n 1 3 (c4t+1 + (2/3)sn−1/32t+1) + O(1/n) � + O(1/n) = on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To prove this we begin by observing some combinatorial results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the following lemmas, we show that the influence of deleting one vertex is bounded, with high probability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{deleting a vertex b gives birth to k newly generated dominated vertices} ≤ O( 1 n3k−4 ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We first claim that deleting a vertex b gives birth to k newly generated dominated vertices then b atleast have k neighbors one of which is the dominating vertex of b.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the following diagram, the solid arrow denotes domination and the white arrow denotes 10 future domination in the next phase only after deleting vertex b.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The pointy head of the arrow is towards the dominated vertex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Vertices a, b, c may be connected to other vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The following diagrams exhibits some of the potential arrangements.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a b c a b c a b c1 ci cj .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' A careful inspection will show that these kind of arrangements are impossible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Indeed if it happens that will imply that the would-be-dominated vertices are already dominated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This is because we are only deleting b which is a common neighbor of all the would-be-dominated- dominating pairs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus neighbors of b can not have white arrows between themselves.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus fig:1 gives the necessary minimal arrangements for the birth of k newly generated dominated vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In the following diagram, all the ci’s and their corresponding d’s are assumed to be connected to some non-neighbor of a which lies in the set {e1, · · · , el′}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We claim that in such case f1 − f0 ≥ (k − 2) + (k − 1) + (k − 1) ≥ 3k − 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall prove our claim by induction on k ≥ 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The case k = 2 is evident from the following diagram.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a b c1 d e We now prove the induction step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Consider the following figure again.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a b c1 ck−2 ck−1 {d1, · · · , dl} {e1, · · · , el′} .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now assume that the claim holds for k − 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now just adding the kth vertex ck−1 increases f1 − f0 by 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also the corresponding d and e increases f1 − f0 by 1 each.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This ends the induction step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So in the all the possible minimal arrangements f1 − f0 ≥ 3k − 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus expected number of such arrangements is � n f0 � (c/n)f1 = O( 1 n3k−4 ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus the result follows from Markov’s inequality.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Corollary 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{deleting a vertex b gives birth to 3 newly generated dominated vertices} ≤ O( 1 n5 ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Corollary 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, p) and e ∈ f1(X), then Pr{|f0(Rt(X)) \\ f0(Rt(X \\ {e}))| ≥ 2t+1} ≤ O( 1 n5 ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 11 Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' If such an event happens then there must be a dominated vertex in the process whose deletion creates atleast 3 new dominating vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus the result follows from the previous corollary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Critical Complexes denote the minimal simplicial complexes corresponding to k = 3 (see the following diagrams).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Precritical complexes be any of the Critical Complex without any four of the edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='. Let N denote the set of complexes from X(n, p) that contains a Critical Complex and N′ denote the set of complexes contains a Precritical Complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly, N′ ⊇ N.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a b c1 c2 d e a b c1 c2 d1 d2 e a b c1 c2 d e1 e2 a b c1 c2 d1 d2 e1 e2 The following result is immediate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let X ∼ X(n, p).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then, Pr{X ∈ N} ≤ O( 1 n5 ), and Pr{X ∈ N′} ≤ O( 1 n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now define stopping time τ on {Fi}m i=0 such that τ = t if t = min(s≤t){Fs ∈ N′}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define a stopped martingale with respect to {Fi}m i=0 by Mi := Yi∧τ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We first prove the following theorem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Theorem 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' (Stopped Martingale inequality) Let {Mi}m i=0 be the stopped martingale defined as above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then for any s ≥ 0 we have, Pr{|Mm − M0| ≥ s · n2/3} ≤ 2 exp � − s2 · n1/3 (c4t+1 + (2/3)sn−1/32t+1) + O(1/n) � .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In order to prove the above theorem, we shall use the following lemma from Warnke [20].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Assume that {FK}0≤k≤N is an increasing sequence of σ-algebras, and {MK}0≤k≤N is an {FK}0≤k≤N-adapted bounded martingale.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' (2-sided version of Bounded Variance martingale Inequality) Let Uk be a Fk−1 variable satisfying |Mk − Mk−1| ≤ Uk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Set Ck = maxi∈[k] Uk and Vk = � i∈[k] V (Mi−Mi−1|Fi−1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let φ(x) = (1 + x) log(1 + x) − x.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For every s ≥ 0 and V, C > 0 we have Pr{|MK − M0| ≥ s, Vk ≤ V, Ck ≤ C for some k ∈ [N]} ≤ 2e−s2/(2V +2Cs/3) Theorem 11 essentially follows from Theorem 16 and Lemma 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 12 Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Theorem 16 Let X ∈ X(n, p).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall first try to calculate Pr{X ∈ N|ei, · · · , e1} where (e1, · · · , ei) does not form any precritical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let M ⊂ N be the set of complexes that contains some critical complex not involving any of the edges from {ei, · · · , e1} and M′ ⊂ N be the set of complexes where all the critical complexes involves some edges from {ei, · · · , e1}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly, N = M ⊔ M′.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, Pr{X ∈ N|ei, · · · , e1} = Pr{X ∈ M ⊔ M′|ei, · · · , e1} = Pr{X ∈ M|ei, · · · , e1} + Pr{X ∈ M′|ei, · · · , e1} = Pr{X ∈ M} + Pr{X ∈ M′|ei, · · · , e1} Pr{X ∈ M} is the probability that {ei+1, · · · , em} contains a critical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' By reasoning similar to the proof of Lemma 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We get Pr{X ∈ M} = O(1/n5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' On the other hand, note that as (ei, · · · , e1) does not contain any precrtitical complex, atleast 5 more edges is needed for X to form a critical complex involving some edges {ei, · · · , e1}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Suppose, depending on (e1, · · · , ei), k more edges are needed to complete a critical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly 5 ≤ k ≤ 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also note that, in a critical complex, there are atmost 2 vertices of degree two and rests have degree atleat 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus even in the worst case one need to choose 3 vertices and construct 5 particular edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus Pr{X ∈ M′|ei, · · · , e1} = O(1/n2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Hence, Pr{X ∈ N|ei, · · · , e1} = O(1/n2) given (e1, · · · , ei) does not form any precritical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' In particular, Pr{|f0(Rt(X)) \\ f0(Rt(X \\ {ei+1}))| ≥ 2t+1|ei, · · · , e1} ≤ O( 1 n2 ) under the same assumption.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus E(|f0(Rt(X)) \\ f0(Rt(X \\ {ei+1}))||ei, · · · , e1) ≤ 2t+1 + n · O(1/n2) ≤ 2t+1 + O(1/n) whenever (ei, · · · , e1) does not contain any precrtitical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We now claim that |Mi+1 − Mi| ≤ 2t+1 + O(1/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' If (ei, · · · , e1) contains a precritical complex then the martingale stops and the claim holds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now suppose (ei, · · · , e1) does not contain any precritical complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then |[Mi+1 − Mi](1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1)| = |Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − Eei+1[Mi+1]| = |Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − p · (Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1)) − (1 − p) · (Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))| = |(1 − p) · (Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))| ≤ (1 − p)(2t+1 + O(1/n)) Similarly,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' |[Mi+1 − Mi](0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1)| = |Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − Eei+1[Mi+1]| = |Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − p · (Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1)) − (1 − p) · (Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))| = |p · (Mi+1(0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) − Mi+1(1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))| ≤ p(2t+1 + O(1/n)) Hence the claim follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Next we claim that V ar(Mi+1 − Mi|Fi) = V ar(Mi+1|Fi) ≤ (c/n)(4t+1 + O(1/n)) ≤ O(1/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Indeed if (ei, · · · , e1) contains a precritical complex then the martingale stops and the variance is zero.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Otherwise 13 V ar(Mi+1 − Mi|ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1) = p · ([Mi+1 − Mi](1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))2 + (1 − p) · ([Mi+1 − Mi](0,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ei,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' · · · ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' e1))2 ≤ p(1 − p)2(2t+1 + O(1/n))2 + (1 − p)p2(2t+1 + O(1/n))2 ≤ p(1 − p)(4t+1 + O(1/n)) ≤ (c/n)(4t+1 + O(1/n)) Thus by Lemma 17,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{|Mm − M0| ≥ s · n 2 3 } ≤ 2 exp(− s2 · n 4 3 (n2 − n) · (c/n)(4t+1 + O(1/n)) + 2/3 · (2t+1 + O(1/n)) · s · n) ≤ 2 exp(− s2 · n 4 3 (n − 1)c4t+1 + (2/3)sn2/32t+1 + O(1)) ≤ 2 exp(− s2 · n 4 3 nc4t+1 + (2/3)sn2/32t+1 + O(1)) ≤ 2 exp(− s2 · n 4 3 n(c4t+1 + (2/3)sn−1/32t+1) + O(1)) ≤ 2 exp(− s2 · n 1 3 (c4t+1 + (2/3)sn−1/32t+1) + O(1/n)) Proof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Theorem 11 Theorem 11 follows from Theorem 16 and Lemma 15 via the following inequalities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{|Ym − Y0| ≥ s} = Pr{|Ym − Y0| ≥ s and ¬N′} + Pr{|Ym − Y0| ≥ s and N′} ≤ Pr{|Mm − M0| ≥ s} + Pr{N′} Thus Pr{|Ym − Y0| ≥ s · n 2 3 } ≤ 2 exp � − s2 · n 1 3 (c4t+1 + (2/3)sn−1/32t+1) + O(1/n) � + O(1/n) = on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now set X′ 0 := |f0(Rt(X))| − |f0(Rt+1(X))|.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For any s > 0, Pr{|X′ 0 − E[X′ 0]| > sn 2 3 } < on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Observe that |X′ 0 − E[X′ 0]| > t =⇒ |(|f0(Rt−1(X))| − |f0(Rt(X))|) − (E[|f0(Rt−1(X))|] − E[|f0(Rt(X))|])| > t =⇒ ||f0(Rt(X)| − E[|f0(Rt(X))|]| + ||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > t =⇒ ||f0(Rt(X)| − E[|f0(Rt(X))|]| > t/2 or ||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > t/2 Hence,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' by union bound,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{|X′ 0 − E[X′ 0]| > sn 2 3 } ≤ Pr{||f0(Rt(X)| − E[|f0(Rt(X))|]| > (s/2)n 2 3 }+Pr{||f0(Rt−1(X)| − E[|f0(Rt−1(X))|]| > (s/2)n 2 3 } ≤ on(1) Let X0 be the random variable that denotes the number of dominated vertices at the end of the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly 0 ≤ X0 ≤ |f0(Rt(X))| − |f0(Rt+1(X))| = X′ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' As X′ 0 ≤ E[X′ 0] + o(n) a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' we get that 0 ≤ X0 ≤ E[|f0(Rt(X))|] − E[|f0(Rt+1(X))|] + o(n) a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 14 7 Second Epoch The second epoch will be a slower version of the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Here a dominated vertex is chosen uniformly randomly and is removed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The process continues until there is no more dominated vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Similar to the proof of [3], our strategy shall be to show that when a dominated vertex is deleted, the expected number of newly created dominated vertices is strictly less than 1, so that within o(n) steps, the strong collapse process comes to a halt.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus the size of the core will be – up to a o(n)-factor – the number of vertices remaining after the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let after t pruning phases the first epoch ends and the second epoch begins.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Also, Let Yi be the random variable that denotes number of newly generated dominated vertices solely by the deletion of the dominated vertex at the i-th step of the second epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that Yi ∈ {0, · · · , n}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' First we try to calculate Pr{Yi = 1}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For any i ≤ 1 12n(1 − γ)(1 − cγ),we have E[Yi] ≤ 1 − 3 4(1 − cγ) + on(1) < 1 + on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall say that a vertex is affected by ith collapse in the second epoch if its degree is changed by that collapsing step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Define Qi be the subset of the event {Yi = 1} that the newly generated vertex by the ith collapse is affected for the first time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly the event {{Yi = 1} ∩ Qi} represents the fact that only one vertex, say v, is newly generated by the ith collapse (of vertex u) and v is affected for the first time.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus that particular vertex retains the local structure since the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The idea here is that the edge {u, v} can be attached to any of the possible places after the first epoch ends.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We are only calculating the probability that is is attached to a suitable vertex of Rt(X) \\ {{u, v}, {u}}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To calculate Pr{{Yi = 1} ∩ Qi} we shall further partition it into two events.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To this end, define P be the event that deg(v) = 2 after i − 1 steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus the probability Pr{{Yi = 1} ∩ Qi ∩ P} is the ratio of the numbers of degree one vertex in Rt(X) \\ {{u, v}, {u}} to the number of non-isolated vertices after t − 1 phase of the first epoch, as done in eq.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 8 of [3].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It can be shown, by using similar arguments like section 6, that both these quantities are concentrated around their mean.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' These two quantities are, respectively, equal to c(1 − γt)γt+1n + o(n) and (1 − γt)n + o(n) a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For the event {Yi = 1} ∩ Qi ∩ P to occur v must be a part of a 2-simplex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we shall bound the number of 2-simplices remaining after the first epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Observe that during the collapsing phases number of 2-simplices can only decrease.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let us define the random variables T := |f2(X)| and T ′ := |f2(Rt(X))| for X ∼ X(n, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly T ′ ≤ T.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' From Markov’s inequality we get that Pr{T > log(n)} ≤ O(1/ log(n)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, Pr{T ′ > log(n)} ≤ O(1/ log(n)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So Pr{{Yi = 1} ∩ Qi ∩ P} ≤ O(log(n))/(1 − γt)n a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{{Yi = 1} ∩ Qi} ≤ c(1−γt)γt+1n (1−γt)n + O(log(n))/(1 − γt)n ≤ c(1−γt)γt+1 (1−γt) + on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we need to calculate Pr{{Yi = 1} ∩ Qi}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To do this we shall again partition this event into two disjoint events.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Ai denote the number of affected vertices at ith step of the second epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now define the event Bi := �i j=1{Aj ≤ 3}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So, Pr{{Yi = 1} ∩ Qi ∩ Bi−1} ≤ 3(i−1) n(1−γt).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To calculate Pr{{Yi = 1} ∩ Qi ∩ Bi−1} first observe that Pr{{Yi = 1} ∩ Qi ∩ Bi−1} ≤ Pr{Bi−1} ≤ Σi−1 j=1{Aj ≥ 4} .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' But for {Ai ≥ 4} to happen the corresponding dominated vertex u must be a part of the following arrangement.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' a u ck ci cj Let S and S′ denote the number of such arrangements in X and Rt(X), respectively, for X ∼ X(n, c/n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly, S′ ≤ S.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' From Markov’s inequality we get Pr{S ≥ 1} ≤ O(1/n2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, Pr{S′ ≥ 1} ≤ O(1/n2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Hence, a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' {Bi} never happens.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 15 Similar argument combined with lemma 12 gives that Pr{Yi ∈ {2, · · · , n}} ≤ O(1/n2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' By collecting all the terms we have the following inequality.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' E[Yi] = Σn j=0j · Pr{Yi = j} ≤ Pr{Yi = 1} + n · O(1/n2) ≤ Pr{{Yi = 1} ∩ Qi} + Pr{{Yi = 1} ∩ Qi} + n · O(1/n2) ≤ Pr{{Yi = 1} ∩ Qi} + Pr{{Yi = 1} ∩ Qi ∩ Bi−1} + Pr{{Yi = 1} ∩ Qi ∩ Bi−1} + n · O(1/n2) ≤ c(1 − γt)γt+1 1 − γt + 3(i − 1) n(1 − γt) + O(1/n) + on(1) ≤ cγt+1 + 3(i − 1) n(1 − γ) + on(1) ≤ cγ + ϵi + on(1) ≤ cγ + 1 4(1 − cγ) + on(1) ≤ 1 − 3 4(1 − cγ) + on(1) < 1 + on(1), by lemma 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that for any fixed i, ϵi = on(1) and for c > 1 we have cγ < 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Xi be the number of dominated vertices at the end of the ith step of the second epoch.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then we have Xi = Xi−1 − 1 + Yi = X0 − n + Σn i=1Yi Untill the second epoch ends.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' If the second epoch stops at i′th step then Xj = 0 ∀j > i′.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus we have E[X0] ≤ E[|f0(Rt(X))|] − E[|f0(Rt+1(X))|] = (1 − γt+1 − cγt + cγ2 t )n − (1 − γt+2 − cγt+1 + cγ2 t+1)n and, E[Xi] = E[Xi−1] − 1 + Yi = E[X0] − n + Σn i=1Yi as long as the second epoch continues.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now let us define δ ≡ δ(t) := (1 − γt+1 − cγt + cγ2 t ) − (1 − γt+2 − cγt+1 + cγ2 t+1) so that E[X0] ≤ nδ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we present the main lemmas of this section.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The first lemma below shows that with high probability, for any sufficiently small ε > 0, we can choose a sufficiently large t, such that the number of vertices deleted in the second epoch is less than εn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The proof is by modelling the number of remaining dominated vertices after i steps of the epoch, as a biased random walk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ∀0 < ϵ < min{ 1 12(1 − γ)(1 − cγ), 5 192(1 − γ)(1 − cγ)2} ∃T such that ∀t > T a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' at most ϵn vertices will be deleted from Rt(X) before algorithm reaches the core.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Choose t such that δ ≡ δ(t) < 1 8ϵ(1 − cγ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' This can be done because as t increases γt − γt+1 and γt+1 − γt+2 approaches zero.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now suppose that the second epoch runs for ρ = ϵn steps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall show that E[Xρ] = 0 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=', i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=', there is no more dominated vertex left to be deleted.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' To this end we define a sequence of new random variable {Zi} as follows: Z0 := X0 16 and, Zi := Zi−1 − 1 + Yi = Z0 − n + Σn i=1Yi Note that Xi ≤ Zi and Zi ≤ 0 =⇒ Xi = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' As ρ = ϵn ≤ 1 4n(1 − γ)(1 − cγ), at the end of the ρ steps number of dominated vertices remaining is E[Xρ] ≤ E[Zρ] = E[Z0] − Σρ i 1 + Σρ i E[Yi] ≤ nδ − 3 4ρ(1 − cγ) by lemma 19 ≤ 1 8nϵ(1 − cγ) − 3 4nϵ(1 − cγ) ≤ − 5 96(1 − γ)(1 − cγ)2n ≤ 0 Hence E[Xρ] = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we shall proving the concentration.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let us define l := 5 96(1 − γ)(1 − cγ)2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Next we proceed to show Pr{Zρ > 0} ≤ Pr{Zρ − E[Zρ] > l · n} < on(1) Write Zρ as Zρ ≡ Z0 + Z′ ρ(Y1, · · · , Yρ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' First observe that, from lemma 18, Pr{Z0 − E[Z0] > (l/2)n} ≤ Pr{|Z0 − E[Z0]| > (l/2)n} ≤ on(1) for any s > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' From the main geometric lemma we get E[et(Yi−E[Yi])] ≤ E[etYi] ≤ 1 + et + O(e2t n2 · 1 − (et/n3)n−1 1 − et/n3 ) Fix t > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Pr{Z′ ρ − E[Z′ ρ] > (l/2) · n} = Pr{Σρ i Yi − Σρ i E[Yi] > (l/2) · n} = Pr{et(Σρ i Yi−Σρ i E[Yi]) > etn(l/2)} ≤ et(Σρ i Yi−Σρ i E[Yi])/etn(l/2) ≤ (1 + et + O( e2t n2 · 1−(et/n3)n−1 1−et/n3 ))ρ etn(l/2) setting t = log(n) we get Pr{Z′ ρ − E[Z′ ρ] > (l/2) · n} ≤ (1 + n + O( 1−(1/n2)n−1 1−1/n2 ))ρ nn(l/2) ≤ (1 + n + O( 1 1−1/n2 ))ϵn nn(l/2) ≤ ((O(1) + n)ϵ)n (n(l/2))n ≤ ((O(1) + n)ϵ n(l/2) )n ≤ on(1) As ϵ < l/2 ,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='the quantity approaches zero as n increases,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' thus the last inequality follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' So, Pr{Zρ − E[Zρ] > l · n} ≤ Pr{Z0 − E[Z0] > (l/2) · n} + Pr{Z′ ρ − E[Z′ ρ] > (l/2) · n} ≤ on(1) 17 The next lemma follows from properties of γt and the concentration bounds presented in Section 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' ∀0 < δ ∃T such that ∀t > T a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' (1 − γ)(1 − cγ)n + o(n) ≤ |f0(Rt(X))| ≤ (1 − γ)(1 − cγ)n + δn + o(n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' From theorem 6 and theorem 11 it can the shown that a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' |f0(Rt(X))| = (1 − γt+1 − cγt + cγ2 t )n + o(n) Define h(x) := 1 − e−c(1−x) − cx(1 − x) on the interval (0, 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It can be checked that on this interval h′(x) < 0, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=', h(x) is strictly decreasing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus we have that (1−γt+2 −cγt+1 +cγ2 t+1) ≤ (1 − γt+1 − cγt + cγ2 t ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Hence the left inequality follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Note that {γt}t is a monotonically increasing sequence that converges to γ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Therefore, {(1−γt+1−cγt+cγ2 t )}t is a monotonically decreasing sequence that converges to (1−γ−cγ+cγ2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, by choosing sufficiently large T, we can restrict {(1 − γt+1 − cγt + cγ2 t )}t>T inside a δ-ball round (1 − γ − cγ + cγ2) for any δ > 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Hence the right inequality follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Using above two lemmas we have the proof of our first main result Theorem 1 about the size of the core (after strong collapse) of a ER complex.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Theorem 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' By Lemma 20 and Lemma 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' 8 End Range Phase Transition Let P(X) denote the number all possible dominated-dominating pairs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' It can be shown that for X ∼ X(n, p), E[P(X)] = (n(n − 1)/2)p(1 − p(1 − p))n−2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For p = λ log(n) n , where λ > 1, E[P(X)] = O( n log(n) nλ ) = on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus, by Markov’s inequality, a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' there is no dominated vertex to start the collapsing procedure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we shall focus on the behavior of X ∼ X(n, p) where p = 1 − λ log(n) n .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For λ > 2, E[P(X)] = O( n2 nλ ) = on(1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Thus a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' there is no dominated vertex to start the collapsing procedure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' But the situation is quite opposite when λ < 1 as the following lemma claims.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Lemma 22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' For X ∼ X(X, 1 − λ log n n ) and λ < 1, a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' X is collapsible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Proof of Lemma 22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' We shall show that, in this range, a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' there exits a vertex adjacent to every other vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let us define the random variable V ∈ {0, · · · , n} that counts the number vertices that are adjacent to all other vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Clearly E[V ] = npn−1 = n(1− λ log(n) n )n−1 = Θ( n nλ ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Now we shall calculate V ar(V ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Let Ii denote the indicator random variable that vi is adjacent to all other vertices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Then, V ar(V ) = nV ar(I1) + n(n − 1)cov(I1, I2) = npn−1(1 − pn−1) + n(n − 1)(p2n−3 − p2n−2) Thus, Pr{V = 0} ≤ V ar(V ) (E[V ])2 ≤ npn−1(1 − pn−1) + n(n − 1)(p2n−3 − p2n−2) n2p2n−2 ≤ 1/(npn−1) + (1/p − 1) ≤ Θ(nλ n ) + λ log(n) n − λ log(n) = on(1) 18 Thus V ≥ 1 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content='s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' References [1] N.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Alon and J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Spencer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' The Probabilistic Method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/29E1T4oBgHgl3EQf5wUG/content/2301.03514v1.pdf'} +page_content=' Wiley, New York, 3rd edition, 2008.' metadata={'source': 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Chew1, William D. Weisman1, Jingying Huang1, Seth Frey1,* +1 Department of Communication, University of California Davis, Davis, CA, USA +* Correspondence: Seth Frey (sethfrey@ucdavis.edu) 376 Kerr Hall, 1 Shields Dr., Davis, +CA 95616, USA + +Machine Translation for Accessible Multi-Language Text Analysis +Abstract +English is the international standard of social research, but scholars are increasingly conscious +of their responsibility to meet the need for scholarly insight into communication processes +globally. This tension is as true in computational methods as any other area, with +revolutionary advances in the tools for English language texts leaving most other languages +far behind. In this paper, we aim to leverage those very advances to demonstrate that +multi-language analysis is currently accessible to all computational scholars. We show that +English-trained measures computed after translation to English have adequate-to-excellent +accuracy compared to source-language measures computed on original texts. We show this for +three major analytics—sentiment analysis, topic analysis, and word embeddings—over 16 +languages, including Spanish, Chinese, Hindi, and Arabic. We validate this claim by +comparing predictions on original language tweets and their backtranslations: double +translations from their source language to English and back to the source language. Overall, +our results suggest that Google Translate, a simple and widely accessible tool, is effective in +preserving semantic content across languages and methods. Modern machine translation can +thus help computational scholars make more inclusive and general claims about human +communication. +Keywords: multi-language text analysis, multi-lingual text analysis, computational text +analysis, natural language processing, backtranslation, topic modeling, word embedding, +sentiment analysis. + +Introduction +Humans communicate in thousands of languages, and yet a single language, English, +attracts the bulk of communication research. This not only has the effect of depriving other +languages of adequate attention, but depriving English-focused scholars of any sense of where +the language stands relative to others. The general use of English-trained tools for +English-focused analyses in the social science community is particularly notable given the +ubiquity of multi-lingual data and the power of modern computational natural language +processing. For example, social media researchers on Twitter typically begin with raw data +that is highly multilingual, before filtering out all tweets except for English, or some other +single language. With such practices scholars miss a tremendous opportunity to test the +generalizability of social media-observed big data claims. But bringing standard text analysis +tools to the level of training and refinement that English-trained tools receive is a forbidding +prospect that few multi-lingual scholars have the training, resources, and language +background to pursue. We propose a simple alternative approach that makes texts from over +100 languages accessible to the full variety of analyses that are typically available to only +English-focused scholars. Specifically we demonstrate that modern machine translation has +reached a level of refinement necessary to preserve sentiment, lexical topics, and semantic +distance, making multi-language datasets legible to state of the art English-trained tools. By +providing a validation of state-of-the-art machine translation, along with easily adaptable +demonstration code, we aim to broaden the horizon of computational research and support +Communication scholars in increasing the relevance and generality of their work. +Google Translate, the most popular, accurate, and accessible multilingual neural +machine translation service, offers translations for over 133 languages (Caswell, 2022). In this + +paper, we demonstrate the efficacy of Google Translate in retaining sentiment valence across +translations of large hand-coded and machine-coded Twitter datasets composed of tweets in +16 global non-English languages from four language families, being of Indo-European, +Uralic, Semitic, and Sinitic origin. With our findings that Google Translate preserves the +sentiment of tweets, as well as other dimensions of semantics, scholars may be emboldened to +utilize Google Translate and other multilingual neural machine translation services to expand +the generalizability of their research. In so doing, non-English languages can benefit from +advanced English-trained natural language processing tools, and computational findings +normally restricted to the English language can be expanded upon to broaden scholars’ +knowledge of global social phenomena. +Academics use Twitter datasets for a wide range of scholarship, including sentiment +analysis (e.g. Gautam & Yadav, 2014), algorithmic training (e.g. Braithwaite et al., 2016), and +even coronavirus disease 2019 detection (e.g. Gharavi et al., 2020). English-language corpora +have been used to predict election results (Nausheen & Begum, 2018), analyze consumer +preferences (Ahmed & Danti, 2016), and explore pro- and anti-childhood vaccine +communities’ influence on Twitter (Featherstone et al., 2020). +As valuable as this work is, it can only be more valuable extended across languages. +Frey et al. (2018) use a corpus of six languages to document general ripple effects of +emotional influence through others and back around to the self. Mocanu et al. (2013) use data +on 78 languages to characterize inter-linguistic diversity and intra-linguistic drift across +municipalities and regions. And Alshaabi et al. (2021) compare the dynamics of social +influence on Twitter over 150 languages. In other disciplines, large-scale multi-language +comparisons in other disciplines have identified universal patterns in the cross-language + +naming of colors (Lindsey & Brown, 2009), a well as a universal preference for the shortening +of dependency length in human sentence production (Futrell et al., 2015). +Our research demonstrates the effectiveness of Google Translate on the maintenance +of sentiments, topic clusters, and semantic distance for tweets in all languages we examine. +We validate the approach using “backtranslation,” a classic validation method of machine +translation in which scholars compare an original text to a version of that text that has been +translated from its original language to another language (in our case English) and then back +again to the original (Figure 1). This makes it possible to directly compare the accuracy of +English-trained tools on English translations to original-language-trained tools on +original-language texts, while controlling for semantic drift introduced by the translation +process itself. We first test the preservation of sentiments using two large public multi-lingual +Twitter datasets, one with hand-coded sentiments (Mozetič et al., 2016) and another with +machine-coded sentiments (Imran et al., 2022) for this analysis. The second portion of our +research applies the same two datasets to show that Google Translate preserves topic clusters +after backtranslation, thereby demonstrating a similar level of semantic conservation for this +second common text analysis task. In the third and final portion of our present study we +demonstrate the effectiveness of out-of-the-box machine translation on a third common text +analysis approach: neural word embeddings. Here, after backtranslation, 10 of 16 languages +examined performed better than chance in maintaining a minimal embedding distance. Our +findings provide strong support for the use of modern machine translation for expanding +academic attention to the languages spoken by most humans. +Method + +Datasets +We utilized two large, multilingual Twitter datasets. First, we examine the Mozetič et +al. (2016) dataset, which contains over 1.6 million general Twitter posts hand-labeled as +containing “positive”, “negative”, or “neutral” labels for 15 European languages: Albanian, +Bosnian, Bulgarian, Croatian, English, German, Hungarian, Polish, Portuguese, Russian, +Serbian, Slovak, Slovenian, Spanish, and Swedish. To expand the scope of our research +beyond European languages, we added tweets from the Imran et al. (2022) COVID-19 dataset, +a larger (70 million tweet) corpus including tweets in Chinese, Hindi, and Arabic. While these +two datasets are comparable (both include sentiment labels), they differ in subject and date, as +well as in how they determined sentiment scores. Those in Mozetič et al. (2016) were applied +by human language-domain experts, while tweets from Imran et al. (2022) dataset were +determined by algorithms (all trained within-language). +Data cleaning +Before translation and subsequent analysis, we preprocessed all Twitter data to remove +Twitter handles, return handles, URLs, numbers, empty tweets, and converting all content to +lowercase. We dropped Serbian from our analysis halfway through the study, after discovering +that the Mozetič dataset contains Cyrillic Serbian, but Google Translate only supports +Latin-character Serbian. We obviously excluded all English language tweets from validation +by backtranslation through English. +To reduce our dataset to a more manageable, and affordable, size (the Google +Translate API is paid), we randomly sampled 30,000 tweets from each of the 13 applicable + +European languages from Mozetič et al. (2016) dataset, and 10,000 tweets from Chinese, +Hindi, and Arabic from the Imran et al. (2022) dataset, for a total of 16 languages. +Translation process +Utilizing the Google Translate API, we translate all tweets from their “original +language” datasets into English, saving the results as our “English translated” dataset. We then +translate all the English translated tweets back to their original language, saving it as our +“backtranslated” dataset (Figure 1). Our results are based only partly on three-way +comparisons between these datasets. Where there is not a meaningful correspondence between +English- and original-language analyses we use only two-way comparisons between the +original and backtranslated datasets. +With this manuscript we share the scripts and instructions, to enable researchers to +easily extend their single-language corpus research to multiple languages. The code is +available at https://osf.io/jx476/. +Sentiment analysis +We conduct our sentiment analysis task with the free open-source software Polyglot +(Al-Rfou, 2015). Polyglot allows the generation of sentiment labels in more than 100 +languages, with “-1” indicating negative sentiment, “0” indicating neutral sentiment, and “1” +indicating positive sentiment for each word in each original-language tweet. Based on the +difference between the number of positive sentiment words and negative sentiment words, we +generate an overall polarity for each tweet. Polyglot’s lexicon-based sentiment analysis relies +on a valence dictionary of positive and negative words, computing the sentiment of a text as + +the simple sum of the valences of its words, normalized back down to the [-1, 1] interval. Our +pipeline excluded neutrally labeled tweets: as a result of Polyglot’s lexicon-based sentiments, +short texts like Twitter posts are overwhelmingly labeled as neutral which makes it difficult to +distinguish the performance of sentiment analyses across translations. +We computed confidence intervals around the accuracy of each language’s sentiments +with bootstrapping (1000x). The final sentiment accuracies are the bootstrapped medians. +Topic clustering +While sentiment analysis is a common application for natural language tools, it only +serves to answer a small range of questions. We expand our investigation of Google +Translate’s ability to preserve the content of translated text through topic analysis. Compared +to sentiment analysis, topic analysis provides a more technical, but much more flexible +approach to computationally representing the meanings of text. Although the process of topic +analysis is language agnostic, common computational tools are typically built to only support +the English language, from stopwords to supported character sets. +We model our topic clustering approach after Yin and Wang (2014) who present the +open-source software GSDMM (“Gibbs Sampling algorithm of the Dirichlet Multinomial +Mixture). GSDMM is trained upon short text posts such as those found within social media +environments such as Twitter (Yin & Wang, 2014). We follow the original work’s data +cleaning steps of removing both emojis and stopwords. We excluded Albanian and Bosnian +due to their incompatibility with our data cleaning dependencies. + +Our cluster analysis process was as follows. For each language, we used a total of five +iterations of the clustering algorithm. We then classified the backtranslated tweets to the +clusters generated on the original language tweets. To estimate the success of machine +translation at semantic preservation under topic analysis, we computed the proportion of +backtranslated tweet that were correctly assigned to the cluster of their original-language +version. We compare these proportions to the baseline “null” proportions expected by chance, +as derived from random permutations of original cluster assignments. Like many clustering +algorithms, GSDMM requires researchers to impose a desired number of clusters, rather than +identifying the number of clusters through the same emergent process as cluster assignments. +But the ability of backtranslation to preserve topic clusters depends on the number of clusters. +Therefore, we observe the effectiveness of topic preservation across a range of clusterings by +training models on each original language dataset for 2, 5, 10, 15, 20, 50, 100, 150, and 200 +clusters. +Unlike with our evaluation of sentiment analysis, the analysis of topics is only able to +compare original language and backtranslated analytics: it is not able to compare either to +English. While the framework of sentiment analysis imposes the same meaning to the idea of +“positive” and “negative” sentiments across languages, topics emerge from a narrow +understanding of a word as the sequence of characters that constitutes it. To the extent that +original language and backtranslated tweets use the same characters (as in languages +borrowings from each other), they can be assigned to the same set of clusters. But lexicons in +English and each original language are mostly non-overlapping, and there is ultimately no +basis to map English translations to original-language-derived topics. +Word embedding + +Polyglot (Al-Rfou, 2015) also supports semantic word embeddings across its +languages. We determine semantic preservation under word embedding by embedding +original and backtranslated tweets (as the normalized sum of the embeddings of their words) +and calculating their (cosine) distance in the embedding’s high-dimensional semantic space. +Under this formalism, a distance of zero indicates perfect preservation of semantics after +translation. Because Polyglot has a different semantic space for each language, it was not +possible to compare the distance of the intermediate English texts to the original and +backtranslated texts. +To measure how well machine translation preserves semantics under word embedding, +we compared the embedding distances after backtranslation to two baseline distances. We +computed the average minimum distance of tweets from 5,000 other tweets in that language +and their average average distances. Our rationale is that meaning is preserved despite +semantic drift imposed by the process of (double) machine translation if the average distance +of backtranslated tweets from their originals is smaller than the average distances of different +original language tweets from each other. +Results +Our primary finding is that Google Translate is faithful enough to preserve the +semantics of multilingual texts under three common text analysis tasks: sentiment analysis, +topic analysis, and word embeddings. +Application 1: Preservation of sentiment + +We find that overall accuracy of sentiment scores decreases less than 1% after +backtranslation, from a median 65.17% accuracy (with a very tight 99% high-confidence +interval (HCI) of [65.16, 65.18]) to 64.76% [64.75, 64.77]. While small, this decline was +statistically significant, as measured by the separation of the 99% HCI bars. We display this +result in Figure 2, below. +We did have one surprise from this process. We expected that the accuracy of +English-trained sentiment on the English-translated tweets would be between or below the +accuracy of the original or backtranslated tweets, whose “ground truth” sentiments were +computed with models trained specifically for those languages. Instead median sentiment +accuracy increases 4.95% following original languages’ translation into English (original +language median accuracy: 65.17%, HCI [65.16, 65.18]; English translated median accuracy: +70.12%, HCI [70.11, 70.13]). Somehow sentiments extracted from English translations are +more accurate than sentiments of original language tweets, despite the process of translation +in between (Figure 2). We speculate on this result in the Discussion section. +Looking specifically at how different languages performed, we found the expected +decrease in accuracy rates between the original language datasets and the backtranslated +datasets for Albanian, Arabic, Chinese, Slovak, and Spanish (Figure 3). Unexpectedly, the +remaining language datasets, belonging to the languages of Bosnian, Bulgarian, Croatian, +German, Hindi, Hungarian, Polish, Portuguese, Russian, Slovenian, and Swedish, experienced +an increase in sentiment accuracy from original language to backtranslated form. Although +languages on average showed higher accuracy in English translation, the original language +datasets of Portuguese, Russian, Slovenian, and Swedish show a drop in sentiment accuracy + +when translated to English (while the remaining others, Albanian, Bosnian, Bulgarian, +Croatian, English, German, Hungarian, Polish, Slovak, and Spanish all improve). +Application 2: Preservation of lexical topic assignments +Our primary finding from Application 2 is that machine translation also preserves +topic structure (Figure 4). Specifically, backtranslated tweets are assigned to the same cluster +and their original language version at a rate well above chance. As expected, the ability of +backtranslation to preserve topic structure declines as the number of topics increases (Figure +5). Performance accuracy of topic cluster preservation is 78% when there are two topic +clusters, and declines to about 60% when there are 10 or more clusters. However, chance +accuracy declines much faster, from 52% to 10% over the same span. In other words, the +relative accuracy of topic recovery actually improves with the number of clusters, even as +absolute efficacy declines. +It may seem peculiar that chance performance of topic assignment remains at 10% +even with 200 clusters. This is probably due to an unequal distribution of cluster sizes. For +200 equally sized clusters, the baseline, null probability of a backtranslated tweet being +randomly assigned to its correct topic is 0.05%, one half of a percent. Chance performance +higher than this is easy to arrange in a system with a few large clusters and a large number of +very small ones. +Overall, we find that Google Translate preserves topic clusters across languages, with +accuracy ranging from 60% to 80% depending on the number of topics we set the GSDMM +algorithm to impose. + +Application 3: Preservation of semantics in embedding space +In the final application of this work, we examine the multilingual preservation of +semantic vectors in high-dimensional neural embeddings after machine translation and +backtranslation. +On average, original language tweets are significantly closer to their backtranslations +than to other original language tweets in the same collection (Figure 6). Across languages, +average distances of original language tweets from each other are 0.041–0.184 units, their +minimum distances from each other are 0.028–0.132, and their distances from their +backtranslations are 0.203–0.492. Being less than half of the average distance (except +Chinese) and below or slightly above the minimum distance, we can conclude that the +semantic change introduced by the translation algorithm is enough to change the meaning of a +backtranslated tweet to be mistakable for a different closely related tweet, but not the typical +more distantly related tweet. +Of the 16 languages involved in the analysis, 6 languages (Albanian, Arabic, Chinese, +German, Hindi, and Portuguese) failed the minimum baseline test, with backtranslated tweets +having greater semantic distance from their originals than the average closest outside tweet. +The Albanian, German, and Portuguese corpora failed by small margins (mean distance of +0.065 compared to minimum baseline distance 0.059 in Albanian; distance 0.110 compared to +baseline 0.094 in German; 0.089 against 0.085 in Portuguese). But in Arabic, Chinese, and +Hindi, embeddings of translations were even further from their original (distance 0.146 +against 0.101 in Arabic; 0.184 against 0.053 in Chinese; 0.041 against 0.028 in Hindi). It +should be noted that Arabic, Chinese, and Hindi were drawn from the Imran et al. (2022) + +dataset focused on COVID-19 related tweets, included as part of our effort to expand this +project’s analysis beyond languages of European origin. As baseline measures were calculated +on the distance between random tweets relative to their distance with all other tweets, and +these tweets were semantically more closely related, these languages’ baseline measures may +have been especially narrow relative to those of the other languages as a result of their shared +topic. Although they failed the rigorous minimum distance test, even Arabic, Chinese, and +Hindi passed the mean distance test: they were closer in meaning to their original than the +average tweet (mean baseline distances 0.416, 0.352, and 0.203, respectively). +Discussion +As the global academic world becomes increasingly interconnected, Communication +scholars must meet the challenge to make claims about communication processes more +globally relevant. Fortunately, with recent advances in natural language processing, +quantitative Communication research has an opportunity to be multilingual by default. +Advances that bring equal attention to more of the world’s languages will not only provide +greater generality of results, but greater attention to the work of Communication scholars from +all parts of the world. Standard approaches to large multilingual corpora will also allow the +rapid transfer of groundbreaking knowledge to and from the international Communication +community. +Of course, these advances have downsides. When multi-language analyses are +conducted by scholars who can’t speak all of those languages, it becomes harder for them to +“gut check” or “sanity check” their results, culturally contextualize those results, and interpret +whatever valid cross-linguistic differences that do appear,. By encouraging researchers to + +conduct multilingual studies by default, we are almost necessarily advocating for a +circumstance in which scholars are making conclusions about languages that they do not +know. Although this approach has some acceptance in other fields, such as large-scale +comparative linguistics, it would be understandable to see it as controversial. As novel as this +problem may be, the way forward may not be novel at all. Quantitative and qualitative +methods have a fundamental complementarity, with the former bringing generality as the +latter brings depth and sensitivity to context. By supporting the summary quantitative claims +of non-speakers with citations to other work by native speakers and other domain experts, +scholars may be able to justify not knowing the languages they are engaging with. This +complementary approach will be particularly valuable for understanding outliers. In the case +of our research, Chinese, Arabic, and Hindi all perform worse than the other languages. +Having ruled out explanations that go to the phylogeny, character set, and geography of these +languages, domain experts become the best candidates for understanding how and why +specific languages deviate from the majority of their peers. This illustrates the importance of +framing our contribution as a complement to expert-based multi-language communication +research, rather than a substitute. +In this work we are able to validate the performance of Google Translate by leveraging +source-language versions of our three methods: sentiment analysis, topic analysis, and word +embeddings. However, as others make use of machine translation, they will not have the +comfort of source-language tools, and may feel that they are “flying blind”. Although we +succeed in showing that translation introduces negligible drift, it may still be uncomfortable to +apply it to a new dataset, particularly with text analysis methods beyond the three that we +validate here (such as custom classifiers). To address this concern, researchers can take not + +only our conclusions, but the backtranslation method itself, to perform partial validations for +their own case. Most likely, it should be possible to find “home language” tools for at least a +handful of languages in a larger corpus. If an author can show satisfactory and stable +performance across this subset, by comparing original and backtranslated texts, they can +assure their audience that the method is probably working for other languages as well. Even +lacking such “ground truth,” there may be ways of using our method to instill confidence in a +multilingual result. For example, a scholar could perform iterative backtranslations to +calculate how many cycles must be introduced for the statistical significance of their result to +degrade below threshold. If it takes a large number of backtranslations to degrade a result, +readers can have confidence that artifacts introduced by the method are not sufficient to +explain those results. Conversely, if machine translation is artificially amplifying a result, +scholars can measure this effect with iterated backtranslation to suggest an appropriate amount +of caution. +Another design choice of this work ensures the generality of the method we introduce. +All three applications of this work were performed with tweets. Tweets are short, making +them challenging for text analysis methods like sentiment and topic analysis. That our method +is very effective on challenging text is encouraging for scholars who would extend this +method to more typical (longer) texts. +A limitation of our approach is its accessibility. We have argued that Google Translate +is very accessible, and this is true in that it requires a small amount of code (that we provide) +to translate large quantities of text to English. However, our approach is not as financially +accessible. The Google’s Translation API costs $20 USD per million characters. In practice, +this translates to roughly $100 USD per 130,000 tweets. Fortunately, free translation tools of + +comparable quality are increasingly common, and can also be validated in practice using +backtranslation. +One surprising result from this work was that the accuracy of sentiment detection after +translation into English, and in some cases after backtranslation, was higher than in the +original texts. This finding is easier to understand with an appreciation of how sentiment +analysis works in libraries like Polyglot. Polyglot uses the “dictionary” method, in which +hundreds to thousands of high-frequency words are given sentiment scores, and the score of a +statement is calculated from the sum of scores of the subset of words that are in the detector’s +sentiment dictionary. If the dictionary is large, or the text is long, then its assigned sentiment +score will be based on a lot of signal. Consequently, this method is less suitable for rarer +languages and shorter texts (like tweets), which are less likely to contain scored words. It is +also more suitable to texts with more common words, since uncommon words are less likely +to appear in a language’s sentiment dictionary. +Why would translation to English, or backtranslation from English, improve task +performance? Translation to English may be improving dictionary-based sentiment detection +because English-language sentiment dictionaries tend to be longer. And subsequent +backtranslation may be improving detection performance if it results in uncommon unscored +words from the source text being backtranslated into more common words that are scored. We +believe that this finding can be explained by Polyglots’ apparent relative greater capacity to +detect sentiment in English language content, relative to the content of other languages. This +result underscores the need to validate Google Translate for each natural language task that it +is being used to support. +Conclusion + +There is an unmet need to extend Communication scholars’ applications of text +analysis to more languages, particularly in the data-rich context of social media studies. +Translation tools such as Google Translate can be immensely helpful in meeting this need. We +have quantified Google Translate’s effectiveness in maintaining sentence meaning in +translations to and from English. Across 16 non-English languages, sentiment analysis scores +were shown to improve when translated to English, and only diminish marginally when +translated back to their original languages. Similarly, both topic and semantic distances are +preserved during backtranslation. Our findings demonstrate that machine translation is able to +preserve semantic content and make non-English datasets legible to English-trained +computational tools. We hope this analysis gives researchers the confidence to use machine +translation to simply and economically increase the number of languages involved in their +research, and thereby the generality of their findings. +Acknowledgements +We would like to thank Arti Thakur, Communication Ph.D. Candidate at the +University of California, Davis, for her assistance with the analysis. All code is available at +https://osf.io/jx476/. The authors report there are no competing interests to declare. + +Figure 1 +We compare analytics computed on texts in their original languages to translated English +language analytics and texts translated back to the original language. Differences between +the original and translated texts are typically difficult to attribute to semantic differences +between the languages and “semantic” imposed by poor translation. Comparing original and +backtranslated texts enables us to control for the effect of drift and focus on semantics. + +Original +Intermediate +Backtranslated +source +English +source +language +language +language +text +text +textFigure 2 +Sentiment analysis overall retains accuracy after backtranslation by machine methods. +Median sentiment detection accuracy increases 4.9% from original language to English +translated language datasets, and falls less than 1% from original language datasets to +backtranslated language datasets. Note that 99% error bars are too narrow to be displayed. + +0.701 +0.652 +0.648Figure 3 +Comparison of sentiment labeling accuracy across languages, before, during, and after +backtranslation. Seventeen language sentiment detection accuracy from original language > +English translated > backtranslated datasets. Note that 99% error bars are too narrow to be +displayed. +Figure 4 + +Albanian +Arabic +Bosnian +Bulgarian +Chinese +1.0 +1.0 +1.0 +1.0 +1.0 +0.837 +0.783 +0.8 - +0.727 +0.8 +0.756 +0.751 +0.8 +0.8 +0.8 +0.692 +0.683 +0.689 +0.654 +0.626 +0.662 +0.666 +0.615 +0.594 +0.410 +0.2 +0.2 +0.2 +0.2 +0.2 +0.0 +0.0 - +0.0 +0.0 +0.0 +Croatian +English +German +Hindi +Hungarian +1.0 +1.0 +1.0 +1.0 +1.0 +0.892 +0.794 +0.788 +0.813 +0.8 +0.742 +0.8 - +0.8 +0.705 +0.8 +0.8 - +0.742 +0.676 +0.681 +0.665 +0.678 +0.653 +0.654 +0.2 +0.2 +0.2 +0.2 +0.2 - +0.000 +0.000 +0.0 +0.0 +0.0 +0.0 +0.0 +Polish +Portuguese +Russian +Slovak +Slovenian +1.0 - +1.0 +1.0 +1.0 +1.0 +0.8 +0.8 - +0.8 +0.8 +0.8 +0.720 +0.733 +0.693 +0.663 +0.670 +0.695 +0.627 +0.646 +0.610 +0.645 +0.644 +0.614 +0.580 +0.584 +0.564 +0.2 +0.2 - +0.2 - +0.2 +0.2 +0.0 +0.0 +0.0 +0.0 +0.0 +Swedish +Spanish +1.0 - +1.0 +0.8- +0.761 +English Translated w/o Neutrals +0.8 - +0.594 +0.611 +0.548 +0.502 +0.467 +Original Language w/o Neutrals +0.2 - +0.2 - +Backtranslated w/o Neutrals +0.0 +0.0Machine translation preserves topic clusters across languages, regardless of number of +topics. Percentage of backtranslated tweets assigned to the same cluster as original language +tweets by language. White text denotes permutation test accuracy. The 14 languages examined +demonstrate topic clustering accuracy preserved above chance. +2 Clusters +100 Clusters + +0.930 +0.882 +0.876 +0.817 +0.831 +0.827 +0.786 +0.760 +0.764 +0.748 +0.740 +0.670 +0.636 +0.610 +0.590 +0.546 +0.526 +0.537 +0.514 +0.511 +0.514 +0.506 +0.501 +0.502 +0.501 +0.505 +0.512 +0.4980.868 +0.785 +0.794 +0.685 +0.684 +0.651 +0.592 +0.596 +0.570 +0.538 +0.494 +0.474 +0.361 +0.293 +0.229 +0.198 +0.170 +0.118 +0.094 +0.097 +0.093 +0.054 +0.063 +0.056 +0.058 +0.019 +0.037 +0.024Figure 5 +Recovery of topics after backtranslation declines in an absolute sense with number of +topics, but increases relative to baseline. Average topic cluster accuracy by size of topic +cluster. Note that topic cluster accuracy decreases from two to ten clusters, whereby it is +approximately stable to 200 clusters. + +Arabic +Bulgarian +Chinese +Croatian +German +Hindi +Hungarian +Polish +Portuguese +Russian +Slovak +Slovenian +Spanish +Swedish +Average +BaselineFigure 6 +Tweets are closer to their backtranslations on average than to other tweets. +Average distance between original language and backtranslated sentence embeddings by +language. Black lines denote the mean baseline distance and blue lines denote the minimum +baseline distance. All 16 languages have mean distances below their mean baseline. All +languages but Albanian, Arabic, Chinese, German, Hindi, and Portuguese have mean +distances below their minimum baseline. In these languages, tweets backtranslated tweets are +further from their source tweet in meaning than tweets that are very semantically similar to +the source, but tweets in these languages are still consistently closer to their source than the +average tweet. + +0.492 +0.428 +0.416 +0.408 +0.393 +0.399 +0.380 +0.352 +0.343 +0.317 +0.315 +0.314 +0.242 +0.226 +0.228 +0.203 +0.184 +0.132 +0.146 +0.116 +0.106 +0.094 +0.098 +0.099 +0.095 +0.086 +0.085 +0.101 +0.110 +0.078 +0.059 +0.060 +0.097 +0.091 +0.100 +0.065 +0.085 +0.053 +0.089 +0.076 +0.085 +0.065 +0.067 +0.073 +0.059 +0.028 +0.041 +0.044References +Ahmed, S., & Danti, A. (2015). Effective sentimental analysis and opinion mining of web +reviews using rule based classifiers. Advances in Intelligent Systems and Computing, +171–179. https://doi.org/10.1007/978-81-322-2734-2_18 +Al-Rfou, R., Kulkarni, V., Perozzi, B., & Skiena, S. (2015). Polyglot-NER: Massive +Multilingual Named Entity Recognition. 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World color survey color naming reveals universal +motifs and their within-language diversity. Proceedings of the National Academy of +Sciences, 106(47), 19785–19790. https://doi.org/10.1073/pnas.0910981106 +Mocanu, D., Baronchelli, A., Perra, N., Gonçalves, B., Zhang, Q., & Vespignani, A. (2013). +The Twitter of Babel: Mapping World Languages through Microblogging Platforms. +PLOS ONE, 8(4), e61981. https://doi.org/10/f4vdv4 +Mozetič, I., Grčar, M., & Smailović, J. (2016). Multilingual twitter sentiment classification: +The role of human annotators. PLOS ONE, 11(5). +https://doi.org/10.1371/journal.pone.0155036 +Nausheen, F., & Begum, S. H. (2018). Sentiment analysis to predict election results using +Python. 2018 2nd International Conference on Inventive Systems and Control (ICISC). +https://doi.org/10.1109/icisc.2018.8399007 +Yin, J., & Wang, J. (2014). A Dirichlet multinomial mixture model-based approach for short +text clustering. Proceedings of the 20th ACM SIGKDD International Conference on +Knowledge Discovery and Data Mining, 233–242. +https://doi.org/10.1145/2623330.2623715 + diff --git a/2dFAT4oBgHgl3EQfDhxB/content/tmp_files/load_file.txt b/2dFAT4oBgHgl3EQfDhxB/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..5915ed8f0fa863ee324219d6eb285c5456b41d1f --- /dev/null +++ b/2dFAT4oBgHgl3EQfDhxB/content/tmp_files/load_file.txt @@ -0,0 +1,678 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf,len=677 +page_content='Machine Translation for Accessible Multi-Language Text Analysis Edward W.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Chew1, William D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Weisman1, Jingying Huang1, Seth Frey1,* 1 Department of Communication, University of California Davis, Davis, CA, USA Correspondence: Seth Frey (sethfrey@ucdavis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='edu) 376 Kerr Hall, 1 Shields Dr.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', Davis, CA 95616, USA Machine Translation for Accessible Multi-Language Text Analysis Abstract English is the international standard of social research, but scholars are increasingly conscious of their responsibility to meet the need for scholarly insight into communication processes globally.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This tension is as true in computational methods as any other area, with revolutionary advances in the tools for English language texts leaving most other languages far behind.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In this paper, we aim to leverage those very advances to demonstrate that multi-language analysis is currently accessible to all computational scholars.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We show that English-trained measures computed after translation to English have adequate-to-excellent accuracy compared to source-language measures computed on original texts.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We show this for three major analytics—sentiment analysis, topic analysis, and word embeddings—over 16 languages, including Spanish, Chinese, Hindi, and Arabic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We validate this claim by comparing predictions on original language tweets and their backtranslations: double translations from their source language to English and back to the source language.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Overall, our results suggest that Google Translate, a simple and widely accessible tool, is effective in preserving semantic content across languages and methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Modern machine translation can thus help computational scholars make more inclusive and general claims about human communication.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Keywords: multi-language text analysis, multi-lingual text analysis, computational text analysis, natural language processing, backtranslation, topic modeling, word embedding, sentiment analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Introduction Humans communicate in thousands of languages, and yet a single language, English, attracts the bulk of communication research.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This not only has the effect of depriving other languages of adequate attention, but depriving English-focused scholars of any sense of where the language stands relative to others.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The general use of English-trained tools for English-focused analyses in the social science community is particularly notable given the ubiquity of multi-lingual data and the power of modern computational natural language processing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' For example, social media researchers on Twitter typically begin with raw data that is highly multilingual, before filtering out all tweets except for English, or some other single language.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' With such practices scholars miss a tremendous opportunity to test the generalizability of social media-observed big data claims.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' But bringing standard text analysis tools to the level of training and refinement that English-trained tools receive is a forbidding prospect that few multi-lingual scholars have the training, resources, and language background to pursue.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We propose a simple alternative approach that makes texts from over 100 languages accessible to the full variety of analyses that are typically available to only English-focused scholars.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Specifically we demonstrate that modern machine translation has reached a level of refinement necessary to preserve sentiment, lexical topics, and semantic distance, making multi-language datasets legible to state of the art English-trained tools.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' By providing a validation of state-of-the-art machine translation, along with easily adaptable demonstration code, we aim to broaden the horizon of computational research and support Communication scholars in increasing the relevance and generality of their work.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Google Translate, the most popular, accurate, and accessible multilingual neural machine translation service, offers translations for over 133 languages (Caswell, 2022).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In this paper, we demonstrate the efficacy of Google Translate in retaining sentiment valence across translations of large hand-coded and machine-coded Twitter datasets composed of tweets in 16 global non-English languages from four language families, being of Indo-European, Uralic, Semitic, and Sinitic origin.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' With our findings that Google Translate preserves the sentiment of tweets, as well as other dimensions of semantics, scholars may be emboldened to utilize Google Translate and other multilingual neural machine translation services to expand the generalizability of their research.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In so doing, non-English languages can benefit from advanced English-trained natural language processing tools, and computational findings normally restricted to the English language can be expanded upon to broaden scholars’ knowledge of global social phenomena.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Academics use Twitter datasets for a wide range of scholarship, including sentiment analysis (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Gautam & Yadav, 2014), algorithmic training (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Braithwaite et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2016), and even coronavirus disease 2019 detection (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Gharavi et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2020).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' English-language corpora have been used to predict election results (Nausheen & Begum, 2018), analyze consumer preferences (Ahmed & Danti, 2016), and explore pro- and anti-childhood vaccine communities’ influence on Twitter (Featherstone et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2020).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' As valuable as this work is, it can only be more valuable extended across languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Frey et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2018) use a corpus of six languages to document general ripple effects of emotional influence through others and back around to the self.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Mocanu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2013) use data on 78 languages to characterize inter-linguistic diversity and intra-linguistic drift across municipalities and regions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' And Alshaabi et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2021) compare the dynamics of social influence on Twitter over 150 languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In other disciplines, large-scale multi-language comparisons in other disciplines have identified universal patterns in the cross-language naming of colors (Lindsey & Brown, 2009), a well as a universal preference for the shortening of dependency length in human sentence production (Futrell et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2015).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our research demonstrates the effectiveness of Google Translate on the maintenance of sentiments, topic clusters, and semantic distance for tweets in all languages we examine.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We validate the approach using “backtranslation,” a classic validation method of machine translation in which scholars compare an original text to a version of that text that has been translated from its original language to another language (in our case English) and then back again to the original (Figure 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This makes it possible to directly compare the accuracy of English-trained tools on English translations to original-language-trained tools on original-language texts, while controlling for semantic drift introduced by the translation process itself.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We first test the preservation of sentiments using two large public multi-lingual Twitter datasets, one with hand-coded sentiments (Mozetič et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2016) and another with machine-coded sentiments (Imran et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', 2022) for this analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The second portion of our research applies the same two datasets to show that Google Translate preserves topic clusters after backtranslation, thereby demonstrating a similar level of semantic conservation for this second common text analysis task.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In the third and final portion of our present study we demonstrate the effectiveness of out-of-the-box machine translation on a third common text analysis approach: neural word embeddings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Here, after backtranslation, 10 of 16 languages examined performed better than chance in maintaining a minimal embedding distance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our findings provide strong support for the use of modern machine translation for expanding academic attention to the languages spoken by most humans.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Method Datasets We utilized two large, multilingual Twitter datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' First, we examine the Mozetič et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2016) dataset, which contains over 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='6 million general Twitter posts hand-labeled as containing “positive”, “negative”, or “neutral” labels for 15 European languages: Albanian, Bosnian, Bulgarian, Croatian, English, German, Hungarian, Polish, Portuguese, Russian, Serbian, Slovak, Slovenian, Spanish, and Swedish.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To expand the scope of our research beyond European languages, we added tweets from the Imran et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2022) COVID-19 dataset, a larger (70 million tweet) corpus including tweets in Chinese, Hindi, and Arabic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' While these two datasets are comparable (both include sentiment labels), they differ in subject and date, as well as in how they determined sentiment scores.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Those in Mozetič et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2016) were applied by human language-domain experts, while tweets from Imran et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2022) dataset were determined by algorithms (all trained within-language).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Data cleaning Before translation and subsequent analysis, we preprocessed all Twitter data to remove Twitter handles, return handles, URLs, numbers, empty tweets, and converting all content to lowercase.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We dropped Serbian from our analysis halfway through the study, after discovering that the Mozetič dataset contains Cyrillic Serbian, but Google Translate only supports Latin-character Serbian.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We obviously excluded all English language tweets from validation by backtranslation through English.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To reduce our dataset to a more manageable, and affordable, size (the Google Translate API is paid), we randomly sampled 30,000 tweets from each of the 13 applicable European languages from Mozetič et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2016) dataset, and 10,000 tweets from Chinese, Hindi, and Arabic from the Imran et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2022) dataset, for a total of 16 languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Translation process Utilizing the Google Translate API, we translate all tweets from their “original language” datasets into English, saving the results as our “English translated” dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We then translate all the English translated tweets back to their original language, saving it as our “backtranslated” dataset (Figure 1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our results are based only partly on three-way comparisons between these datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Where there is not a meaningful correspondence between English- and original-language analyses we use only two-way comparisons between the original and backtranslated datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' With this manuscript we share the scripts and instructions, to enable researchers to easily extend their single-language corpus research to multiple languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The code is available at https://osf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='io/jx476/.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Sentiment analysis We conduct our sentiment analysis task with the free open-source software Polyglot (Al-Rfou, 2015).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Polyglot allows the generation of sentiment labels in more than 100 languages, with “-1” indicating negative sentiment, “0” indicating neutral sentiment, and “1” indicating positive sentiment for each word in each original-language tweet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Based on the difference between the number of positive sentiment words and negative sentiment words, we generate an overall polarity for each tweet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Polyglot’s lexicon-based sentiment analysis relies on a valence dictionary of positive and negative words, computing the sentiment of a text as the simple sum of the valences of its words, normalized back down to the [-1, 1] interval.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our pipeline excluded neutrally labeled tweets: as a result of Polyglot’s lexicon-based sentiments, short texts like Twitter posts are overwhelmingly labeled as neutral which makes it difficult to distinguish the performance of sentiment analyses across translations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We computed confidence intervals around the accuracy of each language’s sentiments with bootstrapping (1000x).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The final sentiment accuracies are the bootstrapped medians.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Topic clustering While sentiment analysis is a common application for natural language tools, it only serves to answer a small range of questions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We expand our investigation of Google Translate’s ability to preserve the content of translated text through topic analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Compared to sentiment analysis, topic analysis provides a more technical, but much more flexible approach to computationally representing the meanings of text.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Although the process of topic analysis is language agnostic, common computational tools are typically built to only support the English language, from stopwords to supported character sets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We model our topic clustering approach after Yin and Wang (2014) who present the open-source software GSDMM (“Gibbs Sampling algorithm of the Dirichlet Multinomial Mixture).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' GSDMM is trained upon short text posts such as those found within social media environments such as Twitter (Yin & Wang, 2014).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We follow the original work’s data cleaning steps of removing both emojis and stopwords.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We excluded Albanian and Bosnian due to their incompatibility with our data cleaning dependencies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our cluster analysis process was as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' For each language, we used a total of five iterations of the clustering algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We then classified the backtranslated tweets to the clusters generated on the original language tweets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To estimate the success of machine translation at semantic preservation under topic analysis, we computed the proportion of backtranslated tweet that were correctly assigned to the cluster of their original-language version.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We compare these proportions to the baseline “null” proportions expected by chance, as derived from random permutations of original cluster assignments.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Like many clustering algorithms, GSDMM requires researchers to impose a desired number of clusters, rather than identifying the number of clusters through the same emergent process as cluster assignments.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' But the ability of backtranslation to preserve topic clusters depends on the number of clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Therefore, we observe the effectiveness of topic preservation across a range of clusterings by training models on each original language dataset for 2, 5, 10, 15, 20, 50, 100, 150, and 200 clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Unlike with our evaluation of sentiment analysis, the analysis of topics is only able to compare original language and backtranslated analytics: it is not able to compare either to English.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' While the framework of sentiment analysis imposes the same meaning to the idea of “positive” and “negative” sentiments across languages, topics emerge from a narrow understanding of a word as the sequence of characters that constitutes it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To the extent that original language and backtranslated tweets use the same characters (as in languages borrowings from each other), they can be assigned to the same set of clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' But lexicons in English and each original language are mostly non-overlapping, and there is ultimately no basis to map English translations to original-language-derived topics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Word embedding Polyglot (Al-Rfou, 2015) also supports semantic word embeddings across its languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We determine semantic preservation under word embedding by embedding original and backtranslated tweets (as the normalized sum of the embeddings of their words) and calculating their (cosine) distance in the embedding’s high-dimensional semantic space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Under this formalism, a distance of zero indicates perfect preservation of semantics after translation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Because Polyglot has a different semantic space for each language, it was not possible to compare the distance of the intermediate English texts to the original and backtranslated texts.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To measure how well machine translation preserves semantics under word embedding, we compared the embedding distances after backtranslation to two baseline distances.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We computed the average minimum distance of tweets from 5,000 other tweets in that language and their average average distances.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our rationale is that meaning is preserved despite semantic drift imposed by the process of (double) machine translation if the average distance of backtranslated tweets from their originals is smaller than the average distances of different original language tweets from each other.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Results Our primary finding is that Google Translate is faithful enough to preserve the semantics of multilingual texts under three common text analysis tasks: sentiment analysis, topic analysis, and word embeddings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Application 1: Preservation of sentiment We find that overall accuracy of sentiment scores decreases less than 1% after backtranslation, from a median 65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='17% accuracy (with a very tight 99% high-confidence interval (HCI) of [65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='16, 65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='18]) to 64.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='76% [64.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='75, 64.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='77].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' While small, this decline was statistically significant, as measured by the separation of the 99% HCI bars.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We display this result in Figure 2, below.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We did have one surprise from this process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We expected that the accuracy of English-trained sentiment on the English-translated tweets would be between or below the accuracy of the original or backtranslated tweets, whose “ground truth” sentiments were computed with models trained specifically for those languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Instead median sentiment accuracy increases 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='95% following original languages’ translation into English (original language median accuracy: 65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='17%, HCI [65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='16, 65.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='18];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' English translated median accuracy: 70.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='12%, HCI [70.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='11, 70.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='13]).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Somehow sentiments extracted from English translations are more accurate than sentiments of original language tweets, despite the process of translation in between (Figure 2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We speculate on this result in the Discussion section.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Looking specifically at how different languages performed, we found the expected decrease in accuracy rates between the original language datasets and the backtranslated datasets for Albanian, Arabic, Chinese, Slovak, and Spanish (Figure 3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Unexpectedly, the remaining language datasets, belonging to the languages of Bosnian, Bulgarian, Croatian, German, Hindi, Hungarian, Polish, Portuguese, Russian, Slovenian, and Swedish, experienced an increase in sentiment accuracy from original language to backtranslated form.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Although languages on average showed higher accuracy in English translation, the original language datasets of Portuguese, Russian, Slovenian, and Swedish show a drop in sentiment accuracy when translated to English (while the remaining others, Albanian, Bosnian, Bulgarian, Croatian, English, German, Hungarian, Polish, Slovak, and Spanish all improve).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Application 2: Preservation of lexical topic assignments Our primary finding from Application 2 is that machine translation also preserves topic structure (Figure 4).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Specifically, backtranslated tweets are assigned to the same cluster and their original language version at a rate well above chance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' As expected, the ability of backtranslation to preserve topic structure declines as the number of topics increases (Figure 5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Performance accuracy of topic cluster preservation is 78% when there are two topic clusters, and declines to about 60% when there are 10 or more clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' However, chance accuracy declines much faster, from 52% to 10% over the same span.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In other words, the relative accuracy of topic recovery actually improves with the number of clusters, even as absolute efficacy declines.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' It may seem peculiar that chance performance of topic assignment remains at 10% even with 200 clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This is probably due to an unequal distribution of cluster sizes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' For 200 equally sized clusters, the baseline, null probability of a backtranslated tweet being randomly assigned to its correct topic is 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='05%, one half of a percent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Chance performance higher than this is easy to arrange in a system with a few large clusters and a large number of very small ones.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Overall, we find that Google Translate preserves topic clusters across languages, with accuracy ranging from 60% to 80% depending on the number of topics we set the GSDMM algorithm to impose.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Application 3: Preservation of semantics in embedding space In the final application of this work, we examine the multilingual preservation of semantic vectors in high-dimensional neural embeddings after machine translation and backtranslation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' On average, original language tweets are significantly closer to their backtranslations than to other original language tweets in the same collection (Figure 6).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Across languages, average distances of original language tweets from each other are 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='041–0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='184 units, their minimum distances from each other are 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='028–0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='132, and their distances from their backtranslations are 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='203–0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='492.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Being less than half of the average distance (except Chinese) and below or slightly above the minimum distance, we can conclude that the semantic change introduced by the translation algorithm is enough to change the meaning of a backtranslated tweet to be mistakable for a different closely related tweet, but not the typical more distantly related tweet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Of the 16 languages involved in the analysis, 6 languages (Albanian, Arabic, Chinese, German, Hindi, and Portuguese) failed the minimum baseline test, with backtranslated tweets having greater semantic distance from their originals than the average closest outside tweet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The Albanian, German, and Portuguese corpora failed by small margins (mean distance of 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='065 compared to minimum baseline distance 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='059 in Albanian;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' distance 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='110 compared to baseline 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='094 in German;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='089 against 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='085 in Portuguese).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' But in Arabic, Chinese, and Hindi, embeddings of translations were even further from their original (distance 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='146 against 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='101 in Arabic;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='184 against 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='053 in Chinese;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='041 against 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='028 in Hindi).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' It should be noted that Arabic, Chinese, and Hindi were drawn from the Imran et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' (2022) dataset focused on COVID-19 related tweets, included as part of our effort to expand this project’s analysis beyond languages of European origin.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' As baseline measures were calculated on the distance between random tweets relative to their distance with all other tweets, and these tweets were semantically more closely related, these languages’ baseline measures may have been especially narrow relative to those of the other languages as a result of their shared topic.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Although they failed the rigorous minimum distance test, even Arabic, Chinese, and Hindi passed the mean distance test: they were closer in meaning to their original than the average tweet (mean baseline distances 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='416, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='352, and 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='203, respectively).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Discussion As the global academic world becomes increasingly interconnected, Communication scholars must meet the challenge to make claims about communication processes more globally relevant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Fortunately, with recent advances in natural language processing, quantitative Communication research has an opportunity to be multilingual by default.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Advances that bring equal attention to more of the world’s languages will not only provide greater generality of results, but greater attention to the work of Communication scholars from all parts of the world.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Standard approaches to large multilingual corpora will also allow the rapid transfer of groundbreaking knowledge to and from the international Communication community.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Of course, these advances have downsides.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' When multi-language analyses are conducted by scholars who can’t speak all of those languages, it becomes harder for them to “gut check” or “sanity check” their results, culturally contextualize those results, and interpret whatever valid cross-linguistic differences that do appear,.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' By encouraging researchers to conduct multilingual studies by default, we are almost necessarily advocating for a circumstance in which scholars are making conclusions about languages that they do not know.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Although this approach has some acceptance in other fields, such as large-scale comparative linguistics, it would be understandable to see it as controversial.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' As novel as this problem may be, the way forward may not be novel at all.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Quantitative and qualitative methods have a fundamental complementarity, with the former bringing generality as the latter brings depth and sensitivity to context.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' By supporting the summary quantitative claims of non-speakers with citations to other work by native speakers and other domain experts, scholars may be able to justify not knowing the languages they are engaging with.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This complementary approach will be particularly valuable for understanding outliers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In the case of our research, Chinese, Arabic, and Hindi all perform worse than the other languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Having ruled out explanations that go to the phylogeny, character set, and geography of these languages, domain experts become the best candidates for understanding how and why specific languages deviate from the majority of their peers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This illustrates the importance of framing our contribution as a complement to expert-based multi-language communication research, rather than a substitute.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In this work we are able to validate the performance of Google Translate by leveraging source-language versions of our three methods: sentiment analysis, topic analysis, and word embeddings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' However, as others make use of machine translation, they will not have the comfort of source-language tools, and may feel that they are “flying blind”.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Although we succeed in showing that translation introduces negligible drift, it may still be uncomfortable to apply it to a new dataset, particularly with text analysis methods beyond the three that we validate here (such as custom classifiers).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' To address this concern, researchers can take not only our conclusions, but the backtranslation method itself, to perform partial validations for their own case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Most likely, it should be possible to find “home language” tools for at least a handful of languages in a larger corpus.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' If an author can show satisfactory and stable performance across this subset, by comparing original and backtranslated texts, they can assure their audience that the method is probably working for other languages as well.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Even lacking such “ground truth,” there may be ways of using our method to instill confidence in a multilingual result.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' For example, a scholar could perform iterative backtranslations to calculate how many cycles must be introduced for the statistical significance of their result to degrade below threshold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' If it takes a large number of backtranslations to degrade a result, readers can have confidence that artifacts introduced by the method are not sufficient to explain those results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Conversely, if machine translation is artificially amplifying a result, scholars can measure this effect with iterated backtranslation to suggest an appropriate amount of caution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Another design choice of this work ensures the generality of the method we introduce.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' All three applications of this work were performed with tweets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Tweets are short, making them challenging for text analysis methods like sentiment and topic analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' That our method is very effective on challenging text is encouraging for scholars who would extend this method to more typical (longer) texts.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' A limitation of our approach is its accessibility.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We have argued that Google Translate is very accessible, and this is true in that it requires a small amount of code (that we provide) to translate large quantities of text to English.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' However, our approach is not as financially accessible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The Google’s Translation API costs $20 USD per million characters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' In practice, this translates to roughly $100 USD per 130,000 tweets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Fortunately, free translation tools of comparable quality are increasingly common, and can also be validated in practice using backtranslation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' One surprising result from this work was that the accuracy of sentiment detection after translation into English, and in some cases after backtranslation, was higher than in the original texts.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This finding is easier to understand with an appreciation of how sentiment analysis works in libraries like Polyglot.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Polyglot uses the “dictionary” method, in which hundreds to thousands of high-frequency words are given sentiment scores, and the score of a statement is calculated from the sum of scores of the subset of words that are in the detector’s sentiment dictionary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' If the dictionary is large, or the text is long, then its assigned sentiment score will be based on a lot of signal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Consequently, this method is less suitable for rarer languages and shorter texts (like tweets), which are less likely to contain scored words.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' It is also more suitable to texts with more common words, since uncommon words are less likely to appear in a language’s sentiment dictionary.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Why would translation to English, or backtranslation from English, improve task performance?' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Translation to English may be improving dictionary-based sentiment detection because English-language sentiment dictionaries tend to be longer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' And subsequent backtranslation may be improving detection performance if it results in uncommon unscored words from the source text being backtranslated into more common words that are scored.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We believe that this finding can be explained by Polyglots’ apparent relative greater capacity to detect sentiment in English language content, relative to the content of other languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' This result underscores the need to validate Google Translate for each natural language task that it is being used to support.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Conclusion There is an unmet need to extend Communication scholars’ applications of text analysis to more languages, particularly in the data-rich context of social media studies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Translation tools such as Google Translate can be immensely helpful in meeting this need.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We have quantified Google Translate’s effectiveness in maintaining sentence meaning in translations to and from English.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Across 16 non-English languages, sentiment analysis scores were shown to improve when translated to English, and only diminish marginally when translated back to their original languages.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Similarly, both topic and semantic distances are preserved during backtranslation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Our findings demonstrate that machine translation is able to preserve semantic content and make non-English datasets legible to English-trained computational tools.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' We hope this analysis gives researchers the confidence to use machine translation to simply and economically increase the number of languages involved in their research, and thereby the generality of their findings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Acknowledgements We would like to thank Arti Thakur, Communication Ph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Candidate at the University of California, Davis, for her assistance with the analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' All code is available at https://osf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='io/jx476/.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' The authors report there are no competing interests to declare.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Figure 1 We compare analytics computed on texts in their original languages to translated English language analytics and texts translated back to the original language.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Differences between the original and translated texts are typically difficult to attribute to semantic differences between the languages and “semantic” imposed by poor translation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Comparing original and backtranslated texts enables us to control for the effect of drift and focus on semantics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Original Intermediate Backtranslated source English source language language language text text textFigure 2 Sentiment analysis overall retains accuracy after backtranslation by machine methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Median sentiment detection accuracy increases 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='9% from original language to English translated language datasets, and falls less than 1% from original language datasets to backtranslated language datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Note that 99% error bars are too narrow to be displayed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='701 0.' metadata={'source': 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backtranslation declines in an absolute sense with number of topics, but increases relative to baseline.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Average topic cluster accuracy by size of topic cluster.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Note that topic cluster accuracy decreases from two to ten clusters, whereby it is approximately stable to 200 clusters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Arabic Bulgarian Chinese Croatian German Hindi Hungarian Polish Portuguese Russian Slovak Slovenian Spanish Swedish Average BaselineFigure 6 Tweets are closer to their backtranslations on average than to other tweets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Average distance between original language and backtranslated sentence embeddings by language.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Black lines denote the mean baseline distance and blue lines denote the minimum baseline distance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' All 16 languages have mean distances below their mean baseline.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' All languages but Albanian, Arabic, Chinese, German, Hindi, and Portuguese have mean distances below their minimum baseline.' metadata={'source': 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' Proceedings of the 52nd Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), 383–389.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' https://doi.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='org/10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='3115/v1/p14-2063 Featherstone, J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=', & Barnett, G.' metadata={'source': 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Mining, 233–242.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content=' https://doi.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='org/10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='1145/2623330.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} +page_content='2623715' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2dFAT4oBgHgl3EQfDhxB/content/2301.08416v1.pdf'} diff --git a/2tAzT4oBgHgl3EQffPw3/content/tmp_files/2301.01448v1.pdf.txt b/2tAzT4oBgHgl3EQffPw3/content/tmp_files/2301.01448v1.pdf.txt new file mode 100644 index 0000000000000000000000000000000000000000..e3b48ab001a5f4056f3c50604099d973cb72b3a8 --- /dev/null +++ b/2tAzT4oBgHgl3EQffPw3/content/tmp_files/2301.01448v1.pdf.txt @@ -0,0 +1,2181 @@ +1 +A deep local attention network for pre-operative +lymph node metastasis prediction in pancreatic +cancer via multiphase CT imaging +Zhilin Zheng, Xu Fang, Jiawen Yao, Mengmeng Zhu, Le Lu Fellow, IEEE, Lingyun Huang, Jing Xiao, Yu Shi, +Hong Lu, Jianping Lu, Ling Zhang, Chengwei Shao*, Yun Bian* +Abstract—Lymph node (LN) metastasis status is one of the +most critical prognostic and cancer staging factors for patients +with resectable pancreatic ductal adenocarcinoma (PDAC), or in +general, for any types of solid malignant tumors. Preoperative +prediction of LN metastasis from non-invasive CT imaging +is highly desired, as it might be straightforwardly used to +guide the following neoadjuvant treatment decision and surgical +planning. Most studies only capture the tumor characteristics +in CT imaging to implicitly infer LN metastasis and very few +work exploit direct LN’s CT imaging information. LN staging +is usually confirmed from pathological images acquired after +invasive procedures of biopsy or surgery. To the best of our +knowledge, this is the first work to propose a fully-automated +LN segmentation and identification network to directly facilitate +the LN metastasis status prediction task. Nevertheless LN seg- +mentation/detection is very challenging since LN can be easily +confused with other hard negative anatomic structures (e.g., +vessels) from radiological images. 1) We explore the anatomical +spatial context priors of pancreatic LN locations by generating a +guiding attention map from related organs and vessels to assist +segmentation and infer LN status. As such, LN segmentation +is impelled to focus on regions that are anatomically adjacent +or plausible with respect to the specific organs and vessels +(thus hard negative samples with certain distance ranges can +be ignored). 2) The metastasized LN identification network is +trained to classify the segmented LN instances into positives +or negatives by reusing the segmentation network as a pre- +trained backbone and padding a new classification head. 3) +More importantly, we develop a LN metastasis status prediction +network that combines the patient-wise aggregation results of LN +segmentation/identification and deep imaging features extracted +from the tumor region. 4) Extensive quantitative nested five- +fold cross-validation is conducted on a discovery dataset of 749 +patients with PDAC. External multi-center clinical evaluation is +further performed on two other hospitals of 191 patients in total. +Our final multi-staged LN status prediction network statistically +significantly outperforms the strong baseline of nnUNet and +several other compared methods, including CT-reported LN +status, radiomics, and deep learning models. +Index Terms—Pancreatic ductal adenocarcinoma (PDAC), +Z. Zheng, L. Huang, J. Xiao are with Ping An Technology (Shanghai & +Shenzhen), People’s Republic of China, (e-mail: zhilin.zheng95@gmail.com). +X. Fang, M. Zhu and J. Lu are with Changhai Hospital, Shanghai, People’s +Republic of China. J. Yao, L. Lu and L. Zhang were with PAII Inc., Bethesda, +MD 20817, USA. X. Fang and J. Yao contributed equally. +Y. Shi is with Department of Radiology, Shengjing Hospital of China +Medical University, Shenyang, China. +H. Lu is with Department of Radiology, Tianjin Medical University Cancer +Institute and Hospital, National Clinical Research Center of Cancer, Key +Laboratory of Cancer Prevention and Therapy, Tianjin, China. +*s indicate joint corresponding authors. Y. Bian and C. Shao are +with Changhai Hospital, Shanghai, People’s Republic of China, (email: +bianyun2012@foxmail.com, cwshao@sina.com). +Lymph node metastasis, Lymph node segmentation, Contrast- +enhanced computed tomography +I. INTRODUCTION +P +ANCREATIC cancer is the third leading cause of overall +cancer death in the United States [1], of which approx- +imately 95% is pancreatic ductal adenocarcinoma (PDAC) +[2]. With the poorest prognosis (i.e., 5-year overall survival +(OS) of 10% approximately), surgical resection is the most +effective way to achieve long-term survival for patients with +PDAC [2]. However, not all patients can benefit from the +margin-negative (R0) resection and comprehensive treatment +protocol is usually established for pancreatic cancer. The +patients’ treatment selections can be determined by whether +their peripancreatic lymph nodes (LNs) have metastasized with +the options of adjuvant radiotherapy (RT) or chemotherapy. +It was found that neoadjuvant therapy before surgery was +associated with improved survival and time to recurrence in +patients with LN metastasis, since neoadjuvant therapy can +not only treat lymphovascular invasion but also benefit tumor +downstaging [3], [4]. The accurate preoperative detection of +LN metastasis becomes vital and would aid in treatment +planning and management. +Contrast-enhanced CT is used as the typical imaging pro- +tocol for identifying the presence of peripancreatic metastatic +disease to LNs, but it is a very challenging task for radiologists +to determine whether a patient has LN metastasis by using only +CT scans. To this end, poor diagnostic accuracy of CT with a +pooled sensitivity of 25% and positive predictive value (PPV) +of 28% was reported in a meta-analysis [5] on assessing extra- +regional LN metastasis in pancreatic and peri-ampullary can- +cer. Recently, several radiomics based approaches have been +proposed to tackle the LN metastasis differentiation problem +of various cancer types +[6]–[12]. However, these methods +require hand-crafted feature design which can bring concerns +of reproducibility and human bias is often introduced due to +manual selection of 2D tumor slice with limited representation +power. Although there are some deep learning work that report +promising performance on predicting LN metastasis status in +gastric cancer [13], [14], those models assume that the risk of +metastases is fundamentally driven by the primary tumor. They +rely on LN CT report information for the integration model +without using any LNs detection or segmentation. The model +that takes both tumor morphology and lymphatic anatomy into +arXiv:2301.01448v1 [eess.IV] 4 Jan 2023 + +2 +Arterial +Arterial +Venous +Patient with metastasis +Patient without metastasis +Tumor +LN +Tumor-LN anatomy +Negative LN +Positive LN +Tumor +Tumor & LN +Spleen +Esophagus +Stomach +Aorta +Pancreas +Duodenum +SMA +TC +LGA +CHA&PHA +Organs & Vessels +Venous +LN +LN +LN +LN +LN +Tumor +LN +LN +LN +LN +LN +Tumor +LN +LN +LN +LN +Tumor +LN +LN +LN +LN +Tumor +Fig. 1. A visualization of pancreatic tumor (in dark red) and LNs (in pink red for positives or green for negatives) in multi-phase CT images +and their spatial distributions corresponding to key anatomical structures as follows. SMA: superior mesenteric artery. TC&SA: truncus +coeliacus and splenic artery. LGA: left gastric artery; CHA&PHA: common hepatic artery and proper hepatic artery. +account could be of more clinically usefulness on addressing +these aforementioned issues, similarly as in the diagnostic +processes performed by radiologist readers. PET/CT is another +imaging modality worth exploring. PET/CT based approaches +[15]–[17] generally use maximum standardized uptake value +(SUVmax) of manually-drawn LN RoIs as the prediction +element, but it comes with challenges of numerous false +positives from inflammatory LNs and false negatives from +small-sized metastatic LNs [18], [19]. Also, it is relatively +not as common as CT, which is less affordable, available and +accessible, hence we opt for CT for our research purpose. +In this paper, we tackle the LN metastasis status prediction +problem in patients with PDAC by first segmenting and +identifying instances of LNs and then classifying the patients +into metastasis-positive or -negative group. LNs are tiny struc- +tures that anatomically locate surrounding organs and vessels. +Their locations have been mapped into 18 stations that are +relevant for pancreatic cancer tumor according to their relative +positions against adjacent anatomical structures, as defined +by Japan Pancreas Society (JPS) [20] (see Supplementary +Table 1 in the supplementary material for details). Examples +of their spatial distribution are shown in Fig. 1. Metastasis +happens when cancer cells spread from the primary tumor +to LNs, causing enlargement of LNs and other underlying +changes. Response Evaluation Criteria in Solid Tumors (RE- +CIST) criteria [21] defines the criteria for LN metastasis +suspicion, i.e., nodes with short axis greater than 10mm, +heterogeneity and central necrosis. However, these criteria are +not pathognomonic since there exist false negatives associated +with small node micrometastases and false positives with +inflammatory nodes larger than 10mm in short axis. Hence, +finding LNs in CT images is quite time-consuming and can be +inconsistent depending on radiologists’ subjective experiences. +It is ambiguous for radiologists to identify nodal positivity +accurately from CT without referring to pathology reports. +The gold standard for determination of metastasis is based on +post-operative pathological evaluation of pancreatectomy spec- +imens. Automated yet reliable pre-operative LN segmentation +and identification are highly desirable for patient surgical or +RT treatment planing. +LN segmentation is inherently challenging due to two +reasons: 1) small to tiny sizes of LN cause extreme foreground- +background class imbalance problem; 2) LNs have CT atten- +uation values similar to vessels and other soft-tissue struc- +tures, resulting in visual confusions. Existing work [22]–[24] +mainly adopt U-Net based deep networks [25]–[27] as strong +backbones, in which skip connections aggregate multi-level +semantic representation and alleviate vanishing gradient prob- +lem. They incorporate anatomical context by directly taking +organs&vessels segmentation masks as either supervision tar- +gets [22] or additional inputs [24], [28]. Concerns are remained +that the relationship between lymphatic anatomy and adjacent +anatomical structures is not well explored. We address it by +introducing a distance-guided attention map to fully utilize the +spatial priors. In our segmentation framework, the LN attention +map is obtained via a pre-defined mapping from distance +maps of related organs/vessels that have been integrated into +UNet-based backbone to control the segmentation network’s + +TO: +B +TVN00SL0003TO五 +TO +TVNO0O0003TO: +BTVN001O0003TO: +B +TVN00SL0003TO: +B3 +spatial focus. It simultaneously assists in improving sample +selection strategy that filters out non-informative negative +samples (called ”informative negative selection”) to tackle the +class imbalance problem. The segmented LNs are labeled as +positive/negative using radiologist’s judgement as the standard +that combines information from pathological results and CT +intensities. A classification network is subsequently derived by +sharing the same backbone with segmentation and initialized +with the trained segmentation parameters. This strategy ben- +efits the classification task from densely structured prediction +in segmentation. By predicting LN metastasis in patients +with PDAC, we employ a modified ResNet [29] classification +model. Tumor characteristics are proven to be important cues +for metastasis [8], [9], [11], so we integrate both tumor and +LN cues by taking as inputs the image patches of tumor +and the patient-wise aggregation of LN segmentation and +identification. +Our main contribution is four folds: 1) To the best of +our knowledge, this work is the first to directly incorporate +automated LN segmentation and identification for assisting +preoperative LN metastasis status prediction for patients with +PDAC. 2) We propose an attention-based LN segmentation +network with the guidance of distances to nearby anatomical +structures, explicitly exploiting the spatial priors and simul- +taneously addressing the foreground-background imbalance +issue. 3) We design a compositive LN metastasis status +prediction network combining both tumor and positive LN +characteristics, showing the potential of tumor-LN guided +cues. 4) Extensive quantitative experiments are conducted to +evidently validate the effectiveness of our deep local attention +network in both tasks of LN segmentation and LN metastasis +status prediction, and external multi-center clinical evaluation +is performed to demonstrate the generalization ability. Without +loss of generality, our proposed method is applicable for +finding the preoperative LN metastasis status of other types +of solid tumor or cancers, such as liver or gastric cancers. +II. RELATED WORK +A. Lymph Node Segmentation +Automated LN segmentation in CT images is an essential +yet challenging task in medical image analysis. Traditional +approaches tackle this problem by the means of atlas based +search space restriction [30], spatial prior features combination +[31], [32], supervoxel clustering [33], etc. In recent years, U- +Net based deep networks have shown remarkable performance +in numerous organ or tumor segmentation tasks [34]–[38]. +nnUNet [27] further proposes a self-configuring approach, +with automatic configurations including preprocessing, net- +work architecture, training and post-processing, that achieves +robust performance and general applicability. To address the +strong class imbalance issues in LN segmentation, four other +anatomical structures are included as training targets [22] +using 3D U-Net [26] framework. [23] utilizes parallel net- +works of 2D U-Net [25] and Mask R-CNN [39] with the +supervision of all considered anatomical structures and LNs, +benefiting from both semantic and instance segmentation. +Another strategy to incorporate anatomical context is to take +organ segmentation masks as additional channels of the input. +[28] proposes an ensemble approach for a slab-wise and +a downsampled full volume based LN segmentation, taking +the concatenation of CT image and segmented anatomical +structure mask as input. DeepStationing [24] presents a key +referencing organ auto-search strategy and combines selected +organs into the network via input concatentation for LN station +parsing. All above methods implicitly exploit spatial priors +of LNs by injecting the anatomical structure masks either as +inputs or supervisions, hence the prior knowledge has not been +fully exploited. More importantly, there is a lack of studies on +how LN segmentation could be used for predicting metastasis. +B. Lymph Node Metastasis Prediction +Radiomics Methods. Radiomics is a powerful technique +for extracting quantitative image features with the purpose +of clinical decision support, and thus widely used in can- +cer research [11], [12], [40]–[42]. It converts imaging data +into different types of hand-crafted features, including shape, +intensity, texture and filter-based (e.g., wavelet, Laplacian of +Gaussian) features. Applications of radiomics on predicting +LN metastasis from primary tumor have been explored in +many recent works [6]–[10]. Radiomics features are first +extracted from manually delineated tumor regions in any +contrast-enhanced CT images. Feature selection and classifi- +cation model construction (e.g., logistic regression, random +forest) are then performed to give LN metastasis prediction +for various cancer types like gastric cancer [7], [12], biliary +tract cancer [6] and PDAC [8], [9], [11]. Relying only on +primary tumor radiomics without considering LNs character- +istics may limit the prediction performance, thus [10] uses +manual annotations of the largest LN visible in the gastric +region and combines LN radiomics into the prediction model +for gastric cancer. However, problem still remains because it +simply involves the largest LN without identifying the nodal +positivity. +Deep Learning based Methods. Recent advances in deep +learning have made it a mainstream method of addressing the +entire workflow of diagnosis and treatment for various cancer +types on medical imaging, such as orapharageal cancer [43], +lung cancer [44], as well as pancreatic cancer [45]–[47]. Deep +neural networks are applied to LN metastasis in many studies +[13], [14], [48], [49]. In [48], deep features are extracted +from tumor ROIs in bimodal image (i.e., US and SWE) using +ResNet [29], and then fed into a SVM model for predicting +axillary LN status in breast cancer. For gastric cancer, [14] +combines DenseNet [50] features with some hand-crafted +features, extracted from the 2D tumor ROI with the largest +area in multi-phase CT images. To investigate metastasis in +individual LN stations for gastric cancer, [13] develops a +system of multiple independent ResNets with tumor ROIs and +corresponding annotation masks as inputs where each ResNet +is responsible to predict metastasis at one specific nodal sta- +tion. Most existing studies capture only tumor characteristics +for LN metastasis prediction, while the one leveraging LN +radiomics requires manual delineation and considers simply +the LN with the largest size [10]. An automated and accurate + +4 +b) LN metastasis status prediction network +Volume +Image +PDAC +Mask +Metastasis +-positive +Metastasis- +Negative +√ +Cropping +Cropping +c +Lymph node +segmentation & +identification +Lymph node +segmentation & +identification +Volume +Image +PDAC +Mask +Metastasis +-positive +Metastasis- +Negative +√ +Cropping +Cropping +c +Lymph node +segmentation & +identification +Image +Lymph Node +Segmentation +Instance-wise +Lymph Node +Identification +Organ& +Vessel +Distance +Transform +Non-linear +Mapping +Attention +Mechanism +GAP +a) Lymph node segmentation & identification network +c +concatenation +element-wise +multiplication +Downsampling +Fig. 2. The proposed framework for (a) two-stage LN segmentation and identification and (b) LN metastasis status prediction . +process of LN segmentation and nodal positivity identification +is hence of high importance for assisting metastasis prediction. +III. METHODOLOGY +The overall framework is illustrated in Fig. 2, which is com- +posed of (a) distance-guided attention-based LN segmentation +and identification network, and (b) tumor and LN combined +metastasis status prediction network. +A. Distance-guided Attention-based Lymph Node Segmenta- +tion and Identification Network +We perform LN detection from any input CT scan by a two- +stage strategy: segmenting the image into two classes of LN +and background voxels, followed by identifying segmented LN +instances as positive or negative. +1) Stage 1: Class-agnostic Lymph Node Segmentation: +Based on the spatial prior that LN stations are geometrically +distributed or constrained around certain anatomical structures, +we propose an attention based LN segmentation network by +taking the distances to nearby organs/vessels into account. +Our LN segmentation network differs from the strong baseline +(i.e., nnUNet [27]) in that attention mechanism is applied to +guide possible LN locations, with the advantage of reducing +false positive predictions outside those locations. The intuition +behind the attention module is that the attention map can cover +regions adjacently constrained to those organs and vessels. +Attention Map Generation. To explicitly capture and +model the lymphatic anatomy, attention computation is im- +plemented as a pre-defined geometric mapping function from +organ&vessel distance maps. An example of attention map +generation process is shown in Fig. 3. Specifically, given a +multi-phase input CT volume X ∈ RN×W ×H×D, we first +obtain organ&vessel segmentation mask using nnUNet [27] +model trained with 19 classes of annotations. Ten classes +among them involved with 17 LN stations are used (see +Supplementary Table 1 in the supplementary material for the +definition of LN stations), i.e., spleen, esophagus, stomach, +aorta, pancreas, duodenum, superior mesenteric artery (SMA), +truncus coeliacus and splenic artery (TC&SA), left gastric +artery (LGA), common hepatic artery and proper hepatic +artery (CHA&PHA). Note that station 15# (LNs along middle +Spleen +Aorta +SMA +LGA +Image +Organ&Vessel +Organ/Vessel +Distance Map +Organ/Vessel +Attention Map +Integrated +Attention Map +CHA&PHA +Esophagus +Duodenum +Non-linear +Mapping +0 +1 +d imin +min +d imin +dmax +imax +i +dmax +i +d imin +min +d imin-3 +d imin-3 +dmax +imax +i +dmax +i ++3 +dmax +i ++3 d +fifi +Stomach +Pancreas +TC&SA +Fig. 3. An illustration of attention map generation process. +colic artery) is left aside here since it is related to distant +metastasis that rarely happens in our patient population. A +SDT is applied to each class of the segmentation mask M ∈ +{0, 1, 2, ..., 10}W ×H×D, generating a total of 10 organ/vessel +distance maps Di where i ∈ {1, 2, ..., 10} is the index of +organ/vessel class. Di has positive values at the voxels outside +the i-th organ/vessel and negative scores inside it. Intuitively, +LNs are likely to appear within a certain range of distance +to each organ/vessel, which requires paying attention to. To +obtain the distance-guided attention maps, Di is passed to an +isosceles trapezium-shaped non-linear mapping function (see + +TO +B +c000.r100.ocbqT0 +B +E000_100_3sbq5 +Fig. 3), formulated as +f i(d) = +� +� +� +� +� +� +� +� +� +� +� +� +� +� +� +� +� +1, +di +min ≤ d ≤ di +max +− (d − di +max − 3) +3 +, +di +max 0 (called informative patches) for training. +This sampling strategy further boosts the network’s concen- +tration on targeted regions of interest (ROIs) surrounding +organs/vessels. +For training objectives to better balance precision and recall +, we modify the Dice loss in nnUNet with Tversky loss [51]: +LT = − 2 +|V | +� +v p1,vy1,v +2 � +v p1,vy1,v + α � +v p1,vy0,v + β � +v p0,vy1,v +(3) +where |V | is the number of voxels. p1,v is the probability +of voxel v being a LN, and p0,v is the probability being a +non-LN. Also, y1,v is 1 for a LN voxel and 0 for a non-LN +voxel, and vice versa for the y0,v. In practice, we set α = 0.5 +and β = 1.5 to emphasis on false negatives and boost recall. +The whole network is trained by the combination of cross +entropy loss LCE and Tversky loss LT with equal weights as +in nnUNet. +LCE = − 1 +|V | +� +v +� +k=0,1 +yk,v log(pk,v) +(4) +LSEG = LCE + LT +(5) +Following nnUNet, the network is trained with deep supervi- +sion, i.e., losses are calculated over multi-resolution outputs +given by final and intermediate layers of the decoder, and +the corresponding downsampled ground-truth (GT) masks are +used as targets. Here attention mechanism is applied in a multi- +scale manner. That is, the attention map, after downsampled +to match the resolution, is injected to the intermediate decoder +feature for each deep supervision output. +2) Stage 2: Instance-wise Lymph Node Identification: After +segmenting LN instances from the whole CT image, we then +classify them into either positive or negative class. To benefit +from the already trained dense segmentation network of stage +1, the task of LN instance identification reuses 3D nnUNet +backbone and is initialized using the trained segmentation +parameters, with a new classification head added upon it. +Cross entropy loss is adopted to finetune the whole network +for classifying the instance as positive/negative. To generate +LN instances, we crop patches centered at the connected +components of the segmentation mask. GT LN instances are +cropped and employed in the training phase. While at inference +time, we can apply the classification network to identify +each segmented LN of stage 1, and obtain a class-aware LN +segmentation mask. +B. Tumor and Lymph Node Combined LN Metastasis Status +Prediction Network +Besides LNs themselves, imaging characteristics in the +primary tumor play an important role in predicting the status +of LN metastasis. To further boost the performance, we build +a combined classification network, integrating both PDAC and +LNs related information. In contrast to previous work that +only consider tumor characteristics [8], [9], [11], our method +benefits from directly observing the status of LN instances by +automated LN segmentation and identification. +Given a CT image and the corresponding PDAC mask, +2D slices with the top three largest PDAC areas in each of +axial, sagittal, and coronal planes are cropped, resulting in +nine image patches in total. Each image patch is fed into +a ResNet [29] pre-trained on ImageNet [52] for metastasis +prediction. Inspired by [53], a side branch with the PDAC +mask as input is added to encourage the network to concentrate +on the PDAC region. Specifically, the side branch consists of +a Conv-ReLU block and maps the input mask to a feature +map with the same shape as the output of “Conv1” layer in +ResNet. It is then integrated into the backbone by element-wise + +6 +multiplication with the “Conv1” feature. Our initial experiment +empirically shows that such incorporation produces better per- +formance than direct input-level fusion, as the convolution in +the side branch learns which region to focus on in each channel +of “Conv1” feature (e.g., regions inside the mask, around the +mask border or outside the mask). To be better aligned with +the pre-trained backbone and eliminate the initial effect of the +side branch, the weights and biases in the convolution layer +are initialized to 0 and 1 respectively. Before classification, we +additionally employ a Texture Encoding Layer (TEL) [54] on +top of the “Layer4” feature FL4 to extract respective texture +representation. TEL serves as an orderless feature pooling +layer that encodes spatially invariant representation describing +the feature distributions, which benefits texture recognition of +the PDAC region. The original deep feature is merged with +the texture feature to form an enhanced representation F: +F = Concat(GAP(FL4), TEL(FL4)) +(6) +where Concat and GAP denote feature concatenation and +global average layer, respectively. +We further integrate LN-related cues into the network given +the LN segmentation and identification results described in +Section III-A. A patient is considered as metastasis-positive if +there exists at least one positive LN, thus it is very sensitive +to the false positives in LN identification. Therefore, we +employ the volume of positive LN as the feature instead +of its binary status of presence/absence, based on the fact +that positive LNs tend to have larger volume than negative +ones. The volume of the largest positive LN in each patient +Vmax +pLN = +max +ln∈{positive LNs} Vln (in mm3) is mapped to a vector- +shaped feature, and fused with F by element-wise addition, +formulated as follows: +Fcomb = FC(BN(Vmax +pLN)) + F +(7) +where FC and BN denote the full-connected layer and batch +normalization layer, respectively. Other LN features, such as +the average or total volume of positive LNs, are also evaluated, +with the current setting giving the best result. Finally, the +classification probabilities generated from nine image patches +are averaged to given an ensembled prediction for a patient. +IV. EXPERIMENTS +In this section, we first demonstrate the multicenter datasets +(i.e. the discovery dataset and two external datasets) and +implementation details, and then elaborate the strategy we +use to generate PDAC segmentation masks. Subsequently we +present results on the discovery dataset in each step of our +method, including organ&vessel segmentation, attention map +generation, LN segmentation and identification, and LN metas- +tasis status prediction. Finally, external validation is conducted +to evaluate the generalization performance of LN metastasis +status prediction, with only pathology reports accessible in two +external datasets. +A. Experimental Settings +1) Dataset: +We conduct a multicenter study on three +independent datasets with a total of 940 patients collected +from Changhai Hospital in Shanghai, Shengjing Hospital in +Liaoning Province, and Tianjin Cancer Hospital in Tianjin. All +patients had a pathologically confirmed diagnosis of PDAC, +and contrast-enhanced CT scans of arterial (A) and venous +(V) phases acquired before treatment were included in this +study. We labeled LNs on the dataset from Changhai Hospital +(denoted as Discovery dataset), and developed our model on +it using nested cross-validation (CV). The rest two datasets +from Shengjing Hospital and Tianjin Cancer Hospital (denoted +as Ext-validation dataset 1 and Ext-validation dataset 2) were +used as external validation sets with only pathologically diag- +nosed LN metastasis status provided. This study was reviewed +and approved by the Biomedical Research Ethics Committee +of the institution (No. CHEC2021164), and was performed in +accordance with the ethical standards of the 1964 Declaration +of Helsinki. The requirement for patient informed consent +was waived by the Institutional Review Board due to the +retrospective nature of the study and because all procedures +performed were part of routine care. +Discovery dataset contains CT scans of 749 patients, +among which there are 351 positive samples (patients with +LN metastasis) and 398 negative samples (patients without +LN metastasis). The annotation of LNs was performed by +two board-certified radiologists (XF with 7 and MZ with 5 +years of experiences in pancreatic imaging) with referring to +pathology report under supervision of a senior radiologist (YB) +with 17 years of experiences in pancreatic imaging. There are +totally 2,467 labeled LNs, of which 476 are positive and the +rest are negative. In specific, 351 metastasis-positive patients +contain 476 labeled positive and 322 labeled negative LNs, and +398 metastasis-negative patients have the rest 1,669 labeled +negative LNs. +This dataset was split using nested five-fold CV, with 64%, +16% and 20% as training, validation and testing sets in each +CV round. As for the primary tumor, 163 patients among the +whole dataset were annotated with 3D tumor masks by two +radiologists (XF and MZ). We use these 163 patients as the +testing set and the remaining unlabeled 586 patients as the +training set for an annotation-efficient PDAC segmentation. +Additionally, we generate pseudo annotations of 17 classes +of organs and vessels using the self-learning segmentation +model described in [55], and manually annotate extra two +vessels (LGA, CHA&PHA) and extend other two vessels +(SMA and TC&SA) under the supervision of a radiologist +(XF) for 50 patients randomly sampled from our dataset. 40/10 +of these patients are used as training and validation sets for +organ&vessel segmentation, respectively. +Ext-validation dataset 1 contains CT scans of 132 patients +with 39 positive and 93 negative patients; Ext-validation +dataset 2 contains 59 patients with 37 positive and 22 negative +patients. More detailed information on three datasets can be +seen in Table I. +2) Implementation Details: In our experiments, CT images +of arterial phase are registered to venous phase using DEEDS +[56], and they are all resampled to a median spacing of 0.68 +× 0.68 × 0.80 mm. For LN segmentation and organ&vessel +segmentation, sub-volumes of 160 × 192 × 80 are randomly +cropped as training patches. In the non-linear mapping from + +7 +TABLE I +DEMOGRAPHIC DISTRIBUTIONS AND TUMOR CHARACTERISTICS IN THE THREE DATASETS (DISCOVERY DATASET, EXT-VALIDATION +DATASET 1 AND EXT-VALIDATION DATASET 2). MEDIAN [INTERQUARTILE RANGE, 25TH–75TH PERCENTILE] VALUES ARE REPORTED +FOR CONTINUOUS VARIABLES. +Characteristics +Discovery dataset +Ext-validation dataset 1 +Ext-validation dataset 2 +(n=749) +(n=132) +(n=59) +Gender, n (%) +Female +282 (38%) +60 (45%) +28 (47%) +Male +467 (62%) +72 (55 %) +31 (53%) +Age at Diagnosis, yrs +63 [56-69] +60 [53-65] +58 [51-62] +pT Stage, n (%) +pT1 / pT2 +92 (12%) / 314 (42%) +24 (18%)/ 80 (61%) +10 (17%) / 31 (53%) +pT3 / pT4 +316 (42%) / 13 (2%) +15 (11%)/ 13 (10%) +5 (8%)/ 13 (22%) +Missing +14 (2%) +0 (0 %) +0 (0 %) +pN Stage, n (%) +pN0 +398 (53%) +93 (70%) +22 (37%) +pN1 +242 (32%) +32 (24%) +22 (37%) +pN2 +109 (15%) +7 (5%) +15 (25%) +Tumor Size, cm +3.0 [2.5-4.1] +2.7 [2.2-3.0] +2.9 [2.2-3.4] +Tumor Location, n (%) +Head / Uncinate +475 (63%) +56 (42%)/ 52 (39%) +35 (59%)/ 22 (37%) +Body / Tail +274 (37%) +2 (2%)/ 22 (17%) +2 (3%)/ 0 (0%) +Positive LN Volume, mm3 +665[210-804] +- +- +Negative LN Volume, mm3 +300[106-377] +- +- +distance maps to attention maps for our LN segmentation, +parameters of the mapping function are determined by group- +ing GT LN voxels according to which organ/vessel is closest +to, and calculating the minimum and maximum distances to +organ/vessel boundaries in each group. Parameters are listed +in Table II, in which negative values indicate voxels inside +organ/vessel. +TABLE II +PARAMETERS (I.E. dmin AND dmax) OF NON-LINEAR MAPPING FUNCTION +FOR EACH ORGAN OR VESSEL. SMA: SUPERIOR MESENTERIC ARTERY. +TC&SA: TRUNCUS COELIACUS AND SPLENIC ARTERY. LGA: LEFT +GASTRIC ARTERY; CHA&PHA: COMMON HEPATIC ARTERY AND PROPER +HEPATIC ARTERY. +Organ/Vessel +dmin (mm) +dmax (mm) +Spleen +0 +16 +Esophagus +0 +25 +Stomach +-2 +18 +Aorta +0 +28 +Pancreas +-5 +20 +Duodenum +-5 +22 +SMA +-1 +20 +TC&SA +-2 +18 +LGA +0 +21 +CHA&PHA +0 +20 +As for instance-wise LN identification, 3D image training +samples are generated by cropping a 96 × 96 × 80 sub-volume +centered per each GT LN. SGD optimizer with Nesterov +momentum (µ = 0.95) is adopted to train the network, whose +initial learning rate and weight decay are 5 × 10−4 and +1 × 10−4, respectively. Furthermore, the final LN metastasis +status prediction model takes 2D inputs of 224 × 224 cen- +tered at PDAC, and is trained using the same optimizer as +above. Details of the network architecture are presented in the +supplementary material. +B. PDAC Segmentation Mask Acquisition/Harvesting +We employ an annotation-efficient strategy to generate +3D masks of tumors for the labor cost reduction purpose. +Specifically, we start with the PDAC segmentation model +trained with arterial-late phase described in [46] to generate +pseudo annotations. Next, the model is fine-tuned under the +supervision of pseudo annotations and then applied to produce +segmentation masks on our dataset. To obtain the PDAC +segmentation model on venous phase, those segmentation +masks are registered to venous phase and are then used to +train a nnUNet model from scratch to generate the final 3D +masks of tumors. We evaluate the final PDAC segmentation +model on the labeled testing set. Median Dice score, average +surface distance (ASD, mm), and Hausdorff distance (HD, mm) +are 0.683, 2.186, and 12.805 respectively. +C. Evaluation of Organ&Vessel Segmentation and Attention +Maps +To evaluate the performance of organ&vessel segmentation, +a testing set of 19 randomly selected CT volumes with ten +classes of organ/vessel is manually annotated by a radiologist +(XF). To reduce the annotation burden, all dense CT volumes +are downsampled to 5mm in the slice thickness dimension. We +compare our self-learning model with the pseudo annotation +generator [55], which is able to segment eight of ten classes +(except for LGA and CHA&PHA) on single-phase CT. Dice +score, ASD (mm), and HD (mm) are adopted as the evaluation +metrics and the results are provided in Table III. Our model +that is trained on two phases outperforms [55] on seven +of eight organs/vessels. Note that SMA and TC&SA masks +segmented by [55] contain shorter parts compared with those +segmented by our model, therefore, resulting in significantly +lower performance than ours (0.331 lower Dice score in SMA, +and 0.171 lower in TC&SA). + +8 +TABLE III +QUANTITATIVE PERFORMANCE OF ORGAN&VESSEL +SEGMENTATION. A: ARTERIAL. V: VENOUS. SMA: SUPERIOR +MESENTERIC ARTERY. TC&SA: TRUNCUS COELIACUS AND +SPLENIC ARTERY. LGA: LEFT GASTRIC ARTERY; CHA&PHA: +COMMON HEPATIC ARTERY AND PROPER HEPATIC ARTERY. +Organ/Vessel +Methods +CT Phases +Dice +ASD (mm) +HD (mm) +Spleen +[55] +A +0.938 +0.643 +14.252 +[55] +V +0.954 +0.422 +11.107 +Ours +A+V +0.959 +0.384 +8.129 +Esophagus +[55] +A +0.557 +0.936 +13.897 +[55] +V +0.598 +0.854 +11.003 +Ours +A+V +0.745 +0.641 +8.125 +Stomach +[55] +A +0.846 +2.223 +35.338 +[55] +V +0.813 +3.765 +43.114 +Ours +A+V +0.905 +1.519 +19.183 +Aorta +[55] +A +0.893 +0.519 +8.130 +[55] +V +0.924 +0.417 +6.158 +Ours +A+V +0.920 +0.359 +5.863 +Pancreas +[55] +A +0.712 +2.905 +25.880 +[55] +V +0.756 +1.897 +19.258 +Ours +A+V +0.847 +0.975 +12.859 +Duodenum +[55] +A +0.613 +2.976 +34.187 +[55] +V +0.665 +3.366 +32.174 +Ours +A+V +0.764 +1.892 +29.131 +SMA +[55] +A +0.387 +0.663 +68.869 +[55] +V +0.415 +0.710 +68.098 +Ours +A+V +0.746 +0.860 +28.840 +TC&SA +[55] +A +0.563 +0.780 +43.974 +[55] +V +0.407 +1.245 +51.432 +Ours +A+V +0.734 +0.305 +22.224 +LGA +[55] +A +- +- +- +[55] +V +- +- +- +Ours +A+V +0.651 +0.371 +10.420 +CHA&PHA +[55] +A +- +- +- +[55] +V +- +- +- +Ours +A+V +0.715 +1.424 +24.239 +Qualitative evaluation of organ&vessel segmentation exam- +ples as well as the corresponding attention maps are visualized +in Fig. 4 (b). +D. Evaluation of Lymph Node Instance Segmentation and +Identification +TABLE IV +AVERAGE INSTANCE-WISE LN CLASSIFICATION PERFORMANCE +ACROSS 5 FOLDS. THE RESULTS ARE REPORTED ON GT +INSTANCES. +Metric +Performance +AUC +0.854 +Accuracy +0.789 +Balanced accuracy +0.771 +Sensitivity +0.742 +Specificity +0.800 +Quantitative Evaluation. LNs are first detected by the +class-agnostic segmentation model, and then identified as +positive/negative by applying the classification model on the +cropped instances. For positive/negative LN identification, our +classification model is trained with Ground-Truth (GT) LNs, +yielding an average AUC of 0.854 across 5 folds (in Table IV). +At inference, the automatically segmented LNs are cropped +and then identified by the classification model. To evaluate the +segmentation performance before and after identification, we +compare our method with a strong baseline, nnUNet [27]. The +segmentation accuracy is measured by voxel-wise metrics (i.e., +Dice, Recall, Precision) and instance-wise metrics (F-measure, +Recall, Precision). To achieve the statistical analysis, we apply +1,000 iterations of Wilcoxon signed rank test to voxel-wise +Dice and instance-wise F-measure. Results are provided in +Table V. An instance is considered successfully detected if +its (intersect-over-union) IoU score between the segmentation +mask and GT mask is ≥ 30 %. Before identification, our +segmentation model significantly outperforms nnUNet on both +voxel-wise and instance-wise metrics, with the voxel-wise +Dice increasing from 45.9% to 47.7% and the instance-wise +F-measure increasing from 36.1% to 40.6%, as shown in Table +V. In addition, our model also yields superior performance in +terms of both positive and negative LNs after identification, +achieving 1.8% higher voxel-wise Dice and 1.8% higher +instance-wise F-measure in terms of positive LNs, and 0.2% +higher voxel-wise Dice and 1.2% higher instance-wise F- +measure in terms of negative LNs. In total five out of six +comparisons, our method is statistically significantly better or +more accurate (i.e., with p-value < 0.05) in LN segmentation +than the nnUNet baseline (implemented without the attention +maps). +Qualitative Evaluation. Examples of LN segmentation +and identification results are shown in Fig. 4 (a) for qual- +itative comparison. Our segmentation model leverages prior +knowledge of LNs’ position distribution by incorporating the +attention mechanism to remove false positives that are far +from anatomically plausible LN areas. In Fig. 4 (a), we can +observe that nnUNet tends to falsely detect an instance inside +some organs or located very far, while our method provides +noticeably less false positives. +E. Evaluation of Patient-wise Lymph Node Metastasis Status +Prediction +Metrics. In this section, we evaluate various performance +metrics of LN metastasis status prediction. For this binary +classification problem, AUC, accuracy, balanced accuracy, +sensitivity and specificity are adopted as evaluation metrics +and the average results across 5 folds are reported. Statistical +analysis is also carried out to verify the significance of +performance improvement. We collect the predictions of all +5 folds, repeat 1,000 times of bootstrapping for calculating +balanced accuracy, and apply Wilcoxon signed rank test to +balanced accuracy distributoins to compare our method with +several other configurations. For comparing ROC curves, +DeLong test is performed. P-values < 0.05 are considered +as statistically significant. To compute 95% CI, the 2.5th +percentile and 97.5th percentile are estimated after 1,000 times +of bootstrapping. +Ablation Study. We first investigate the impact of each +component in our framework. To evaluate the metastasis +prediction performance of LN segmentation and identification, +the results can be aggregated into patient-level prediction, +based on the definition that a patient with at least one positive +LN is metastasis-positive. However, due to a large number of +false positives produced by segmentation (LN segmentation +in CT images is challenging after all), it will lead to a poor +performance if predicting metastasis simply based on the + +9 +TABLE V +PERFORMANCE COMPARISON ON LN SEGMENTATION BEFORE AND AFTER INSTANCE-WISE IDENTIFICATION (DENOTED AS +Class-agnostic Seg AND Class-aware Seg). POS AND NEG DENOTE POSITIVE AND NEGATIVE LNS. RESULTS ARE AVERAGED ACROSS 5 +FOLDS. WILCOXON SIGNED RANK TEST IS CONDUCTED ON VOXEL-WISE DICE AND INSTANCE-WISE F-MEASURE. * INDICATES +p-VALUE < 0.05. NS INDICATES NO SIGNIFICANCE. +Stage +Class +Method +Voxel-wise Metrics (%) +Instance-wise Metrics (%) +Dice +Recall +Precision +F-measure +Recall +Precision +Class-agnostic Seg +- +nnUNet +45.9∗ +75.4 +36.2 +36.1∗ +81.0 +25.3 +(before identification) +Ours +47.7ref +77.7 +37.5 +40.6ref +80.9 +29.9 +Pos +nnUNet +10.2∗ +32.3 +11.3 +11.7∗ +36.1 +12.0 +Class-aware Seg +Ours +12.0ref +38.9 +11.7 +13.5ref +41.5 +13.3 +(after identification) +Neg +nnUNet +27.5NS +51.1 +25.4 +27.7∗ +60.0 +22.9 +Ours +27.7ref +49.0 +27.0 +28.9ref +56.2 +25.8 +Image +Label +nnUNet +Ours +Positive Lymph Node +Negative Lymph Node +Attmap +Organ&Vessel +Organ&Vessel Anatomy +(a) Lymph Node Segmentation and Identification Results +(b) Organ&Vessel Segmentation and Attention Map Results +Spleen +RightKidney +LeftKidney +Gallbladder +Esophagus +Liver +Stomach +Aorta +IVC +PV&SV +Pancreas +RAG +LAG +Duodenum +SMV +SMA +TC +LGA +CHA&PHA +Spleen +RightKidney +LeftKidney +Gallbladder +Esophagus +Liver +Stomach +Aorta +IVC +PV&SV +Pancreas +RAG +LAG +Duodenum +SMV +SMA +TC +LGA +CHA&PHA +Organs & Vessels +Lymph Nodes +1.0 +0.8 +0.6 +0.4 +0.2 +0.0 +Fig. 4. Examples of (a) LN segmentation and identification results, and (b) Organ&Vessel segmentation and attention map results. +presence of positive LN in the segmentation results. We instead +conduct ROC analysis on the volume of the largest positive +LN in each case, and find an optimal threshold with the best +balanced accuracy in the validation set. Then the threshold +is applied to the testing set. A patients with positive LNs +larger than the threshold are classified into metastasis-positive; +otherwise, it is classified into metastasis-negative. The ablation +models for consideration/comparison are listed as follows: +• ClsfromPDAC: The straightforward strategy combining +ResNet2D [29] feature and DeepTEN [54] feature, extracted + +N980-2021103010 +TABLE VI +PERFORMANCE COMPARISON AND ABLATION STUDY ON LN METASTASIS STATUS PREDICTION OF DISCOVERY DATASET. RESULTS ARE +AVERAGED ACROSS 5 FOLDS. WILCOXON SIGNED RANK TEST IS CONDUCTED ON BALANCED ACCURACY. * INDICATES p-VALUE < +0.05. NS INDICATES NO SIGNIFICANCE. +Method +Balanced Accuracy +AUC +Accuracy +Sensitivity +Specificity +[95% CI] +[95% CI] +[95% CI] +[95% CI] +[95% CI] +CT-reported LN status +0.599∗ +- +0.599 +0.588 +0.609 +[0.564-0.634] +[0.565-0.634] +[0.538-0.635] +[0.558-0.657] +Radiomics +0.597∗ +0.648 +0.603 +0.508 +0.686 +[0.563-0.633] +[0.598-0.681] +[0.569-0.637] +[0.456-0.561] +[0.638-0.734] +Radiomics + +0.604∗ +0.654 +0.610 +0.524 +0.684 +CT-reported LN status +[0.572-0.641] +[0.612-0.692] +[0.575-0.644] +[0.470-0.581] +[0.641-0.731] +ResNet3D +0.562∗ +0.609 +0.554 +0.599 +0.524 +[0.521-0.593] +[0.550-0.631] +[0.519-0.587] +[0.538-0.644] +[0.475-0.568] +ResNet2D +0.571∗ +0.631 +0.574 +0.568 +0.574 +[0.540-0.609] +[0.590-0.667] +[0.537-0.607] +[0.519-0.624] +[0.530-0.628] +DeepTEN +0.588∗ +0.634 +0.593 +0.609 +0.566 +[0.560-0.628] +[0.599-0.679] +[0.559-0.628] +[0.564-0.667] +[0.520-0.621] +ClsfromPDAC +0.599∗ +0.654 +0.597 +0.600 +0.597 +[0.558-0.634] +[0.608-0.685] +[0.561-0.633] +[0.547-0.647] +[0.550-0.646] +ClsbyLNSeg w/o Attn +0.545∗ +0.590 +0.566 +0.433 +0.657 +[0.525-0.593] +[0.548-0.625] +[0.534-0.601] +[0.393-0.499] +[0.623-0.716] +ClsbyLNSeg w/ Attn +0.563∗ +0.603 +0.572 +0.351 +0.775 +[0.530-0.594] +[0.564-0.642] +[0.539-0.605] +[0.299-0.396] +[0.731-0.814] +Ours (ClsfromPDAC + +0.633ref +0.682 +0.635 +0.618 +0.649 +ClsbyLNSeg w/ Attn) +[0.599-0.669] +[0.640-0.717] +[0.601-0.669] +[0.567-0.664] +[0.603-696] +(a) +(b) +Fig. 5. ROC curve comparison of (a) ablation study and (b) baseline models and our method using nested five-fold cross-validation in Discovery dataset. +from PDAC slices, in the input of the classification layer. +• ClsbyLNSeg w/o Attn: Patient-level metastasis aggregation +from the results of LN segmentation without attention (i.e. +nnUNet). +• ClsbyLNSeg w/ Attn: Patient-level metastasis aggregation +from the results of our proposed LN segmentation with +attention. +• ClsfromPDAC + ClsbyLNSeg w/ Attn: Combined model +incorporating the volume of the largest positive LN given +by ClsbyLNSeg w/ Attn into the classification layer of +ClsfromPDAC. +The results of the ablation experiments are summarized in +Table VI, and ROC analysis is illustrated in Fig. 5(a). By +using only information about LNs, ClsbyLNSeg w/ Attn gives +better aggregation results compared with ClsbyLNSeg w/o +Attn (balanced accuracy 0.563 versus 0.545). Our final model +(ClsfromPDAC + ClsbyLNSeg w/ Attn) significantly outper- +forms the other three models with a balanced accuracy of 0.633 +(p-value < 0.05), which reveals the success of integrating both +tumor and LNs imaging information for metastasis prediction. +Comparison with Baselines. To validate the effective- +ness of our method, radiomics model [8] and 2D/3D deep +classification models are taken for comparison. To build the +radiomics model, 1688 radiomics features of PDAC for each + +Ablation study: ROC curve on testing set +1.0 +0.8 +True Positive Rate +0.6 +0.4 +0.2 +ClsfromPDAC,AUC=0.654,p=0.038 +ClsbyLNSeg w/o Attn, AUC=0.590, p<0.001 +ClsbyLNSeg w/Attn,AUC=0.603,p<0.001 +0.0 +ClsfromPDAC+ClsbyLNSeg w/ Attn, AUC=0.682, ref +0.0 +0.2 +0.4 +0.6 +0.8 +1.0 +False Positive RateComparison with baselines: ROC curve on testing set +1.0 +0.8 +True Positive Rate +0.6 +0.4 +Radiomics.AUC=0.648.p=0.052 +Radiomics+Radiologists,AUC=0.654,p=0.16 +0.2 +Resnet3D,AUC=0.609,p<0.0001 +Resnet2D,AUC=0.631,p=0.0014 +DeepTEN,AUC=0.634,p=0.0099 +0.0 +Ours, AUC=0.682,ref +0.0 +0.2 +0.4 +0.6 +0.8 +1.0 +False Positive Rate11 +CT phase are extracted using Pyradiomics package [57]1, and +then shrunk using the least absolute shrinkage and selection +operator (LASSO) method. Then a logistic regression model +is applied to the selected features. The combined model of +radiomics and CT-reported LN status is implemented with a +logistic regression model on radiomics signature and radiolo- +gists’ diagnosis. For 2D deep networks, ResNet2D [29] and +DeepTEN [54], we use ResNet-18 backbone pre-trained on +ImageNet [52]; while for 3D deep networks, we adopt 3D- +ResNet-18 [58] backbone pre-trained on Kinetics-700 [59] +and Moments in Time [60]. In all of 2D/3D deep networks, +a side branch with the PDAC mask as input is added to +the backbone, as we implemented in our method, for fair +comparison. Table VI and Fig. 5(b) present the quantitative +results of different models. More importantly, our method +yields the best balanced accuracy (0.633) among all compared +methods, and is significantly better than the radiomics method +and all of 2D/3D deep networks. +F. External Validation +In this section, we demonstrate the generalization ability +of our LN metastasis status prediction in two external multi- +center datasets (i.e., Ext-validation dataset 1 and Ext-validation +dataset 2). After training the model on Discovery dataset +using cross validation, we apply the model to external datasets +for inference. For each patient, the ensemble prediction is +generated by averaging the model predictions from five folds. +We first evaluate the performance of ablation variants, and +then compare our method with baseline models. Metrics are +used the same as Section IV-E. +Ablation Study. We conduct ablation study on two external +datasets, and results are shown in Table VII. With respect +to LN metastasis status prediction using only LN-related +information, our method (ClsbyLNSeg w/ Attn) outperforms +nnUNet (ClsbyLNSeg w/o Attn) on both two datasets (bal- +anced accuracy 0.589 versus 0.579 on Ext-validation dataset 1, +0.639 versus 0.607 on Ext-validation dataset 2). By integrating +PDAC characteristics, our final model (ClsfromPDAC + Cls- +byLNSeg w/ Attn) gives the best results among all ablation +models (balanced accuracy 0.620 on Ext-validation dataset 1 +and 0.684 on Ext-validation dataset 2). +Comparison with Baselines. Table VII validates the gener- +alization performance of our method compared with radiomics +and 2D/3D deep learning models. Note that we skip methods +involved with CT-reported LN status since there is no CT +report available in two external datasets. The radiomics model +shows poor generalization ability with a large drop in perfor- +mance compared with that in Table VI, while deep learning +models are relatively more robust. Our method significantly +surpasses all of 2D/2D deep learning models with p-value < +0.05 on both external datasets (balanced accuracy 0.620 and +0.684 respectively), demonstrating the power of our model to +generalize across different data sites. +1https://pyradiomics.readthedocs.io/ +V. DISCUSSION +Pre-operative LN metastasis status prediction is of vital sig- +nificance for PDAC patients in the following aspects. Firstly, +if diagnosed with LN metastasis, patients with resectable +PDAC are recommended to receive neoadjuvant therapy first +before surgery, according to NCCN guidelines [61]. Secondly, +pancreatectomy could be guided by whether and where their +LNs have metastasized, that is, whether or not a standard or an +extended lymphadenectomy should be performed. This could +make the surgical procedure being more targeted beforehand +which could lead to better patient outcome and avoid over- +treatment. Thirdly, LN metastasis is highly associated with pa- +tients’ survival, which can evidently assist with good prognosis +prediction value [55]. Note that it is very time consuming and +highly dependent on (board-certified radiologist) observer’s +experience and energy level to manually determine whether +a patients has LN metastasis primarily from CT scans (even it +is a very desirable task for patient care). CT-reported LN status +in this study shows limited performance with an accuracy of +0.599, thus accurate LN metastasis status prediction is highly +desired. +In the literature, LN metastasis status prediction has pre- +dominantly been studied through tumor feature extraction, +combined with CT report information, using radiomics [6]– +[12] or deep learning approaches [13], [14], while the one +leveraging LN radiomics requires manual delineation and +considers simply the LN with the largest size [10]. An +automated and accurate process of LN segmentation and +nodal positivity identification is hence of high importance for +assisting metastasis prediction. Predicting the metastasis status +from automated segmented LNs is formulated by detecting +metastatic LNs with Faster R-CNN [62], however the spatial +context priors towards LNs are not exploited. This work +proposes an automated geometric attention mechanism using +LN segmentation and identification to predict the patient-level +status of LN metastasis. +To demonstrate the effectiveness of our method, we pro- +vide extensive quantitative experiments on LN segmenta- +tion/identification and LN metastasis status prediction. Our +LN segmentation model statistically significantly outperforms +the strong baseline nnUNet in voxel-wise and instance-wise +metrics. For LN instance-wise detection, our model achieves +considerable quantitative improvements (4.6%) in precision +(with respect to a similar recall level) as compared to nnUNet +(see Table V). This observation clearly validates that the +proposed distance-guided attention mechanism is beneficial +to remove false positives as we expect. The success of our +model can be attributed to its attention map design and +informative negative selection scheme. The former defines the +LN-plausible regions that deserve network’s focus, and the +latter helps to throw out non-informative negative training +patches accordingly. As such, it becomes more efficient to +train and force the model to learn discriminative features from +possible LN locations. To verify the effect of LN detection +improvements on patient-level metastasis status prediction, we +perform instance-wise positivity identification and patient-wise +aggregation on the LN instances to classify the patients into + +12 +TABLE VII +PERFORMANCE COMPARISON AND ABLATION STUDY ON LN METASTASIS STATUS PREDICTION OF TWO EXTERNAL DATASETS. +PREDICTIONS ARE AVERAGED ACROSS 5 FOLDS. WILCOXON SIGNED RANK TEST IS CONDUCTED ON BALANCED ACCURACY. * +INDICATES p-VALUE < 0.05. NS INDICATES NO SIGNIFICANCE. +Dataset +Method +Balanced +AUC +Accuracy +Sensitivity +Specificity +Accuracy +[95% CI] +[95% CI] +[95% CI] +[95% CI] +[95% CI] +Radiomics +0.493∗ +0.511 +0.672 +0.051 +0.935 +[0.451-0.537] +[0.400-0.620] +[0.626-0.710] +[0.000-0.128] +[0.880-0.978] +ResNet3D +0.508∗ +0.509 +0.527 +0.462 +0.554 +[0.415-0.612] +[0.409-0.617] +[0.450-0.611] +[0.308-0.615] +[0.457-0.663] +ResNet2D +0.563∗ +0.564 +0.542 +0.615 +0.511 +[0.470-0.656] +[0.460-0.676] +[0.466-0.626] +[0.462-0.769] +[0.413-0.609] +DeepTEN +0.556∗ +0.557 +0.511 +0.667 +0.446 +Ext-validation +[0.467-0.647] +[0.454-0.666] +[0.427-0.595] +[0.513-0.795] +[0.348-0.544] +dataset 1 +ClsfromPDAC +0.515∗ +0.554 +0.485 +0.590 +0.441 +[0.423-0.609] +[0.450-0.661] +[0.402-0.568] +[0.436-0.744] +[0.344-0.548] +ClsbyLNSeg w/o Attn +0.579∗ +0.555 +0.689 +0.308 +0.849 +[0.498-0.662] +[0.454-0.641] +[0.621-0.750] +[0.179-0.462] +[0.774-0.914] +ClsbyLNSeg w/ Attn +0.589∗ +0.580 +0.705 +0.308 +0.871 +[0.511-0.672] +[0.474-0.694] +[0.644-0.765] +[0.154-0.462] +[0.796-0.935] +Ours (ClsfromPDAC + +0.620ref +0.603 +0.674 +0.487 +0.753 +ClsbyLNSeg w/ Attn) +[0.538-0.713] +[0.498-0.712] +[0.598-0.742] +[0.333-0.641] +[0.667-0.839] +Radiomics +0.508∗ +0.609 +0.441 +0.243 +0.773 +[0.391-0.626] +[0.452-0.757] +[0.339-0.542] +[0.108-0.378] +[0.591-0.909] +ResNet3D +0.461∗ +0.442 +0.475 +0.514 +0.409 +[0.334-0.584] +[0.300-0.593] +[0.356-0.594] +[0.351-0.676] +[0.182-0.591] +ResNet2D +0.681∗ +0.687 +0.650 +0.577 +0.786 +[0.536-0.810] +[0.508-0.849] +[0.500-0.800] +[0.385-0.731] +[0.571-0.930] +DeepTEN +0.613∗ +0.647 +0.640 +0.697 +0.529 +Ext-validation +[0.465-0.747] +[0.474-0.806] +[0.520-0.760] +[0.545-0.848] +[0.294-0.765] +dataset 2 +ClsfromPDAC +0.620∗ +0.639 +0.593 +0.514 +0.727 +[0.493-0.734] +[0.490-0.781] +[0.475-0.712] +[0.378-0.676] +[0.545-0.909] +ClsbyLNSeg w/o Attn +0.607∗ +0.690 +0.542 +0.351 +0.864 +[0.503-0.716] +[0.554-0.818] +[0.441-0.661] +[0.216-0.487] +[0.682-1.000] +ClsbyLNSeg w/ Attn +0.639∗ +0.695 +0.593 +0.459 +0.818 +[0.525-0.752] +[0.552-0.833] +[0.475-0.695] +[0.297-0.622] +[0.636-0.955] +Ours (ClsfromPDAC + +0.684ref +0.703 +0.661 +0.595 +0.773 +ClsbyLNSeg w/ Attn) +[0.570-0.797] +[0.554-0.846] +[0.542-0.780] +[0.432-0.757] +[0.591-0.909] +metastasis-positive/-negative, and our model presents better +prediction performance than nnUNet (balanced accuracy 0.563 +versus 0.545, Table VI). We further combine the results +with tumor CT imaging characteristics and our final pre- +diction model achieves statistically significant performance +gains compared to radiomics methods and other deep 2D/3D +models (see Table VI), which demonstrates the success and +effectiveness of integrating tumor morphology and lymphatic +anatomy. It is worth noting that our method achieves sta- +tistically significant improvement (balanced accuracy 0.633 +versus 0.604) compared to the approach even with radiologists +involved in “Radiomics + CT-reported LN status” in Table +VI. Nevertheless, using our method, this time-consuming, +subjective and highly challenging manual process of CT- +reported LN status can be fully automated. External multi- +center clinical validation is further conducted on extra two +datasets from different hospitals, and the results evidently +exhibit our superior performance accuracy and generalization +ability with the best results (balanced accuracy 0.620 and +0.684 on the two external datasets) among several compared +models (see Table VII). With all above-mentioned experi- +ments, our model reports highly generalized prediction per- +formance (0.620∼0.684) on multi-center datasets and robust +improvements over CT-reported LN status (0.599) as well as +radiomics and deep learning models, which clearly clarifies +the advantage and stability of our model. +Although recent work [8], [11] report exceedingly high +accuracy (AUC > 0.9), they use small datasets of < 200 +patients, which would be subject to overfitting. Another recent +progress in gastric cancer [12] enrolls over 500 patients from +multiple hospitals, and yields noticeably lower but probably +more reliable AUC score of 0.615∼0.712 in validation using +2D/2.5D/3D radiomics features and under different patient +splits. [12] is probably more suitable to serve as reference +baseline for our work. We employs 940 patients in total in this +study, in which 749 patients are from a high-volume pancreatic +cancer clinical center and 191 are from two external centers. +The studied patient population is arguably much closer and +more realistic to the real-world patient data distributions com- +paring to [8], [11], similar to [12]. We present a very promising +approach that explicitly explores the role of automated LN +segmentation in promoting LN metastasis status prediction +to facilitate future clinical adoption as a fully-automated and +generalizable clinical tool. One limitation of our framework + +13 +lies in the intuitive but simple solution that extracts tumor +and LNs imaging information separately and then integrates +them by feature concatenation, which does not fully exploit +the nature of interactions between tumor and cancer cells +in LNs. This work could be further improved in the future +by designing an enriched deep learning geometric network +representation to encode the tumor-LN topology information +and spatial anatomical interactions, by modeling the pathways +of nodal metastasis explicitly. +Last, without loss of generality, our proposed method is +applicable for finding the preoperative LN metastasis status of +other types of solid tumor or cancers, such as liver or gastric +cancers. We leave this as future work. +VI. CONCLUSION +We present an attention based LN segmentation network and +utilize it on predicting LN metastasis in patients with PDAC. +The proposed LN segmentation network involves an attention +mechanism that encourages the network to focus on regions +around certain anatomical organs/vessels. It outperforms the +strong baseline nnUNet [27] by leveraging the context infor- +mation of surrounding anatomical structures. Our segmenta- +tion model, followed by a nodal positivity identification model, +can serve as a single predictor for LN metastasis. Combined +with tumor imaging characteristics, we further build a compos- +itive LN metastasis status prediction model that is validated +to surpass the CT-reported results, radiomics based method, +and other 2D/3D deep learning models. Further investigations +include conceiving a more complicated way to encode tumor- +LN relationship and exploring its applications to prognosis and +treatment planning in cancer patient management. +ACKNOWLEDGMENTS +This +work +was +supported +in +part +by +the +National +Science Foundation for Scientists of China (81871352, +82171915, and 82171930), Clinical Research Plan of SHDC +(SHDC2020CR4073), 234 Platform Discipline Consolidation +Foundation Project (2019YPT001, 2020YPT001), and The +Natural Science Foundation of Shanghai Science and Technol- +ogy Innovation Action Plan (21ZR1478500, 21Y11910300). +REFERENCES +[1] R. L. Siegel, K. D. Miller, H. E. Fuchs, and A. Jemal, “Cancer statistics, +2021.” CA: a cancer journal for clinicians, vol. 71, no. 1, pp. 7–33, +2021. +[2] A. J. Grossberg, L. C. Chu, C. R. Deig, E. K. Fishman, W. L. Hwang, +A. Maitra, D. L. Marks, A. Mehta, N. Nabavizadeh, D. M. 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Zhang et al., “Identification of metastatic lymph nodes in +mr imaging with faster region-based convolutional neural networks,” +Cancer research, vol. 78, no. 17, pp. 5135–5143, 2018. + diff --git a/2tAzT4oBgHgl3EQffPw3/content/tmp_files/load_file.txt b/2tAzT4oBgHgl3EQffPw3/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..9731b4ef769910c625c462c3194ba88c2a04cb39 --- /dev/null +++ b/2tAzT4oBgHgl3EQffPw3/content/tmp_files/load_file.txt @@ -0,0 +1,2017 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf,len=2016 +page_content='1 A deep local attention network for pre-operative lymph node metastasis prediction in pancreatic cancer via multiphase CT imaging Zhilin Zheng,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Xu Fang,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Jiawen Yao,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Mengmeng Zhu,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Le Lu Fellow,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' IEEE,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lingyun Huang,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Jing Xiao,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Yu Shi,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Hong Lu,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Jianping Lu,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Ling Zhang,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Chengwei Shao*,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Yun Bian* Abstract—Lymph node (LN) metastasis status is one of the most critical prognostic and cancer staging factors for patients with resectable pancreatic ductal adenocarcinoma (PDAC),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' or in general,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' for any types of solid malignant tumors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Preoperative prediction of LN metastasis from non-invasive CT imaging is highly desired, as it might be straightforwardly used to guide the following neoadjuvant treatment decision and surgical planning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Most studies only capture the tumor characteristics in CT imaging to implicitly infer LN metastasis and very few work exploit direct LN’s CT imaging information.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' LN staging is usually confirmed from pathological images acquired after invasive procedures of biopsy or surgery.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To the best of our knowledge, this is the first work to propose a fully-automated LN segmentation and identification network to directly facilitate the LN metastasis status prediction task.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Nevertheless LN seg- mentation/detection is very challenging since LN can be easily confused with other hard negative anatomic structures (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', vessels) from radiological images.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 1) We explore the anatomical spatial context priors of pancreatic LN locations by generating a guiding attention map from related organs and vessels to assist segmentation and infer LN status.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' As such, LN segmentation is impelled to focus on regions that are anatomically adjacent or plausible with respect to the specific organs and vessels (thus hard negative samples with certain distance ranges can be ignored).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 2) The metastasized LN identification network is trained to classify the segmented LN instances into positives or negatives by reusing the segmentation network as a pre- trained backbone and padding a new classification head.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 3) More importantly, we develop a LN metastasis status prediction network that combines the patient-wise aggregation results of LN segmentation/identification and deep imaging features extracted from the tumor region.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 4) Extensive quantitative nested five- fold cross-validation is conducted on a discovery dataset of 749 patients with PDAC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' External multi-center clinical evaluation is further performed on two other hospitals of 191 patients in total.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Our final multi-staged LN status prediction network statistically significantly outperforms the strong baseline of nnUNet and several other compared methods, including CT-reported LN status, radiomics, and deep learning models.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Index Terms—Pancreatic ductal adenocarcinoma (PDAC), Z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Zheng, L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Huang, J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Xiao are with Ping An Technology (Shanghai & Shenzhen), People’s Republic of China, (e-mail: zhilin.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='zheng95@gmail.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='com).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Fang, M.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Zhu and J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lu are with Changhai Hospital, Shanghai, People’s Republic of China.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Yao, L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lu and L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Zhang were with PAII Inc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', Bethesda, MD 20817, USA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' X.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Fang and J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Yao contributed equally.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Y.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Shi is with Department of Radiology, Shengjing Hospital of China Medical University, Shenyang, China.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lu is with Department of Radiology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center of Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' s indicate joint corresponding authors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Y.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Bian and C.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Shao are with Changhai Hospital, Shanghai, People’s Republic of China, (email: bianyun2012@foxmail.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='com, cwshao@sina.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='com).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lymph node metastasis, Lymph node segmentation, Contrast- enhanced computed tomography I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' INTRODUCTION P ANCREATIC cancer is the third leading cause of overall cancer death in the United States [1], of which approx- imately 95% is pancreatic ductal adenocarcinoma (PDAC) [2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' With the poorest prognosis (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', 5-year overall survival (OS) of 10% approximately), surgical resection is the most effective way to achieve long-term survival for patients with PDAC [2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' However, not all patients can benefit from the margin-negative (R0) resection and comprehensive treatment protocol is usually established for pancreatic cancer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The patients’ treatment selections can be determined by whether their peripancreatic lymph nodes (LNs) have metastasized with the options of adjuvant radiotherapy (RT) or chemotherapy.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' It was found that neoadjuvant therapy before surgery was associated with improved survival and time to recurrence in patients with LN metastasis, since neoadjuvant therapy can not only treat lymphovascular invasion but also benefit tumor downstaging [3], [4].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The accurate preoperative detection of LN metastasis becomes vital and would aid in treatment planning and management.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Contrast-enhanced CT is used as the typical imaging pro- tocol for identifying the presence of peripancreatic metastatic disease to LNs, but it is a very challenging task for radiologists to determine whether a patient has LN metastasis by using only CT scans.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To this end, poor diagnostic accuracy of CT with a pooled sensitivity of 25% and positive predictive value (PPV) of 28% was reported in a meta-analysis [5] on assessing extra- regional LN metastasis in pancreatic and peri-ampullary can- cer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Recently, several radiomics based approaches have been proposed to tackle the LN metastasis differentiation problem of various cancer types [6]–[12].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' However, these methods require hand-crafted feature design which can bring concerns of reproducibility and human bias is often introduced due to manual selection of 2D tumor slice with limited representation power.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Although there are some deep learning work that report promising performance on predicting LN metastasis status in gastric cancer [13], [14], those models assume that the risk of metastases is fundamentally driven by the primary tumor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' They rely on LN CT report information for the integration model without using any LNs detection or segmentation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The model that takes both tumor morphology and lymphatic anatomy into arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='01448v1 [eess.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='IV] 4 Jan 2023 2 Arterial Arterial Venous Patient with metastasis Patient without metastasis Tumor LN Tumor-LN anatomy Negative LN Positive LN Tumor Tumor & LN Spleen Esophagus Stomach Aorta Pancreas Duodenum SMA TC LGA CHA&PHA Organs & Vessels Venous LN LN LN LN LN Tumor LN LN LN LN LN Tumor LN LN LN LN Tumor LN LN LN LN Tumor Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' A visualization of pancreatic tumor (in dark red) and LNs (in pink red for positives or green for negatives) in multi-phase CT images and their spatial distributions corresponding to key anatomical structures as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' SMA: superior mesenteric artery.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' TC&SA: truncus coeliacus and splenic artery.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' LGA: left gastric artery;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' CHA&PHA: common hepatic artery and proper hepatic artery.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' account could be of more clinically usefulness on addressing these aforementioned issues, similarly as in the diagnostic processes performed by radiologist readers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' PET/CT is another imaging modality worth exploring.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' PET/CT based approaches [15]–[17] generally use maximum standardized uptake value (SUVmax) of manually-drawn LN RoIs as the prediction element, but it comes with challenges of numerous false positives from inflammatory LNs and false negatives from small-sized metastatic LNs [18], [19].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Also, it is relatively not as common as CT, which is less affordable, available and accessible, hence we opt for CT for our research purpose.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' In this paper, we tackle the LN metastasis status prediction problem in patients with PDAC by first segmenting and identifying instances of LNs and then classifying the patients into metastasis-positive or -negative group.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' LNs are tiny struc- tures that anatomically locate surrounding organs and vessels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Their locations have been mapped into 18 stations that are relevant for pancreatic cancer tumor according to their relative positions against adjacent anatomical structures, as defined by Japan Pancreas Society (JPS) [20] (see Supplementary Table 1 in the supplementary material for details).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Examples of their spatial distribution are shown in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Metastasis happens when cancer cells spread from the primary tumor to LNs, causing enlargement of LNs and other underlying changes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Response Evaluation Criteria in Solid Tumors (RE- CIST) criteria [21] defines the criteria for LN metastasis suspicion, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', nodes with short axis greater than 10mm, heterogeneity and central necrosis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' However, these criteria are not pathognomonic since there exist false negatives associated with small node micrometastases and false positives with inflammatory nodes larger than 10mm in short axis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Hence, finding LNs in CT images is quite time-consuming and can be inconsistent depending on radiologists’ subjective experiences.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' It is ambiguous for radiologists to identify nodal positivity accurately from CT without referring to pathology reports.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The gold standard for determination of metastasis is based on post-operative pathological evaluation of pancreatectomy spec- imens.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Automated yet reliable pre-operative LN segmentation and identification are highly desirable for patient surgical or RT treatment planing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' LN segmentation is inherently challenging due to two reasons: 1) small to tiny sizes of LN cause extreme foreground- background class imbalance problem;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 2) LNs have CT atten- uation values similar to vessels and other soft-tissue struc- tures, resulting in visual confusions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Existing work [22]–[24] mainly adopt U-Net based deep networks [25]–[27] as strong backbones, in which skip connections aggregate multi-level semantic representation and alleviate vanishing gradient prob- lem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' They incorporate anatomical context by directly taking organs&vessels segmentation masks as either supervision tar- gets [22] or additional inputs [24], [28].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Concerns are remained that the relationship between lymphatic anatomy and adjacent anatomical structures is not well explored.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' We address it by introducing a distance-guided attention map to fully utilize the spatial priors.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' In our segmentation framework, the LN attention map is obtained via a pre-defined mapping from distance maps of related organs/vessels that have been integrated into UNet-based backbone to control the segmentation network’s TO: B TVN00SL0003TO五 TO TVNO0O0003TO: BTVN001O0003TO: B TVN00SL0003TO: B3 spatial focus.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' It simultaneously assists in improving sample selection strategy that filters out non-informative negative samples (called ”informative negative selection”) to tackle the class imbalance problem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The segmented LNs are labeled as positive/negative using radiologist’s judgement as the standard that combines information from pathological results and CT intensities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' A classification network is subsequently derived by sharing the same backbone with segmentation and initialized with the trained segmentation parameters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' This strategy ben- efits the classification task from densely structured prediction in segmentation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' By predicting LN metastasis in patients with PDAC, we employ a modified ResNet [29] classification model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Tumor characteristics are proven to be important cues for metastasis [8], [9], [11], so we integrate both tumor and LN cues by taking as inputs the image patches of tumor and the patient-wise aggregation of LN segmentation and identification.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Our main contribution is four folds: 1) To the best of our knowledge, this work is the first to directly incorporate automated LN segmentation and identification for assisting preoperative LN metastasis status prediction for patients with PDAC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 2) We propose an attention-based LN segmentation network with the guidance of distances to nearby anatomical structures, explicitly exploiting the spatial priors and simul- taneously addressing the foreground-background imbalance issue.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 3) We design a compositive LN metastasis status prediction network combining both tumor and positive LN characteristics, showing the potential of tumor-LN guided cues.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 4) Extensive quantitative experiments are conducted to evidently validate the effectiveness of our deep local attention network in both tasks of LN segmentation and LN metastasis status prediction, and external multi-center clinical evaluation is performed to demonstrate the generalization ability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Without loss of generality, our proposed method is applicable for finding the preoperative LN metastasis status of other types of solid tumor or cancers, such as liver or gastric cancers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' II.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' RELATED WORK A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lymph Node Segmentation Automated LN segmentation in CT images is an essential yet challenging task in medical image analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Traditional approaches tackle this problem by the means of atlas based search space restriction [30], spatial prior features combination [31], [32], supervoxel clustering [33], etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' In recent years, U- Net based deep networks have shown remarkable performance in numerous organ or tumor segmentation tasks [34]–[38].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' nnUNet [27] further proposes a self-configuring approach, with automatic configurations including preprocessing, net- work architecture, training and post-processing, that achieves robust performance and general applicability.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To address the strong class imbalance issues in LN segmentation, four other anatomical structures are included as training targets [22] using 3D U-Net [26] framework.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' [23] utilizes parallel net- works of 2D U-Net [25] and Mask R-CNN [39] with the supervision of all considered anatomical structures and LNs, benefiting from both semantic and instance segmentation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Another strategy to incorporate anatomical context is to take organ segmentation masks as additional channels of the input.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' [28] proposes an ensemble approach for a slab-wise and a downsampled full volume based LN segmentation, taking the concatenation of CT image and segmented anatomical structure mask as input.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' DeepStationing [24] presents a key referencing organ auto-search strategy and combines selected organs into the network via input concatentation for LN station parsing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' All above methods implicitly exploit spatial priors of LNs by injecting the anatomical structure masks either as inputs or supervisions, hence the prior knowledge has not been fully exploited.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' More importantly, there is a lack of studies on how LN segmentation could be used for predicting metastasis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' B.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Lymph Node Metastasis Prediction Radiomics Methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Radiomics is a powerful technique for extracting quantitative image features with the purpose of clinical decision support, and thus widely used in can- cer research [11], [12], [40]–[42].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' It converts imaging data into different types of hand-crafted features, including shape, intensity, texture and filter-based (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', wavelet, Laplacian of Gaussian) features.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Applications of radiomics on predicting LN metastasis from primary tumor have been explored in many recent works [6]–[10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Radiomics features are first extracted from manually delineated tumor regions in any contrast-enhanced CT images.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Feature selection and classifi- cation model construction (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', logistic regression, random forest) are then performed to give LN metastasis prediction for various cancer types like gastric cancer [7], [12], biliary tract cancer [6] and PDAC [8], [9], [11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Relying only on primary tumor radiomics without considering LNs character- istics may limit the prediction performance, thus [10] uses manual annotations of the largest LN visible in the gastric region and combines LN radiomics into the prediction model for gastric cancer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' However, problem still remains because it simply involves the largest LN without identifying the nodal positivity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Deep Learning based Methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Recent advances in deep learning have made it a mainstream method of addressing the entire workflow of diagnosis and treatment for various cancer types on medical imaging, such as orapharageal cancer [43], lung cancer [44], as well as pancreatic cancer [45]–[47].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Deep neural networks are applied to LN metastasis in many studies [13], [14], [48], [49].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' In [48], deep features are extracted from tumor ROIs in bimodal image (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', US and SWE) using ResNet [29], and then fed into a SVM model for predicting axillary LN status in breast cancer.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' For gastric cancer, [14] combines DenseNet [50] features with some hand-crafted features, extracted from the 2D tumor ROI with the largest area in multi-phase CT images.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To investigate metastasis in individual LN stations for gastric cancer, [13] develops a system of multiple independent ResNets with tumor ROIs and corresponding annotation masks as inputs where each ResNet is responsible to predict metastasis at one specific nodal sta- tion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Most existing studies capture only tumor characteristics for LN metastasis prediction, while the one leveraging LN radiomics requires manual delineation and considers simply the LN with the largest size [10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' An automated and accurate ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='4 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='b) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='LN metastasis status prediction network ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Volume ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Image ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='PDAC ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Mask ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Metastasis ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='positive ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Metastasis- ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Negative ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='√ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Cropping ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Cropping ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='c ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph node ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='segmentation & ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='identification ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph node ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='segmentation & ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='identification ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Volume ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Image ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='PDAC ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Mask ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Metastasis ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='positive ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Metastasis- ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Negative ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='√ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Cropping ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Cropping ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='c ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph node ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='segmentation & ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='identification ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Image ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph Node ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Segmentation ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Instance-wise ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph Node ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Identification ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Organ& ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Vessel ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Distance ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Transform ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Non-linear ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Mapping ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Attention ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Mechanism ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='GAP ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='a) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Lymph node segmentation & identification network ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='c ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='concatenation ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='element-wise ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='multiplication ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Downsampling ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The proposed framework for (a) two-stage LN segmentation and identification and (b) LN metastasis status prediction .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' process of LN segmentation and nodal positivity identification is hence of high importance for assisting metastasis prediction.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' III.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' METHODOLOGY The overall framework is illustrated in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 2, which is com- posed of (a) distance-guided attention-based LN segmentation and identification network, and (b) tumor and LN combined metastasis status prediction network.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Distance-guided Attention-based Lymph Node Segmenta- tion and Identification Network We perform LN detection from any input CT scan by a two- stage strategy: segmenting the image into two classes of LN and background voxels, followed by identifying segmented LN instances as positive or negative.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 1) Stage 1: Class-agnostic Lymph Node Segmentation: Based on the spatial prior that LN stations are geometrically distributed or constrained around certain anatomical structures, we propose an attention based LN segmentation network by taking the distances to nearby organs/vessels into account.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Our LN segmentation network differs from the strong baseline (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', nnUNet [27]) in that attention mechanism is applied to guide possible LN locations, with the advantage of reducing false positive predictions outside those locations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' The intuition behind the attention module is that the attention map can cover regions adjacently constrained to those organs and vessels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Attention Map Generation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To explicitly capture and model the lymphatic anatomy, attention computation is im- plemented as a pre-defined geometric mapping function from organ&vessel distance maps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' An example of attention map generation process is shown in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Specifically, given a multi-phase input CT volume X ∈ RN×W ×H×D, we first obtain organ&vessel segmentation mask using nnUNet [27] model trained with 19 classes of annotations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Ten classes among them involved with 17 LN stations are used (see Supplementary Table 1 in the supplementary material for the definition of LN stations), i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', spleen, esophagus, stomach, aorta, pancreas, duodenum, superior mesenteric artery (SMA), truncus coeliacus and splenic artery (TC&SA), left gastric artery (LGA), common hepatic artery and proper hepatic artery (CHA&PHA).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Note that station 15# (LNs along middle Spleen Aorta SMA LGA Image Organ&Vessel Organ/Vessel Distance Map Organ/Vessel Attention Map Integrated Attention Map CHA&PHA Esophagus Duodenum Non-linear Mapping 0 1 d imin min d imin dmax imax i dmax i d imin min d imin-3 d imin-3 dmax imax i dmax i +3 dmax i +3 d fifi Stomach Pancreas TC&SA Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' An illustration of attention map generation process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' colic artery) is left aside here since it is related to distant metastasis that rarely happens in our patient population.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' A SDT is applied to each class of the segmentation mask M ∈ {0, 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', 10}W ×H×D, generating a total of 10 organ/vessel distance maps Di where i ∈ {1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=', 10} is the index of organ/vessel class.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Di has positive values at the voxels outside the i-th organ/vessel and negative scores inside it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' Intuitively, LNs are likely to appear within a certain range of distance to each organ/vessel, which requires paying attention to.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' To obtain the distance-guided attention maps, Di is passed to an isosceles trapezium-shaped non-linear mapping function (see TO B c000.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='r100.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content='ocbqT0 B E000_100_3sbq5 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/2tAzT4oBgHgl3EQffPw3/content/2301.01448v1.pdf'} +page_content=' 3), formulated as f i(d) = � � � � � � � � � � � � � � � � � 1, di min ≤ d ≤ di max − (d − di max − 3) 3 , di max 0 only, the model is frustrated, and orderings with +q ∈ [1,q,0] are degenerate [13, 39, 40]. The degenerate mani- +fold includes q = [1,0,0] (“Type I”) ordering, which is favored +by fluctuations [13, 14, 41] and is observed in Ba2YRuO6 +and Ba2LuRuO6 [34]. Henceforth, we therefore restrict our +discussion to q = [1,0,0] ordering. For a collinear structure, +spins may be either parallel or perpendicular to q; the former +is favored by K < 0 and the latter by K > 0 [38–40]. +Figure 1(a) shows the collinear (1-q) and noncollinear +arXiv:2301.11395v1 [cond-mat.str-el] 26 Jan 2023 + +2 +1-q +tetragonal +2-q +tetragonal +3-q +cubic +3-q +cubic +2-q +tetragonal +1-q +orthorhombic +(a) +�������� +���������������� +������� +� +��� +� +��� +� +��� +��������� +������� +� +��� +� +��� +� +��� +�������� +������� +� +��� +� +��� +� +��� +��������� +������� +� +��� +� +��� +� +��� +K ≥ 0, mX5 ++ +K ≤ 0, mX3 ++ +(b) +Figure 1. +(a) Symmetry-allowed magnetic structures with propagation vector q = [1,0,0] on the FCC lattice for Ba2MRuO6 (space group +Fm¯3m; a = 8.29 and 8.24 Å for M = Y and Lu, respectively). The 1-q, 2-q, and 3-q structures are shown for the mX+ +3 irrep (left) and the +mX+ +5 irrep (right). Spins along different directions are colored differently; note that 1-q, 2-q, and 3-q structures have [100], ⟨110⟩, and ⟨111⟩ +spin directions, respectively. (b) Elastic scattering data (−1.3 ≤ E ≤ 1.3 meV) measured at T = 5 K with Ei = 11.8 meV for Ba2YRuO6 and +Ba2LuRuO6 (black circles), Rietveld refinements (red lines), and data – fit (blue lines). Tick marks show (top to bottom): nuclear, impurity +M2O3, and magnetic phases. The mX+ +3 irrep (left) does not reproduce our data, whereas the mX+ +5 irrep (right) agrees well with our data. +(multi-q) structures associated with Type I antiferromag- +netism. A remarkable property of the FCC lattice is that 1-q, +2-q, and 3-q structures are energetically degenerate for all bi- +linear interactions for which Type I ordering is stable [39, 40]. +Moreover, uniaxial anisotropy (∼S2 +z) and antisymmetric ex- +change terms are forbidden by Fm¯3m symmetries, and quartic +anisotropy (∼S4 +x +S4 +y +S4 +z) is forbidden for S = 3/2 operators +in a cubic environment. Consequently, interactions that would +usually favor collinear magnetic structures are inactive in the +S = 3/2 FCC antiferromagnet. This remarkable property po- +tentially allows noncollinear structures to appear. +To identify candidate systems for 3-q spin textures among +the diverse magnetic ground states of double perovskites [42– +50], we consider two criteria: Type I antiferromagnetic or- +dering, and strictly cubic symmetry below the magnetic or- +dering temperature, TN. The second criterion is key because +3-q structures have cubic symmetry, while 1-q and 2-q struc- +tures have tetragonal or orthorhombic symmetry that could +drive a crystallographic distortion via spin-lattice coupling +[Figure 1(a)]. +We investigate Ba2YRuO6 and Ba2LuRuO6 +because they are chemically well-ordered and show no evi- +dence for low-temperature deviations from cubic symmetry +[34, 36]. Moreover, recent first-principles calculations predict +that their magnetic structures might not be collinear [51], in +apparent contradiction with interpretations of previous exper- +iments [34]. +We prepared ∼8 g polycrystalline samples of Ba2YRuO6 +and Ba2LuRuO6 by solid-state reaction [52]. +Rietveld re- +finement revealed stoichiometric samples with minor Lu2O3 +(1.94 wt.%) or Y2O3 (0.65 wt.%) impurities. The magnetic +ordering temperature TN ≈ 37 K is the same for both sam- +ples, and is suppressed compared to the Weiss temperature +θ ∼ −500 K, indicating strong magnetic frustration [36]. We +performed inelastic neutron-scattering measurements on the +SEQUOIA instrument at ORNL [53] using incident neutron +energies Ei = 62 and 11.8 meV, yielding elastic energy reso- +lutions δ ins ≈ 1.68 and 0.27 meV, respectively. +Figure 1(b) shows magnetic Rietveld refinements to our +elastic neutron-scattering data, measured with Ei = 11.8 meV +at T ≈ 5 K. Applying the q = [1,0,0] propagation vector to +Fm¯3m crystal symmetry generates two magnetic irreducible +representations (irreps), notated mX+ +3 and mX+ +5 [54, 55]. +These irreps can be distinguished by their magnetic Bragg +profiles. The mX+ +5 irrep agrees well with our elastic-scattering +data for both materials; we obtain ordered magnetic moment +lengths of 2.56(2) and 2.43(2) µB per Ru for Ba2YRuO6 and +Ba2LuRuO6, respectively, from Rietveld refinement. Since +the magnetic form factor for Ru5+ is not known, we tested +several 4d magnetic form factors [56]; while this choice does +not qualitatively affect our results, the form factor for Zr+ +(isoelectronic with Ru5+) yields optimal agreement with our +data and is used throughout. In contrast to the mX+ +5 irrep, the +mX+ +3 irrep strongly disagrees with our data, as it yields zero +intensity for the strong (100) magnetic Bragg peak. This can +be understood intuitively for a collinear 1-q structure, because +neutrons are only sensitive to spin components perpendicular +to the scattering wavevector, and the mX3+ irrep has S ∥ q +while the mX5+ irrep has S ⊥ q [Figure 1(a)]. A previous elas- + +3 +Figure 2. Broadband inelastic neutron-scattering data (Ei = 62 meV) +measured at T = 5 K for Ba2YRuO6 (upper panels) and Ba2LuRuO6 +(lower panels), showing (a) intensity as a color plot, and (b) energy +dependence integrated over 4.0 ≤ Q ≤ 4.5 Å−1, where experimental +data are shown as black circles, and Gaussian fits to the ∼14 meV +phonon band as red lines. +tic neutron-scattering study of Ba2YRuO6 and Ba2LuRuO6 +considered only collinear 1-q structures [34], but could not +rule out multi-q structures, due to the multi-q problem. +To overcome the multi-q problem, we consider the en- +ergy dependence of our neutron-scattering data [57]. +Fig- +ure 2(a) shows our inelastic data measured with Ei = 62 meV +at T ≈ 5 K. A structured inelastic signal appears at T < TN +for small scattering wavevectors, Q ≲ 2 Å−1, which we iden- +tify as magnon scattering. +The top of the magnetic band +overlaps with an intense phonon signal for Q ≳ 2 Å−1. Fig- +ure 2(b) shows the scattering intensity integrated over 4.0 ≤ +Q ≤ 4.5 Å−1, from which we extract the average energy Eph +and width σph of this phonon band via Gaussian fits for each +material. The energy overlap of magnon and phonon modes +suggests that spin-lattice coupling may be significant, which +we consider further below. +Our starting point for modeling the magnetic scattering is +the Heisenberg-Kitaev model, Eq. (1). For all models, we re- +quire J > 0 and K > 0 to stabilize mX+ +5 ordering. We con- +sider three additional interactions in turn. First, the symmet- +ric off-diagonal interaction HΓ = Γ∑⟨i, j⟩γ +� +Sα +i Sβ +j +Sβ +i Sα +j +� +is +the only additional bilinear nearest-neighbor interaction al- +lowed by symmetry. +Second, the Heisenberg next-nearest +neighbor interaction H2 = J2 ∑⟨⟨i, j⟩⟩ Si · Sj has been invoked +for Ba2YRuO6 [37]; we require J2 ≤ 0 to stabilize Type +I ordering. +Third, the nearest-neighbor biquadratic cou- +pling Hbq = Jbq ∑⟨i, j⟩(Si · Sj)2 has been invoked in density- +functional-theory calculations for 4d double perovskites due +to their increased electron hopping relative to 3d analogs [51]. +For Jbq = 0, the classical energy of 1-q, 2-q, and 3-q struc- +tures is equal for all K, Γ, and J2 that stabilize Type I or- +dering. Nonzero Jbq removes this degeneracy, and stabilizes +���� +���� +���� +���� +���� +���� +���� +���� +� +� +�� +�� +�� +���� +���� +���� +���� +���� +���� +���� +���� +�� +� +�� +�� +�� +Rwp (%) +1-q +2-q +3-q +(a) +(b) +Jbq +K +3-q +mX5 ++ +1-q +mX5 ++ +3-q +mX3 ++ +1-q +mX3 ++ +Figure 3. (a) Schematic phase diagram showing the magnetic ground +states of the J-K-Jbq model. (b) Goodness-of-fit metric Rwp for can- +didate magnetic structures and interaction models of Ba2YRuO6 (up- +per graph) and Ba2LuRuO6 (lower graph). The graphs show Rwp for +refinements of the Heisenberg-Kitaev (J-K) model including a third +refined parameter Γ (red bars), J2 (blue bars), or Jbq (green bars); +note that the 2-q structure is stable only for Jbq = 0. +J (K) +K (K) +Jbq (K) A (meV) +Ba2YRuO6 21.85(3) 0.39(1) 1.32(2) 0.97(3) +Ba2LuRuO6 22.27(4) 0.36(2) 1.17(3) 2.25(5) +Table I. Refined values of magnetic interaction parameters for the J- +K-Jbq model and 3-q structure. Uncertainties indicate 1σ statistical +confidence intervals. +1-q ordering for Jbq < 0 and 3-q ordering for Jbq > 0 [Fig- +ure 3(a)]. Importantly, since single-ion anisotropies are for- +bidden for S = 3/2 in a cubic environment, biquadratic ex- +change is the only physically-plausible mechanism that can +remove the degeneracy of 1-q and 3-q structures. +We performed extensive fits to our inelastic neutron- +scattering data to optimize the magnetic structure and inter- +actions simultaneously. For each structure associated with the +mX+ +5 irrep (1-q, 2-q, or 3-q), we optimized three spin Hamil- +tonian parameters (J, K, and either Γ, J2, or Jbq) against the +broadband inelastic data shown in Figure 4(a) and the energy +dependence near the (100) magnetic Bragg position shown +in Figure 4(b). The powder-averaged magnon spectrum was +calculated within a renormalized linear spin-wave theory [58] +using the SpinW program [59]. The renormalization factor, +which takes into account higher-order corrections in the 1/S +expansion, is strictly necessary to extract a correct value of +Jbq, since the unrenormalized spin-wave theory would lead to +a value of Jbq that is 2.25 times smaller than the correct value +[60]. The parameter values were optimized to minimize the +sum of squared residuals using nonlinear least-squares refine- +ment [52]. We calculated the energy-dependent broadening of +the magnon spectrum as δ(E) = δins(E) + Ae−(E−Eph)2/2δ 2 +ph, +where δ(E) is the overall Gaussian energy width, δins(E) is +the instrumental resolution, and A is a refined parameter that +phenomenologically accounts for magnon broadening due to +coupling with phonons at E ∼ Eph. +Figure 4(a) compares our broadband inelastic data (Ei = +62 meV) with the best fit for each of the 1-q, 2-q, and 3-q + +4 +Figure 4. (a) Broadband inelastic neutron-scattering data (Ei = 62 meV) and optimal spin-wave fits for different magnetic structures, showing +(left to right) experimental data, 1-q fit, 2-q fit, and 3-q fit. (b) Low-energy inelastic neutron-scattering data (Ei = 11.8 meV) and 3-q model +calculations, showing (left to right) a cut at Q = 0.7450±0.0175 Å−1 comparing experimental data (black circles) and spin-wave fit (red lines), +experimental data as a Q-E slice, and spin-wave calculation. +structures. The data show two V-shaped features centered at +≈ 0.85 and ≈ 1.70 Å−1, with a sharp cutoff of magnetic signal +for energies above ∼14 meV. For both materials, these char- +acteristics are best reproduced by the 3-q structure, while the +1-q structure disagrees with our experimental data. These ob- +servations are confirmed by the goodness-of-fit metric Rwp, +shown in Figure 3(b). For both materials and for every in- +teraction model we considered, the 3-q structure yields better +agreement with our data than the 1-q or 2-q structures. No- +tably, the goodness-of-fit is more sensitive to the structure than +the precise magnetic interactions; indeed, the main differences +between 1-q and 3-q spectra are apparent for Heisenberg ex- +change only [52]. The global best fit is for the 3-q structure +and J, K, and Jbq interactions with the refined values given in +Table I. The refined values of A indicate significant magnon +broadening, which is larger for Ba2LuRuO6 and is likely due +to magnon-phonon coupling. Importantly, for both materi- +als, the biquadratic term is significant, with Jbq/J ∼ 0.06. +Hence, our key results are that only the 3-q spin texture agrees +well with our neutron data, and this state is stabilized by bi- +quadratic interactions in Ba2YRuO6 and Ba2LuRuO6. +Our model provides insight into the mechanism of gap +opening [35]. Figure 4(b) compares our low-energy inelastic +data (Ei = 11.8 meV) with the 3-q magnon spectrum for the +optimal J-K-Jbq model [Table I]. This calculation reproduces +the observed ≈ 2.8 meV gap, unlike the J-K-J2 model that +yields the next-best Rwp [52]. Since single-ion anisotropies +are forbidden here, the mechanism of gap opening is subtle. +If K = 0, there is no gap, because the energy of the Heisenberg +and biquadratic terms is unchanged by global spin rotations. +For K > 0, whether a gap opens depends on both structure +and interactions. If the structure is 1-q with Jbq < 0, the clas- +sical energy is unchanged by global spin rotations in the plane +perpendicular to q. In this case, there is no gap at the linear +spin-wave level; a gap is generated only by magnon interac- +tions in the quantum (S = 1/2) limit [61]. By contrast, if the +structure is 3-q with Jbq > 0, a gap is present at the linear spin- +wave level, because Jbq > 0 and K > 0 together favor ⟨111⟩ +spin alignment. Since Ba2YRuO6 and Ba2LuRuO6 are not in +the quantum limit, the experimental observation of a gap sup- +ports the presence of biquadratic and Kitaev interactions in a +3-q structure. +We have shown that the magnetic ground states of +Ba2YRuO6 and Ba2LuRuO6 are noncoplanar 3-q structures +stabilized by biquadratic interactions. Macroscopic topolog- +ical physical responses may be generated synthesizing thin +films of these materials with [111] strain [62]. Our exper- +imental results strikingly confirm recent first-principles pre- +dictions [51]. The positive sign of Jbq suggests that the ef- +fect of inter-site electron hopping outweighs spin-lattice cou- +pling, since the latter would give a negative contribution to +Jbq [11, 12]. Crucially, we quantify the magnetic interactions +that stabilize the noncoplanar state, in contrast to other pro- +posed 3-q structures in NiS2 [63–65], MnTe2 [66], and UO2 +[67–70], where the relevant interactions are not yet well un- +derstood. Our work provides several guiding principles to fa- +cilitate the identification of multi-q spin textures. First, the +near-degeneracy of 1-q and multi-q structures on the FCC lat- +tice makes double perovskites enticing systems. In candidate +materials, the crystal symmetry should be higher than a 1-q +model would imply. Second, magnets that are not deep in- +side the Mott-insulating regime are expected to have larger +Jbq and, consequently, more robust 3-q orderings. This cri- +terion hints that cubic Ba2YOsO6 [71, 72] may also host a +3-q state, due to its extended Os 5d orbitals, potentially offer- +ing a route to investigate the effect of increased electron hop- +ping. 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Tennessee 37831,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' USA 5Theoretical Division,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Los Alamos National Laboratory,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Los Alamos,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' New Mexico 87545,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' USA 6Department of Physics and Astronomy,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The University of Tennessee,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Knoxville,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Tennessee 37996,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' USA Magnetic materials with noncoplanar magnetic structures can show unusual physical properties driven by nontrivial topology.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Topologically-active states are often multi-q structures, which are challenging to stabilize in models and to identify in materials.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Here, we use inelastic neutron-scattering experiments to show that the insulating double perovskites Ba2YRuO6 and Ba2LuRuO6 host a noncoplanar 3-q structure on the face-centered cubic lattice.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Quantitative analysis of our neutron-scattering data reveals that these 3-q states are stabilized by biquadratic interactions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our study identifies double perovskites as a highly promising class of materials to realize topological magnetism, elucidates the stabilization mechanism of the 3-q state in these materials, and establishes neutron spectroscopy on powder samples as a valuable technique to distinguish multi-q from single-q states, facilitating the discovery of topologically-nontrivial magnetic materials.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Most magnetic materials order with simple magnetic struc- tures in which spins are collinear or coplanar.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Noncopla- nar magnetic structures are relatively rare, but are of great current interest, because they can exhibit topological charac- ter and exotic physical properties [1, 2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For example, the finite scalar spin chirality of noncoplanar spin textures can generate a topological magneto-optical effect [3] and anoma- lous quantum Hall effect [4, 5], even in the absence of spin- orbit coupling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Topologically-nontrivial spin textures are typ- ically multi-q structures, which superpose magnetic modula- tions with symmetry-related wavevectors q [2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Multi-q spin textures with long-wavelength modulations, such as skyrmion and hedgehog crystals, are well-studied as hosts of topology- driven phenomena [6–8].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' In this context, multi-q antiferro- magnets are increasingly important [9], because they offer higher densities of topological objects with the potential to generate stronger physical responses [10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' To probe the relationships between spin structure, interac- tions, topology, and physical response, it is crucial to identify real materials that host noncoplanar spin textures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This has proved a challenging task, for three main reasons.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' First, it is necessary to identify noncoplanar spin textures that are ro- bust to subleading effects such as magnetic anisotropies, spin- lattice coupling [11, 12], fluctuations [13–16], and anisotropic interactions [17], which usually favor collinear states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Sec- ond, most noncoplanar states are found in metals, such as USb [18, 19] and γ-Mn alloys [20–25], and are often stable only under an applied magnetic field [6, 26].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' On the one hand, itinerant electrons can support the generation of phys- ical responses;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' on the other hand, modeling the magnetic in- teractions of metals presents fundamental challenges [27–32], such that insulators are often more suitable as model materi- als.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Third, powder neutron-diffraction measurements play a central role in solving magnetic structures, but suffer from a “multi-q problem”: Such measurements are generally unable to distinguish 1-q from multi-q structures [33].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Therefore, multi-q spin textures are challenging to stabilize in models, and to identify in real materials.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Here, we identify the Mott-insulating double perovskites Ba2YRuO6 and Ba2LuRuO6 [34–37] as prototypical exam- ples of noncoplanar 3-q magnetism on the face-centered cu- bic (FCC) lattice in zero magnetic field.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We obtain evidence for 3-q magnetism from a spin-wave analysis of neutron spec- troscopy data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' By optimizing the magnetic structure and inter- actions simultaneously against our data, we show that the 3- q structure is stabilized by biquadratic interactions within an antiferromagnetic Heisenberg-Kitaev model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our study ex- perimentally establishes that noncoplanar multi-q states are stabilized in frustrated FCC antiferromagnets, identifies cubic double perovskites as model materials to realize this behavior, and identifies guiding principles to facilitate design of materi- als with noncoplanar states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our study is motivated by theoretical results for the FCC antiferromagnet [13, 38–40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The nearest-neighbor Heisenberg-Kitaev spin Hamiltonian on the FCC lattice can be written as H = J ∑ ⟨i, j⟩ Si ·Sj +K ∑ ⟨i, j⟩γ Sγ i Sγ j, (1) where Si is a Ru5+ spin with quantum number S = 3/2, J and K denote the Heisenberg and Kitaev interactions, respec- tively, and γ ∈ {x,y,z} is perpendicular to the cubic plane con- taining the bond between neighbors ⟨i, j⟩.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For antiferromag- netic J > 0 only, the model is frustrated, and orderings with q ∈ [1,q,0] are degenerate [13, 39, 40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The degenerate mani- fold includes q = [1,0,0] (“Type I”) ordering, which is favored by fluctuations [13, 14, 41] and is observed in Ba2YRuO6 and Ba2LuRuO6 [34].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Henceforth, we therefore restrict our discussion to q = [1,0,0] ordering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For a collinear structure, spins may be either parallel or perpendicular to q;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' the former is favored by K < 0 and the latter by K > 0 [38–40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Figure 1(a) shows the collinear (1-q) and noncollinear arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='11395v1 [cond-mat.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='str-el] 26 Jan 2023 2 1-q tetragonal 2-q tetragonal 3-q cubic 3-q cubic 2-q tetragonal 1-q orthorhombic (a) �������� ���������������� ������� � ��� � ��� � ��� ��������� ������� � ��� � ��� � ��� �������� ������� � ��� � ��� � ��� ��������� ������� � ��� � ��� � ��� K ≥ 0, mX5 + K ≤ 0, mX3 + (b) Figure 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (a) Symmetry-allowed magnetic structures with propagation vector q = [1,0,0] on the FCC lattice for Ba2MRuO6 (space group Fm¯3m;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' a = 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='29 and 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='24 Å for M = Y and Lu, respectively).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The 1-q, 2-q, and 3-q structures are shown for the mX+ 3 irrep (left) and the mX+ 5 irrep (right).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Spins along different directions are colored differently;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' note that 1-q, 2-q, and 3-q structures have [100], ⟨110⟩, and ⟨111⟩ spin directions, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (b) Elastic scattering data (−1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='3 ≤ E ≤ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='3 meV) measured at T = 5 K with Ei = 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV for Ba2YRuO6 and Ba2LuRuO6 (black circles), Rietveld refinements (red lines), and data – fit (blue lines).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Tick marks show (top to bottom): nuclear, impurity M2O3, and magnetic phases.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The mX+ 3 irrep (left) does not reproduce our data, whereas the mX+ 5 irrep (right) agrees well with our data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (multi-q) structures associated with Type I antiferromag- netism.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' A remarkable property of the FCC lattice is that 1-q, 2-q, and 3-q structures are energetically degenerate for all bi- linear interactions for which Type I ordering is stable [39, 40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Moreover, uniaxial anisotropy (∼S2 z) and antisymmetric ex- change terms are forbidden by Fm¯3m symmetries, and quartic anisotropy (∼S4 x +S4 y +S4 z) is forbidden for S = 3/2 operators in a cubic environment.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Consequently, interactions that would usually favor collinear magnetic structures are inactive in the S = 3/2 FCC antiferromagnet.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This remarkable property po- tentially allows noncollinear structures to appear.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' To identify candidate systems for 3-q spin textures among the diverse magnetic ground states of double perovskites [42– 50], we consider two criteria: Type I antiferromagnetic or- dering, and strictly cubic symmetry below the magnetic or- dering temperature, TN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The second criterion is key because 3-q structures have cubic symmetry, while 1-q and 2-q struc- tures have tetragonal or orthorhombic symmetry that could drive a crystallographic distortion via spin-lattice coupling [Figure 1(a)].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We investigate Ba2YRuO6 and Ba2LuRuO6 because they are chemically well-ordered and show no evi- dence for low-temperature deviations from cubic symmetry [34, 36].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Moreover, recent first-principles calculations predict that their magnetic structures might not be collinear [51], in apparent contradiction with interpretations of previous exper- iments [34].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We prepared ∼8 g polycrystalline samples of Ba2YRuO6 and Ba2LuRuO6 by solid-state reaction [52].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Rietveld re- finement revealed stoichiometric samples with minor Lu2O3 (1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='94 wt.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='%) or Y2O3 (0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='65 wt.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='%) impurities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The magnetic ordering temperature TN ≈ 37 K is the same for both sam- ples, and is suppressed compared to the Weiss temperature θ ∼ −500 K, indicating strong magnetic frustration [36].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We performed inelastic neutron-scattering measurements on the SEQUOIA instrument at ORNL [53] using incident neutron energies Ei = 62 and 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV, yielding elastic energy reso- lutions δ ins ≈ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='68 and 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='27 meV, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Figure 1(b) shows magnetic Rietveld refinements to our elastic neutron-scattering data, measured with Ei = 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV at T ≈ 5 K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Applying the q = [1,0,0] propagation vector to Fm¯3m crystal symmetry generates two magnetic irreducible representations (irreps), notated mX+ 3 and mX+ 5 [54, 55].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' These irreps can be distinguished by their magnetic Bragg profiles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The mX+ 5 irrep agrees well with our elastic-scattering data for both materials;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' we obtain ordered magnetic moment lengths of 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='56(2) and 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='43(2) µB per Ru for Ba2YRuO6 and Ba2LuRuO6, respectively, from Rietveld refinement.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Since the magnetic form factor for Ru5+ is not known, we tested several 4d magnetic form factors [56];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' while this choice does not qualitatively affect our results, the form factor for Zr+ (isoelectronic with Ru5+) yields optimal agreement with our data and is used throughout.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' In contrast to the mX+ 5 irrep, the mX+ 3 irrep strongly disagrees with our data, as it yields zero intensity for the strong (100) magnetic Bragg peak.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This can be understood intuitively for a collinear 1-q structure, because neutrons are only sensitive to spin components perpendicular to the scattering wavevector, and the mX3+ irrep has S ∥ q while the mX5+ irrep has S ⊥ q [Figure 1(a)].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' A previous elas- 3 Figure 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Broadband inelastic neutron-scattering data (Ei = 62 meV) measured at T = 5 K for Ba2YRuO6 (upper panels) and Ba2LuRuO6 (lower panels), showing (a) intensity as a color plot, and (b) energy dependence integrated over 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='0 ≤ Q ≤ 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='5 Å−1, where experimental data are shown as black circles, and Gaussian fits to the ∼14 meV phonon band as red lines.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' tic neutron-scattering study of Ba2YRuO6 and Ba2LuRuO6 considered only collinear 1-q structures [34], but could not rule out multi-q structures, due to the multi-q problem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' To overcome the multi-q problem, we consider the en- ergy dependence of our neutron-scattering data [57].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Fig- ure 2(a) shows our inelastic data measured with Ei = 62 meV at T ≈ 5 K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' A structured inelastic signal appears at T < TN for small scattering wavevectors, Q ≲ 2 Å−1, which we iden- tify as magnon scattering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The top of the magnetic band overlaps with an intense phonon signal for Q ≳ 2 Å−1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Fig- ure 2(b) shows the scattering intensity integrated over 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='0 ≤ Q ≤ 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='5 Å−1, from which we extract the average energy Eph and width σph of this phonon band via Gaussian fits for each material.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The energy overlap of magnon and phonon modes suggests that spin-lattice coupling may be significant, which we consider further below.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our starting point for modeling the magnetic scattering is the Heisenberg-Kitaev model, Eq.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For all models, we re- quire J > 0 and K > 0 to stabilize mX+ 5 ordering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We con- sider three additional interactions in turn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' First, the symmet- ric off-diagonal interaction HΓ = Γ∑⟨i, j⟩γ � Sα i Sβ j +Sβ i Sα j � is the only additional bilinear nearest-neighbor interaction al- lowed by symmetry.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Second, the Heisenberg next-nearest neighbor interaction H2 = J2 ∑⟨⟨i, j⟩⟩ Si · Sj has been invoked for Ba2YRuO6 [37];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' we require J2 ≤ 0 to stabilize Type I ordering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Third, the nearest-neighbor biquadratic cou- pling Hbq = Jbq ∑⟨i, j⟩(Si · Sj)2 has been invoked in density- functional-theory calculations for 4d double perovskites due to their increased electron hopping relative to 3d analogs [51].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For Jbq = 0, the classical energy of 1-q, 2-q, and 3-q struc- tures is equal for all K, Γ, and J2 that stabilize Type I or- dering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Nonzero Jbq removes this degeneracy, and stabilizes ���� ���� ���� ���� ���� ���� ���� ���� � � �� �� �� ���� ���� ���� ���� ���� ���� ���� ���� �� � �� �� �� Rwp (%) 1-q 2-q 3-q (a) (b) Jbq K 3-q mX5 + 1-q mX5 + 3-q mX3 + 1-q mX3 + Figure 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (a) Schematic phase diagram showing the magnetic ground states of the J-K-Jbq model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (b) Goodness-of-fit metric Rwp for can- didate magnetic structures and interaction models of Ba2YRuO6 (up- per graph) and Ba2LuRuO6 (lower graph).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The graphs show Rwp for refinements of the Heisenberg-Kitaev (J-K) model including a third refined parameter Γ (red bars), J2 (blue bars), or Jbq (green bars);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' note that the 2-q structure is stable only for Jbq = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' J (K) K (K) Jbq (K) A (meV) Ba2YRuO6 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='85(3) 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='39(1) 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='32(2) 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='97(3) Ba2LuRuO6 22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='27(4) 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='36(2) 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='17(3) 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='25(5) Table I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Refined values of magnetic interaction parameters for the J- K-Jbq model and 3-q structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Uncertainties indicate 1σ statistical confidence intervals.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' 1-q ordering for Jbq < 0 and 3-q ordering for Jbq > 0 [Fig- ure 3(a)].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Importantly, since single-ion anisotropies are for- bidden for S = 3/2 in a cubic environment, biquadratic ex- change is the only physically-plausible mechanism that can remove the degeneracy of 1-q and 3-q structures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We performed extensive fits to our inelastic neutron- scattering data to optimize the magnetic structure and inter- actions simultaneously.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For each structure associated with the mX+ 5 irrep (1-q, 2-q, or 3-q), we optimized three spin Hamil- tonian parameters (J, K, and either Γ, J2, or Jbq) against the broadband inelastic data shown in Figure 4(a) and the energy dependence near the (100) magnetic Bragg position shown in Figure 4(b).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The powder-averaged magnon spectrum was calculated within a renormalized linear spin-wave theory [58] using the SpinW program [59].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The renormalization factor, which takes into account higher-order corrections in the 1/S expansion, is strictly necessary to extract a correct value of Jbq, since the unrenormalized spin-wave theory would lead to a value of Jbq that is 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='25 times smaller than the correct value [60].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The parameter values were optimized to minimize the sum of squared residuals using nonlinear least-squares refine- ment [52].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We calculated the energy-dependent broadening of the magnon spectrum as δ(E) = δins(E) + Ae−(E−Eph)2/2δ 2 ph, where δ(E) is the overall Gaussian energy width, δins(E) is the instrumental resolution, and A is a refined parameter that phenomenologically accounts for magnon broadening due to coupling with phonons at E ∼ Eph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Figure 4(a) compares our broadband inelastic data (Ei = 62 meV) with the best fit for each of the 1-q, 2-q, and 3-q 4 Figure 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (a) Broadband inelastic neutron-scattering data (Ei = 62 meV) and optimal spin-wave fits for different magnetic structures, showing (left to right) experimental data, 1-q fit, 2-q fit, and 3-q fit.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' (b) Low-energy inelastic neutron-scattering data (Ei = 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV) and 3-q model calculations, showing (left to right) a cut at Q = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='7450±0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='0175 Å−1 comparing experimental data (black circles) and spin-wave fit (red lines), experimental data as a Q-E slice, and spin-wave calculation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' structures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The data show two V-shaped features centered at ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='85 and ≈ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='70 Å−1, with a sharp cutoff of magnetic signal for energies above ∼14 meV.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For both materials, these char- acteristics are best reproduced by the 3-q structure, while the 1-q structure disagrees with our experimental data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' These ob- servations are confirmed by the goodness-of-fit metric Rwp, shown in Figure 3(b).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For both materials and for every in- teraction model we considered, the 3-q structure yields better agreement with our data than the 1-q or 2-q structures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' No- tably, the goodness-of-fit is more sensitive to the structure than the precise magnetic interactions;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' indeed, the main differences between 1-q and 3-q spectra are apparent for Heisenberg ex- change only [52].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The global best fit is for the 3-q structure and J, K, and Jbq interactions with the refined values given in Table I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The refined values of A indicate significant magnon broadening, which is larger for Ba2LuRuO6 and is likely due to magnon-phonon coupling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Importantly, for both materi- als, the biquadratic term is significant, with Jbq/J ∼ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='06.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Hence, our key results are that only the 3-q spin texture agrees well with our neutron data, and this state is stabilized by bi- quadratic interactions in Ba2YRuO6 and Ba2LuRuO6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our model provides insight into the mechanism of gap opening [35].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Figure 4(b) compares our low-energy inelastic data (Ei = 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV) with the 3-q magnon spectrum for the optimal J-K-Jbq model [Table I].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This calculation reproduces the observed ≈ 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content='8 meV gap, unlike the J-K-J2 model that yields the next-best Rwp [52].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Since single-ion anisotropies are forbidden here, the mechanism of gap opening is subtle.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' If K = 0, there is no gap, because the energy of the Heisenberg and biquadratic terms is unchanged by global spin rotations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For K > 0, whether a gap opens depends on both structure and interactions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' If the structure is 1-q with Jbq < 0, the clas- sical energy is unchanged by global spin rotations in the plane perpendicular to q.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' In this case, there is no gap at the linear spin-wave level;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' a gap is generated only by magnon interac- tions in the quantum (S = 1/2) limit [61].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' By contrast, if the structure is 3-q with Jbq > 0, a gap is present at the linear spin- wave level, because Jbq > 0 and K > 0 together favor ⟨111⟩ spin alignment.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Since Ba2YRuO6 and Ba2LuRuO6 are not in the quantum limit, the experimental observation of a gap sup- ports the presence of biquadratic and Kitaev interactions in a 3-q structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' We have shown that the magnetic ground states of Ba2YRuO6 and Ba2LuRuO6 are noncoplanar 3-q structures stabilized by biquadratic interactions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Macroscopic topolog- ical physical responses may be generated synthesizing thin films of these materials with [111] strain [62].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our exper- imental results strikingly confirm recent first-principles pre- dictions [51].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' The positive sign of Jbq suggests that the ef- fect of inter-site electron hopping outweighs spin-lattice cou- pling, since the latter would give a negative contribution to Jbq [11, 12].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Crucially, we quantify the magnetic interactions that stabilize the noncoplanar state, in contrast to other pro- posed 3-q structures in NiS2 [63–65], MnTe2 [66], and UO2 [67–70], where the relevant interactions are not yet well un- derstood.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Our work provides several guiding principles to fa- cilitate the identification of multi-q spin textures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' First, the near-degeneracy of 1-q and multi-q structures on the FCC lat- tice makes double perovskites enticing systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' In candidate materials, the crystal symmetry should be higher than a 1-q model would imply.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Second, magnets that are not deep in- side the Mott-insulating regime are expected to have larger Jbq and, consequently, more robust 3-q orderings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This cri- terion hints that cubic Ba2YOsO6 [71, 72] may also host a 3-q state, due to its extended Os 5d orbitals, potentially offer- ing a route to investigate the effect of increased electron hop- ping.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' For small Jbq, we anticipate a thermally-induced tran- sition from 3-q to 1-q ordering, since thermal fluctuations fa- 5 vor collinear states.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Third, quartic single-ion anisotropy may play a role in FCC magnets with S > 3/2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' in particular, easy- ⟨111⟩ axis anisotropy should favor 3-q ordering.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' Finally, our key methodological insight is that refining the magnetic struc- ture and interactions simultaneously enables 1-q and multi-q structures to be distinguished on the FCC lattice, even when single-crystal samples are not available.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/4dFIT4oBgHgl3EQf6yuB/content/2301.11395v1.pdf'} +page_content=' This work was supported by the U.' metadata={'source': 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index 0000000000000000000000000000000000000000..8e4c60206d25fcd063175300e95d168b77086930 --- /dev/null +++ b/9dE4T4oBgHgl3EQfDQsU/content/tmp_files/2301.04867v1.pdf.txt @@ -0,0 +1,1524 @@ +arXiv:2301.04867v1 [physics.chem-ph] 12 Jan 2023 +Model for vibrationally enhanced tunneling of +proton transfer in hydrogen bond +A.E. Sitnitsky, +Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of +RAS, P.O.B. 30, 420111, Russian Federation. e-mail: sitnitsky@kibb.knc.ru +Abstract +Theoretical analysis of the effect of an external vibration on proton transfer (PT) in +a hydrogen bond (HB) is carried out. It is based on the two-dimensional Schr¨odinger +equation with trigonometric double-well potential. Its solution obtained within the +framework of the standard adiabatic approximation is available. An analytic for- +mula is derived that provides the calculation of PT rate with the help of elements +implemented in Mathematica. We exemplify the general theory by calculating PT +rate constant for the intermolecular HB in the Zundel ion H5O+ +2 (oxonium hydrate). +This object enables one to explore a wide range of the HB lengths. Below some crit- +ical value of the frequency of the external vibration the calculated PT rate yields +extremely rich resonant behavior (multiple manifestations of bell-shaped peaks). It +takes place at symmetric coupling of the external vibration to the proton coordinate. +This phenomenon is absent for anti-symmetric and squeezed mode couplings. +Key words: Schr¨odinger equation, double-well potential, quantum tunneling, +spheroidal function, Zundel ion. +1 +Introduction +Proton transfer (PT) in hydrogen bonds (HB) is one of the main processes +in the reaction rate theory. It takes place in the most important biological +molecules such as proteins (participating in some enzymatic reactions) and +DNA (arguably participating in the occurrence of mutations). In particular +the phenomenon of vibrationally enhanced (or assisted or promoted) tunnel- +ing at PT (i.e., resonant acceleration of the process by a coupled oscillation +in some frequency range) [1], [2] is of great interest especially in regard of its +Email address: sitnitsky@kibb.knc.ru ( A.E. Sitnitsky). +Preprint submitted to Chemical Physics Letters +13 January 2023 + +possible role in a mechanism for enzymatic hydrogen transfer [3-6]. Within +the context of enzyme catalysis it is a specific case of the more general trend +named ”rate-promoting vibration” [6-11]. There are several cases in which a +vibration can be coupled to the proton coordinate in HB. First of all there +is the heavy atoms stretching mode which is an intrinsic degree of freedom +in HB. It is thoroughly studied theoretically since the pioneer articles [12], +[13], [1] dealing with vibrationally promoted PT in solids. Unfortunately it +is an internal vibration and its fixed frequency is not an experimentally con- +trollable parameter. Then there are external vibrations exerted on HB and +provided either by protein scaffold for HB in enzymes or by some means from +the researcher’s toolkit for HB in model compounds. One of the most effi- +cient ways for such purpose is the usage of the IR electromagnetic field of an +optical cavity. The phenomenon of resonant activation (or, in contrast, sup- +pression) of reaction rates is widely discussed for modifying chemical kinetics +by optical cavities (for recent articles in this field which is sometimes called +vibrational polariton chemistry see, e.g., [14-16] and refs. therein). The reso- +nance, i.e., maximal cavity induced enhancement of the reaction rate under +the vibrational resonance condition is produced in this case by mixing the +electromagnetic field with quantum states of molecular systems. The cavity is +equivalent to a harmonic oscillator of a given frequency coupled to the molec- +ular system. The Hamiltonian of the molecule degree of freedom coupled to +the field oscillator in the electric dipole approximation of light-matter interac- +tion has the same structure as those used for PT coupled to the heavy atoms +stretching mode in HB. In this regard constructing reliable theoretical models +of PT which take into account the possibility of varying the frequency of the +external vibration exerted on HB is a long-standing problem for the reaction +rate theory and seems to be of interest for perspectives of various application. +A proton in HB is known to be sufficiently light to exhibit full-fledged quan- +tum behavior leading to tunneling effect, energy levels splitting, etc (see, e.g., +[12,13,17-28] and refs. therein). Physical models of PT based on simplified +Hamiltonians take their peculiar place in the enormous amount of literature on +HB including also ab initio calculations by the methods of quantum chemistry, +DFT, their combination with molecular dynamics simulations (considering nu- +clei as classical Newtonian particles), QM/MM, chemical physics approaches +within the framework of modern trends in TST, quantum-classical Liouville +dynamics, etc. In physical models of PT the reaction coordinate is singled out +and studied separately from the environment for which various approxima- +tions are assumed. The problem of PT rate estimate is inevitably reduced to +a one-dimensional path on the potential energy surface (PES) and as a result +to a one-dimensional cross-section of PES for HB which usually has the form +of a double-well potential (DWP). Quantum mechanical models of PT are +motivated by the necessity to take into account other (than the reaction co- +ordinate) internal dynamic modes, e.g., the heavy atoms stretching mode and +to account for vibrationally and/or thermally assisted tunneling. The modern +2 + +physical approach to taking into account dissipative effects at tunneling is +based on the Lindblad master equation (describing the dynamics of Marko- +vian open quantum systems) for the time evolution of the density matrix and +Caldeira-Leggett model of the thermal bath. For PT such scheme was initiated +in [12,13] and by now it has been thoroughly studied within the framework of +the general context for the reaction rate theory (see, e.g., [17] and refs. therein). +The problem of the rate-promoting vibration for PT is considered with the +help of this theory in [28]. The authors obtained the desired increase of the PT +rate at adding the vibrational mode. However they came to a conclusion that +the lower its frequency the stronger the enhancement of PT rate. Our aim is to +find out the conceptual possibility of resonant activation (bell-shaped peaks) +with frequency. In the present article we avoid the complications of the above +mentioned theory (ensuing from the necessity to deal with numerous evolution +equations for the density matrix elements) which seem to be unimportant for +our aims. For calculating PT rate we make use of the Weiner’s theory [18,19]. +Our model of HB is maximally simple and constructed in an ad hoc manner +for studying the effect of PT resonant activation. It corresponds to HB in a +gas phase and does not touch upon the effects of environment taking place +in solution. It deals only with two salient degrees of freedom, i.e., the proton +coordinate and that of an oscillator (e.g., the heavy atoms stretching mode or +an external vibration) with symmetric coupling between them. We treat both +degrees of freedom quantum-mechanically by solving the corresponding two- +dimensional Schr¨odinger equation (SE). We make use of literature data for +the one-dimensional cross-section of PES from quantum-chemical calculations +and model it by a suitable phenomenological DWP. For the case of the heavy +atoms stretching mode we use literature data of IR-spectroscopy for HB to +determine its frequency and the strength of proton coordinate coupling to it. +The calculation of PT rate in HB requires the knowledge of the energy levels +which are the eigenvalues of the corresponding SE with DWP. PT is a typical +example of a quantum particle in DWP which is an omnipresent problem in +physics and chemistry [23,26,29-41]. Most DWPs used for the analysis of HB +and composed of polynomials, exponentials (e.g., the double Morse potential) +or their combinations are amenable only to numerical solutions (even in one- +dimensional case let alone its two-dimensional generalization) or approximate +analytic approaches like the quasi-classical (WKB) method. This restriction +was inevitable until 2010-s because of the lack of a convenient DWP for which +SE would have an exact analytic solution (see [29] and refs. therein). Since then +a number of exactly solvable DWPs suitable for chemical problems (taking +infinite values at the boundaries of the spatial variable interval) appeared. For +them analytic solutions of SE are feasible via the confluent Heun’s function +[23], [31-38] or the spheroidal function [39,40]. The latter is a well-studied +special function of mathematical physics [42] implemented in Mathematica. +The case which is amenable to the treatment by both functions [23,31,39] +makes use of the so-called trigonometric DWP (TDWP). In the previous years +3 + +TDWP was applied to numerous objects [23,24,25,31,39,40,43,44]. The aim +of the present article is to show that TDWP enables one to construct an +analytically tractable model for PT resonant activation in HB. We exemplify +the general theory by the analysis of PT rate for intermolecular HB in the +Zundel ion H5O+ +2 (oxonium hydrate H2O · · · H · · · OH2 in which the proton is +equally shared between two water molecules). For the Zundel ion the detailed +data of IR spectroscopy [20-22] along with the quantum chemical ab initio +calculations [45,46] are available. As a result the Zundel ion suits well for the +purpose of demonstrating the capability of our approach to the calculation of +PT rate in HB. For the Zundel ion the distance between the oxygen atoms ROO +is not a fixed and predetermined value but can be varied in a wide range. In the +present article the case ROO = 3.0 A is chosen because it provides sufficiently +high barrier to exclude the contribution of the over-barrier transition into PT +rate constant even at high temperature. This choice is in accord with the aim +of the article to study the effect of an external vibration on the tunneling +contribution into the rate constant. +The paper is organized as follows. In the preliminary Sec.2 we remind some +results of the Weiner’s theory in the form suitable for our analysis. In Sec.3 +we briefly summarize the results of [25] which are necessary for the calculation +of PT rate in HB. In Sec.4 we derive the expression for the PT rate constant. +In Sec.5 the results are discussed and the conclusions are summarized. In +Appendix some technical information is presented. +2 +Weiner’s theory +In the Weiner’s theory [18,19] the proton position is described by the sta- +tionary one-dimensional SE (which we write in the dimensionless form) with +symmetric DWP U(x) which has the solutions for the energy levels ǫq and the +corresponding wave functions ψq(x) +ψ′′ +q (x) + [ǫq − U(x)] ψq(x) = 0 +(1) +The rate constant consists of the contribution from the tunneling process and +that from the over-barrier transition. Concerning the former the Weiner’s the- +ory deals with two important values. The first one is the probability flux to the +right of particles in the left well when the particle is in the q-th state Jq. The +second one is the quantum transmission coefficient, i.e., the fraction of those +right-moving particles which are transmitted to the right well | Tq |2. Accord- +ing to [18,19] the reaction rate constant is a result of Boltzmann averaging of +4 + +the product Jq | Tq |2 calculated over the doublets +k = + + +∞ +� +q=0 +e−βǫq + + +−1  + + +N +� +n=0 +e−βǫ2nJ2n | T2n |2 + +∞ +� +m=2N+2 +e−βǫm + + + +(2) +where n = 0, 1, 2, ..., N , ǫ2n is the energy for the level 2n described by the wave +function ψ2n(x). In the Weiner’s theory the quantum transmission coefficient +is calculated for the doublets which are counted by the even energy levels. For +this reason n is fixed to be even in the first sum in the curly brackets (see the +text below the formula (3.1) in Sec.III of [19] the formulas from which are used +in the present article). The first sum in the curly brackets corresponds to the +contribution due to the tunneling process in the reaction rate. It is over the +energy levels below the barrier top for which the notions of J2n and | T2n |2 +have sense. In (2) it is suggested by Weiner that the quantum transmission +coefficient of the lower level in the doublet is determined by the splitting of +the energy levels in it. Thus N +1 is the number of doublets below the barrier +top and ǫ2N is the lower energy level in the last doublet in this region. As a +result only the sum over doublets (i.e., even levels q = 2n) is left. The second +sum in the curly brackets corresponds to the over-barrier transition and ǫ2N+2 +is the the first energy level above the barrier top. The Weiner’s theory is based +on the quasi-classical approximation of the solution of SE [19] +ψ2n(x) = +B2n +� +P2n(x) +cos + + +x +� +0 +dξ P2n(ξ) + S2n + + +(3) +for x ≥ 0. Taking into account that for even energy levels the wave function +is symmetric (ψ′ +2n(0)) one obtains that +tan S2n = − P ′ +2n(0) +2P 2 +2n(0) +(4) +The function Pq(x) satisfies the so-called Milne equation +P 2 +q + U(x) + 1 +2 + +P ′′ +q +Pq +− 3 +2 +� +P ′ +q +�2 +P 2 +q + + = ǫq +(5) +The expression for | T2n |2 follows from (3.5) of [19] +| T2n |2= ψ2 +2n(0)P2n(0) +B2 +2n +(6) +5 + +The expression for J2n is given by (2.14) of [19] +J2n = B2 +2n +2 +(7) +In the particular case P ′ +2n(0) = 0 (which will be pertinent in our further +consideration) it follows from (4) that +S2n = 0 +(8) +Substitution of the results into (2) yields +k = + + +∞ +� +q=0 +e−βǫq + + +−1  + + +1 +2 +N +� +n=0 +e−βǫ2nB2 +2n + +∞ +� +m=2N+2 +e−βǫm + + + +(9) +It is worthy to note that in the original Weiner’s approach both ǫq and ψq(x) +are unknown and all efforts are directed to obtain formulas that do not con- +tain values like ψq(0) or ψ′ +q(0). In contrast for TDWP the exact solution of +SE ψq(x) as well as the corresponding energy levels ǫq are available and we +make use of the them. Also it should be stressed that the Weiner’s theory is +originally written for the infinite range of the space variable −∞ < x < ∞ +with the requirement | ψq(x) |→ 0 at x → ±∞. In our case of TDWP we +have the requirement | ψq(x) |→ 0 at x → ±π/2. For this reason we apply the +corresponding formulas to the case −π/2 ≤ x ≤ π/2. We consider SE (1) in +this range with the dimensionless form of the symmetric TDWP [39] +U(x) = +� +m2 − 1 +4 +� +tan2 x − p2 sin2 x +(10) +Here m is an integer number and p is a real number. The two parameters of +TDWP m and p are related to two main characteristics of the potential energy +surface, i.e., the barrier height and the barrier width (see Appendix). The +example of TDWP for intermolecular HB in the Zundel ion with ROO = 3.0 A +distance between oxygen atoms is presented in Fig.1. For TDWP the exact +solution of SE is available [39] +ψq(x) = cos1/2 x ¯Sm(q+m) (p; sin x) +(11) +q = 0, 1, 2, ... and ¯Sm(q+m) (p; s) is the normalized angular prolate spheroidal +function [42]. It is implemented in Mathematica as SpheroidalPS[(q+m), m, ip, s] +(note that the latter is a non-normalized one). The energy levels are +ǫq = λm(q+m) (p) + 1 +2 − m2 − p2 +(12) +6 + +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +�7 +0=57.9;ωmax≈0.0064 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ6 +0=22.85 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ4 +0=-57.705 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ5 +0=-58.386 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ2 +0=-191.406 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ3 +0=-191.782 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ0 +0=-346.192919 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ1 +0=-346.197925 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ7 +0=77.2;ωc≈0.0112 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ6 +0=32.94 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ5 +0=-39.296 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ4 +0=-45.915 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ3 +0=-163.7194636 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ2 +0=-163.8071785 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ1 +0=-306.41765635 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Λ0 +0=-306.41765771 +-0.5 +0.5 +x +-400 +-300 +-200 +-100 +U(x) +Zundel ion ROO=3.0 A +Fig. 1. The trigonometric double-well potential (10) at the values of the parameters +m = 57; p = 76. The parameters are chosen to describe the hydrogen bond in the +Zundel ion H5O+ +2 (oxonium hydrate) for the case ROO = 3.0 ˚A (they are extracted +from the data of quantum chemistry [46]). Several energy levels are indicated for the +coupling constant α = 0.3. They are given by (19) and calculated at two frequencies +of the external oscillator (for that of the main peak ωmax ≈ 0.0064 depicted by long +dashes and for the critical frequency ωc ≈ 0.0112 depicted by short dashes). +Here λm(q+m) (p) is the spectrum of eigenvalues for ¯Sm(q+m) (p; s). It is imple- +mented in Mathematica as λm(q+m) (p) ≡ SpheroidalEigenvalue[(q+m), m, ip]. +For TDWP the position of the right minimum is defined by the requirement +cos xmin = +�m2 − 1/4 +p2 +�1/4 +(13) +3 +Solution of two-dimensional Schr¨odinger equation with trigono- +metric double-well potential +For the two-dimensional SE the wave function is the function of the proton +coordinate x and that of the oscillator z. The interaction Hamiltonian for +various types of the mode coupling can be schematically depicted by the form +αf(x)g(z) where α is the coupling constant. For the symmetric mode coupling +it is αzx2, for anti-symmetric and squeezed mode couplings it is αzx and αz2x2 +respectively. In the present article we consider the case of the symmetric mode +coupling (see a comment on other types of interaction in Sec.5). For TDWP +it is more natural for the mathematical convenience to make for x in the +interaction term the transformation x → sin x so that the coupling term is +αz sin2 x. In fact the external vibration always interacts with some function +f(x) of the proton coordinate x (e.g., the with the dipole moment if the +vibration is produced by an electro-magnetic field). The term αzx2 for the +symmetric mode coupling means that only the linear approximation for the +function f(x) ≈ x is taken into account. However the linear approximation can +be valid within the interval of a sufficiently small x only. In our opinion it is +7 + +reasonable to go beyond the linear approximation, i.e., to make the replacing +x −→ sin x at −π/2 ≤ x ≤ π/2. In the case of the dipole moment it deflects to +slower growth than the linear one (see, e.g., Fig. 10.54 in [47]. The necessity to +go beyond the framework of the linear approximation for HB in the Zundel ion +was stressed in [22]. To achieve this goal we model such deflection by replacing +the linear term by the trigonometric one x −→ sin x at −π/2 ≤ x ≤ π/2. Then +the dimensionless form of the two-dimensional SE with the symmetric mode +coupling and TDWP is [25] +� +δ ∂2 +∂z2 + ∂2 +∂x2 + Λ − +� +m2 − 1 +4 +� +tan2 x + p2 sin2 x− +ω2z2 +2 +− αz sin2 x +� +Φ(x, z) = 0 +(14) +Here ω is the frequency of the oscillator coupled to the proton coordinate. The +dimensionless variables and parameters are discussed in Appendix for the case +when the oscillator is produced by the heavy atoms stretching mode in HB. +The solution of (14) in the adiabatic approximation corresponding to the q-th +state of the particle in TDWP and the j-th state of the oscillator is [25] +Φ(x, q, z, j) ≈ ϕq +j(z)ψq(x) +(15) +Here the quantum number q quantizes the states of the particle in TDWP and +ψq(x) is given by (11). The quantum number j in (15) quantizes the excitation +states of the oscillator +ϕq +j(z) ≈ A exp +� +− +ω +2 +√ +2δ +� +z + cq +ω2 +�2� j!(−2)j +(2j)! H2j + + +�2ω2 +δ +�1/4 � +z + cq +ω2 +� +(16) +j = 0, 1, 2, ... , Hn(x) is the Hermit polynomial and A is a normalization +constant. Making use of N2.20.16.6 from [48] we obtain +A−2 = +�j!(−2)j +(2j)! +�2 +24j +�√ +2δ +ω Γ +� +2j + 1 +2 +� +2F1 +� +−2j, −2j, 1 +2 − 2j; −1 +2 +� +(17) +where +2F1 (a, b, c; x) is the hypergeometric function. The coefficient cq is +cq = α +1 +� +−1 +dη η2 � ¯Sm(q+m) (p; η) +�2 +(18) +8 + +The energy levels corresponding to (15) are [25] +Λj +q ≈ λm(q+m) (p) + 1 +2 − m2 − p2 − (cq)2 +2ω2 + (4j + 1)ω +� +δ +2 +(19) +4 +Proton transfer rate constant +We introduce the dimensionless inverse temperature β (for its expression +via dimensional parameters of the model see Appendix). Further we restrict +ourselves to the relatively high temperature range 200 K ≤ T ≤ 400 K +(0.0345 ≤ β ≤ 0.069) in which the Boltzmann statistics is valid. Then the +partition function is calculated with the help of the energy levels Λk +q given by +the formula (19) +Z(β, ω) = +� +q +∞ +� +j=0 +exp +� +−βΛj +q(ω) +� += +∞ +� +j=0 +e +−β +� +(4j+1)ω√ +δ +2+ 1 +2−m2−p2� +� +q +e +−β +� +λm(q+m)(p)− (cq)2 +2ω2 +� +(20) +With the help of (16) we calculate the average value of z +< z >q= +∞ +� +−∞ +dz z +� +ϕq +j(z) +�2 = − cq +ω2 +(21) +We define the auxiliary parameter +˜pq = +� +p2 − α < z >q +(22) +and the auxiliary TDWP +˜U(x) = +� +m2 − 1 +4 +� +tan2 x − +� +p2 − α < z >q +� +sin2 x +(23) +We introduce the auxiliary wave function ˜ψq(x) which satisfies SE +˜ψ′′ +q (x) + +� +λm(q+m) (˜pq) + 1 +2 − m2 − ˜p2 +q − ˜U(x) +� +˜ψq(x) = 0 +(24) +9 + +Its solution is (11) with taking into account the replacement p → +� +p2 − α < z >q +˜ψq(x) = cos1/2 x ¯Sm(q+m) +�� +p2 − α < z >q; sin x +� +(25) +We seek the solution of (16) in the form +Φ(x, q, z, j) ≈ ϕq +j(z) +Bq +� +Pq(x) +cos + + +x +� +0 +dξ Pq(ξ) + Sq + + +(26) +We take into account the equation for ϕq +j(z) (see argumentation in [25]) +� +δ d2 +dz2 − ǫq + Λj +q − ω2z2 +2 +− cqz +� +ϕq +j(z) = 0 +(27) +Substituting (26) into (14) and replacing z by its average value given by (21) +(z →< z >q) we obtain the Milne equation for Pq(x) +P 2 +q + 1 +2 + +P ′′ +q +Pq +− 3 +2 +� +P ′ +q +�2 +P 2 +q + + = ǫq + cq < z >q − ˜U(x) +(28) +We seek its approximate solution in the form +Pq(x) ≈ +Dq +˜ψ2q(x) +(29) +where Dq is a constant to be determined later. It is noteworthy that Pq(x) +from (29) yields P ′ +2n(0) = 0 because for even energy levels the wave function +is symmetric ( ˜ψ′ +2n(0) = 0). Hence (4) yields that S2n = 0 in (26). Substitution +of (29) in (28) results in the relationship +D2 +q +˜ψ4q(x) = λm(q+m) (p) − λm(q+m) (˜pq) + < z >q (cq − α) +(30) +We require that the approximate solution of SE (3) (i.e., the corresponding +term in (26)) coincides with our exact solution (11) for TDWP in the crucial +points x = 0 and x = xmin. The exact wave function ψq(x) given by (11) is +a normalized function in the range −π/2 ≤ x ≤ π/2 and its known values +ψq(0) and ψq(xmin) further replace the corresponding unknown values for the +approximation (3). The requirement for (30) to be satisfied at x = 0 yields +Dq = ˜ψ2 +q(0) +� +λm(q+m) (p) − λm(q+m) (˜pq) + < z >q (cq − α) +(31) +10 + +With the help of thus defined P2n(x) we calculate from (3) (with taking into +account that P ′ +2n(0) = 0 yielding (8)) the wave function at xmin +ψ2n(xmin) = +B2n +� +P2n(xmin) +cos + + +xmin +� +0 +dξ P2n(ξ) + + +(32) +As a result we obtain +B2 +2n = ψ2 +2n(xmin)D2n +˜ψ2 +2n(xmin) +cos−2 + +D2n +xmin +� +0 +dξ +˜ψ2 +2n(ξ) + + +(33) +Then the expression for the two-dimensional generalization of (9) takes the +form +k(β, ω) ≈ +1 +Z(β, ω) +�1 +2 +� +n +∞ +� +j=0 +exp +� +−βΛj +2n(ω) +� ψ2 +2n(xmin)D2n +˜ψ2 +2n(xmin) +× +cos−2 + +D2n +xmin +� +0 +dξ +˜ψ2 +2n(ξ) + + + +∞ +� +l=2N+2 +∞ +� +j=0 +exp +� +−βΛj +l (ω) +�� +(34) +It should be stressed that the summation over j yields the same factor as +that in the partition function Z(β, ω) and as a result they are canceled out. +Substituting (25) and (31) in (34) we finally obtain +k(β, ω) ≈ + + + +∞ +� +q=0 +e +−β +� +λm(q+m)(p)− (cq)2 +2ω2 +� + + +−1 �1 +2 +N +� +n=0 +e +−β +� +λm(2n+m)(p)− (c2n)2 +2ω2 +� +× +cos−2 +�� +λm(2n+m) (p) − λm(2n+m) +�� +p2 − α < z >2n +� ++ < z >2n (c2n − α) × +¯S2 +m(2n+m) +�� +p2 − α < z >2n; 0 +� xmin +� +0 +dξ cos−1 ξ +¯S2 +m(2n+m) +�√p2 − α < z >2n; sin ξ +� +� +× +¯S2 +m(2n+m) +�√p2 − α < z >2n; 0 +� ¯S2 +m(2n+m) (p; sin xmin) +¯S2 +m(2n+m) +�√p2 − α < z >2n; sin xmin +� +× +� +λm(2n+m) (p) − λm(2n+m) +�� +p2 − α < z >2n +� ++ < z >2n (c2n − α)+ +∞ +� +l=2N+2 +e +−β +� +λm(l+m)(p)− (cl)2 +2ω2 +�� +(35) +11 + +where < z >2n is given by (21). The sum over n is that over the doublets +below the barrier top (see the discussion below (2)). +5 +Results and discussion +Notwithstanding to be cumbersome the formula (35) is easily programmed in +Mathematica because the crucial elements λm(q+m) (p) and ¯Sm(q+m) (p; s) are +implemented in this software package. We take the rate constant k(β, ωref) +for the internal stretching mode of the heavy atoms in the Zundel ion (with +a fixed frequency ωref) as a natural reference point. For this object there are +potential energy surfaces for several ROO as a result of quantum chemical +ab initio calculations [45], [46]. For the cases of HB in the Zundel ion with +ROO = 2.5 A, ROO = 2.6 A and ROO = 2.7 A the authors of [20] provide the +estimates of the dimensional coupling constant λ (a21 in their Table.1) as 0.1 +a.u., 0.1 a.u. and 0.05 a.u. respectively. For the dimensional frequency Ω/2 +(a02 in their Table.1) they present the value 0.039 a.u. for all three distances. +From here we obtain the reference value of α = 0.6 at ROO = 2.5 A and +α = 0.3 at ROO = 2.7 A. Also from the above results of [20] we obtain that +the reference value for the dimensionless frequency of O-O stretching mode is +ωref = 1.4. In the present article we are interested in the effect of the external +vibration on the tunneling process. To make the contribution into PT rate +constant from the over-barrier transition to be negligible compared with the +tunneling one even at T = 400 K (β = 0.0345) we restrict ourselves by the +case of PT for HB in the Zundel ion with very high barrier. For this reason +we consider ROO = 3.0 A from data of [46]. TDWP for this case is depicted +Fig.1. We carry out the parametric analysis of PT rate constant for HB in +the Zundel ion with large ROO = 3.0 A taking the above mentioned reference +value α = 0.3 and varying ω in the range 0.005 ≤ ω ≤ ωref. In this case there +are three doublets below the barrier top (see Fig.1) that means N = 2 in (35). +In the calculations of the rate constant we also take into account two levels +above the barrier top (i.e., replace ∞ in (35) by Nmax = 7) to make sure that +the contribution of the over-barrier transition can be discarded. +Fig.2 shows that at decreasing the frequency from the reference value ωref +we obtain the monotonic increase of PT rate constant in agreement with the +conclusion of [28]. However there is a critical value of the frequency ωc (for +α = 0.3 this value is ωc ≈ 0.01125) below which a drastic change of the +behavior takes place. In Fig.3, Fig.4 and Fig.5 the dependence of PT rate +constant on the frequency of the oscillator at ω < ωc is depicted. For a given +value of the coupling constant α at the corresponding ωc there is Λ0 +1 = Λ0 +0 and +a reversal in the total energy levels takes place (the energy levels of TDWP +do not depend on ω and retain their natural order ǫq+1 > ǫq). At ω > ωc we +have the normal sequence Λ0 +2n+1 > Λ0 +2n where n = 0, 1, 2, ... while at ω < ωc +12 + +  + + + + +  +-1.5 +-1.0 +-0.5 +0.0 +log10 ω +-9 +-8 +-7 +-6 +-5 +log10 k(β, ω) + β=0.0345 (T=400 K) +▲ ▲ +▲ +▲ +▲ +▲ ▲ +-1.5 +-1.0 +-0.5 +0.0 +log10 ω +-9 +-8 +-7 +-6 +-5 +log10 k(β, ω) +▲ β=0.069 (T=200 K) +Fig. 2. The dependence of proton transfer rate constant on the frequency of the +external oscillator above the critical value ω > ωc in the Zundel ion H5O+ +2 (oxonium +hydrate) with ROO = 3.0 A. The critical frequency is ωc ≈ 0.01125 for the value +of the coupling constant α = 0.3 between the proton coordinate and that of the +oscillator. + + + + +    + +-2.2 +-2.1 +-2.0 +-1.9 +log10 ω +-5 +0 +5 +10 +15 +log10 k(β, ω) + β=0.0345 (T=400 K) +Fig. 3. The dependence of proton transfer rate constant on the frequency of the +external oscillator below the critical value ω < ωc in the Zundel ion H5O+ +2 (oxonium +hydrate) with ROO = 3.0 A at high temperature (T = 400 K (β = 0.0345). The +critical frequency is ωc ≈ 0.01125 for the value of the coupling constant α = 0.3 +between the proton coordinate and that of the oscillator. Low resolution picture of +the whole interval 0.005 < ω < ωc. +an anomalous picture Λ0 +2n+1 < Λ0 +2n occurs at first for the ground state doublet +(n = 0) and at further decrease of the frequency for higher ones below the +barrier top (see, e.g., the case for ωmax in Fig.1). This transformation leads to +an extraordinary alteration in the behavior of PT rate constant. Fig.3, Fig.4 +and Fig.5 vividly exhibit that in this case there are very rich manifestations +of resonant activation, i.e., the bell-shaped peaks of PT rate enhancement +by the external vibration at its symmetric coupling to the proton coordinate. +The height of the main peak at ωmax = 0.006429109800232905 is temperature +dependent (e.g., k(0.046, ωmax)/k(0.046, ωref) = 5.31 · 1022 at T = 300K and +k(0.0345, ωmax)/k(0.0345, ωref) = 3.13 · 1023 at T = 400K). Fig.3 shows that +13 + + + + + + + + + + + + + + + + + + +   + + + + + + + + + + + + + + + + +-2.14 +-2.12 +-2.10 +-2.08 +-2.06 +log10 ω +-4.0 +-3.5 +-3.0 +-2.5 +-2.0 +log10 k(β, ω) + β=0.0345 (T=400 K) +Fig. 4. The dependence of proton transfer rate constant on the frequency of the +external oscillator below the critical value ω < ωc in the Zundel ion H5O+ +2 (oxonium +hydrate) with ROO = 3.0 A at high temperature (T = 400 K (β = 0.0345). The +critical frequency is ωc ≈ 0.01125 for the value of the coupling constant α = 0.3 +between the proton coordinate and that of the oscillator. High resolution picture of +the interval 0.00693 < ω < 0.009. +▲▲ ▲▲ ▲▲▲▲ +▲▲▲ +▲▲▲▲▲▲ +▲ +▲▲▲▲▲▲▲▲ +▲▲▲▲▲▲▲▲ ▲ +▲ ▲ +▲ +▲ +-2.2 +-2.1 +-2.0 +-1.9 +-1.8 +-1.7 +log10 ω +-5 +0 +5 +10 +15 +log10 k(β, ω) +▲ β=0.069 (T=200 K) +Fig. 5. The dependence of proton transfer rate constant on the frequency of the +external oscillator below the critical value ω < ωc in the Zundel ion H5O+ +2 (oxonium +hydrate) with ROO = 3.0 A at low temperature (T = 200 K (β = 0.069). The critical +frequency is ωc ≈ 0.01125 for the value of the coupling constant α = 0.3 between +the proton coordinate and that of the oscillator. +at high temperature β = 0.0345 the approach to the main peak from the side +of higher frequencies is not smooth. There is a sequence of comb-like regions of +increasing intensity with the decrease of the frequency ω (see Fig.4 for higher +resolution picture). The intensity of these combs decreases with the decrease of +temperature and at β = 0.069 they are not discernable (see Fig.5). At α = 0.3 +and ω < ωc the ground state doublet approaches the bottom of TDWP (see, +e.g., Fig.1) and at ω < 0.005 the former becomes below the latter. +By attaining the resonance condition ωmax one can obtain a very efficient +mechanism of PT rate enhancement. For α = 0.3 we have the acceleration +up to 23 orders of magnitude compared with the reference value ωref = 1.4. +14 + +The mathematical reason for the phenomenon of such PT resonance acti- +vation is in the fact that the function ¯Sm(2n+m) +�� +p2 − α +� +−c2n +ω2 +� +; sin xmin +� +taking place in the denominators of (35) becomes extremely small for the +second doublet n = 1 at ω = ωmax. In our opinion the descriptive physical +origin of the phenomenon can be revealed from the following empirical obser- +vation. Let us consider the wave functions in the left and the right wells for +the j-th doublet (j = 1, 2, 3) defined as usual ψ(j) +R = 1/ +√ +2 +� +ψ(j) ++ − ψ(j) +− +� +and +ψ(j) +L += 1/ +√ +2 +� +ψ(j) ++ + ψ(j) +− +� +respectively where ψ(j) +± +are given by (11). Here + +means the upper energy level in the doublet while − means the lower one. +Then we recall the notion of the Rabi frequency in energetic units (multiplied +by the Planck constant) as the module of the interaction energy, i.e., that of +the product of the electromagnetic field strength and the matrix element of +the dipole moment for the transition between the corresponding energy lev- +els. The dimensional resonance condition Ef − Ei = ℏΩRabi +if +=| Hint | in the +dimensionless form is ǫf − ǫi = +√ +2δ ωRabi +if +=| hint |. Analogously we equate +the difference between the energy levels ǫ(j) ++ − ǫ(j) +− in the j-th doublet and the +module of the matrix element of the interaction energy term | αz sin2 x | from +(14) with the functions ψ(j) +R and ψ(j) +L . For sin2 x we take the value of its matrix +element +< ψ(j) +R | sin2 x | ψ(j) +L >= +π/2 +� +−π/2 +dx ψ(j) +R sin2 x ψ(j) +L +(36) +For z we take the average < z >− given by (21), i.e., < z >−= −c(j) +− /ω2. As +a result we have an empirical relationship +ǫ(j) ++ − ǫ(j) +− = α | −c(j) +− < ψ(j) +R | sin2 x | ψ(j) +L >| +ω2 +(37) +From (37) we obtain the resonance frequency ω(j) +± +ω(j) +± = +� +� +� +� +�α | −c(j) +− < ψ(j) +R | sin2 x | ψ(j) +L >| +ǫ(j) ++ − ǫ(j) +− +(38) +At α = 0.3 and δ = 1/8 we have for j = 2, i.e., for the second doublet +ω(2) +± += 0.00673 which is rather close to ωmax ≈ 0.00643 for the main peak. +In our opinion such quantitative agreement can not be fortuitous. It suggests +the physical interpretation of PT resonant activation as an analog of the Rabi +transition between the left and the right wells under the influence of the vibra- +tion with a suitable frequency applied to the proton in DWP. The case j = 1 +15 + +yields the resonance frequency ω(1) +± = 0.00795 which is within the range of the +right comb-like region in Fig.4. Constructing various matrix elements between +wave functions of different doublets for both wells ψin +R = 1/ +√ +2 (ψi − ψn) and +ψlm +L = 1/ +√ +2 (ψl + ψm) yields +ǫ(j) ++ − ǫ(j) +− = α | −ck < ψin +R | sin2 x | ψlm +L >| +ω2 +(39) +where j = 1, 2, 3 and {k, i, n, l, m = 0, 1, 2, 3, 4, 5}. Then we obtain for the +third doublet j = 3 the resonance frequencies: 0.00722 at +{l = 2, m = 5, i = 1, k = n = 0}; 0.00725 at {k = l = 0, m = 3, i = 1, n = 4}; +0.00753 at +{l = 1, k = m = 4, i = 2, n = 5} which are within the range of the left comb- +like region in Fig.4. Constructing various matrix elements between wave func- +tions of different doublets for the left well yields +ǫ(j) ++ − ǫ(j) +− = α | −ck < ψlm +L | sin2 x | ψl′m′ +L +>| +ω2 +(40) +Then we obtain for the third doublet j = 3 the resonance frequencies: 0.00787 +at +{l = 1, k = m = 4, l′ = 5, m′ = 4} which is within the range of the right comb- +like region in Fig.4 and 0.00723 at {l = 0, m = 3, l′ = 4, k = m′ = 5} which is +within the range of the left comb-like region in Fig.4. In our opinion these +numerous resonance frequencies provide qualitative explanation of severe os- +cillations in Fig.4. +Also in this connection it is worthy to note that for the symmetric mode cou- +pling (Hint = λZX2) the effect of resonant activation results from the term +− (cq)2 /2ω2 in the total energy levels Λk +q (19). The energy levels of TDWP ǫq +are re-normalized due to the coupling of the proton coordinate to the oscilla- +tor. For anti-symmetric (Hint = λZX) and squeezed (Hint = λZ2X2) mode +couplings this effect is absent. In the former case the coupling strength is zero +c{as} +q += 0 due to the symmetry of the wave functions [25] that leads to the +actual lack of the crucial term − +� +c{as} +q +�2 / (2ω2) in the formula (19) for Λk +q. In +the latter case the expression for Λk +q [25] +Λk +q|{sq} ≈ λm(q+m) (p) + 1 +2 − m2 − p2 + (4k + 1) +� +� +� +�δ +� +ω2 + 2c{sq} +q +� +2 +(41) +does not contain the required term at all. For instance the interaction of the +proton in HB with an IR laser field in the dipole approximation (the dipole +moment d ∝ x) belongs to the anti-symmetric type and does not fit our +16 + +requirement for PT resonant activation by a low-frequency vibration (high- +frequency Rabi transitions between different doublets stimulated by an IR +laser field certainly can considerably interfere PT process). Only taking into +account that a realistic dipole moment contains the appropriate higher or- +der contributions (d ∝ x + const x2 + ...) may provide the required type of +interaction in this case. +We conclude that the suggested approach enables one to obtain an analytically +tractable expression for proton transfer rate constant in a hydrogen bond. It +is based on the Schr¨odinger equation with the model Hamiltonian taking into +account only the proton coordinate and an external oscillator coupled to it +(the heavy atoms stretching mode, a low-frequency vibration of the protein +scaffold in an enzyme, etc). The literature data from quantum chemical ab +initio calculations of the potential energy surface are transformed into the +parameters of the model trigonometric double-well potential. For the two- +dimensional Schr¨odinger equation with this potential the analytic solution +within the framework of the standard adiabatic approximation is available. +The parameters of the model for the Zundel ion in the case of the heavy atoms +stretching mode are extracted from the literature data on IR spectroscopy and +serve as a reference point. The approach yields the pronounced resonant effect +of proton transfer acceleration in some frequency range of the oscillator (below +the corresponding critical value of the frequency) at its symmetric coupling +to the proton coordinate. The phenomenon is absent for anti-symmetric and +squeezed mode couplings. +6 +Appendix +In dimensional units the one-dimensional SE for a quantum particle with the +reduced mass M (proton in our case of usual HB or deuterium in the case of +a deuterated HB) has the form +d2ψ(X) +dX2 ++ 2M +ℏ2 [E − V (X)] ψ(X) = 0 +(42) +where −L ≤ X ≤ L and V (X) is a DWP. The latter is assumed to be infinite +at the boundaries of the finite interval for the spatial variable X = ±L. The +dimensionless values for the distance x, the potential U(x) and the energy ǫ +are introduced as follows +x = πX +2L ; +U(x) = 8ML2 +ℏ2π2 V (X); +ǫ = 8ML2E +ℏ2π2 +(43) +where −π/2 ≤ x ≤ π/2. As a result we obtain the dimensionless SE (1). In +17 + +the case of the trigonometric DWP (10) the transformation formulas for the +parameters {m, p} into {B, D} (B is the barrier height and D is the barrier +width) are [24] +p = +√ +B +1 − [cos (D/2)]2; +m2 − 1 +4 = +B [cos (D/2)]4 +� +1 − [cos (D/2)]2�2 +(44) +The Hamiltonian of the two-dimensional SE includes the spatial variable Z +(e.g., that for the reduced mass of the heavy atoms in HB which in the case of +the Zundel ion is the O-O stretching mode) of the harmonic potential ΩZ2/2 +with the frequency Ω. We introduce the dimensionless distance x = πX/ (2L) +where −π/2 ≤ x ≤ π/2 and dimensionless coordinate z = πZ/ (2L) where +−∞ < z < ∞. The dimensionless coupling constant α in (14) for the symmet- +ric mode coupling (this case was proved in [20] to be pertinent for the Zundel +ion), the dimensionless inverse temperature β in (20), (34) and (35) and the +dimensionless frequency ω in (14) are +α = 26λML5 +ℏ2π5 +; +β = +ℏ2π2 +8ML2kBT ; +ω = 4√2MµL2Ω +ℏπ2 +; +µ = +M1M2 +M1 + M2 +(45) +Here λ is a dimensional coupling constant for the case of the symmetric mode +coupling term (λZX2) and µ is the reduced mass of the heavy atoms in HB +A1 − H · · · A2. In the case of the Zundel ion it is µ = MO/2. As a result δ in +(14) is δ = M/µ = 2M/MO. Taking the proton mass M = 1 a.u and that of +the oxygen atom MO = 16 a.u. we have δ = 1/8. +Acknowledgements. The author is grateful to Prof. Yu.F. Zuev for helpful dis- +cussions. The work was supported from the government assignment for FRC +Kazan Scientific Center of RAS. +18 + +References +[1] N.D. Sokolov, M.V. Vener, Chem.Phys. 168 (1992) 29-40. +[2] S.Hammes-Schiffer, J.C. Tully, J.Phys.Chem. 99 (1995) 5193-5191. +[3] W.J. Bruno, W, Bialek, Biophys.J. 63 (1992) 689-699. +[4] J. Basran, M.J. Sutcliffe, N.S. Scrutton, Biochemistry 38 (1999) 3218-3222. +[5] A. Kohen, J.P. Klinman, Chem.Biol. 6 (1999) R191-R198. +[6] D. Antoniou, S.D. Schwartz, J.Phys.Chem. B 105 (2001) 5553-5558. +[7] K.O. Alper, M. Singla, J.L. Stone, C.K. Bagdassarian, Prot.Sci. 10 (2001) 1319- +1330. +[8] P.K. Agarwal, J.Am.Chem.Soc. 127 (2005) 15248-15256. +[9] A.E. Sitnitsky, Physica A 371 (2006) 481-491. +[10] A.E. Sitnitsky, Physica A 387 (2008) 5483-5497. +[11] A. Kohen, Acc.Chem.Res. 48 (2015) 466-473. +[12] R. Meyer, R. R. Ernst, J.Chem.Phys. 86 (1987) 784-801. +[13] R. Meyer, R. R. Ernst, J.Chem.Phys. 93 (1990) 5518-5532. +[14] P.-Y. Yang, J. 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Special +functions., 2-d ed., FIZMATLIT, Moscow, 2003. +21 + diff --git a/9dE4T4oBgHgl3EQfDQsU/content/tmp_files/load_file.txt b/9dE4T4oBgHgl3EQfDQsU/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..764f2b99e3040f2572be9acd6c25d26ce30e1753 --- /dev/null +++ b/9dE4T4oBgHgl3EQfDQsU/content/tmp_files/load_file.txt @@ -0,0 +1,1113 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf,len=1112 +page_content='arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='04867v1 [physics.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='chem-ph] 12 Jan 2023 Model for vibrationally enhanced tunneling of proton transfer in hydrogen bond A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Sitnitsky, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, P.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='O.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='B.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 30, 420111, Russian Federation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' e-mail: sitnitsky@kibb.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='knc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ru Abstract Theoretical analysis of the effect of an external vibration on proton transfer (PT) in a hydrogen bond (HB) is carried out.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is based on the two-dimensional Schr¨odinger equation with trigonometric double-well potential.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Its solution obtained within the framework of the standard adiabatic approximation is available.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' An analytic for- mula is derived that provides the calculation of PT rate with the help of elements implemented in Mathematica.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We exemplify the general theory by calculating PT rate constant for the intermolecular HB in the Zundel ion H5O+ 2 (oxonium hydrate).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' This object enables one to explore a wide range of the HB lengths.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Below some crit- ical value of the frequency of the external vibration the calculated PT rate yields extremely rich resonant behavior (multiple manifestations of bell-shaped peaks).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It takes place at symmetric coupling of the external vibration to the proton coordinate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' This phenomenon is absent for anti-symmetric and squeezed mode couplings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Key words: Schr¨odinger equation, double-well potential, quantum tunneling, spheroidal function, Zundel ion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 1 Introduction Proton transfer (PT) in hydrogen bonds (HB) is one of the main processes in the reaction rate theory.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It takes place in the most important biological molecules such as proteins (participating in some enzymatic reactions) and DNA (arguably participating in the occurrence of mutations).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In particular the phenomenon of vibrationally enhanced (or assisted or promoted) tunnel- ing at PT (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', resonant acceleration of the process by a coupled oscillation in some frequency range) [1], [2] is of great interest especially in regard of its Email address: sitnitsky@kibb.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='knc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ru ( A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Sitnitsky).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Preprint submitted to Chemical Physics Letters 13 January 2023 possible role in a mechanism for enzymatic hydrogen transfer [3-6].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Within the context of enzyme catalysis it is a specific case of the more general trend named ”rate-promoting vibration” [6-11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' There are several cases in which a vibration can be coupled to the proton coordinate in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' First of all there is the heavy atoms stretching mode which is an intrinsic degree of freedom in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is thoroughly studied theoretically since the pioneer articles [12], [13], [1] dealing with vibrationally promoted PT in solids.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Unfortunately it is an internal vibration and its fixed frequency is not an experimentally con- trollable parameter.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Then there are external vibrations exerted on HB and provided either by protein scaffold for HB in enzymes or by some means from the researcher’s toolkit for HB in model compounds.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' One of the most effi- cient ways for such purpose is the usage of the IR electromagnetic field of an optical cavity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The phenomenon of resonant activation (or, in contrast, sup- pression) of reaction rates is widely discussed for modifying chemical kinetics by optical cavities (for recent articles in this field which is sometimes called vibrational polariton chemistry see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', [14-16] and refs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' therein).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The reso- nance, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', maximal cavity induced enhancement of the reaction rate under the vibrational resonance condition is produced in this case by mixing the electromagnetic field with quantum states of molecular systems.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The cavity is equivalent to a harmonic oscillator of a given frequency coupled to the molec- ular system.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The Hamiltonian of the molecule degree of freedom coupled to the field oscillator in the electric dipole approximation of light-matter interac- tion has the same structure as those used for PT coupled to the heavy atoms stretching mode in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In this regard constructing reliable theoretical models of PT which take into account the possibility of varying the frequency of the external vibration exerted on HB is a long-standing problem for the reaction rate theory and seems to be of interest for perspectives of various application.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' A proton in HB is known to be sufficiently light to exhibit full-fledged quan- tum behavior leading to tunneling effect, energy levels splitting, etc (see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', [12,13,17-28] and refs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' therein).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Physical models of PT based on simplified Hamiltonians take their peculiar place in the enormous amount of literature on HB including also ab initio calculations by the methods of quantum chemistry, DFT, their combination with molecular dynamics simulations (considering nu- clei as classical Newtonian particles), QM/MM, chemical physics approaches within the framework of modern trends in TST, quantum-classical Liouville dynamics, etc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In physical models of PT the reaction coordinate is singled out and studied separately from the environment for which various approxima- tions are assumed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The problem of PT rate estimate is inevitably reduced to a one-dimensional path on the potential energy surface (PES) and as a result to a one-dimensional cross-section of PES for HB which usually has the form of a double-well potential (DWP).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Quantum mechanical models of PT are motivated by the necessity to take into account other (than the reaction co- ordinate) internal dynamic modes, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the heavy atoms stretching mode and to account for vibrationally and/or thermally assisted tunneling.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The modern 2 physical approach to taking into account dissipative effects at tunneling is based on the Lindblad master equation (describing the dynamics of Marko- vian open quantum systems) for the time evolution of the density matrix and Caldeira-Leggett model of the thermal bath.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For PT such scheme was initiated in [12,13] and by now it has been thoroughly studied within the framework of the general context for the reaction rate theory (see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', [17] and refs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' therein).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The problem of the rate-promoting vibration for PT is considered with the help of this theory in [28].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The authors obtained the desired increase of the PT rate at adding the vibrational mode.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' However they came to a conclusion that the lower its frequency the stronger the enhancement of PT rate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Our aim is to find out the conceptual possibility of resonant activation (bell-shaped peaks) with frequency.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the present article we avoid the complications of the above mentioned theory (ensuing from the necessity to deal with numerous evolution equations for the density matrix elements) which seem to be unimportant for our aims.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For calculating PT rate we make use of the Weiner’s theory [18,19].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Our model of HB is maximally simple and constructed in an ad hoc manner for studying the effect of PT resonant activation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It corresponds to HB in a gas phase and does not touch upon the effects of environment taking place in solution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It deals only with two salient degrees of freedom, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the proton coordinate and that of an oscillator (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the heavy atoms stretching mode or an external vibration) with symmetric coupling between them.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We treat both degrees of freedom quantum-mechanically by solving the corresponding two- dimensional Schr¨odinger equation (SE).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We make use of literature data for the one-dimensional cross-section of PES from quantum-chemical calculations and model it by a suitable phenomenological DWP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the case of the heavy atoms stretching mode we use literature data of IR-spectroscopy for HB to determine its frequency and the strength of proton coordinate coupling to it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The calculation of PT rate in HB requires the knowledge of the energy levels which are the eigenvalues of the corresponding SE with DWP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' PT is a typical example of a quantum particle in DWP which is an omnipresent problem in physics and chemistry [23,26,29-41].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Most DWPs used for the analysis of HB and composed of polynomials, exponentials (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the double Morse potential) or their combinations are amenable only to numerical solutions (even in one- dimensional case let alone its two-dimensional generalization) or approximate analytic approaches like the quasi-classical (WKB) method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' This restriction was inevitable until 2010-s because of the lack of a convenient DWP for which SE would have an exact analytic solution (see [29] and refs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' therein).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Since then a number of exactly solvable DWPs suitable for chemical problems (taking infinite values at the boundaries of the spatial variable interval) appeared.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For them analytic solutions of SE are feasible via the confluent Heun’s function [23], [31-38] or the spheroidal function [39,40].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The latter is a well-studied special function of mathematical physics [42] implemented in Mathematica.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The case which is amenable to the treatment by both functions [23,31,39] makes use of the so-called trigonometric DWP (TDWP).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the previous years 3 TDWP was applied to numerous objects [23,24,25,31,39,40,43,44].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The aim of the present article is to show that TDWP enables one to construct an analytically tractable model for PT resonant activation in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We exemplify the general theory by the analysis of PT rate for intermolecular HB in the Zundel ion H5O+ 2 (oxonium hydrate H2O · · · H · · · OH2 in which the proton is equally shared between two water molecules).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the Zundel ion the detailed data of IR spectroscopy [20-22] along with the quantum chemical ab initio calculations [45,46] are available.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' As a result the Zundel ion suits well for the purpose of demonstrating the capability of our approach to the calculation of PT rate in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the Zundel ion the distance between the oxygen atoms ROO is not a fixed and predetermined value but can be varied in a wide range.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the present article the case ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A is chosen because it provides sufficiently high barrier to exclude the contribution of the over-barrier transition into PT rate constant even at high temperature.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' This choice is in accord with the aim of the article to study the effect of an external vibration on the tunneling contribution into the rate constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The paper is organized as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the preliminary Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 we remind some results of the Weiner’s theory in the form suitable for our analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 we briefly summarize the results of [25] which are necessary for the calculation of PT rate in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 we derive the expression for the PT rate constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 the results are discussed and the conclusions are summarized.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In Appendix some technical information is presented.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 2 Weiner’s theory In the Weiner’s theory [18,19] the proton position is described by the sta- tionary one-dimensional SE (which we write in the dimensionless form) with symmetric DWP U(x) which has the solutions for the energy levels ǫq and the corresponding wave functions ψq(x) ψ′′ q (x) + [ǫq − U(x)] ψq(x) = 0 (1) The rate constant consists of the contribution from the tunneling process and that from the over-barrier transition.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Concerning the former the Weiner’s the- ory deals with two important values.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The first one is the probability flux to the right of particles in the left well when the particle is in the q-th state Jq.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The second one is the quantum transmission coefficient, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the fraction of those right-moving particles which are transmitted to the right well | Tq |2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Accord- ing to [18,19] the reaction rate constant is a result of Boltzmann averaging of 4 the product Jq | Tq |2 calculated over the doublets k = \uf8ee \uf8f0 ∞ � q=0 e−βǫq \uf8f9 \uf8fb −1 \uf8f1 \uf8f2 \uf8f3 N � n=0 e−βǫ2nJ2n | T2n |2 + ∞ � m=2N+2 e−βǫm \uf8fc \uf8fd \uf8fe (2) where n = 0, 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', N , ǫ2n is the energy for the level 2n described by the wave function ψ2n(x).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the Weiner’s theory the quantum transmission coefficient is calculated for the doublets which are counted by the even energy levels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For this reason n is fixed to be even in the first sum in the curly brackets (see the text below the formula (3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1) in Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='III of [19] the formulas from which are used in the present article).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The first sum in the curly brackets corresponds to the contribution due to the tunneling process in the reaction rate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is over the energy levels below the barrier top for which the notions of J2n and | T2n |2 have sense.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In (2) it is suggested by Weiner that the quantum transmission coefficient of the lower level in the doublet is determined by the splitting of the energy levels in it.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Thus N +1 is the number of doublets below the barrier top and ǫ2N is the lower energy level in the last doublet in this region.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' As a result only the sum over doublets (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', even levels q = 2n) is left.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The second sum in the curly brackets corresponds to the over-barrier transition and ǫ2N+2 is the the first energy level above the barrier top.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The Weiner’s theory is based on the quasi-classical approximation of the solution of SE [19] ψ2n(x) = B2n � P2n(x) cos \uf8eb \uf8ed x � 0 dξ P2n(ξ) + S2n \uf8f6 \uf8f8 (3) for x ≥ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Taking into account that for even energy levels the wave function is symmetric (ψ′ 2n(0)) one obtains that tan S2n = − P ′ 2n(0) 2P 2 2n(0) (4) The function Pq(x) satisfies the so-called Milne equation P 2 q + U(x) + 1 2 \uf8ee \uf8ef\uf8f0P ′′ q Pq − 3 2 � P ′ q �2 P 2 q \uf8f9 \uf8fa\uf8fb = ǫq (5) The expression for | T2n |2 follows from (3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5) of [19] | T2n |2= ψ2 2n(0)P2n(0) B2 2n (6) 5 The expression for J2n is given by (2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='14) of [19] ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='J2n = B2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(7) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='In the particular case P ′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n(0) = 0 (which will be pertinent in our further ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='consideration) it follows from (4) that ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='S2n = 0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(8) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Substitution of the results into (2) yields ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='k = ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8ee ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q=0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e−βǫq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f9 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8fb ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='−1 \uf8f1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='N ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='n=0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e−βǫ2nB2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n + ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='m=2N+2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e−βǫm ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8fc ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8fd ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8fe ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(9) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='It is worthy to note that in the original Weiner’s approach both ǫq and ψq(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='are unknown and all efforts are directed to obtain formulas that do not con- ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='tain values like ψq(0) or ψ′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q(0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In contrast for TDWP the exact solution of SE ψq(x) as well as the corresponding energy levels ǫq are available and we make use of the them.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Also it should be stressed that the Weiner’s theory is originally written for the infinite range of the space variable −∞ < x < ∞ with the requirement | ψq(x) |→ 0 at x → ±∞.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In our case of TDWP we have the requirement | ψq(x) |→ 0 at x → ±π/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For this reason we apply the corresponding formulas to the case −π/2 ≤ x ≤ π/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We consider SE (1) in this range with the dimensionless form of the symmetric TDWP [39] U(x) = � m2 − 1 4 � tan2 x − p2 sin2 x (10) Here m is an integer number and p is a real number.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The two parameters of TDWP m and p are related to two main characteristics of the potential energy surface, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the barrier height and the barrier width (see Appendix).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The example of TDWP for intermolecular HB in the Zundel ion with ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A distance between oxygen atoms is presented in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For TDWP the exact solution of SE is available [39] ψq(x) = cos1/2 x ¯Sm(q+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin x) (11) q = 0, 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' and ¯Sm(q+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' s) is the normalized angular prolate spheroidal function [42].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is implemented in Mathematica as SpheroidalPS[(q+m), m, ip, s] (note that the latter is a non-normalized one).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The energy levels are ǫq = λm(q+m) (p) + 1 2 − m2 − p2 (12) 6 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) �7 0=57.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='9;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ωmax≈0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0064 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ6 0=22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='85 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ4 0=-57.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='705 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ5 0=-58.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='386 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ2 0=-191.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='406 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ3 0=-191.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='782 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ0 0=-346.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='192919 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ1 0=-346.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='197925 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ7 0=77.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ωc≈0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0112 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ6 0=32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='94 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ5 0=-39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='296 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ4 0=-45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='915 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ3 0=-163.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='7194636 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ2 0=-163.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='8071785 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ1 0=-306.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='41765635 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Λ0 0=-306.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='41765771 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 x 400 300 200 100 U(x) Zundel ion ROO=3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The trigonometric double-well potential (10) at the values of the parameters m = 57;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' p = 76.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The parameters are chosen to describe the hydrogen bond in the Zundel ion H5O+ 2 (oxonium hydrate) for the case ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 ˚A (they are extracted from the data of quantum chemistry [46]).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Several energy levels are indicated for the coupling constant α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' They are given by (19) and calculated at two frequencies of the external oscillator (for that of the main peak ωmax ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0064 depicted by long dashes and for the critical frequency ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0112 depicted by short dashes).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Here λm(q+m) (p) is the spectrum of eigenvalues for ¯Sm(q+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' s).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is imple- mented in Mathematica as λm(q+m) (p) ≡ SpheroidalEigenvalue[(q+m), m, ip].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For TDWP the position of the right minimum is defined by the requirement cos xmin = �m2 − 1/4 p2 �1/4 (13) 3 Solution of two-dimensional Schr¨odinger equation with trigono- metric double-well potential For the two-dimensional SE the wave function is the function of the proton coordinate x and that of the oscillator z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The interaction Hamiltonian for various types of the mode coupling can be schematically depicted by the form αf(x)g(z) where α is the coupling constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the symmetric mode coupling it is αzx2, for anti-symmetric and squeezed mode couplings it is αzx and αz2x2 respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the present article we consider the case of the symmetric mode coupling (see a comment on other types of interaction in Sec.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For TDWP it is more natural for the mathematical convenience to make for x in the interaction term the transformation x → sin x so that the coupling term is αz sin2 x.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In fact the external vibration always interacts with some function f(x) of the proton coordinate x (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the with the dipole moment if the vibration is produced by an electro-magnetic field).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The term αzx2 for the symmetric mode coupling means that only the linear approximation for the function f(x) ≈ x is taken into account.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' However the linear approximation can be valid within the interval of a sufficiently small x only.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In our opinion it is 7 reasonable to go beyond the linear approximation, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', to make the replacing x −→ sin x at −π/2 ≤ x ≤ π/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the case of the dipole moment it deflects to slower growth than the linear one (see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='54 in [47].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The necessity to go beyond the framework of the linear approximation for HB in the Zundel ion was stressed in [22].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' To achieve this goal we model such deflection by replacing the linear term by the trigonometric one x −→ sin x at −π/2 ≤ x ≤ π/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Then the dimensionless form of the two-dimensional SE with the symmetric mode coupling and TDWP is [25] � δ ∂2 ∂z2 + ∂2 ∂x2 + Λ − � m2 − 1 4 � tan2 x + p2 sin2 x− ω2z2 2 − αz sin2 x � Φ(x, z) = 0 (14) Here ω is the frequency of the oscillator coupled to the proton coordinate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dimensionless variables and parameters are discussed in Appendix for the case when the oscillator is produced by the heavy atoms stretching mode in HB.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The solution of (14) in the adiabatic approximation corresponding to the q-th state of the particle in TDWP and the j-th state of the oscillator is [25] Φ(x, q, z, j) ≈ ϕq j(z)ψq(x) (15) Here the quantum number q quantizes the states of the particle in TDWP and ψq(x) is given by (11).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The quantum number j in (15) quantizes the excitation states of the oscillator ϕq j(z) ≈ A exp � − ω 2 √ 2δ � z + cq ω2 �2� j!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' (−2)j (2j)!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' H2j \uf8eb \uf8ed �2ω2 δ �1/4 � z + cq ω2 �\uf8f6 \uf8f8(16) j = 0, 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' , Hn(x) is the Hermit polynomial and A is a normalization constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Making use of N2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='6 from [48] we obtain A−2 = �j!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' (−2)j (2j)!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' �2 24j �√ 2δ ω Γ � 2j + 1 2 � 2F1 � −2j, −2j, 1 2 − 2j;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' −1 2 � (17) where 2F1 (a, b, c;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' x) is the hypergeometric function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The coefficient cq is cq = α 1 � −1 dη η2 � ¯Sm(q+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' η) �2 (18) 8 The energy levels corresponding to (15) are [25] Λj q ≈ λm(q+m) (p) + 1 2 − m2 − p2 − (cq)2 2ω2 + (4j + 1)ω � δ 2 (19) 4 Proton transfer rate constant We introduce the dimensionless inverse temperature β (for its expression via dimensional parameters of the model see Appendix).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Further we restrict ourselves to the relatively high temperature range 200 K ≤ T ≤ 400 K (0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345 ≤ β ≤ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='069) in which the Boltzmann statistics is valid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Then the partition function is calculated with the help of the energy levels Λk q given by the formula (19) Z(β,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ω) = ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j=0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='exp ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='−βΛj ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q(ω) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='= ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j=0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='−β ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(4j+1)ω√ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='δ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2+ 1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2−m2−p2� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='−β ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='λm(q+m)(p)− (cq)2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2ω2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(20) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='With the help of (16) we calculate the average value of z ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='< z >q= ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='−∞ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='dz z ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ϕq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j(z) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='�2 = − cq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ω2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(21) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='We define the auxiliary parameter ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜pq = ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='p2 − α < z >q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(22) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='and the auxiliary TDWP ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜U(x) = ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='m2 − 1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='tan2 x − ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='p2 − α < z >q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='sin2 x ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(23) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='We introduce the auxiliary wave function ˜ψq(x) which satisfies SE ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψ′′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q (x) + ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='λm(q+m) (˜pq) + 1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 − m2 − ˜p2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q − ˜U(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψq(x) = 0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(24) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='9 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Its solution is (11) with taking into account the replacement p → ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='p2 − α < z >q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψq(x) = cos1/2 x ¯Sm(q+m) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='�� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='p2 − α < z >q;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin x � (25) We seek the solution of (16) in the form Φ(x,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' q,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' z,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' j) ≈ ϕq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j(z) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Bq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Pq(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='cos ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8eb ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8ed ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='x ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='dξ Pq(ξ) + Sq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f6 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f8 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(26) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='We take into account the equation for ϕq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j(z) (see argumentation in [25]) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='δ d2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='dz2 − ǫq + Λj ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q − ω2z2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='− cqz ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ϕq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='j(z) = 0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(27) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Substituting (26) into (14) and replacing z by its average value given by (21) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(z →< z >q) we obtain the Milne equation for Pq(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='P 2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q + 1 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8ee ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8ef\uf8f0P ′′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Pq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='− 3 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='P ′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='�2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='P 2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f9 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8fa\uf8fb = ǫq + cq < z >q − ˜U(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(28) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='We seek its approximate solution in the form ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Pq(x) ≈ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Dq ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψ2q(x) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(29) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='where Dq is a constant to be determined later.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is noteworthy that Pq(x) from (29) yields P ′ 2n(0) = 0 because for even energy levels the wave function is symmetric ( ˜ψ′ 2n(0) = 0).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Hence (4) yields that S2n = 0 in (26).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Substitution of (29) in (28) results in the relationship D2 q ˜ψ4q(x) = λm(q+m) (p) − λm(q+m) (˜pq) + < z >q (cq − α) (30) We require that the approximate solution of SE (3) (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the corresponding term in (26)) coincides with our exact solution (11) for TDWP in the crucial points x = 0 and x = xmin.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The exact wave function ψq(x) given by (11) is a normalized function in the range −π/2 ≤ x ≤ π/2 and its known values ψq(0) and ψq(xmin) further replace the corresponding unknown values for the approximation (3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The requirement for (30) to be satisfied at x = 0 yields ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Dq = ˜ψ2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='q(0) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='λm(q+m) (p) − λm(q+m) (˜pq) + < z >q (cq − α) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(31) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='10 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='With the help of thus defined P2n(x) we calculate from (3) (with taking into ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='account that P ′ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n(0) = 0 yielding (8)) the wave function at xmin ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='ψ2n(xmin) = ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='B2n ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='P2n(xmin) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='cos ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8eb ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8ed ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='xmin ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='dξ P2n(ξ) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f6 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f8 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(32) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='As a result we obtain ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='B2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n = ψ2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n(xmin)D2n ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψ2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n(xmin) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='cos−2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8eb ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8edD2n ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='xmin ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='� ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='dξ ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='˜ψ2 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2n(ξ) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f6 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='\uf8f8 ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='(33) ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Then the expression for the two-dimensional generalization of (9) takes the ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='form ' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='k(β,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ω) ≈ 1 Z(β,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ω) �1 2 � n ∞ � j=0 exp � −βΛj 2n(ω) � ψ2 2n(xmin)D2n ˜ψ2 2n(xmin) × cos−2 \uf8eb \uf8edD2n xmin � 0 dξ ˜ψ2 2n(ξ) \uf8f6 \uf8f8 + ∞ � l=2N+2 ∞ � j=0 exp � −βΛj l (ω) �� (34) It should be stressed that the summation over j yields the same factor as that in the partition function Z(β,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ω) and as a result they are canceled out.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Substituting (25) and (31) in (34) we finally obtain k(β, ω) ≈ \uf8f1 \uf8f2 \uf8f3 ∞ � q=0 e −β � λm(q+m)(p)− (cq)2 2ω2 �\uf8fc \uf8fd \uf8fe −1 �1 2 N � n=0 e −β � λm(2n+m)(p)− (c2n)2 2ω2 � × cos−2 �� λm(2n+m) (p) − λm(2n+m) �� p2 − α < z >2n � + < z >2n (c2n − α) × ¯S2 m(2n+m) �� p2 − α < z >2n;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 0 � xmin � 0 dξ cos−1 ξ ¯S2 m(2n+m) �√p2 − α < z >2n;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin ξ � � × ¯S2 m(2n+m) �√p2 − α < z >2n;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 0 � ¯S2 m(2n+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin xmin) ¯S2 m(2n+m) �√p2 − α < z >2n;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin xmin � × � λm(2n+m) (p) − λm(2n+m) �� p2 − α < z >2n � + < z >2n (c2n − α)+ ∞ � l=2N+2 e −β � λm(l+m)(p)− (cl)2 2ω2 �� (35) 11 where < z >2n is given by (21).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The sum over n is that over the doublets below the barrier top (see the discussion below (2)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 5 Results and discussion Notwithstanding to be cumbersome the formula (35) is easily programmed in Mathematica because the crucial elements λm(q+m) (p) and ¯Sm(q+m) (p;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' s) are implemented in this software package.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We take the rate constant k(β, ωref) for the internal stretching mode of the heavy atoms in the Zundel ion (with a fixed frequency ωref) as a natural reference point.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For this object there are potential energy surfaces for several ROO as a result of quantum chemical ab initio calculations [45], [46].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the cases of HB in the Zundel ion with ROO = 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 A, ROO = 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='6 A and ROO = 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='7 A the authors of [20] provide the estimates of the dimensional coupling constant λ (a21 in their Table.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1) as 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' and 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='05 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the dimensional frequency Ω/2 (a02 in their Table.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1) they present the value 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='039 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' for all three distances.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' From here we obtain the reference value of α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='6 at ROO = 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 A and α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 at ROO = 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='7 A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Also from the above results of [20] we obtain that the reference value for the dimensionless frequency of O-O stretching mode is ωref = 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the present article we are interested in the effect of the external vibration on the tunneling process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' To make the contribution into PT rate constant from the over-barrier transition to be negligible compared with the tunneling one even at T = 400 K (β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345) we restrict ourselves by the case of PT for HB in the Zundel ion with very high barrier.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For this reason we consider ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A from data of [46].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' TDWP for this case is depicted Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We carry out the parametric analysis of PT rate constant for HB in the Zundel ion with large ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A taking the above mentioned reference value α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 and varying ω in the range 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='005 ≤ ω ≤ ωref.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In this case there are three doublets below the barrier top (see Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1) that means N = 2 in (35).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the calculations of the rate constant we also take into account two levels above the barrier top (i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', replace ∞ in (35) by Nmax = 7) to make sure that the contribution of the over-barrier transition can be discarded.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 shows that at decreasing the frequency from the reference value ωref we obtain the monotonic increase of PT rate constant in agreement with the conclusion of [28].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' However there is a critical value of the frequency ωc (for α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 this value is ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='01125) below which a drastic change of the behavior takes place.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3, Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 and Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 the dependence of PT rate constant on the frequency of the oscillator at ω < ωc is depicted.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For a given value of the coupling constant α at the corresponding ωc there is Λ0 1 = Λ0 0 and a reversal in the total energy levels takes place (the energy levels of TDWP do not depend on ω and retain their natural order ǫq+1 > ǫq).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' At ω > ωc we have the normal sequence Λ0 2n+1 > Λ0 2n where n = 0, 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' while at ω < ωc 12 \uf750 \uf750 \uf750 \uf750\uf750\uf750 \uf750 \uf750 \uf750 \uf750 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 log10 ω 9 8 7 6 5 log10 k(β, ω) \uf750 β=0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345 (T=400 K) ▲ ▲ ▲ ▲ ▲ ▲ ▲ 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 log10 ω 9 8 7 6 5 log10 k(β, ω) ▲ β=0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='069 (T=200 K) Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dependence of proton transfer rate constant on the frequency of the external oscillator above the critical value ω > ωc in the Zundel ion H5O+ 2 (oxonium hydrate) with ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The critical frequency is ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='01125 for the value of the coupling constant α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 between the proton coordinate and that of the oscillator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' \uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='9 log10 ω 5 0 5 10 15 log10 k(β, ω) \uf750 β=0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345 (T=400 K) Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dependence of proton transfer rate constant on the frequency of the external oscillator below the critical value ω < ωc in the Zundel ion H5O+ 2 (oxonium hydrate) with ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A at high temperature (T = 400 K (β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The critical frequency is ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='01125 for the value of the coupling constant α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 between the proton coordinate and that of the oscillator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Low resolution picture of the whole interval 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='005 < ω < ωc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' an anomalous picture Λ0 2n+1 < Λ0 2n occurs at first for the ground state doublet (n = 0) and at further decrease of the frequency for higher ones below the barrier top (see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the case for ωmax in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' This transformation leads to an extraordinary alteration in the behavior of PT rate constant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3, Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 and Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 vividly exhibit that in this case there are very rich manifestations of resonant activation, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', the bell-shaped peaks of PT rate enhancement by the external vibration at its symmetric coupling to the proton coordinate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The height of the main peak at ωmax = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='006429109800232905 is temperature dependent (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', k(0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='046, ωmax)/k(0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='046, ωref) = 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='31 · 1022 at T = 300K and k(0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345, ωmax)/k(0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345, ωref) = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='13 · 1023 at T = 400K).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 shows that 13 \uf750 \uf750\uf750\uf750\uf750\uf750\uf750\uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750\uf750 \uf750 \uf750 \uf750 \uf750\uf750\uf750 \uf750 \uf750\uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 \uf750 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='14 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='12 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='10 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='08 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='06 log10 ω 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 log10 k(β, ω) \uf750 β=0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345 (T=400 K) Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dependence of proton transfer rate constant on the frequency of the external oscillator below the critical value ω < ωc in the Zundel ion H5O+ 2 (oxonium hydrate) with ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A at high temperature (T = 400 K (β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The critical frequency is ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='01125 for the value of the coupling constant α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 between the proton coordinate and that of the oscillator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' High resolution picture of the interval 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00693 < ω < 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='009.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ▲▲ ▲▲ ▲▲▲▲ ▲▲▲ ▲▲▲▲▲▲ ▲ ▲▲▲▲▲▲▲▲ ▲▲▲▲▲▲▲▲ ▲ ▲ ▲ ▲ ▲ 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='2 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='9 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='8 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='7 log10 ω 5 0 5 10 15 log10 k(β, ω) ▲ β=0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='069 (T=200 K) Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dependence of proton transfer rate constant on the frequency of the external oscillator below the critical value ω < ωc in the Zundel ion H5O+ 2 (oxonium hydrate) with ROO = 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0 A at low temperature (T = 200 K (β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='069).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The critical frequency is ωc ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='01125 for the value of the coupling constant α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 between the proton coordinate and that of the oscillator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' at high temperature β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='0345 the approach to the main peak from the side of higher frequencies is not smooth.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' There is a sequence of comb-like regions of increasing intensity with the decrease of the frequency ω (see Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 for higher resolution picture).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The intensity of these combs decreases with the decrease of temperature and at β = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='069 they are not discernable (see Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='5).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' At α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 and ω < ωc the ground state doublet approaches the bottom of TDWP (see, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='1) and at ω < 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='005 the former becomes below the latter.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' By attaining the resonance condition ωmax one can obtain a very efficient mechanism of PT rate enhancement.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 we have the acceleration up to 23 orders of magnitude compared with the reference value ωref = 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 14 The mathematical reason for the phenomenon of such PT resonance acti- vation is in the fact that the function ¯Sm(2n+m) �� p2 − α � −c2n ω2 � ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' sin xmin � taking place in the denominators of (35) becomes extremely small for the second doublet n = 1 at ω = ωmax.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In our opinion the descriptive physical origin of the phenomenon can be revealed from the following empirical obser- vation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Let us consider the wave functions in the left and the right wells for the j-th doublet (j = 1, 2, 3) defined as usual ψ(j) R = 1/ √ 2 � ψ(j) + − ψ(j) − � and ψ(j) L = 1/ √ 2 � ψ(j) + + ψ(j) − � respectively where ψ(j) ± are given by (11).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Here + means the upper energy level in the doublet while − means the lower one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Then we recall the notion of the Rabi frequency in energetic units (multiplied by the Planck constant) as the module of the interaction energy, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', that of the product of the electromagnetic field strength and the matrix element of the dipole moment for the transition between the corresponding energy lev- els.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dimensional resonance condition Ef − Ei = ℏΩRabi if =| Hint | in the dimensionless form is ǫf − ǫi = √ 2δ ωRabi if =| hint |.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Analogously we equate the difference between the energy levels ǫ(j) + − ǫ(j) − in the j-th doublet and the module of the matrix element of the interaction energy term | αz sin2 x | from (14) with the functions ψ(j) R and ψ(j) L .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For sin2 x we take the value of its matrix element < ψ(j) R | sin2 x | ψ(j) L >= π/2 � −π/2 dx ψ(j) R sin2 x ψ(j) L (36) For z we take the average < z >− given by (21), i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', < z >−= −c(j) − /ω2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' As a result we have an empirical relationship ǫ(j) + − ǫ(j) − = α | −c(j) − < ψ(j) R | sin2 x | ψ(j) L >| ω2 (37) From (37) we obtain the resonance frequency ω(j) ± ω(j) ± = � � � � �α | −c(j) − < ψ(j) R | sin2 x | ψ(j) L >| ǫ(j) + − ǫ(j) − (38) At α = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='3 and δ = 1/8 we have for j = 2, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', for the second doublet ω(2) ± = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00673 which is rather close to ωmax ≈ 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00643 for the main peak.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In our opinion such quantitative agreement can not be fortuitous.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It suggests the physical interpretation of PT resonant activation as an analog of the Rabi transition between the left and the right wells under the influence of the vibra- tion with a suitable frequency applied to the proton in DWP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The case j = 1 15 yields the resonance frequency ω(1) ± = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00795 which is within the range of the right comb-like region in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Constructing various matrix elements between wave functions of different doublets for both wells ψin R = 1/ √ 2 (ψi − ψn) and ψlm L = 1/ √ 2 (ψl + ψm) yields ǫ(j) + − ǫ(j) − = α | −ck < ψin R | sin2 x | ψlm L >| ω2 (39) where j = 1, 2, 3 and {k, i, n, l, m = 0, 1, 2, 3, 4, 5}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Then we obtain for the third doublet j = 3 the resonance frequencies: 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00722 at {l = 2, m = 5, i = 1, k = n = 0};' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00725 at {k = l = 0, m = 3, i = 1, n = 4};' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00753 at {l = 1, k = m = 4, i = 2, n = 5} which are within the range of the left comb- like region in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Constructing various matrix elements between wave func- tions of different doublets for the left well yields ǫ(j) + − ǫ(j) − = α | −ck < ψlm L | sin2 x | ψl′m′ L >| ω2 (40) Then we obtain for the third doublet j = 3 the resonance frequencies: 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00787 at {l = 1, k = m = 4, l′ = 5, m′ = 4} which is within the range of the right comb- like region in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4 and 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='00723 at {l = 0, m = 3, l′ = 4, k = m′ = 5} which is within the range of the left comb-like region in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In our opinion these numerous resonance frequencies provide qualitative explanation of severe os- cillations in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Also in this connection it is worthy to note that for the symmetric mode cou- pling (Hint = λZX2) the effect of resonant activation results from the term − (cq)2 /2ω2 in the total energy levels Λk q (19).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The energy levels of TDWP ǫq are re-normalized due to the coupling of the proton coordinate to the oscilla- tor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For anti-symmetric (Hint = λZX) and squeezed (Hint = λZ2X2) mode couplings this effect is absent.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the former case the coupling strength is zero c{as} q = 0 due to the symmetry of the wave functions [25] that leads to the actual lack of the crucial term − � c{as} q �2 / (2ω2) in the formula (19) for Λk q.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the latter case the expression for Λk q [25] Λk q|{sq} ≈ λm(q+m) (p) + 1 2 − m2 − p2 + (4k + 1) � � � �δ � ω2 + 2c{sq} q � 2 (41) does not contain the required term at all.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For instance the interaction of the proton in HB with an IR laser field in the dipole approximation (the dipole moment d ∝ x) belongs to the anti-symmetric type and does not fit our 16 requirement for PT resonant activation by a low-frequency vibration (high- frequency Rabi transitions between different doublets stimulated by an IR laser field certainly can considerably interfere PT process).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Only taking into account that a realistic dipole moment contains the appropriate higher or- der contributions (d ∝ x + const x2 + .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=') may provide the required type of interaction in this case.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We conclude that the suggested approach enables one to obtain an analytically tractable expression for proton transfer rate constant in a hydrogen bond.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' It is based on the Schr¨odinger equation with the model Hamiltonian taking into account only the proton coordinate and an external oscillator coupled to it (the heavy atoms stretching mode, a low-frequency vibration of the protein scaffold in an enzyme, etc).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The literature data from quantum chemical ab initio calculations of the potential energy surface are transformed into the parameters of the model trigonometric double-well potential.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' For the two- dimensional Schr¨odinger equation with this potential the analytic solution within the framework of the standard adiabatic approximation is available.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The parameters of the model for the Zundel ion in the case of the heavy atoms stretching mode are extracted from the literature data on IR spectroscopy and serve as a reference point.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The approach yields the pronounced resonant effect of proton transfer acceleration in some frequency range of the oscillator (below the corresponding critical value of the frequency) at its symmetric coupling to the proton coordinate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The phenomenon is absent for anti-symmetric and squeezed mode couplings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 6 Appendix In dimensional units the one-dimensional SE for a quantum particle with the reduced mass M (proton in our case of usual HB or deuterium in the case of a deuterated HB) has the form d2ψ(X) dX2 + 2M ℏ2 [E − V (X)] ψ(X) = 0 (42) where −L ≤ X ≤ L and V (X) is a DWP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The latter is assumed to be infinite at the boundaries of the finite interval for the spatial variable X = ±L.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dimensionless values for the distance x, the potential U(x) and the energy ǫ are introduced as follows x = πX 2L ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' U(x) = 8ML2 ℏ2π2 V (X);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ǫ = 8ML2E ℏ2π2 (43) where −π/2 ≤ x ≤ π/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' As a result we obtain the dimensionless SE (1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In 17 the case of the trigonometric DWP (10) the transformation formulas for the parameters {m, p} into {B, D} (B is the barrier height and D is the barrier width) are [24] p = √ B 1 − [cos (D/2)]2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' m2 − 1 4 = B [cos (D/2)]4 � 1 − [cos (D/2)]2�2 (44) The Hamiltonian of the two-dimensional SE includes the spatial variable Z (e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=', that for the reduced mass of the heavy atoms in HB which in the case of the Zundel ion is the O-O stretching mode) of the harmonic potential ΩZ2/2 with the frequency Ω.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' We introduce the dimensionless distance x = πX/ (2L) where −π/2 ≤ x ≤ π/2 and dimensionless coordinate z = πZ/ (2L) where −∞ < z < ∞.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The dimensionless coupling constant α in (14) for the symmet- ric mode coupling (this case was proved in [20] to be pertinent for the Zundel ion), the dimensionless inverse temperature β in (20), (34) and (35) and the dimensionless frequency ω in (14) are α = 26λML5 ℏ2π5 ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' β = ℏ2π2 8ML2kBT ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' ω = 4√2MµL2Ω ℏπ2 ;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' µ = M1M2 M1 + M2 (45) Here λ is a dimensional coupling constant for the case of the symmetric mode coupling term (λZX2) and µ is the reduced mass of the heavy atoms in HB A1 − H · · · A2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' In the case of the Zundel ion it is µ = MO/2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' As a result δ in (14) is δ = M/µ = 2M/MO.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Taking the proton mass M = 1 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u and that of the oxygen atom MO = 16 a.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='u.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' we have δ = 1/8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Acknowledgements.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The author is grateful to Prof.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Yu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='F.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Zuev for helpful dis- cussions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' The work was supported from the government assignment for FRC Kazan Scientific Center of RAS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 18 References [1] N.' metadata={'source': 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metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='E.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Sitnitsky, J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Mol.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Spectr.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 372 (2020) 111347.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 19 [26] D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 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metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Smedarchina, W.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Siebrand, A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Fern´andez-Ramos, J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Chem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Phys.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 148 (2018) 102307.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} 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metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='-H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' Dong, J.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Math.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='Chem.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' 60 (2022) 605- 612.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content=' [39] A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/9dE4T4oBgHgl3EQfDQsU/content/2301.04867v1.pdf'} +page_content='E.' 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+Depsys, Puidoux - Switzerland + +manijeh.alipour@depsys.com +omid.mousavi@depsys.com + +ABSTRACT +Renewable energy productions and electrification of +mobility are promising solutions to reduce greenhouse gas +emissions. Their effective integration in a power grid +encounters several challenges. The uncertain nature of +renewable energy productions as well as stochastic +consumptions of electric vehicles introduce remarkable +intermittency to a distribution grid and results in bi- +uncertain characteristics of both supply and demand sides. +One way to verify the secure grid operation within +acceptable voltage and loading levels is to assess its +required flexibility considering possible boundaries of +uncertain variables. In this paper, first a comprehensive +linear model of distribution grid considering all pertaining +constraints is presented. Then, a flexibility estimation +technique is proposed based on the feasibility study of the +uncertain space of photovoltaic power productions and +load +containing +electric +vehicles. +The +proposed +methodology uses grid monitoring data to determine grid +state and to model uncertain parameters. The model is +applied on a real low voltage (LV) system equipped with +grid monitoring devices. +INTRODUCTION +The deployment of renewable energy productions has +many advantages, comprising economic convenience, +reducing the reliance on fossil fuel markets (especially, gas +and oil) and environmental friendliness. In addition, the +wide penetration of renewable energy sources accelerates +occupation in the EU, by job creation in different ‘green’ +technologies. Aim behind the European Green Deal +(COM(2019) 640 final) is to be the world’s first climate- +neutral continent by 2050. In spite of renewable +generation’s significant advantages, it has the defects of +uncertainty and fluctuation. Besides to renewable +generations, electric vehicles as a new variable load +increase the intermittency of distribution grid and leads to +bi-uncertain characteristics of both demand and supply +sides. With the increased penetration of these uncertainty +sources, the modern power system is confronted with a +challenge to preserve the reliability, security, and quality +of supply. Thus, a more flexible distribution grid is +required. +The distribution grid flexibility can be defined from +different perspectives [1]. In [2], the flexibility is specified +as the degree to which a system can change its electricity +consumption and production in response to anticipated or +unanticipated variabilities. The flexibility envelope +method is presented in [3] to assess the flexibility potential +of individual power system assets and their aggregation at +the system level. A flexibility measure is developed in [4] +which indicates the largest uncertainty deviation that a +system can bear. In [5] an algorithm is proposed which +allocates aggregate-level control decisions amongst +individual +systems +economically. +Concerning +the +flexibility estimation of distribution grids, an index is +proposed in [6] that is related to specific viewpoints such +as power regulation ability and energy balance ability of +distribution grids. In [7] the net load uncertainty is +considered in the flexibility assessment of distribution +grids. +The secure grid operation can be verified by assessing the +required flexibility considering boundaries of uncertain +variables. A hyper-rectangle is implemented for heat +exchanger networks [8] to define the multi-dimensional +region of uncertain variables. In this paper, the flexibility +and the lack of flexibility are quantified by determining +acceptable boundaries of uncertain parameters in +distribution grids. +A large portion of uncertainty resources are not monitored +by the Distribution System Operator (DSO) and as a +consequence, the level of available flexibility of the grid +as well as the lack of flexibility caused by the uncertain +resources are not identified. In such a situation, the power +flows from unmonitored and uncontrolled resources may +cause voltage violations and congestions. Therefore, the +monitoring of grid and the control of resources connected +to the grid are vital for the secure operation of distribution +grid. +The DSOs around the world are going through the roll-out +of smart metering and grid monitoring devices [9, 10]. +However, equipping all the nodes of distribution grid with +monitoring devices is practically impossible due to costs +of required underlying infrastructure. In addition, although +all the grid topology information is usually available in the +DSO’s Geographic Information System (GIS), a trustable +and up-to-date data of LV grid topology and parameters is +not available to take decisions for the secure grid operation +[11]. To face these challenges, the grid sensitivity +coefficients of a subset of grid nodes can be used as an +approximation of the power flow model. The sensitivity +coefficients can be calculated between a plurality of +measurement nodes without using the information of grid +parameters [13], hereafter called model-less approach. +This approach significantly reduces the required number +of monitored nodes, thus reducing the cost of required grid +monitoring infrastructure, and does not rely on the +availability of an accurate and up-to-date grid parameters. +This paper proposes a flexibility estimation model for +distribution grids. The main contributions are as follows: +1) The proposed flexibility estimation method is based on +the feasibility study of the uncertain space of load +containing electric vehicles and photovoltaic powers. It +allows evaluating the flexibility and lack of flexibility +based on the coverage of the feasible space to the + +CIRED CIRED workshop on E-mobility and power distribution systems +Porto, 2-3 June 2022 + +Paper n° 1347 + + +CIRED 2022 Workshop +2/4 +uncertain region. +2) The projection of each direction in the uncertain space +to the feasible space is illustrated and investigated. The +illustrated projection to the feasible space can assist in +determining the reason of flexibility inadequacy. +3) The linear power flow model based on the sensitivity +coefficients is used to model the grid operation +constraints. It properly accounts for the secure grid +operation within acceptable voltage levels and without +congestions. +4) The proposed model for the calculation of the +flexibility index is a linear and convex mathematical +optimization problem that can be solved efficiently +with non-commercial solvers and the optimality of the +solution is guaranteed. +The remaining parts of the paper is structured as following. +Next section provides the definition of distribution grid +flexibility. Then, the proposed mathematical formulation +is presented. The results of applying the method on a real +LV grid are evaluated. Finally, the conclusions and +outcomes are discussed. +THE FLEXIBILITY OF DISTRIBUTION GRID +In this paper, the flexibility of distribution grid is described +as the capability of distribution grid to effectively cope +with multiple uncertainties of grid operation. Fig. 1 +illustrates the structure of the proposed flexibility +estimation algorithm in a LV distribution grid. The power +grid contains Electric Vehicles (EV), EV charging +stations, photovoltaic arrays and commercial load. In the +proposed method, grid monitoring data are used to +calculate the grid state and the sensitivity coefficients as +well as to model uncertain parameters. Fig. 1 shows the +way that flexibility quantification is realized using the grid +monitoring data. + +Flexibility assessment and quantification +MV/LV +DSO + Real-time data acquisition +Monitoring device + +Fig. 1. Proposed monitoring based flexibility +quantification structure + +In fact, the proposed model is accomplished by detailed +and accurate information of the resources from the grid +monitoring facilities. Fig. 2 shows the concept of proposed +flexibility quantification method. The uncertain space is +calculated using historic data and prediction methods. The +margin of feasible space characterizes the maximum +feasible deviation from the expected operation point ‘O’. +Any operation point in the uncertain space can be +characterized by two components: the direction vector and +the normalized variation value. The direction matrix +expresses the direction vector, in which each diagonal +element indicates an uncertain variable, and the range of +element’s value is [−1, 1] [12]. In order to guarantee that +direction matrix elements represent a unique direction, at +least one of the direction matrix elements must be set to - +1 or 1. This will refrain the duplication of direction +matrices with the same direction like diag(1, 0.5) and +diag(0.8, 0.4). +Any point outside the feasible region indicates an +infeasible grid operation point where the technical +constraints of the grid are not satisfied. The minimum +feasible deviation direction stands for the critical direction. +The boundary point, shown by ‘C’ in Fig.2, corresponding +to the critical direction is the flexibility index which +reveals the adequacy or insufficiency of flexibility +resources in the system. +O +C +Feasible Region +Max +pv +P +min +pv +P +min +lP +Max +lP +Uncertain Region +pv +P +lP +pv +P +lP + +Fig. 2. The concept of the proposed flexibility +quantification method +MATHEMATICAL FORMULATION +A mathematical optimization problem is formulated to +determine the feasible space. The objective function is the +minimum value of maximum feasible variation in the +direction D (𝛽𝐷) of feasible operation region. In addition, +the flexibility (F) is defined as the minimum value of 𝛽𝐷. + +𝐹 = 𝑚𝑖𝑛𝛽𝐷 +(1) +𝛽𝐷 = 𝑚𝑎𝑥(𝛽) +(2) +𝑋 = 𝑋̃ + 𝛽𝐷∆𝑋 +(3) + +where 𝑋 and 𝑋̃ represent the uncertain parameter and its +expected value which are distribution grid’s load and PV +generation. ∆𝑋 indicates the expected value and +maximum/minimum value of uncertain parameter’s +difference. If the flexibility index is equal to one (F=1), the +flexibility resources are enough for the secure operation of +the grid. In addition, it means that feasible region covers +the uncertain region. However, if the flexibility index is +less than one (F <1), there is not sufficient margin for the +technically secure grid operation and additional flexibility +resources are required. The direction matrix D is a +diagonal matrix that can be defined as: +𝐷 = +[ + + + 𝑑1 +𝑑2 +⋱ +𝑑𝑛] + + + + +(4) + +CIRED CIRED workshop on E-mobility and power distribution systems +Porto, 2-3 June 2022 + +Paper n° 1347 + + +CIRED 2022 Workshop +3/4 +where diagonal element di is the direction on the ith +uncertain parameter and n is the number of uncertain +parameters. +For the flexibility estimation a linear power flow model is +used based on the sensitivity coefficients calculated using +the model-less approach. The formulation is described +below. +Δ𝑉𝑚 = ∑ [𝐾𝑚,𝑛 +𝑉𝑃 Δ𝑃𝑛 + 𝐾𝑚,𝑛 +𝑉𝑄 Δ𝑄𝑛] +𝑛 + +(5) +Δ𝐼𝑙 = ∑ [𝐾𝑙,𝑛 +𝐼𝑃Δ𝑃𝑛 + 𝐾𝑙,𝑛 +𝐼𝑄Δ𝑄𝑛 ] +𝑛 + +(6) +𝑉𝑚𝑖𝑛 ≤ 𝑉𝑚 +0 + ∆𝑉𝑚 ≤ 𝑉𝑚𝑎𝑥 +(7) +−𝐼𝑚𝑎𝑥 ≤ 𝐼𝑙 +0 + ∆𝐼𝑙 +≤ 𝐼𝑚𝑎𝑥 +(8) +∆𝑉𝑚 = 𝑉𝑚 − 𝑉𝑚 +0 +(9) +∆𝐼𝑙 += 𝐼𝑙 − 𝐼𝑙 +0 +(10) +0 ≤ 𝑆𝑔𝑟𝑖𝑑 ≤ 𝑠𝑇𝑟𝑎𝑓𝑜 +𝑚𝑎𝑥 +(11) +The voltage and current sensitivity coefficients are used in +equations (5) and (6), respectively, to model the impacts +of nodal active and reactive power changes (Δ𝑃𝑛 and +Δ𝑄𝑛 ) on the nodal voltage variations (Δ𝑉𝑚) and branch +current variations (Δ𝐼𝑙). The sensitivity coefficients, i.e., +𝐾𝑉𝑃, 𝐾𝑉𝑄, 𝐾𝐼𝑃𝑎𝑛𝑑 𝐾𝐼𝑄, are computed around the grid +operation point corresponding to voltage 𝑉𝑚 +0 and current +𝐼𝑙,𝑡 +0 . The voltage level at each node and the branch current +should be within the allowed limits as given in (7) and (8), +respectively. The voltage and current deviations can be +calculated as given by equations (9) and (10). The +constraint (11) limits the apparent power flow in the +MV/LV transformer (𝑆𝑔𝑟𝑖𝑑) by the capacity of transformer +(𝑠𝑚𝑎𝑥 +𝑇𝑟𝑎𝑓𝑜). +RESULTS AND DISCUSSIONS +In this section, the performance of proposed flexibility +calculation method is tested and validated in a modified +LV grid of Switzerland. The LV grid includes a PV unit +with known capacity to the DSO, and connected to bus 101 +with the capacity of 72 kVA. Further, EVSEs are +connected to the buses 102 and 106. The grid with several +GridEye monitoring devices is illustrated in Fig. 3. The +real-time information of the aggregated loads and +productions are provided by the GridEye monitoring +devices. Figs. 4 and 5 illustrate the 10-minute granularity +of PV generation and load profiles used in the simulations. +In this work, the DSO’s objective is to estimate the +distribution grid’s flexibility value, the value of flexibility +insufficiency and the periods with insufficient flexibility. + + +Fig. 3. The LV grid topology with grid monitoring devices + +Fig. 4. Load profile of LV grid + + +Fig. 5. PV generation at node 101 + +Table 1 provides the simulation results for time slots that +there is insufficient flexibility in the grid, considering the +uncertainties of load and PVs. For the remaining time slots, +the flexibility value is equal to one indicating that there is +adequate flexibility in the grid. At the time periods from +09:20 to 10:10 and from 17:40 to 18:20 on Nov 28, 2021 +due to the high level of load and the thermal capacity of +lines, the flexibility is less than one. The uncertain and +feasible regions for two sample time slots are depicted in +Figs. 6 and 7. The value of flexibility at time slot 18:00 +(Fig. 7) has the lowest value 0.49. In this time slot, the load +level is higher than the average consumption and the PV +generation has the lowest value. Moreover, at time slot +09:40 (Fig. 6), the load is at its highest value and the value +of flexibility is 0.74. At this time slot, although the load +has the highest value, the flexibility index is higher than +the one at time slot 18:00. The higher level of flexibility is +due to the high level of PV generation at this time which is +20.4 kW. + + +CIRED100 +103 +104 +101 +Low voltage grid +105 +102 +EVSE +Grid monitoring device +EVSE240- +220 +(M)peo +200 +180 +160- +00:00 +06:00 +12:00 +18:00 +Nov28,2021 +Time20- +15- +PV (kW) +10- +5- +00:00 +06:00 +12:00 +18:00 +Nov28,2021 +Time CIRED workshop on E-mobility and power distribution systems +Porto, 2-3 June 2022 + +Paper n° 1347 + + +CIRED 2022 Workshop +4/4 +Table 1. Flexibility results for insecure time slots +Time slot +Flexibility +Nov 28, 2021, 09:20 +0.93 +Nov 28, 2021, 09:30 +0.84 +Nov 28, 2021, 09:40 +0.74 +Nov 28, 2021, 09:50 +0.84 +Nov 28, 2021, 10:00 +0.80 +Nov 28, 2021, 10:10 +0.80 +Nov 28, 2021, 17:40 +0.67 +Nov 28, 2021, 17:50 +0.57 +Nov 28, 2021, 18:00 +0.49 +Nov 28, 2021, 18:10 +0.72 +Nov 28, 2021, 18:20 +0.90 + + +Fig. 6. Feasible and uncertain regions on Nov 28, 2021 at +09:40. + + +Fig. 7. Feasible and uncertain regions on Nov 28, 2021 at +18:00. +CONCLUSIONS +In this paper, a flexibility estimation methodology is +proposed taking into account the feasible grid operation +region and the uncertain region of load containing electric +vehicle and photovoltaic powers. The method is applicable +by using the information of grid monitoring devices. The +simulation results on the LV grid illustrated the inadequate +flexibility in time slots with the higher level of load and +the lower level of PV generation than the average level. +However, the model can detect other factors like voltage +limit violation regarding the grid constraints that limit the +grid’s flexibility. The outcome of proposed model informs +the grid operator regarding the time slots with sufficient +and insufficient flexibility along with the value of +insufficiency considering the uncertainty space. + +Acknowledgments +This project is supported by the European Union’s Horizon +2020 programme under the Marie Sklodowska-Curie grant +agreement no. 101026259. + +REFERENCES + +[1] North American Electric Reliability Corporation, +"Accommodating high levels of variable generation" +(North American Electric Reliability Corp, 2009) +[2] International Energy Agency, "Harnessing variable +renewables: A guide to the balancing challenge" +(Organisation for Economic Co-operation and +Development, 2011) +[3] H. Nosair, F. Bouffard, 2015. "Flexibility envelopes for +power +system +operational +planning", +IEEE +Transactions on Sustainable Energy, 6(3), pp.800- +809. +[4] J. Zhao, T. Zheng, E. Litvinov, 2015. "A unified +framework for defining and measuring flexibility in +power system". IEEE Transactions on power systems, +31(1), 339-347 +[5] F.L. Müller, J. Szabó, O. Sundström, and J. Lygeros, +2017. "Aggregation and disaggregation of energetic +flexibility from distributed energy resources", IEEE +Transactions on Smart Grid, 10(2), 1205-1214.. +[6] F. Chen, C. Huang, L. Wang, C. Zhu, C. Wang, and +Xie, N., 2017, November. "Flexibility evaluation of +distribution network with high penetration of variable +generations." In 2017 IEEE Conference on Energy +Internet and Energy System Integration (EI2), 1-6 +[7] A. Majzoobi, A. Khodaei, 2016. "Application of +microgrids in supporting distribution grid flexibility." +IEEE Transactions on Power Systems, 32(5), +pp.3660-3669. +[8] Li, J. , Du, J. , Zhao, Z. , et al.: "An Efficient Method +for Flexibility Analysis of Large -scale Nonconvex +Heat Exchanger Networks", Industrial & Engineering +Chemistry Research , 2015, 54, (43), 10757 -10767 +[9] European Commission. "Smart Metering deployment +in the European Union", http://bit.ly/2MbDfeL, +accessed Feb 2021. +[10] Swiss Federal Office of Energy. "Smart Grids", +http://bit.ly/3pB8vS5, accessed Feb 2021 +[11] L. Richaud, R. Pellerej, C. Benoit, and E .Ramos, +CIRED 2019, "Analysis of voltage patterns for +topology identification and GIS correction". +[12] L. Jilong, J. Du, Z. Zhao, and P. Yao, 2015, "Efficient +method for flexibility analysis of large-scale +nonconvex heat exchanger networks. " Industrial & +Engineering Chemistry Research 54, no. 43, 10757- +10767. +[13] Method of determining mutual voltage sensitivity +coefficients between a plurality of measuring nodes of +an electric power network, US patent, 0003811, Jan. +2, 2020. + + +CIRED300- +Load (kW) +Uncertain region +250 +Feasible region +200- +16 +18 +20 +22 +24 +26 +PV(kW)300- +Load (kW) +Uncertain region +250 +Feasible region +200 +16 +18 +20 +22 +24 +26 +PV(kW) \ No newline at end of file diff --git a/AtE2T4oBgHgl3EQfRQeF/content/tmp_files/load_file.txt b/AtE2T4oBgHgl3EQfRQeF/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..f3c7334ca03189a8fa39e06212b357ed654d8afd --- /dev/null +++ b/AtE2T4oBgHgl3EQfRQeF/content/tmp_files/load_file.txt @@ -0,0 +1,207 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf,len=206 +page_content='CIRED workshop on E-mobility and power distribution systems Porto, 2-3 June 2022 Paper n° 1347 CIRED 2022 Workshop 1/4 ESTIMATING REQUIRED FLEXIBILITY FOR SECURE DISTRIBUTION GRID OPERATION CONSIDERING THE UNCERTAINTIES OF EV AND PV Manijeh ALIPOUR Omid ALIZADEH-MOUSAVI Depsys, Puidoux - Switzerland Depsys, Puidoux - Switzerland manijeh.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='alipour@depsys.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='com omid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='mousavi@depsys.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='com ABSTRACT Renewable energy productions and electrification of mobility are promising solutions to reduce greenhouse gas emissions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Their effective integration in a power grid encounters several challenges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The uncertain nature of renewable energy productions as well as stochastic consumptions of electric vehicles introduce remarkable intermittency to a distribution grid and results in bi- uncertain characteristics of both supply and demand sides.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' One way to verify the secure grid operation within acceptable voltage and loading levels is to assess its required flexibility considering possible boundaries of uncertain variables.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In this paper, first a comprehensive linear model of distribution grid considering all pertaining constraints is presented.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Then, a flexibility estimation technique is proposed based on the feasibility study of the uncertain space of photovoltaic power productions and load containing electric vehicles.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The proposed methodology uses grid monitoring data to determine grid state and to model uncertain parameters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The model is applied on a real low voltage (LV) system equipped with grid monitoring devices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' INTRODUCTION The deployment of renewable energy productions has many advantages, comprising economic convenience, reducing the reliance on fossil fuel markets (especially, gas and oil) and environmental friendliness.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In addition, the wide penetration of renewable energy sources accelerates occupation in the EU, by job creation in different ‘green’ technologies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Aim behind the European Green Deal (COM(2019) 640 final) is to be the world’s first climate- neutral continent by 2050.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In spite of renewable generation’s significant advantages, it has the defects of uncertainty and fluctuation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Besides to renewable generations, electric vehicles as a new variable load increase the intermittency of distribution grid and leads to bi-uncertain characteristics of both demand and supply sides.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' With the increased penetration of these uncertainty sources, the modern power system is confronted with a challenge to preserve the reliability, security, and quality of supply.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Thus, a more flexible distribution grid is required.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The distribution grid flexibility can be defined from different perspectives [1].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In [2], the flexibility is specified as the degree to which a system can change its electricity consumption and production in response to anticipated or unanticipated variabilities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The flexibility envelope method is presented in [3] to assess the flexibility potential of individual power system assets and their aggregation at the system level.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' A flexibility measure is developed in [4] which indicates the largest uncertainty deviation that a system can bear.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In [5] an algorithm is proposed which allocates aggregate-level control decisions amongst individual systems economically.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Concerning the flexibility estimation of distribution grids, an index is proposed in [6] that is related to specific viewpoints such as power regulation ability and energy balance ability of distribution grids.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In [7] the net load uncertainty is considered in the flexibility assessment of distribution grids.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The secure grid operation can be verified by assessing the required flexibility considering boundaries of uncertain variables.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' A hyper-rectangle is implemented for heat exchanger networks [8] to define the multi-dimensional region of uncertain variables.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In this paper, the flexibility and the lack of flexibility are quantified by determining acceptable boundaries of uncertain parameters in distribution grids.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' A large portion of uncertainty resources are not monitored by the Distribution System Operator (DSO) and as a consequence, the level of available flexibility of the grid as well as the lack of flexibility caused by the uncertain resources are not identified.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In such a situation, the power flows from unmonitored and uncontrolled resources may cause voltage violations and congestions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Therefore, the monitoring of grid and the control of resources connected to the grid are vital for the secure operation of distribution grid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The DSOs around the world are going through the roll-out of smart metering and grid monitoring devices [9, 10].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' However, equipping all the nodes of distribution grid with monitoring devices is practically impossible due to costs of required underlying infrastructure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In addition, although all the grid topology information is usually available in the DSO’s Geographic Information System (GIS), a trustable and up-to-date data of LV grid topology and parameters is not available to take decisions for the secure grid operation [11].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' To face these challenges, the grid sensitivity coefficients of a subset of grid nodes can be used as an approximation of the power flow model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The sensitivity coefficients can be calculated between a plurality of measurement nodes without using the information of grid parameters [13], hereafter called model-less approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' This approach significantly reduces the required number of monitored nodes, thus reducing the cost of required grid monitoring infrastructure, and does not rely on the availability of an accurate and up-to-date grid parameters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' This paper proposes a flexibility estimation model for distribution grids.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The main contributions are as follows: 1) The proposed flexibility estimation method is based on the feasibility study of the uncertain space of load containing electric vehicles and photovoltaic powers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' It allows evaluating the flexibility and lack of flexibility based on the coverage of the feasible space to the CIRED CIRED workshop on E-mobility and power distribution systems Porto, 2-3 June 2022 Paper n° 1347 CIRED 2022 Workshop 2/4 uncertain region.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 2) The projection of each direction in the uncertain space to the feasible space is illustrated and investigated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The illustrated projection to the feasible space can assist in determining the reason of flexibility inadequacy.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 3) The linear power flow model based on the sensitivity coefficients is used to model the grid operation constraints.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' It properly accounts for the secure grid operation within acceptable voltage levels and without congestions.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 4) The proposed model for the calculation of the flexibility index is a linear and convex mathematical optimization problem that can be solved efficiently with non-commercial solvers and the optimality of the solution is guaranteed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The remaining parts of the paper is structured as following.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Next section provides the definition of distribution grid flexibility.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Then, the proposed mathematical formulation is presented.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The results of applying the method on a real LV grid are evaluated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Finally, the conclusions and outcomes are discussed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' THE FLEXIBILITY OF DISTRIBUTION GRID In this paper, the flexibility of distribution grid is described as the capability of distribution grid to effectively cope with multiple uncertainties of grid operation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 1 illustrates the structure of the proposed flexibility estimation algorithm in a LV distribution grid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The power grid contains Electric Vehicles (EV), EV charging stations, photovoltaic arrays and commercial load.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In the proposed method, grid monitoring data are used to calculate the grid state and the sensitivity coefficients as well as to model uncertain parameters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 1 shows the way that flexibility quantification is realized using the grid monitoring data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Flexibility assessment and quantification MV/LV DSO Real-time data acquisition Monitoring device Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Proposed monitoring based flexibility quantification structure In fact, the proposed model is accomplished by detailed and accurate information of the resources from the grid monitoring facilities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 2 shows the concept of proposed flexibility quantification method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The uncertain space is calculated using historic data and prediction methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The margin of feasible space characterizes the maximum feasible deviation from the expected operation point ‘O’.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Any operation point in the uncertain space can be characterized by two components: the direction vector and the normalized variation value.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The direction matrix expresses the direction vector, in which each diagonal element indicates an uncertain variable, and the range of element’s value is [−1, 1] [12].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In order to guarantee that direction matrix elements represent a unique direction, at least one of the direction matrix elements must be set to - 1 or 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' This will refrain the duplication of direction matrices with the same direction like diag(1, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='5) and diag(0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='8, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='4).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Any point outside the feasible region indicates an infeasible grid operation point where the technical constraints of the grid are not satisfied.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The minimum feasible deviation direction stands for the critical direction.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The boundary point, shown by ‘C’ in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='2, corresponding to the critical direction is the flexibility index which reveals the adequacy or insufficiency of flexibility resources in the system.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' O C Feasible Region Max pv P min pv P min lP Max lP Uncertain Region pv P lP pv P lP Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The concept of the proposed flexibility quantification method MATHEMATICAL FORMULATION A mathematical optimization problem is formulated to determine the feasible space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The objective function is the minimum value of maximum feasible variation in the direction D (𝛽𝐷) of feasible operation region.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In addition, the flexibility (F) is defined as the minimum value of 𝛽𝐷.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 𝐹 = 𝑚𝑖𝑛𝛽𝐷 (1) 𝛽𝐷 = 𝑚𝑎𝑥(𝛽) (2) 𝑋 = 𝑋̃ + 𝛽𝐷∆𝑋 (3) where 𝑋 and 𝑋̃ represent the uncertain parameter and its expected value which are distribution grid’s load and PV generation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' ∆𝑋 indicates the expected value and maximum/minimum value of uncertain parameter’s difference.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' If the flexibility index is equal to one (F=1), the flexibility resources are enough for the secure operation of the grid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In addition, it means that feasible region covers the uncertain region.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' However, if the flexibility index is less than one (F <1), there is not sufficient margin for the technically secure grid operation and additional flexibility resources are required.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The direction matrix D is a diagonal matrix that can be defined as: 𝐷 = [ 𝑑1 𝑑2 ⋱ 𝑑𝑛] (4) CIRED CIRED workshop on E-mobility and power distribution systems Porto, 2-3 June 2022 Paper n° 1347 CIRED 2022 Workshop 3/4 where diagonal element di is the direction on the ith uncertain parameter and n is the number of uncertain parameters.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' For the flexibility estimation a linear power flow model is used based on the sensitivity coefficients calculated using the model-less approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The formulation is described below.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Δ𝑉𝑚 = ∑ [𝐾𝑚,𝑛 𝑉𝑃 Δ𝑃𝑛 + 𝐾𝑚,𝑛 𝑉𝑄 Δ𝑄𝑛] 𝑛 (5) Δ𝐼𝑙 = ∑ [𝐾𝑙,𝑛 𝐼𝑃Δ𝑃𝑛 + 𝐾𝑙,𝑛 𝐼𝑄Δ𝑄𝑛 ] 𝑛 (6) 𝑉𝑚𝑖𝑛 ≤ 𝑉𝑚 0 + ∆𝑉𝑚 ≤ 𝑉𝑚𝑎𝑥 (7) −𝐼𝑚𝑎𝑥 ≤ 𝐼𝑙 0 + ∆𝐼𝑙 ≤ 𝐼𝑚𝑎𝑥 (8) ∆𝑉𝑚 = 𝑉𝑚 − 𝑉𝑚 0 (9) ∆𝐼𝑙 = 𝐼𝑙 − 𝐼𝑙 0 (10) 0 ≤ 𝑆𝑔𝑟𝑖𝑑 ≤ 𝑠𝑇𝑟𝑎𝑓𝑜 𝑚𝑎𝑥 (11) The voltage and current sensitivity coefficients are used in equations (5) and (6), respectively, to model the impacts of nodal active and reactive power changes (Δ𝑃𝑛 and Δ𝑄𝑛 ) on the nodal voltage variations (Δ𝑉𝑚) and branch current variations (Δ𝐼𝑙).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The sensitivity coefficients, i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=', 𝐾𝑉𝑃, 𝐾𝑉𝑄, 𝐾𝐼𝑃𝑎𝑛𝑑 𝐾𝐼𝑄, are computed around the grid operation point corresponding to voltage 𝑉𝑚 0 and current 𝐼𝑙,𝑡 0 .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The voltage level at each node and the branch current should be within the allowed limits as given in (7) and (8), respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The voltage and current deviations can be calculated as given by equations (9) and (10).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The constraint (11) limits the apparent power flow in the MV/LV transformer (𝑆𝑔𝑟𝑖𝑑) by the capacity of transformer (𝑠𝑚𝑎𝑥 𝑇𝑟𝑎𝑓𝑜).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' RESULTS AND DISCUSSIONS In this section, the performance of proposed flexibility calculation method is tested and validated in a modified LV grid of Switzerland.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The LV grid includes a PV unit with known capacity to the DSO, and connected to bus 101 with the capacity of 72 kVA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Further, EVSEs are connected to the buses 102 and 106.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The grid with several GridEye monitoring devices is illustrated in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The real-time information of the aggregated loads and productions are provided by the GridEye monitoring devices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Figs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 4 and 5 illustrate the 10-minute granularity of PV generation and load profiles used in the simulations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In this work, the DSO’s objective is to estimate the distribution grid’s flexibility value, the value of flexibility insufficiency and the periods with insufficient flexibility.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The LV grid topology with grid monitoring devices Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Load profile of LV grid Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' PV generation at node 101 Table 1 provides the simulation results for time slots that there is insufficient flexibility in the grid, considering the uncertainties of load and PVs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' For the remaining time slots, the flexibility value is equal to one indicating that there is adequate flexibility in the grid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' At the time periods from 09:20 to 10:10 and from 17:40 to 18:20 on Nov 28, 2021 due to the high level of load and the thermal capacity of lines, the flexibility is less than one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The uncertain and feasible regions for two sample time slots are depicted in Figs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 6 and 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The value of flexibility at time slot 18:00 (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 7) has the lowest value 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' In this time slot, the load level is higher than the average consumption and the PV generation has the lowest value.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Moreover, at time slot 09:40 (Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 6), the load is at its highest value and the value of flexibility is 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='74.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' At this time slot, although the load has the highest value, the flexibility index is higher than the one at time slot 18:00.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The higher level of flexibility is due to the high level of PV generation at this time which is 20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='4 kW.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' CIRED100 103 104 101 Low voltage grid 105 102 EVSE Grid monitoring device EVSE240- 220 (M)peo 200 180 160- 00:00 06:00 12:00 18:00 Nov28,2021 Time20- 15- PV (kW) 10- 5- 00:00 06:00 12:00 18:00 Nov28,2021 Time CIRED workshop on E-mobility and power distribution systems Porto, 2-3 June 2022 Paper n° 1347 CIRED 2022 Workshop 4/4 Table 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Flexibility results for insecure time slots Time slot Flexibility Nov 28, 2021, 09:20 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='93 Nov 28, 2021, 09:30 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='84 Nov 28, 2021, 09:40 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='74 Nov 28, 2021, 09:50 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='84 Nov 28, 2021, 10:00 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='80 Nov 28, 2021, 10:10 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='80 Nov 28, 2021, 17:40 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='67 Nov 28, 2021, 17:50 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='57 Nov 28, 2021, 18:00 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='49 Nov 28, 2021, 18:10 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='72 Nov 28, 2021, 18:20 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content='90 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Feasible and uncertain regions on Nov 28, 2021 at 09:40.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Feasible and uncertain regions on Nov 28, 2021 at 18:00.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' CONCLUSIONS In this paper, a flexibility estimation methodology is proposed taking into account the feasible grid operation region and the uncertain region of load containing electric vehicle and photovoltaic powers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The method is applicable by using the information of grid monitoring devices.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The simulation results on the LV grid illustrated the inadequate flexibility in time slots with the higher level of load and the lower level of PV generation than the average level.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' However, the model can detect other factors like voltage limit violation regarding the grid constraints that limit the grid’s flexibility.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' The outcome of proposed model informs the grid operator regarding the time slots with sufficient and insufficient flexibility along with the value of insufficiency considering the uncertainty space.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' Acknowledgments This project is supported by the European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement no.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' 101026259.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/AtE2T4oBgHgl3EQfRQeF/content/2301.03779v1.pdf'} +page_content=' REFERENCES [1] North American Electric Reliability Corporation, "Accommodating high levels of variable generation" (North American 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+++ b/EtE0T4oBgHgl3EQfgwHQ/content/tmp_files/2301.02423v1.pdf.txt @@ -0,0 +1,3613 @@ +Learning Personalized Brain Functional Connectivity of MDD +Patients from Multiple Sites via Federated Bayesian Networks +Shuai Liu ∗ +Xiao Guo † +Shun Qi ‡ +Huaning Wang § +Xiangyu Chang ¶ +January 9, 2023 +Abstract +Identifying functional connectivity biomarkers of major depressive disorder (MDD) patients is +essential to advance understanding of the disorder mechanisms and early intervention. However, +due to the small sample size and the high dimension of available neuroimaging data, the +performance of existing methods is often limited. Multi-site data could enhance the statistical +power and sample size, while they are often subject to inter-site heterogeneity and data-sharing +policies. In this paper, we propose a federated joint estimator, NOTEARS-PFL, for simultaneous +learning of multiple Bayesian networks (BNs) with continuous optimization, to identify disease- +induced alterations in MDD patients. We incorporate information shared between sites and +site-specific information into the proposed federated learning framework to learn personalized +BN structures by introducing the group fused lasso penalty. We develop the alternating direction +method of multipliers, where in the local update step, the neuroimaging data is processed at +each local site. Then the learned network structures are transmitted to the center for the global +update. In particular, we derive a closed-form expression for the local update step and use the +iterative proximal projection method to deal with the group fused lasso penalty in the global +update step. We evaluate the performance of the proposed method on both synthetic and +real-world multi-site rs-fMRI datasets. The results suggest that the proposed NOTEARS-PFL +yields superior effectiveness and accuracy than the comparable methods. +1 +Introduction +Major depressive disorder (MDD) is one of the most prevalent, costly, and disabling mental disorders +worldwide [Cassano and Fava, 2002, Jia et al., 2010]. It is often characterized by persistent sadness, +worthlessness, hopelessness, anxiety, and cognitive impairments [Fu et al., 2008]. The negative +psychology of MDD can lead to severe consequences, including suicide [Jia et al., 2015]. The +∗Department of Information Systems and Intelligent Business, School of Management, Xi’an Jiaotong University; +email: hljliushuai@stu.xjtu.edu.cn. +†Corresponding author: Center for Modern Statistics, School of Mathematics, Northwest University; email: +xiaoguo@nwu.edu.cn. +‡Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and +Rehabilitation Science, School of Life Science and Technology, Xi’an Jiaotong University; email: qishun@xjtu.edu.cn. +§Department of Psychiatry, Xijing Hospital, Air Force Medical University; email: xskzhu@fmmu.edu.cn. +¶Center for Intelligent Decision-Making and Machine Learning, School of Management, Xi’an Jiaotong University; +email: xiangyuchang@xjtu.edu.cn. +1 +arXiv:2301.02423v1 [cs.LG] 6 Jan 2023 + +productivity loss and disability due to MDD also pose a severe burden to society and affected +families [Vos et al., 2017]. Therefore, understanding the pathogenesis of MDD is crucial for effective +intervention, diagnosis, and treatment [Belmaker and Agam, 2008]. Diagnostic neuroimaging has +been shown to be an effective modality to understand the underlying pathological mechanisms +and cognitive information of brain diseases [Liu et al., 2016, 2017], and has been used for early +identification of MDD [Smith et al., 2013]. Resting-state functional magnetic resonance imaging (rs- +fMRI) is one of the most widely used imaging modes for MDD identification [Hamilton et al., 2011, Liu +et al., 2013, Lin et al., 2016]. It can detect abnormal brain functional connectivity in MDD patients, +allowing non-invasive investigation of the disease [Ye et al., 2015]. Functional connectivity (FC), +an essential biomarker in neurological disorders, is traditionally defined as the Pearson correlation +between different regions of interest (ROIs) [Ryali et al., 2012]. However, this association still does +not truly determine the direction of interactions between ROIs. An accurate understanding of this +directional information is critical to understanding the brain functional integration of MDD [Price +et al., 2017]. To further investigate FC with rs-fMRI data, a number of approaches beyond the +Pearson correlation are proposed. For example, Kandilarova et al. [2018] used a dynamic causal +modeling (DCM) method to reveal differences of FC in anterior insula between healthy control (HC) +participants and MDD patients. Hamilton et al. [2011] used Granger causality (GC) analysis method +to investigate the aberrant patterns of FC in MDD, and identify the limbic inhibition of dorsal cortex +as a key biomarker for MDD diagnosis . Nevertheless, these methods are not robust for analyzing +specific individuals or large-scale ROIs [Molenaar, 2004, Friston et al., 2011]. +Bayesian network (BN), an approach for studying the conditional dependencies between variables +in a system via a directed acyclic graph (DAG), has been used for detecting abnormal brain FC +in MDD patients [Koller and Friedman, 2009, Ide et al., 2014, Liu et al., 2022]. Compared with +DCM and GC methods, BN benefits from utilizing more samples to improve the robustness and +stability of the resulting FC. Note that the amount of rs-fMRI data collected at a single imaging site +is limited due to the difficult and expensive data acquisition in practice. Therefore, it is difficult +to provide enough data from a single site to make a good BN estimate. Fortunately, multiple +rs-fMRI datasets from different sites provide the possibility for enhancing the quality of learned BNs. +However, multi-site data are often subject to inter-site heterogeneity and data-sharing policies [Li +et al., 2020, Tong et al., 2022]. How to learn more helpful heterogeneous information from multi-site +data with considering data-sharing policies is still one of the research hotspots of BN learning. +In this paper, we consider the problem of learning BN structures using multiple datasets. Our +initial interest arises from discovering noninvasive biomarkers inherent in multi-site rs-fMRI data. +Generally, data collected at multiple imaging sites have a common disease of interest (such as MDD), +which results in that they may share similar disease-induced connectivity abnormalities. Therefore, +we consider leveraging data from multi-site to learn multiple BNs. We are committed to addressing +the three challenges: (1) computational inefficiency of the structural learning algorithms of +BNs, which partially comes from the DAG constraint and the resulting combinatorial optimization +problem; (2) large heterogeneity of multi-site rs-fMRI data, which is caused by inter-site variation +in scanners, image acquisition protocols, and patient populations across sites [Wang et al., 2022]; +(3) data sharing barriers, that is, patients worry that sharing their medical data will lead to +personal information disclosure [Li et al., 2020]. The government is likely to promulgate some privacy +protection regulations and inflict severe penalties for medical data breach events [Jin et al., 2019]. +To address the above issues, we propose a federated joint estimator for the simultaneous learning +of multiple BNs with continuous optimization. In pursuit of computational efficiency, we convert the +2 + +traditional combinatorial BN structure learning problem into a continuous numerical optimization +problem inspired by the NOTEARS method [Zheng et al., 2018]. To capture the heterogeneity, we +learn multiple BNs from multi-site data but with similar structures by introducing the group fused +lasso penalty instead of learning a single BN. To lighten the data-sharing barriers, we study the +structure learning of multiple BNs in the federated learning (FL) setting, which is a natural method to +tackle the data-sharing problem [Pfitzner et al., 2021]. We refer to the proposed NOTEARS-based +Personalized Federated Learning framework of learning multiple BNs’ structures as NOTEARS-PFL, +whose whole protocol is shown in Figure 1. +Figure 1: Illustration of the learning framework of NOTEARS-PFL. Each site stores and processes +rs-fMRI data locally. In the t-th iteration, each site estimates the local weighted adjacency matrix +W k +(t) through the local update step. Then, each site transmits the estimated local matrix to the +center. Center updates the global weighted adjacency matrices ˜Z(t) through the global update step +based on the received ˜ +W(t) = {W 1 +(t), . . . , W K +(t)}. Finally, the center transmits the estimated global +matrix to each site for the (t + 1)-th iteration update. +3 + +Center +Global model: Z(t) ← argmin [L, (W(t),z,O(t-1)) +①(t) ←[W(t),Z(t), O(t-1)) +Wh +() +Z2 +02 +-1),0h +W(t) +-1) +Local model: W() arg win [L, (wK, z(-1), (-1)) ++2 +data +data +data +rs-fMRI +preprocessing +rs-fMRI +preprocessing +preprocessing +rs-fMRI +scan + scan +scan +Site K +Site 1 +Site 2The merits of the proposed NOTEARS-PFL are multi-fold. +• NOTEARS-PFL is capable of learning site-specific BNs from multi-site rs-fMRI data, which +makes full use of the multi-site data while still being flexible enough to capture the site-specific +BN structures. +• NOTEARS-PFL is subtly fitted in an FL framework without sharing and exchanging the +original data. +• NOTEARS-PFL overcomes the computational intractability of traditional BNs by transforming +the discrete combinatorial optimization to continuous numerical optimization. +• NOTEARS-PFL can effectively detect the common abnormal FC in MDD patients among +multiple sites, especially the connectivity between the insula, thalamus cortex, and middle +temporal gyrus. Meanwhile, NOTEARS-PFL can also identify the site-specific abnormal FC +due to the differences in scanners, protocols, and patient populations. +The paper is organized as follows. In Section 2, we briefly review directed FC estimation methods +for rs-fMRI data and BN structure learning with continuous optimization. We present the formulation +and optimization approach of NOTEARS-PFL in Section 3. We conduct simulation experiments to +validate NOTEARS-PFL in Section 4, and analyze the real-world multi-site rs-fMRI data in Section +5. Finally, we conclude this paper in Section 6. +2 +Related Work +2.1 +Directed FC Estimation Methods for rs-fMRI Data +The directed FC, also known as effective FC, helps depict the abnormalities or dysfunction of the +brain connectivity network [Smith, 2012] and shows how information flows in the brain connectivity +network [Henry and Gates, 2017]. Based on rs-fMRI data, many directed FC estimation methods +have been developed, including the following four types. +(1) Granger causality (GC). GC establishes a model in the framework of vector autoregression +(VAR) and determines the edges to be added after considering the autoregressive effect of each region +[Granger, 1969, Liao et al., 2009]. GC is applied to detect the effects of psychostimulants on youths +with attention deficit hyperactivity disorder (ADHD) [Peterson et al., 2009]. However, when GC is +applied to analyze specific individuals, heterogeneity across individuals may lead to spurious results +[Molenaar, 2004]. +(2) Dynamic Causal Modeling (DCM). DCM is a method to capture nonlinear relationships +between brain regions that may be affected by different stimuli during scanning [Friston et al., 2003], +and has been used to detect the propagation of epileptic seizures [Murta et al., 2012]. The limitation +of DCM is that it cannot handle large amounts of ROIs or analysis group rs-fMRI data. [Friston +et al., 2011]. +(3) Constraint-based methods. Constraint-based methods estimate directed edges by conditional +independence tests. Common constraint-based methods include Peter Spirtes, and Clark Glymour +(PC) algorithm [Spirtes and Glymour, 1991], conservative PC (CPC) [Ramsey et al., 2006], fast +causal inference (FCI) [Spirtes, 2001], and cyclic causal discovery (CCD) [Richardson, 1996]. The +PC algorithm can obtain reliable networks on data aggregated across individuals [Smith et al., 2011]. +4 + +However, according to results from Smith et al. [2011], PC can detect the existence of edges but can +not accurately determine the directions at the individual level. +(4) Score-based methods. Score-based methods define a score function that measures how well the +BN structure fits the observed data and searches for the best network structure. Standard score-based +methods include greedy equivalent search (GES) [Chickering, 2002], independent multiple-sample +greedy equivalent search (IMaGES) [Ramsey et al., 2010], and group iterative multiple model +Estimation (GIMME) [Gates and Molenaar, 2012]. Score-based methods typically require large +samples to identify edges and directions, which limits the utility of these methods when using rs-fMRI +data for individual-level analysis [Mumford and Ramsey, 2014]. Meanwhile, the performance of +score-based methods is poor on data with a large number of ROIs, which makes it difficult to analyze +the complete parcellation of the brain. Due to the combinatorial acyclicity constraint of DAG, it is +often hard to find BN with the optimal score. And its scalability is also limited [Liu et al., 2022]. +2.2 +BN Structure Learning with Continuous Optimization +In this work, we focus on BN learning. +BN is a probabilistic graphical model that captures +dependencies among a collection of random variables. Each model is associated with a directed +network G = (V, E), where the vertex set V corresponds to the random variables and the edge set E +corresponds to the set of conditional independence [Drton and Maathuis, 2017]. +BN models the conditional independence among random variables via Markov properties [Cowell, +1998, Marrelec et al., 2004]. Denote X = (X1, . . . , Xd)⊤ that satisfies the local Markov property +with respect to a DAG G if +Xv⊥XndG(v)\paG(v) | XpaG(v), +where paG(v) = {w ∈ V : {w, v} ∈ E} denotes the parents of node v in G, ndG(v) = V \deG(v) +denotes the non-descendants of v in G with deG(v) = {w ∈ V : w = v or v → . . . → w in G} +representing the descendants of v in G. +Alternatively, if X is a continuous random vector and it has a density P(X) with respect to a +product measure, then the local Markov property is equivalent to the following factorization property +[Verma and Pearl, 1990], +P(X) = +d +� +v=1 +P +� +Xv | XpaG(v) +� +. +(1) +The structure learning of BN is to estimate the DAG G using the observations from the density +P(X). Score-based methods seek the optimal G by minimizing the score function S(W) with respect +to the corresponding weighted adjacency matrix W ∈ Rd×d, subject to that the induced graph g(W ) +is a DAG; see the LHS of equation (2). The DAG constraint initiates a combinatorial optimization +problem, which is computationally costly when d is large. +Recently, Zheng et al. [2018] proposed a NOTEARS method which enforces the acyclicity via +setting a smooth function h(W ) exactly at zero; see the RHS of equation (2). By this novel +characterization of acyclicity, the resulting optimization problem can be solved efficiently using +standard algorithms. +minW ∈Rd×d S(W ), +minW ∈Rd×d S(W ), +s.t. g(W ) ∈ DAGs, +s.t. h(W ) = 0. +(2) +5 + +Currently, NOTEARS has been extended to handle problems in many situations. For example, +DAG Graph Neural Network (DAG-GNN) extends NOTEARS to solve nonlinear cases by incor- +porating neural networks [Yu et al., 2019]. Graph AutoEncoder (GAE) extends NOTEARS and +DAG-GNN into a graph autoencoder model, facilitating vector-valued variables [Ng et al., 2019]. +Pamfil et al. [2020] proposed DYNOTEARS method to learn dynamic BNs from time-series data. +Huang et al. [2020] used reinforcement learning to find the optimal DAGs from incomplete data +based on NOTEARS. +To the best of our knowledge, few studies have focused on using NOTEARS to learn personalized +BNs from fMRI data. Zhang et al. [2022] proposed a joint BN estimation model to detect abnormal +directed FC in schizophrenia (SZ) patients. However, the joint estimation model proposed by Zhang +et al. [2022] is not applicable for the FL setting. Ng and Zhang [2022] proposed NOTEARS-ADMM +model to estimate the structure of BN in FL setting. However, they did not consider the data +heterogeneity, which can lead to model bias [Zhao et al., 2018, Jiang et al., 2022]. Compared with +Zhang et al. [2022] and Ng and Zhang [2022], the proposed NOTEARS-PFL is powerful because it +captures the data heterogeneity, overcomes the data sharing barriers, and attains computational +efficiency, simultaneously. +3 +NOTEARS-based Personalized Federated Learning Framework +3.1 +Preliminary +The BN associated with a DAG G can also be thought of as a structural equation model [Bollen, +1989] +Xi = fi(W T +i X) + Zi, i = 1, 2, . . . , d, +(3) +where W = (W1, . . . , Wd) ∈ Rd×d denotes the weighted adjacency matrix whose nonzero coefficients +correspond to the directed edges in G, fi’s are functions related to the conditional distributions of +Xi’s, and Zi’s are jointly independent random noises. Equation (3) is equivalent to the local Markov +property and factorization property introduced in Section 2 [Drton and Maathuis, 2017]. +We consider the linear structural equation model +Xi = W T +i X + Zi, i = 1, 2, . . . , d. +(4) +Actually, the multivariate Gaussian distribution can be modeled as equation (4) with Zi’s being +independent Gaussian noises. +Let the data matrix x ∈ Rn×d. Zheng et al. [2018] formulates the structure learning of BNs as +min +W ∈Rd×d +1 +2n ∥x − xW ∥2 +F + λ∥W ∥1, +s.t. +h(W ) = 0, +(5) +where +h(W ) := tr +� +eW ⊙W � +− d = 0, +(6) +⊙ denotes the Hadamard product, eA = �∞ +k=0 +1 +k!Ak denotes the the matrix exponential operator +[Leonard, 1996], ∥A∥F denotes the Frobenius norm, ∥A∥1 refers to the entry-wise ℓ1 norm and the +tuning parameter λ > 0 controls the amount of sparsity. +6 + +3.2 +Problem Formulation +We now proceed to formulate our NOTEARS-PFL method, which can efficiently learn multiple +heterogeneous BNs without sharing data. +We consider the setting in which there is a fixed set of K sites in total, and each site has its +own local dataset. The k-th site holds nk i.i.d. samples, denoted by xk = +� +xk +i +�nk +i=1 ∈ Rnk×d. Let +D = {x1, . . . , xK} be the K overall observational datasets. The goal is to infer the K weighted +adjacency matrices ˜ +W0 = {W 1 +0 , . . . , W K +0 } (correspond to the BN structures) using D. +To incorporate the heterogeneity among K sites, we consider the following optimization problem: +min +˜ +W +K +� +k=1 +1 +2nk +���xk − xkW k��� +2 +F + R( ˜ +W ), +s.t. +h(W k) = 0, k = 1, . . . , K, +(7) +where h(W k) is defined in the same way as equation (6) and R( ˜ +W ) is a penalty function for inducing +the similarity and sparsity within ˜ +W . +With the data sharing constraint, we formulate equation (7) into the framework of ADMM, +which is a natural solution to distributed learning and FL [Ng and Zhang, 2022]. Define a set of +consensus variables ˜Z = {Z1, . . . , ZK}, which can be thought of as the global weighted adjacency +matrices, in contrast to the local weighted adjacency matrices ˜ +W . Then we rewrite equation (7) as +min +˜ +W , ˜ +Z +K +� +k=1 +L(W k, xk) + R( ˜Z), +s.t. +h(Zk) = 0, +W k = Zk, +k = 1, . . . , K, +(8) +where +L(W k, xk) := +1 +2nk +���xk − xkW k��� +2 +F , +(9) +h(Zk) is defined in the same way as equation (6), and R( ˜Z) is defined by +R( ˜Z) := λ1 +K +� +k=1 +∥Zk∥1 + λ2 +K−1 +� +k=1 +∥Zk+1 − Zk∥F , +(10) +where λ1 > 0 controls the sparsity of Zk and λ2 > 0 controls the similarity within ˜Z. +The general optimization procedure can be summarized as follows. First, each site estimates the +local weighted adjacency matrix W k by using local dataset xk. Then, instead of transmitting the +original data, each site only transmits its local weighted adjacency matrix to the center. After that, +the center updates the global weighted adjacency matrices ˜Z0 = {Z1 +0, . . . , ZK +0 }, based on received +˜ +W0, Finally, the center transmits the updated ˜Z to each site, which performs the next update locally +based W k = Zk. +In the next subsection, we provide the computational details of NOTEARS-PFL. +7 + +3.3 +Optimization Algorithm +By applying the augmented Lagrangian method [Bertsekas, 2014], the equation (8) can be written as +L +� +˜ +W , ˜Z, Θ +� += +K +� +k=1 +L(W k, xk) + R( ˜Z) + +K +� +k=1 +αkh(Zk) + ρ1 +2 +K +� +k=1 +|h(Zk)|2 + +K +� +k=1 +tr(βk(W k − Zk)⊤) ++ ρ2 +2 +K +� +k=1 +���W k − Zk��� +2 +F , +(11) +where ˜Θ = {ρ1, ρ2, α1, . . . , αK, β1, . . . , βK}, ρ1, ρ2 are the penalty coefficients, α1, . . . , αK and +β1, . . . , βK are the Lagrange multiplies. +At the t-th iteration, we can solve equation (11) as follows: +(1) Local update: +˜ +W(t) ← arg min +˜ +W +� +L +� +˜ +W , ˜Z(t−1), ˜Θ(t−1) +�� +. +(12) +(2) Global update: +˜Z(t) ← arg min +˜ +Z +� +L +� +˜ +W(t), ˜Z, ˜Θ(t−1) +�� +. +(13) +(3) Global update: +˜Θ(t) ← +� +˜ +W(t), ˜Z(t), ˜Θ(t−1) +� +. +(14) +3.3.1 +Federated Local Update of ˜ +W +Taking the derivative of equation (11) with respect to ˜ +W , we can update each W k +(t) of ˜ +W(t) as +W k +(t) := arg min +W k +(L(W k, xk) + ρ2,(t−1) +2 +���W k − Zk +(t−1) +��� +2 +F + tr(βk,(t−1)(W k − Zk +(t−1))⊤)). +(15) +Let U k = +1 +nk (xk)⊤xk and assume U k + ρ2I is invertible. Equation (15) has a closed form expression +W k +(t) = (U k + ρ2,(t−1)I)−1(ρ2,(t−1)Zk +(t−1) − βk,(t−1) + U k), +(16) +where the details of the derivation are given in Appendix A. +3.3.2 +Federated Global Update of ˜Z +Similar to equation (15), we can update each Zk +(t) of ˜Z(t) as +Zk +(t) := arg min +Zk +{L( ˜Z) + R( ˜Z)}, +(17) +8 + +Algorithm 1 Dykstra-like iterative proximal algorithm (DIPA) +Input: K: Number of site; ˜Z: global adjacency matrices; ˜ +W : local adjacency matrices; N: The +number of iterations; ϵ: Tolerance. +Output: ˜Z: The result of equation (19). +1: ∇Lk +� +Zk� += equation (20). +2: for k = 1, . . . , K do +3: +U k = Zk − 1 +C ∇L +� +Zk� +. +4: end for +5: ¯U ← Transform (U k). +6: Set A0 = ¯U, Mn = 0, Qn = 0. +7: for n = 0, . . . , N do +8: +V(n) ← proxR2 +� +A(n) + M(n) +� +, see equation (28). +9: +M(n+1) ← A(n) + M(n) − V(n). +10: +A(n+1) ← proxR1 +� +V(n) + Q(n) +� +, see equation (25). +11: +Q(n+1) ← V(n) + Q(n) − A(n+1). +12: +Break: if +��A(n+1) − A(n) +�� +F < ϵ. +13: end for +14: ¯U ← A(N+1). +15: ˜Z ← Inverse-Transform ( ¯U). +16: return ˜Z. +where +L( ˜Z) := +K +� +k=1 +αk,(t−1)h(Zk) + ρ1,(t−1) +2 +K +� +k=1 +|h(Zk)|2 + ρ2,(t−1) +2 +K +� +k=1 +���W k +(t) − Zk��� +2 +F ) ++ +K +� +k=1 +tr(βk,(t−1)(W k +(t) − Zk)⊤). +Due to the acyclicity term h(Zk), we are not able to derive a closed-form solution for equation +(17). To tackle this issue, we utilize a proximal gradient method which constructs a quadratic +approximation of L( ˜Z) at ˜Z(t−1), and updates ˜Z(t) by +˜Z(t) = arg min +˜ +Z +{L( ˜Z(t−1)) + +K +� +k=1 +� +Zk − Zk +(t−1), ∇Lk(Zk +(t−1)) +� ++ C +2 +K +� +k=1 +���Zk − Zk +(t−1) +��� +2 +F + R( ˜Z)}, +(18) +where ∇Lk(·) is the gradient of Lk(·), C > 0 is the Lipschitz constant of ∇Lk(·). After some simple +9 + +manipulations of equation (18), e.g., ignoring constant terms of Zk +(t−1), we have +˜Z(t) = arg min +˜ +Z +{C +2 +K +� +k=1 +����Zk − +� +Zk +(t−1) − 1 +L∇Lk +� +Zk +t−1 +������ +2 +F ++ R( ˜Z)}, += proxCR +� K +� +k=1 +� +Zk +(t−1) − 1 +L∇Lk +� +Zk +(t−1) +��� +, +(19) +where +∇Lk +� +Zk +(t−1) +� += αk,(t−1)∇h(Zk +(t−1))+ρ1,(t−1)h(Zk +(t−1))∇h(Zk +(t−1))−βk,(t−1)+ρ2,(t−1)(Zk +(t−1)−W k), +(20) +and proxg(v) = arg min +x +( 1 +2∥x − v∥2 +F + g(x)) denotes the proximal operator. +Unlike the calculation of W k, we cannot separate the equation (19) by k because of the grouped +constraint R( ˜Z). Instead, we must estimate the whole set of matrices ˜Z(t) jointly. Inspired by +Gibberd and Nelson [2017], we use the following iterative proximal projection step to solve. +Let U k = Zk +(t−1) − 1 +C ∇Lk +� +Zk +(t−1) +� +, and perform transform procedure (see AppendixB) for +U k → ¯U. Then, equation (19) can be re-written as +min +¯ +Z +1 +2 +�� ¯Z − ¯U +��2 +F +� +�� +� +L( ¯ +Z) ++ λ1∥ ¯Z∥1 +� �� � +R1( ¯ +Z) ++ λ2∥D ¯Z∥2,1 +� +�� +� +R2( ¯ +Z) +, +(21) +where D ∈ R(K−1)×K is a backwards difference matrix of the form Di,i = −1, Di,i+1 = 1 for i = +1, . . . , K − 1, and ∥A∥2,1 := � +k ∥Ak,·∥2 denotes the group ℓ2,1 norm. Actually, equation (21) is +equivalent to the Group-Fused Lasso Signal Approximator (GFLSA) defined by Gibberd and Nelson +[2017]. We denote the objective in equation (21) by f +� ¯U; λ1, λ2 +� += proxR1+R2 +� ¯U +� +. Then, we adopt +the Dykstra-like iterative proximal algorithm (DIPA) [Combettes and Pesquet, 2011] to handle +proxR1+R2 +� ¯U +� +and find a feasible solution for both the group fused lasso penalty and the lasso +penalty. We summarize the details of iteration in Algorithm 1. +3.3.3 +Federated Global Update of ˜Θ +The update of ˜Θ follows the following iterative steps +βk,t := βk,t−1 + ρ2,t−1 +� +W k +(t) − Zk +(t) +� +, +αk,t := αk,t−1 + ρ1,t−1h +� +Zk +(t) +� +, +ρ1,t := γ1ρ1,t−1, +ρ2,t := γ2ρ2,t−1, +(22) +where γ1, γ1 ∈ R are hyperparameters that respectively control the increasing speeds of the coefficients +ρ1, ρ2. The overall ADMM algorithm of NOTEARS-PFL is thereby given in Algorithm 2. +10 + +Algorithm 2 ADMM of NOTEARS-PFL +Input: K: Number of site; xk: Original data; ˜Z(0): Initial global adjacency matrices; ρ1,0, ρ2,0, +α1,0, . . . , αK,0, β1,0, . . . , βK,0: Initial parameters; T: The maximum of iterations; ϵ: Tolerance. +Output: +ˆ +Zk: Estimated adjacency matrix. +for iterations t = 1 to T do +Local update step: +for site k = 1, . . . , K do +Update W k +(t) according to equation (16). +end for +Global update step: +for variables ˜Z(t−1), Θ(t−1) in the center do +Zk +(t) ← DIPA (W k +(t), Zk +(t−1)). +Update ˜Θ(t−1) according to equation (22). +end for +Break: if +K +� +k=1 +���Zk +(t) − Zk +(t−1) +��� +F +���Zk +(t) +��� +2 +< ϵ. +end for +return ˜Z = (Z1 +(T), ..., ZK +(T)). +11 + +4 +Simulations +4.1 +Simulation Design of Synthetic Data +We simulate synthetic data according to equation (4). First, we generate a random graph Gtruth +based on Erdös–Rényi (ER) model [Erdös et al., 1960]. To obtain a set of related graphs, we apply +perturbations to Gtruth to create K similar but different graphs ˜G = {G1, . . . , GK}. The details of +the definition of perturbation are shown in Appendix C, and we denote the perturbation level as pl. +Given ˜G, we assign uniformly random edge weights to obtain K weights matrices +˜ +W = +{W 1, . . . , W K}, where the non-zero entries are sampled uniformly at random form [−2, −0.5]∪[0.5, 2]. +Given ˜ +W , we generate the datasets D = {x1, . . . , xK} based on equation (4) with standard Gaussian +noise. +To evaluate and compare the performance of the proposed method, we apply the NOTEARS +[Zheng et al., 2018] method to estimate each network independently from each site’s local data +(NOTEARS-SIG for short), and apply the NOTEARS method to learn a common network structure +for all contexts (NOTEARS-AVG for short), i.e., an “average” network that treats all site’s data as +samples in one dataset. We also compare the performance between NOTEARS-ADMM [Ng and +Zhang, 2022] and the proposed method. +We use the following four metrics to evaluate the learning performance of different methods (see +Appendix C for a detailed definition of metrics). +• Edge arrowhead error: +Error = +FP + FN +TP + TN + FP + FN . +(23) +• Edge arrowhead precision: +Precision = +TP +TP + FP . +• Edge arrowhead F-score: +F-score = 2 · Precision · Recall +Precision + Recall , +where Recall = TP/(TP + FN). +• Edge arrowhead structural Hamming distance (SHD): Given two structures, this +measure is the minimum number of edges needed to convert the learned graph into the true +one. +We compare the performance of the proposed NOTEARS-PFL, NOTEARS-SIG, NOTEARS- +AVG, and NOTEARS-ADMM on the following three aspects. +Performance vs. the number of variable: We fix the number of sites K = 10, perturbation +level pl = 10%, set the total sample size nt = �K +k=1 nk equals to three times the number of variable d +(nt = 3d, nk = 0.3d), and compare the model performance of network structure learning for different +variable number d = 10, 20, 30, 40, 50, 60, 70, 80. +12 + +Performance vs. the number of site: We fix the number of variable d = 50, perturbation +level pl = 10%. We set the total sample size nt = 256, and distributed evenly across the number of +site K = 2, 4, 8, 16, 32, 64. +Performance vs. perturbation level: We fix the number of site K = 10, the number of +variable d = 30, sample size nt = 3d, and vary the perturbation level pl = 5%, 10%, 15%, 20%, 30%. +The evaluation metrics for one simulation run are averaged over the K sites’ dataset, and we +repeat each experiment 10 times. The final evaluation metrics are thereby averaged over the ten +simulation runs. +(a) +(b) +(d) +(c) +Figure 2: Simulation results for synthetic data under different variable numbers. (a) Average edge +arrowhead error (lower is better); (b) Average edge arrowhead SHD (lower is better); (c) Average +edge arrowhead precision (higher is better); (d) Average edge arrowhead F-score (higher is better). +In the synthetic data experiment, we first evaluate the effect of the number of variables d on +the performance of each compared method. The results are shown in Figure 2. It is clear that +NOTEARS-PFL performs the best among all the methods. The average arrowhead adjacency error of +NOTEARS-PFL has a relatively low level ranging from 0.02 to 0.13. In contrast, for NOTEARS-SIG, +the average arrowhead adjacency error is far larger than NOTEARS-PFL, ranging from 0.04 to +0.43. This may be because the sample size of a single dataset is too small for NOTEARS-SIG to +give a satisfactory estimate. The same result is observed in the average arrowhead SHD. For the +other two metrics, NOTEARS-PFL consistently results in higher average arrowhead precision and +F-score than the other three methods. Compared with NOTEARS-SIG and NOTEARS-AVG, the +average arrowhead precision of NOTEARS-PFL is also more stable with respect to different variable +numbers, indicating that it can successfully identify most of the edges in high-dimensional settings. +We also test the effect of the number of sites K on the performance of each method. The +results are shown in Figure 3. Clearly, NOTEARS-PFL performs better than NOTEARS-SIG, +NOTEARS-AVG, and NOTEARS-ADMM for all the tested cases. As K increases, the performance +13 + +0.4 +100 +0.3 - +80 - +SHD +60 +0.2 +40 - +0.1 - +20 - +0.0 - +0 +20 +50 +10 +30 +40 +60 +70 +80 +10 +20 +30 +40 +50 +60 +70 +80 +Number of variables +Number of variables +0.9 +1.0- +0.8 - +0.7 +0.8 +0.6 +ion +0.5 +Preci +0.4 - +0.4 +0.3 +0.2 +0.2 +0.1 +10 +20 +30 +40 +50 +80 +60 +70 +10 +20 +30 +40 +50 +60 +70 +80 +Number of variables +Number of variables +NOTEARS-PFL +NOTEARS-SIG +NOTEARS-AVG +NOTEARS-ADMM(a) +(b) +(d) +(c) +Figure 3: Simulation results for synthetic data under different site numbers. (a) Average edge +arrowhead error (lower is better); (b) Average edge arrowhead SHD (lower is better); (c) Average +edge arrowhead precision (higher is better); (d) Average edge arrowhead F-score (higher is better). +(a) +(b) +(d) +(c) +Figure 4: Simulation results for synthetic data under different perturbation levels (a) Average edge +arrowhead error (lower is better); (b) Average edge arrowhead SHD (lower is better); (c) Average +edge arrowhead precision (higher is better); (d) Average edge arrowhead F-score (higher is better). +14 + +0.10 +120 +100: +0.08 +80 - +0.06 +SHD +60 +0.04 +40 - +0.02 +20 - +-0 +0.00 +10 +20 +50 +60 +0 +10 +20 +30 +40 +50 +60 +0 +30 +40 +Number of sites +Number of sites +1.0 +0.8 +0.8 +0.6 +Precisic +0.4 +0.4 +0.2 - +0.2 +0.0 - +0 +10 +20 +30 +40 +50 +60 +0 +10 +20 +30 +50 +60 +40 +Number of sites +Number of sites +NOTEARS-PFL +NOTEARS-SIG +NOTEARS-AVG +NOTEARS-ADMM0.08: +35 - +0.07 +30 +0.06 - +25 +0.05 +D +0.04 +15- +0.03 +10 - +0.02 +5 - +0.01 +5% +10% +15% +20% +30% +5% +10% +15% +20% +30% +Perturbation levels +Perturbation levels +1.00 +0.9 +0.95 +0.8 +0.90 +0.7 +0.85 +ision +core +0.80 +Precis +0.6 +S +F +0.75 +0.5 +0.70 - +0.4 +0.65 +0.60 +0.3 +5% +10% +15% +20% +30% +5% +10% +15% +20% +30% +Perturbation levels +Perturbation levels +NOTEARS-PFL +NOTEARS-SIG +NOTEARS-AVG +NOTEARS-ADMMof NOTEARS-SIG, NOTEARS-AVG decline rapidly. Although the performance of NOTEARS-PFL +also decreases with the increase of K, it still provides a relatively stable and satisfying performance. +As expected, NOTEARS-SIG does not perform better at larger K. A possible reason is that +NOTEARS-SIG only utilizes the information of a single dataset whose sample size decreases with +the increase of K. On the contrary, NOTEARS-PFL works well in the setting with a large site +number because information can be exchanged during optimization. These results are also consistent +with the existing literature [Ng and Zhang, 2022]. +Finally, we examine the effect of the perturbation level pl on the performance of each method. +The results are shown in Figure 4. It is clear that NOTEARS-PFL significantly outperforms the other +three methods. It can be seen that with the increase of perturbation level, average arrowhead error +and SHD increase significantly, while average arrowhead precision and F-score decrease. When the +perturbation level is relatively low, the difference between the four methods is relatively small, but +when the perturbation level is relatively large, the advantage of NOTEARS-PFL is more significant. +5 +Application to Real-world rs-fMRI Data +5.1 +Data and Preprocessing +(1) Data acquisition: The multi-site rs-fMRI datasets in this study were obtained from the +DecNef Project Brain Data Repository1, collected as part of the Japanese Strategic Research Program +for the Promotion of Brain Science (SRPBS) database project [Tanaka et al., 2021]. This dataset +consists of 255 MDD patients (135 men versus 120 women) and 791 HC participants (426 men versus +365 women) from 8 sites. Some samples were discarded as some sites only have rs-fMRI data on +HC participants. As a result, 238 MDD patients and 475 HC participants from 5 sites were used +in this study (see Table 3). The demographic characteristics of all subjects in both datasets are +summarized in Table 4. +(2) Data preprocessing : Each subject of the data underwent a single rs-fMRI session and a +structural MRI session. During the fMRI scan, participants were asked to relax, stay awake and +think about anything in particular. Detailed imaging parameters of rs-fMRI and T1-weighted (T1w) +structural MRI at each site are shown in Table 5. We applied the following preprocessing steps +to the data by using DPARSF [Yan and Zang, 2010] software2. For each participant, we removed +the first 10 MRI volumes. Slice-time correction and head motion were corrected on the remaining +images. The T1-weighted images were unified segment segmentation and diffeomorphic anatomical +registration. The rs-fMRI data were smoothed with a 6mm full-width at half-maximum Gaussian +kernel and the Friston 24-parameter model was used to regress head motion effects further. Then, +all the time series were filtered by linear detrending and a temporal band-pass filter (0.01 - 0.08 Hz). +(3) Feature extraction: After preprocessing, we estimated the time series of 116 ROIs based +on the automated anatomical labeling (AAL) template [Tzourio-Mazoyer et al., 2002]. Details of +cortical and subcortical regions of interest (ROIs) defined in the AAL template are presented in +Table 6 and Table 7. We selected 56 ROIs from 116 ROIs because these regions are considered to +be related to MDD in the literature. The names of the selected ROIs are shown in bold in Table +6 and Table 7. The voxel-wise fMRI time courses were averaged into one regional average time +course within each ROI. The data for each participant was then in the form of an X× 56 matrix (X +1https://bicr-resource.atr.jp/srpbsopen/ +2http://www.rfmri.org/DPARSF +15 + +sampling points in each regional average fMRI time course and 56 selected ROIs). +5.2 +Experimental Setup +We randomly select 70% of MDD patients and HC participants from each site and aggregate their +rs-fMRI data into the MDD discovery dataset and HC discovery dataset for that site, respectively. +Similarly, we aggregate the remaining 30% into the MDD validation dataset and HC validation +dataset for that site, respectively. We analyze the 5 sites’ discovery datasets of MDD patients, which +are regarded as 5 related tasks. Then we can obtain a brain connection network of MDD for each +site. To study the differences in brain FC, the brain connection networks of HC for five sites, which +are viewed as another set of related tasks, are also obtained using the proposed NOTEARS-PFL +method. According to the estimated BN structures, we analyze the abnormal FC in MDD by the +following aspects. +5.2.1 +Important Nodes Identification +By identifying important nodes, we reveal the aberrant nodal characteristics of the brain functional +connectivity networks of MDD from multi-site datasets. +5.2.2 +Overlapping Connections Identification +By identifying overlapping connections, we obtain the common functional connections for MDD +patients from multiple sites. By comparing with the overlapping connections of HC participants, we +further investigate the altered functional connections in MDD patients, which provide the potential +biomarkers for clinic treatment of MDD. +5.2.3 +Site-specific Connections Identification +By identifying the site-specific connections in different sites, we investigate the specific FC alterations +in MDD at each site due to the differences in image acquisition protocols and patient populations at +different sites. +5.2.4 +Comparison with Other Methods +We randomly select 5 MDD patients and 5 HC participants from each site’s MDD validation dataset +and HC validation dataset and repeat such selection 10 times. We then have 10 datasets containing +MDD data and HC data from the 5 sites. Based on these datasets, we compare NOTEARS-PFL with +NOTEARS-SIG and existing standard analysis methods of rs-fMRI data: GES [Chickering, 2002], +PC [Spirtes and Glymour, 1991], and GC [Granger, 1969]. To further test whether NOTEARS-PFL +is able to learn the differences between MDD patients and HC participants. +5.3 +Experimental Results +In this section, we use NOTEARS-PFL method to analyze the multi-site rs-fMRI data from 5 sites. +We can obtain the brain functional connection network of MDD patients for each site. To study the +differences in brain FC, we also obtain the brain functional connection network of HC participants +for each site. +16 + +5.3.1 +Results of Important Nodes +To better understand the differences in brain FC between MDD patients and HC participants through +the estimated directed brain networks from multi-site rs-fMRI data, we further use the connection +degree to identify some important nodes. The connection degree (including in and out degree) is a +commonly used measure of functional connectivity [Liu et al., 2022]. More specifically, it represents +the amount of directed functional connections. The greater the connection degree, the higher the +effective FC. Identifying important nodes further helps to discover the nodes associated with the +disease. Table 1 shows the differences in total connection degrees between MDD patients and HC +participants at 5 sites. The total out connection degrees in Table 1 are 657 for MDD and 478 for +HC, indicating that MDD has 37.4% effective FC than HC. Similarly, MDD also has 23.4% more +effective FC than HC, with a total in connection degrees of 516 and 418, respectively. The rise of FC +is an apparent robust biomarker of MDD disease [Zamoscik et al., 2014], which can also be found in +our results. +Table 1: The top 10 out and in connection degrees of MDD patients and HC participants +Index +ROI +Abbreviation +Degree +Index +ROI +Abbreviation +Degree +MDD (Out) +77 +Thalamus +THA.L +75 +HC (Out) +55 +Fusiform gyrus +FFG.L +58 +29 +Insula +INS.L +74 +37 +Hippocampus +HIP.L +57 +35 +Cingulate gyurs, posterior part +PCG.L +72 +31 +Cingulate gyrus, anterior part +ACG.L +55 +33 +Cingulate gyrus, mid part +DCG.L +68 +38 +Hippocampus +HIP.R +49 +34 +Cingulate gyrus, mid part +DCG.R +67 +9 +Middle frontal gyrus, orbital +HIP.R +47 +31 +Cingulate gyrus, anterior part +ACG.L +63 +29 +Insula +INS.L +46 +72 +Caudate +CAU.R +62 +77 +Thalamus +THA.L +45 +71 +Caudate +CAU.L +61 +33 +Cingulate gyrus, mid part +DCG.L +43 +55 +Fusiform gyrus +FFG.L +58 +56 +Fusiform gyrus +FFG.R +40 +79 +Heschl gyrus +HES.L +57 +79 +Heschl gyrus +HES.L +38 +Total +657 +Total +478 +MDD (In) +24 +Superior frontal gyrus, medial +SFGmed.R +79 +HC (In) +3 +Superior frontal gyrus, dorsolateral +SFGdor.L +55 +90 +Inferior temporal gyrus +ITG.R +62 +9 +Middle frontal gyrus, orbital +ORBmid.L +48 +26 +Superior frontal gyrus, medial orbital ORBsupmed.R +59 +26 +Superior frontal gyrus, medial orbital ORBsupmed.R +45 +89 +Inferior temporal gyrus +ITG.L +54 +90 +Inferior temporal gyrus +ITG.R +44 +3 +Superior frontal gyrus, dorsolateral +SFGdor.L +48 +10 +Middle frontal gyrus, orbital +ORBmid.R +41 +46 +Cuneus +CUN.R +46 +14 +Inferior frontal gyrus, triangular +IFGtriang.R +40 +11 +Inferior frontal gyrus, opercular +IFGoperc.L +45 +24 +Superior frontal gyrus, medial +SFGmed.R +39 +25 +Superior frontal gyrus, medial orbital ORBsupmed.L +42 +1 +Precentral gyrus +PreCG.L +38 +41 +Amygdala +AMYG.L +41 +89 +Inferior temporal gyrus +ITG.L +36 +32 +Cingulate gyrus, anterior part +ACG.R +40 +6 +Superior frontal gyrus, orbital +ORBsup.R +32 +Total +516 +Total +418 +From Table 1, we can find some ROI nodes with high connection degrees, such as THA.L +(thalamus), INS.L (insula), SFGmed.R (superior frontal gyrus, medial) in MDD, and FFG.L (fusiform +gyrus) and HIP.L (hippocampus) in HC. Specifically, THA.L and INS.L have more outgoing +connections in MDD than in HC. It indicates that THA.L and INS.L of MDD have a higher essential +impact on other ROI nodes than HC. The result from NOTEARS-PFL is in line with literature +[Kang et al., 2018, Avery et al., 2014, Porta-Casteràs et al., 2021]. According to Kang et al. [2018], +emerging evidence indicates that the enhanced thalamus FC is an important feature of the underlying +pathophysiology of MDD. This abnormal FC is related to the core clinical symptoms of MDD, such as +anxiety, memory, and attention. Our result further implies that the impaired FC of the hippocampus +is potentially an important biomarker of MDD. Compared to HC, the bilateral hippocampus in +MDD lack FC. As the core region of the limbic system, the hippocampus plays an important role in +regulating motivation and emotion. The mode of emotion regulation in MDD may be related to the +decreased FC of the hippocampus [Cao et al., 2012]. SFGmed.R (superior frontal gyrus, medial) and +ITG.R (inferior temporal gyrus) have more incoming connections than outgoing connections, which +indicates that SFGmed.R and ITG.R are mainly affected by other ROI nodes. These findings are +also consistent with the physiological discoveries of MDD disease [Porta-Casteràs et al., 2021]. +17 + +5.3.2 +Results of Overlapping Connections +Figure 5 depicts the overlapping connections between the directed networks of 5 sites of MDD +patients and HC participants. The overlapping connection refers to the connection shared by five +sites. We can use it to study the universal connection between MDD and compare the differences +between MDD and HC. From Figure 5, we can find some abnormal functional connections in MDD: +INS.R (insula) → ORBmid.R (middle frontal gyrus, orbital), INS.R (insula) → INS.L (insula), INS.R +(insula) → ACG.R (cingulate gyrus, anterior part), PCG.L (cingulate gyurs, posterior part) → +PCG.R (cingulate gyurs, posterior part), THA.L (thalamus) → CAU.R (caudate), STG.R (superior +temporal gyrus) → MTG.R (middle temporal gyrus). Three common functional connections are +associated with the insula, which further demonstrates the important role of the insula in identifying +abnormal functional connections in MDD. The insula has been shown to be a potential primary +biomarker for the diagnosis of MDD [McGrath et al., 2013]. In MDD patients, the insula show +increased FC with other limbic or paralimbic structures, particularly with the ventromedial prefrontal +cortex (vmPFC) and orbitofrontal cortex (OFC) [Avery et al., 2014, Drevets et al., 2008], which is +also illustrated in our results. +Figure 5: The overlapping connections between the directed networks of 5 sites of MDD patients +and HC participants. +In addition to the abnormal insula structure in MDD patients, we also observe the abnormalities +of FC in posterior cingulate gyurs, thalamus, inferior temporal gyrus, and middle temporal gyrus, +which are also consistent with findings in the works of literature [Khundakar and Thomas, 2009, +Zhao et al., 2014]. These cortices belong to the default mode network (DMN) and are considered +to contribute greatly to MDD [Gong and He, 2015]. The abnormalities of FC in DMN have been +reported in many MDD studies [Vasudev et al., 2018], especially the frontal lobe and temporal +lobe. These lobes are suggested to be closely associated to the cognitive and information-processing +abilities of MDD patients [Brzezicka, 2013]. +18 + +R +L +R +L +SFGdo +MFG.R +CG.1 +R +14 1 +13 11 9 +14 +INS. +ACGL +ACG.R +DCG.L +3 +DCG.R +3 +PCG.L +、PCG.R +3 +% +HIP.R + Frontal +41 39 37 +PHG.L +40 +PHG.R + Insula and Cingulate Gyri +42 +Temporal +41 + CUN.R +CUN.L +4 +Occipital +Pariental + Subcortial region +5 +FFG.R +18 +5 +LL 6L T8 +TVHL +58 Z8 68 06 88 98 +STG.R +MTG.L +MTG.R +ITG.L +MTG.R +ITG.L +(a) MDD patients +(b) HC participantsFigure 6: The site-specific connections between the directed networks of 5 sites of MDD patients. +Site 1: Center of Innovation in Hiroshima (COI), Site 2: Kyoto University (KUT), Site 3: University +of Tokyo (UTO), Site 4: Hiroshima Kajikawa Hospital (HKH), Site 5: Hiroshima University Hospital +(HUH). +5.3.3 +Results of Site-specific Connections +In this study, we are also interested in the connections specific to a site. A site-specific connection is +a connection that only exists on one site. By identifying the site-specific connections in different +sites, we can better understand the specificity of FC in MDD patients due to the differences in image +acquisition protocols and patient populations at different sites. The site-specific connections of 5 +sites of MDD patients are visualized in Figure 6. In the results of site 1, we can find the increased +functional connection from frontal to pariental and from frontal to temporal, especially the increased +afferent connections to precuneus. The precuneus is considered one of the hubs of DMN, which is +generally associated with the rumination of negative and sad thoughts in MDD [Cheng et al., 2018]. +It has been shown to play a key role in identifying MDD [Peng et al., 2015]. A study of effective +FC in MDD has shown a significant increase in forward connectivity from the middle and inferior +temporal cortical areas to the precuneus [Öngür et al., 2003], which is consistent with our study (the +connections IFGoperc.L → PCUN.R, IFGtriang.L → PCUN.L). +Similarly, in site 2, we find the enhanced FC within the frontal cortex, particularly the connections +associated with the orbitofrontal cortex (the connections ORBsup.L → ORBsupmed.L, MFG.L → +ORBmid.R, AMYG.L → ORBmid.L). The increased FC in the orbitofrontal cortex in MDD patients +is associated with emotionally negative self-perception [Cheng et al., 2016]. The orbitofrontal cortex +is also a part of the brain’s affective network (AN), and the increased functional connections of the +orbitofrontal cortex in MDD have been consistently reported [Townsend et al., 2010]. The different +effective FC patterns of the orbitofrontal cortex can also be used to reveal different pathophysiological +mechanisms of different depression types or groups. +19 + +Sitel +Site4 +Site2 +Site5 +Site3Table 2: Two-sample proportion tests for published overlapped connections. +Connection +NOTEARS-PFL NOTEARS-SIG +GES +PC +GC +INS.R→INS.L +0.0002 +0.0016 +0.0022 0.0512 0.0057 +INS.R→ORBmid.R +0.0012 +0.0029 +0.0055 0.0234 0.0133 +THA.L →CAU.R +0.0016 +0.0040 +0.0126 0.1636 0.0264 +PCG.L→PCG.R +0.0040 +0.0091 +0.0283 0.0984 0.0549 +INS.R →ACG.R +0.0049 +0.0234 +0.0133 0.2625 0.0289 +STG.R→MTG.R +0.0055 +0.0264 +0.0549 0.0721 0.0567 +MTG.L→ORBmid.R +0.0126 +0.0283 +0.0264 0.1556 0.1018 +5.3.4 +Comparison Results with Other Methods +To further test whether NOTEARS-PFL is able to learn the differences between MDD patients and +HC participants, we use different methods to learn the BN structures from the test validation dataset +established in Section 5. Based on the learned BN structures, we perform a two-sample proportion +test for each published overlapping connection of MDD in Figure 5, and report the p-values in Table +2. The smaller p value indicates that NOTEARS-PFL recognizes the connection more easily in MDD +group than in HC group. We also included test results for NOTEARS-SIG, GES, PC, and GS for +comparison. In order to ensure the consistency of measurement standards, we control these methods +to learn the same sparsity network structure. +6 +Conclusion +In this work, we focus on learning the heterogeneous brain functional connectivity in MDD patients +using multi-site data efficiently and with the data sharing constraint. To this end, we developed a +toolbox called NOTEARS-PFL. To achieve the model heterogeneity and computational efficiency, +NOTEARS-PFL is formulated as minimizing a group fused lasso penalized score function with a +continuous constraint for DAG. 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The first term of the equation (24) can be written as +L(W k, xk) = +1 +2nk +���xk − xkW k��� +2 +F , += +1 +2nk +tr((xk − xkW k)⊤(xk − xkW k)), += +1 +2nk +tr((xk)⊤xk − (W k)⊤(xk)⊤xk − (xk)⊤xkW k + (W k)⊤(xk)⊤xkW k), += 1 +2 tr +� +U k − (W k)⊤U k − U kW k + (W k)⊤U kW k� +, += 1 +2 tr +� +U k − 2(W k)⊤U k + (W k)⊤U kW k� +. +Similarly, the third term of equation (24) can be written as +ρ2 +2 ∥W k − Zk∥2 +F = ρ2 +2 tr +�� +W k − Zk�⊤ � +W k − Zk�� +, += ρ2 +2 tr +� +(W k)⊤W k − 2(W k)⊤Zk + (Zk)⊤Zk� +. +Therefore, we have +f(W k) = 1 +2 tr(U k − 2(W k)⊤U k + (W k)⊤U kW k) + tr(βk(W k)⊤ − βk(Zk)⊤) + ρ2 +2 tr((W k)⊤W k +− 2(W k)⊤Zk + (Zk)⊤Zk), += 1 +2 tr(−2(W k)⊤U k + (W k)⊤U kW k) + tr(βk(W k)⊤)ρ2 +2 tr((W k)⊤W k − 2(W k)⊤Zk + c, +and its derivative is given by +∇W kf +� +W k� += 1 +2(−2U k + ((U k)⊤ + U k)W k) + βk + ρ2 +2 (2W k − 2Zk), += −U k + U kW k + βk + ρ2W k − ρ2Zk, += (U k + ρ2I)W k − U k + βk − ρ2Zk. +Assuming U k + ρ2I is invertible, solving ∇W kf +� +W k� += 0 yields the solution +W k = (U k + ρ2I)−1(ρ2Zk − βk + U k). +27 + +B +Details on the Federated Global Update Step +We provide details of the DIPA algorithm in the federated global update step. For convenience, we +introduce the following procedures and discuss how to transform K matrices into one matrix, so +that we can re-write equation (19) into vector form. +Transform: Given K matrices +˜ +M = {M1, . . . , MK}. For each k = 1, . . . , K, Mk ∈ Rd×d. +Transform Mk into vector form, denote as mk = +� +Mk +i,j | for i, j = 1, . . . , d +�⊤ +. Then, construct a +matrix +¯ +M = +� +m1, . . . , mK�⊤ ∈ RK×d2. +Inverse-Transform: The inverse-transform reverses the steps of the transform, which to +transform the matrix +¯ +M ∈ RK×d2 to K matrices +˜ +M = {M1, . . . , MK}. +The core of DIPA algorithm is to compute the separate proximal operators for R1 and R2. And +then the iterative projection can be used to find a feasible point. The proximal operator for the ℓ1 +term proxR1 +� ¯U +� +is given by the soft-thresholding operator [Tibshirani, 1996]. +proxR1 +� ¯U; λ1 +� += arg min +¯ +Z +1 +2 +�� ¯Z − ¯U +��2 +F + λ1∥ ¯Z∥1, += sign( ¯U) ⊙ max +� +| ¯U| − λ1, 0 +� +. +(25) +where the max and sign functions act in an element-wise manner and ⊙ denotes element-wise +multiplication. +The calculation of group-fused lasso proximal operator proxR2 +� ¯U +� +is more complex, and there +is no obvious closed-form solution. We tackle this through a block-coordinate descent approach +[Bleakley and Vert, 2011]. Then, the proximal operator for the group smoothing aspect of the +regularizer can be written as: +proxR2 +� ¯U; λ2 +� += arg min +¯ +Z +1 +2 +�� ¯Z − ¯U +��2 +F + λ2∥D ¯Z∥2,1. +(26) +Let A = D ¯Z and construct ¯Z as a sum of differences via Zk,• = a+�K−1 +i=1 Ai,•, ( where a = Z1,•). +Then we can interpret the proximal operator as a group lasso probem [Bleakley and Vert, 2011]. +A := arg min +A +1 +2∥ ¯Ucen − ¯RcenA∥2 +F + λ2∥A∥2,1, +(27) +where Xcen denotes a column centered matrix and R ∈ RK×(K−1) is a matrix with entries Ri,j = 1 +for i > j and 0 otherwise. The problem above can be solved through a block-coordinate descent +strategy, sequentially updating the solution for each block Ak,• for k = 1, . . . , K − 1. We can then +construct a solution for ¯Z by summing the differences. And the optimal value for a is given by +a = 11,T (U − RA). Correspondingly, the proximal operator for R2 is +proxR2 +� ¯U; λ2 +� += +� +�a⊤, (a + A1,•)⊤ , . . . , +� +a + +K−1 +� +i=1 +Ai,• +�⊤� +� +⊤ +. +(28) +C +Details of the Synthetic Data Generating +We followed the similar synthetic data generate procedure as in [Liu et al., 2022]. The key is how to +create similar but different graphs by applying perturbations. +28 + +Perturbation level: Denote the adjacency matrix of Gtruth as At = (at +ij) ∈ Rd×d, where at +ij = 1 +if there is an edge from node i to node j, and at +ij = 0 otherwise, i, j = 1, . . . , d. Then the generated +BN, denoted by Ggen, is constructed in the following way. Let Ag be the adjacency matrix of Ggen, +and define the perturbation level as the ratio of the number of changed edges in Ag to the number +of all possible edges. For example, if the perturbation level is 10%, we first set Ag = At, and then +randomly select 10% of the off-diagonal elements at +ij(i ̸= j) in At. For each selected element at +ij, +if at +ij = 0, then we set ag +ij = 1 (adding edge); if at +ij = 1, then with probability 1/2 we set ag +ij = 0 +(deleting edge), otherwise let ag +ji = 1 (reversing edge). We generate K graphs ˜G = {G1, . . . , GK} by +such a perturbation scheme. +Evaluation metric: Let {G1 +output, . . . , GK +output} represent the K BN structures obtained from +NOTEARS-PFL, NOTEARS-SIG, NOTEARS-AVG, NOTEARS-ADMM. The four basic statistics +in the evaluation metrics are defined as follows: true positives (TP), the number of edges that are +both in G1 +output and G1; false positives (FP), the number of edges that are present in G1 +output but +not in G1; false negatives (FN), the number of edges that are present in G1 but not in G1 +output; and +true negatives (TN), the number of vertex pairs that are neither edges in G1 nor in G1 +output. +29 + +D +Supplementary Tables +Table 3: Data summary of the datasets used in this study. +Center of Innovation in Hiroshima +(COI) +Kyoto University +(KUT) +University of Tokyo +(UTO) +Hiroshima Kajikawa Hospital +(HKH) +Hiroshima University Hospital +(HUH) +Total Subject +194 +175 +158 +62 +124 +MDD Subject +70 +16 +62 +33 +57 +HC Subject +124 +159 +96 +29 +67 +MDD Percentage +36% +9% +39% +53% +46% +rs-fMRI Frames +240 +240 +240 +107 +143 +Table 4: Demographic characteristics of participants in multi-site datasets. +Site +Number Male/Female +Age +BDI +MDD COI +70 +31/39 +45.0 ± 12.5 +26.2 ± 9.9 +KUT +16 +10 6 +33.79±10.82 +27.7 ± 10.1 +UTO +62 +36/26 +38.74 ±11.62 21.5±11.3 +HKH +33 +20/13 +44.8±11.5 +28.5±8.7 +HUH +57 +32/25 +43.3±12.2 +30.9±9.0 +HC +COI +124 +46/78 +51.9 ± 13.4 +8.2 ± 6.3 +KUT +159 +93/66 +36.51± 13.59 6.0 ± 5.4 +UTO +96 +33/63 +46.65±15.54 +6.6 ± 6.5 +HKH +29 +12 17 +45.4±9.5 +5.1±4.6 +HUH +67 +30/37 +45.6±9.4 +5.6±4.3 +Table 5: Imaging protocols for rs-fMRI and structural MRI in multi-site datasets. +COI +KUT +UTO +HKH +HUH +rs-fMRI +MRI scanner +Siemens +Verio +Siemens +TimTrio +GE +MR750w +Siemens +Spectra +GE +Sigma HDxt +Magnetic field strength +3.0T +3.0T +3.0T +3.0T +3.0T +Number of channels per coil +12 +32 +24 +12 +8 +FoV (mm) +212 +212 +212 +192 +256 +Matrix +64 x 64 +64 x 64 +64 x 64 +64 x 64 +64 x 64 +Number of slices +40 +40 +40 +38 +32 +Number of volumes +240 +240 +240 +107 +143 +In-plane resolution (mm) +3.3 x 3.3 +3.3125 X 3.3125 +3.3 x 3.3 +3.0 x 3.0 +4.0 x 4.0 +Slice thickness (mm) +3.2 +3.2 +3.2 +3 +4 +Slice gap (mm) +0.8 +0.8 +0.8 +0 +0 +TR (ms) +2500 +2500 +2500 +2700 +2000 +TE (ms) +30 +30 +30 +31 +27 +Flip angel (deg) +80 +80 +80 +90 +90 +Slice acquisition order +Ascending +Ascending +Ascending +Ascending +Ascending +Total scan +time +10 min + 10s +(dummy) +10 min + 10s +(dummy) +10 min + 10s +(dummy) +4 min. 46s. + 14s +(dummy) +4 min. 46s. + 14s +(dummy) +Eye closed/fixate +Fixate +Fixate +Fixate +Fixate +Fixate +Structural MRI FoV (mm) +256 +225x 240 +240 +256 +256 +Matrix +256 x 256 +240 x 256 +256 x 256 +256 x 256 +256 x 256 +Voxel size mm3 +1 x 1x 1 +0.9375 x 0.9375 x 1 +1 x 1x 1.2 +1 x 1x 1 +1 x 1x 1 +TR (ms) +2300 +2000 +7.7 +1900 +6812 +TE (ms) +2.98 +3.4 +3.1 +2.38 +1986 +TI (ms) +900 +990 +400 +900 +450 +Flip angel (deg) +9 +8 +11 +10 +20 +30 + +Table 6: Description of ROIs in AAL template and their Montreal Neurological Institute (MNI) +coordinates. +Index +Region name +Abbreviation +Lobe +x +y +z +1 +Precentral gyrus +PreCG.L +Frontal +-38.65 -5.68 +50.94 +2 +Precentral gyrus +PreCG.R +Frontal +41.37 +-8.21 +52.09 +3 +Superior frontal gyrus, dorsolateral +SFGdor.L +Frontal +-18.45 34.81 +42.20 +4 +Superior frontal gyrus, dorsolateral +SFGdor.R +Frontal +21.90 +31.12 +43.82 +5 +Superior frontal gyrus, orbital +ORBsup.L +Frontal +-16.56 47.32 -13.31 +6 +Superior frontal gyrus, orbital +ORBsup.R +Frontal +18.49 +48.10 -14.02 +7 +Middle frontal gyrus +MFG.L +Frontal +-33.43 32.73 +35.46 +8 +Middle frontal gyrus +MFG.R +Frontal +37.59 +33.06 +34.04 +9 +Middle frontal gyrus, orbital +ORBmid.L +Frontal +-30.65 50.43 +-9.62 +10 +Middle frontal gyrus, orbital +ORBmid.R +Frontal +33.18 +52.59 -10.73 +11 +Inferior frontal gyrus, opercular +IFGoperc.L +Frontal +-48.43 12.73 +19.02 +12 +Inferior frontal gyrus, opercular +IFGoperc.R +Frontal +50.20 +14.98 +21.41 +13 +Inferior frontal gyrus, triangular +IFGtriang.L +Frontal +-45.58 29.91 +13.99 +14 +Inferior frontal gyrus, triangular +IFGtriang.R +Frontal +50.33 +30.16 +14.17 +15 +Inferior frontal gyrus, orbital +ORBinf.L +Frontal +-35.98 30.71 -12.11 +16 +Inferior frontal gyrus, orbital +ORBinf.R +Frontal +41.22 +32.23 -11.91 +17 +Rolandic operculum +ROL.L +Frontal +-47.16 -8.48 +13.95 +18 +Rolandic operculum +ROL.R +Frontal +52.65 +-6.25 +14.63 +19 +Supplementary motor area +SMA.L +Frontal +-5.32 +4.85 +61.38 +20 +Supplementary motor area +SMA.R +Frontal +8.62 +0.17 +61.85 +21 +Olfactory cortex +OLF.L +Frontal +-8.06 +15.05 -11.46 +22 +Olfactory cortex +OLF.R +Frontal +10.43 +15.91 -11.26 +23 +Superior frontal gyrus, medial +SFGmed.L +Frontal +-4.80 +49.17 +30.89 +24 +Superior frontal gyrus, medial +SFGmed.R +Frontal +9.10 +50.84 +30.22 +25 +Superior frontal gyrus, medial orbital ORBsupmed.L +Frontal +-5.17 +54.06 +-7.40 +26 +Superior frontal gyrus, medial orbital ORBsupmed.R +Frontal +8.16 +51.67 +-7.13 +27 +Gyrus rectus +REC.L +Frontal +-5.08 +37.07 -18.14 +28 +Gyrus rectus +REC.R +Frontal +8.35 +35.64 -18.04 +29 +Insula +INS.L +Insula and Cingulate Gyri -35.13 +6.65 +3.44 +30 +Insula +INS.R +Insula and Cingulate Gyri 39.02 +6.25 +2.08 +31 +Cingulate gyrus, anterior part +ACG.L +Insula and Cingulate Gyri -4.04 +35.40 +13.95 +32 +Cingulate gyrus, anterior part +ACG.R +Insula and Cingulate Gyri +8.46 +37.01 +15.84 +33 +Cingulate gyrus, mid part +DCG.L +Insula and Cingulate Gyri -5.48 -14.92 41.57 +34 +Cingulate gyrus, mid part +DCG.R +Insula and Cingulate Gyri +8.02 +-8.83 +39.79 +35 +Cingulate gyurs, posterior part +PCG.L +Insula and Cingulate Gyri -4.85 -42.92 24.67 +36 +Cingulate gyurs, posterior part +PCG.R +Insula and Cingulate Gyri +7.44 +-41.81 21.87 +37 +Hippocampus +HIP.L +Temporal +-25.03 -20.74 -10.13 +38 +Hippocampus +HIP.R +Temporal +29.23 -19.78 -10.33 +39 +Parahippocampus +PHG.L +Temporal +-21.17 -15.95 -20.70 +40 +Parahippocampus +PHG.R +Temporal +25.38 -15.15 -20.47 +41 +Amygdala +AMYG.L +Temporal +-23.27 -0.67 -17.14 +42 +Amygdala +AMYG.R +Temporal +27.32 +0.64 +-17.50 +43 +Calcarine fissure and surrounding cortex +CAL.L +Occipital +-7.14 -78.67 +6.44 +44 +Calcarine fissure and surrounding cortex +CAL.R +Occipital +15.99 -73.15 +9.40 +45 +Cuneus +CUN.L +Occipital +-5.93 -80.13 27.22 +46 +Cuneus +CUN.R +Occipital +13.51 -79.36 28.23 +47 +Lingual gyrus +LING.L +Occipital +-14.62 -67.56 -4.63 +48 +Lingual gyrus +LING.R +Occipital +16.29 -66.93 -3.87 +49 +Superior occipital lobe +SOG.L +Occipital +-16.54 -84.26 28.17 +50 +Superior occipital lobe +SOG.R +Occipital +24.29 -80.85 30.59 +51 +Middle occipital lobe +MOG.L +Occipital +-32.39 -80.73 16.11 +52 +Middle occipital lobe +MOG.R +Occipital +37.39 -79.70 19.42 +53 +Inferior occipital lobe +IOG.L +Occipital +-36.36 -78.29 -7.84 +54 +Inferior occipital lobe +IOG.R +Occipital +38.16 -81.99 -7.61 +55 +Fusiform gyrus +FFG.L +Temporal +-31.16 -40.30 -20.23 +56 +Fusiform gyrus +FFG.R +Temporal +33.97 -39.10 -20.18 +57 +Postcentral gyrus +PoCG.L +Pariental +-42.46 -22.63 48.92 +58 +Postcentral gyrus +PoCG.R +Pariental +41.43 -25.49 52.55 +59 +Superior pariental gyrus +SPG.L +Pariental +-23.45 -59.56 58.96 +60 +Superior pariental gyrus +SPG.R +Pariental +26.11 -59.18 62.06 +61 +Inferior pariental gyrus +IPL.L +Pariental +-42.80 -45.82 46.74 +62 +Inferior pariental gyrus +IPL.R +Pariental +46.46 -46.29 49.54 +63 +Supramarginal gyrus +SMG.L +Pariental +-55.79 -33.64 30.45 +31 + +Table 7: Continue table: Description of ROIs in AAL template and their Montreal Neurological +Institute (MNI) coordinates. +Index +Region name +Abbreviation +Lobe +x +y +z +64 +Supramarginal gyrus +SMG.R +Pariental +57.61 -31.50 34.48 +65 +Angular gyrus +ANG.L +Pariental +-44.14 -60.82 35.59 +66 +Angular gyrus +ANG.R +Pariental +45.51 -59.98 38.63 +67 +Precuneus +PCUN.L +Pariental +-7.24 -56.07 48.01 +68 +Precuneus +PCUN.R +Pariental +9.98 +-56.05 43.77 +69 +Paracentral lobule +PCL.L +Frontal +-7.63 -25.36 70.07 +70 +Paracentral lobule +PCL.R +Frontal +7.48 +-31.59 68.09 +71 +Caudate +CAU.L +Subcortial region -11.46 11.00 +9.24 +72 +Caudate +CAU.R +Subcortial region 14.84 +12.07 +9.42 +73 +Putamen +PUT.L +Subcortial region -23.91 +3.86 +2.40 +74 +Putamen +PUT.R +Subcortial region 27.78 +4.91 +2.46 +75 +Pallidum +PAL.L +Subcortial region -17.75 -0.03 +0.21 +76 +Pallidum +PAL.R +Subcortial region 21.20 +0.18 +0.23 +77 +Thalamus +THA.L +Subcortial region -10.85 -17.56 +7.98 +78 +Thalamus +THA.R +Temporal +13.00 -17.55 +8.09 +79 +Heschl gyrus +HES.L +Temporal +-41.99 -18.88 +9.98 +80 +Heschl gyrus +HES.R +Temporal +45.86 -17.15 10.41 +81 +Superior temporal gyrus +STG.L +Temporal +-53.16 -20.68 +7.13 +82 +Superior temporal gyrus +STG.R +Temporal +58.15 -21.78 +6.80 +83 +Temporal pole: superior temporal gyrus +TPOsup.L +Temporal +-39.88 15.14 -20.18 +84 +Temporal pole: superior temporal gyrus +TPOsup.R +Temporal +48.25 +14.75 -16.86 +85 +Middle temporal gyrus +MTG.L +Temporal +-55.52 -33.80 -2.20 +86 +Middle temporal gyrus +MTG.R +Temporal +57.47 -37.23 -1.47 +87 +Temporal pole: middle temporal gyrus +TPOmid.L +Temporal +-36.32 14.59 -34.08 +88 +Temporal pole: middle temporal gyrus +TPOmid.R +Temporal +44.22 +14.55 -32.23 +89 +Inferior temporal gyrus +ITG.L +Temporal +-49.77 -28.05 -23.17 +90 +Inferior temporal gyrus +ITG.R +Temporal +53.69 -31.07 -22.32 +91 +Cerebellum crus 1 +CRBLCrus1.L +Posterior Fossa +-36.07 -66.72 -28.93 +92 +Cerebellum crus 1 +CRBLCrus1.R +Posterior Fossa +37.46 -67.14 -29.55 +93 +Cerebellum crus 2 +CRBLCrus2.L +Posterior Fossa +-28.64 -73.26 -38.2 +94 +Cerebellum crus 2 +CRBLCrus2.R +Posterior Fossa +32.06 -69.02 -39.95 +95 +Cerebellum 3 +CRBL3.L +Posterior Fossa +-8.8 +-37.22 -18.58 +96 +Cerebellum 3 +CRBL3.R +Posterior Fossa +12.32 -34.47 -19.39 +97 +Cerebellum 4 +CRBL45.L +Posterior Fossa +-15 +-43.49 -16.93 +98 +Cerebellum 4 +CRBL45.R +Posterior Fossa +17.2 +-42.86 -18.15 +99 +Cerebellum 6 +CRBL6.L +Posterior Fossa +-23.24 -59.1 -22.13 +100 +Cerebellum 6 +CRBL6.R +Posterior Fossa +24.69 -58.32 -23.65 +101 +Cerebellum 7 +CRBL7b.L +Posterior Fossa +-32.36 -59.82 -45.45 +102 +Cerebellum 7 +CRBL7b.R +Posterior Fossa +33.14 -63.18 -48.46 +103 +Cerebellum 8 +CRBL8.L +Posterior Fossa +-25.75 -54.52 -47.68 +104 +Cerebellum 8 +CRBL8.R +Posterior Fossa +25.06 -56.34 -49.47 +105 +Cerebellum 9 +CRBL9.L +Posterior Fossa +-10.95 -48.95 -45.9 +106 +Cerebellum 9 +CRBL9.R +Posterior Fossa +9.46 +-49.5 -46.33 +107 +Cerebellum 10 +CRBL10.L +Posterior Fossa +-22.61 -33.8 -41.76 +108 +Cerebellum 10 +CRBL10.R +Posterior Fossa +25.99 -33.84 -41.35 +109 +Vermis12 +Vermis12 +Posterior Fossa +0.76 +-38.79 -20.05 +110 +Vermis3 +Vermis3 +Posterior Fossa +1.38 +-39.93 -11.4 +111 +Vermis45 +Vermis45 +Posterior Fossa +1.22 +-52.36 -6.11 +112 +Vermis6 +Vermis6 +Posterior Fossa +1.14 +-67.06 -15.12 +113 +Vermis7 +Vermis7 +Posterior Fossa +1.15 +-71.93 -25.14 +114 +Vermis8 +Vermis8 +Posterior Fossa +1.15 +-64.43 -34.08 +115 +Vermis9 +Vermis9 +Posterior Fossa +0.86 +-54.87 -34.9 +116 +Vermis10 +Vermis10 +Posterior Fossa +0.36 +-45.8 -31.68 +32 + +Table 8: The overlapping connections between the directed networks of 5 sites of MDD patients and +HC participants. +From +To +Index +ROI +Lobe +Index +ROI +Lobe +MDD +10 +ORBmid.R +Frontal +6 +ORBsup.R +Frontal +24 +SFGmed.R +Frontal +33 +DCG.L +Insula and Cingulate Gyri +30 +INS.R +Insula and Cingulate Gyri +10 +ORBmid.R +Frontal +30 +INS.R +Insula and Cingulate Gyri +29 +INS.L +Insula and Cingulate Gyri +30 +INS.R +Insula and Cingulate Gyri +32 +ACG.R +Insula and Cingulate Gyri +33 +DCG.L +Insula and Cingulate Gyri +3 +SFGdor.L +Frontal +35 +PCG.L +Insula and Cingulate Gyri +36 +PCG.R +Insula and Cingulate Gyri +46 +CUN.R +Occipital +45 +CUN.L +Occipital +56 +FFG.R +Temporal +11 +IFGoperc.L +Frontal +68 +PCUN.R +Pariental +46 +CUN.R +Occipital +68 +PCUN.R +Pariental +26 +ORBsupmed.R +Frontal +71 +CAU.L +Subcortial region +6 +ORBsup.R +Frontal +77 +THA.L +Subcortial region +72 +CAU.R +Subcortial region +82 +STG.R +Temporal +86 +MTG.R +Temporal +85 +MTG.L +Temporal +10 +ORBmid.R +Frontal +89 +ITG.L +Temporal +1 +PreCG.L +Frontal +HC +1 +PreCG.L +Frontal +26 +ORBsupmed.R +Frontal +8 +MFG.R +Frontal +9 +ORBmid.L +Frontal +23 +SFGmed.L +Frontal +24 +SFGmed.R +Frontal +31 +ACG.L +Insula and Cingulate Gyri +23 +SFGmed.L +Frontal +34 +DCG.R +Insula and Cingulate Gyri +67 +PCUN.L +Pariental +38 +HIP.R +Temporal +39 +PHG.L +Temporal +40 +PHG.R +Temporal +3 +SFGdor.L +Frontal +82 +STG.R +Temporal +8 +MFG.R +Frontal +86 +MTG.R +Temporal +89 +ITG.L +Temporal +33 + +Table 9: The site-specific connections between the directed networks of 5 sites of MDD patients. +From +To +Index +ROI +Lobe +Index +ROI +Lobe +Site 1 +1 +PreCG.L +Frontal +10 +ORBmid.R +Frontal +1 +PreCG.L +Frontal +67 +PCUN.L +Pariental +2 +PreCG.R +Frontal +67 +PCUN.L +Pariental +5 +ORBsup.L +Frontal +39 +PHG.L +Temporal +6 +ORBsup.R +Frontal +78 +THA.R +Temporal +7 +MFG.L +Frontal +71 +CAU.L +Subcortial region +8 +MFG.R +Frontal +82 +STG.R +Temporal +11 +IFGoperc.L +Frontal +68 +PCUN.R +Pariental +13 +IFGtriang.L +Frontal +67 +PCUN.L +Pariental +16 +ORBinf.R +Frontal +56 +FFG.R +Temporal +24 +SFGmed.R +Frontal +72 +CAU.R +Subcortial region +26 +ORBsupmed.R +Frontal +42 +AMYG.R +Temporal +29 +INS.L +Insula and Cingulate Gyri +8 +MFG.R +Frontal +42 +AMYG.R +Temporal +87 +TPOmid.L +Temporal +55 +FFG.L +Temporal +68 +PCUN.R +Pariental +77 +THA.L +Subcortial region +31 +ACG.L +Insula and Cingulate Gyri +90 +ITG.R +Temporal +56 +FFG.R +Temporal +Site2 +3 +SFGdor.L +Frontal +7 +MFG.L +Frontal +4 +SFGdor.R +Frontal +1 +PreCG.L +Frontal +5 +ORBsup.L +Frontal +25 +ORBsupmed.L +Frontal +7 +MFG.L +Frontal +10 +ORBmid.R +Frontal +15 +ORBinf.L +Frontal +11 +IFGoperc.L +Frontal +24 +SFGmed.R +Frontal +3 +SFGdor.L +Frontal +29 +INS.L +Insula and Cingulate Gyri +9 +ORBmid.L +Frontal +29 +INS.L +Insula and Cingulate Gyri +16 +ORBinf.R +Frontal +31 +ACG.L +Insula and Cingulate Gyri +5 +ORBsup.L +Frontal +77 +THA.L +Subcortial region +13 +IFGtriang.L +Frontal +81 +STG.L +Temporal +24 +SFGmed.R +Frontal +85 +MTG.L +Temporal +14 +IFGtriang.R +Frontal +33 +DCG.L +Insula and Cingulate Gyri +35 +PCG.L +Insula and Cingulate Gyri +37 +HIP.L +Temporal +12 +IFGoperc.R +Frontal +89 +ITG.L +Temporal +42 +AMYG.R +Temporal +56 +FFG.R +Temporal +35 +PCG.L +Insula and Cingulate Gyri +86 +MTG.R +Temporal +5 +ORBsup.L +Frontal +Site3 +1 +PreCG.L +Frontal +14 +IFGtriang.R +Frontal +2 +PreCG.R +Frontal +57 +PoCG.L +Pariental +5 +ORBsup.L +Frontal +26 +ORBsupmed.R +Frontal +7 +MFG.L +Frontal +35 +PCG.L +Insula and Cingulate Gyri +11 +IFGoperc.L +Frontal +23 +SFGmed.L +Frontal +13 +IFGtriang.L +Frontal +46 +CUN.R +Occipital +23 +SFGmed.L +Frontal +9 +ORBmid.L +Frontal +29 +INS.L +Insula and Cingulate Gyri +3 +SFGdor.L +Frontal +33 +DCG.L +Insula and Cingulate Gyri +42 +AMYG.R +Temporal +33 +DCG.L +Insula and Cingulate Gyri +45 +CUN.L +Occipital +35 +PCG.L +Insula and Cingulate Gyri +85 +MTG.L +Temporal +40 +PHG.R +Temporal +11 +IFGoperc.L +Frontal +39 +PHG.L +Temporal +6 +ORBsup.R +Frontal +72 +CAU.R +Subcortial region +56 +FFG.R +Temporal +78 +THA.R +Temporal +2 +PreCG.R +Frontal +80 +HES.R +Temporal +82 +STG.R +Temporal +Site4 +2 +PreCG.R +Frontal +24 +SFGmed.R +Frontal +5 +ORBsup.L +Frontal +4 +SFGdor.R +Frontal +7 +MFG.L +Frontal +29 +INS.L +Insula and Cingulate Gyri +9 +ORBmid.L +Frontal +57 +PoCG.L +Pariental +12 +IFGoperc.R +Frontal +14 +IFGtriang.R +Frontal +15 +ORBinf.L +Frontal +7 +MFG.L +Frontal +24 +SFGmed.R +Frontal +12 +IFGoperc.R +Frontal +30 +INS.R +Insula and Cingulate Gyri +23 +SFGmed.L +Frontal +31 +ACG.L +Insula and Cingulate Gyri +16 +ORBinf.R +Frontal +32 +ACG.R +Insula and Cingulate Gyri +68 +PCUN.R +Pariental +34 +DCG.R +Insula and Cingulate Gyri +5 +ORBsup.L +Frontal +37 +HIP.L +Temporal +29 +INS.L +Insula and Cingulate Gyri +40 +PHG.R +Temporal +16 +ORBinf.R +Frontal +41 +AMYG.L +Temporal +3 +SFGdor.L +Frontal +45 +CUN.L +Occipital +72 +CAU.R +Subcortial region +56 +FFG.R +Temporal +7 +MFG.L +Frontal +68 +PCUN.R +Pariental +15 +ORBinf.L +Frontal +87 +TPOmid.L +Temporal +33 +DCG.L +Insula and Cingulate Gyri +90 +ITG.R +Temporal +86 +MTG.R +Temporal +34 + +Table 10: Continue table: The site-specific connections between the directed networks of 5 sites of +MDD patients. +From +To +Index +ROI +Lobe +Index +ROI +Lobe +Site 5 +1 +PreCG.L +Frontal +24 +SFGmed.R +Frontal +2 +PreCG.R +Frontal +46 +CUN.R +Occipital +7 +MFG.L +Frontal +2 +PreCG.R +Frontal +10 +ORBmid.R +Frontal +25 +ORBsupmed.L +Frontal +13 +IFGtriang.L +Frontal +15 +ORBinf.L +Frontal +15 +ORBinf.L +Frontal +4 +SFGdor.R +Frontal +24 +SFGmed.R +Frontal +10 +ORBmid.R +Frontal +26 +ORBsupmed.R +Frontal +77 +THA.L +Subcortial region +33 +DCG.L +Insula and Cingulate Gyri +31 +ACG.L +Insula and Cingulate Gyri +34 +DCG.R +Insula and Cingulate Gyri +38 +HIP.R +Temporal +36 +PCG.R +Insula and Cingulate Gyri +39 +PHG.L +Temporal +39 +PHG.L +Temporal +4 +SFGdor.R +Frontal +46 +CUN.R +Occipital +77 +THA.L +Subcortial region +56 +FFG.R +Temporal +32 +ACG.R +Insula and Cingulate Gyri +67 +PCUN.L +Pariental +4 +SFGdor.R +Frontal +78 +THA.R +Temporal +39 +PHG.L +Temporal +86 +MTG.R +Temporal +16 +ORBinf.R +Frontal +89 +ITG.L +Temporal +12 +IFGoperc.R +Frontal +35 + diff --git a/EtE0T4oBgHgl3EQfgwHQ/content/tmp_files/load_file.txt b/EtE0T4oBgHgl3EQfgwHQ/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..9b336cd08a6f270f8b19eb98408e390cfe8a9abf --- /dev/null +++ b/EtE0T4oBgHgl3EQfgwHQ/content/tmp_files/load_file.txt @@ -0,0 +1,1876 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf,len=1875 +page_content='Learning Personalized Brain Functional Connectivity of MDD Patients from Multiple Sites via Federated Bayesian Networks Shuai Liu ∗ Xiao Guo † Shun Qi ‡ Huaning Wang § Xiangyu Chang ¶ January 9, 2023 Abstract Identifying functional connectivity biomarkers of major depressive disorder (MDD) patients is essential to advance understanding of the disorder mechanisms and early intervention.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, due to the small sample size and the high dimension of available neuroimaging data, the performance of existing methods is often limited.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Multi-site data could enhance the statistical power and sample size, while they are often subject to inter-site heterogeneity and data-sharing policies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In this paper, we propose a federated joint estimator, NOTEARS-PFL, for simultaneous learning of multiple Bayesian networks (BNs) with continuous optimization, to identify disease- induced alterations in MDD patients.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We incorporate information shared between sites and site-specific information into the proposed federated learning framework to learn personalized BN structures by introducing the group fused lasso penalty.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We develop the alternating direction method of multipliers, where in the local update step, the neuroimaging data is processed at each local site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then the learned network structures are transmitted to the center for the global update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In particular, we derive a closed-form expression for the local update step and use the iterative proximal projection method to deal with the group fused lasso penalty in the global update step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We evaluate the performance of the proposed method on both synthetic and real-world multi-site rs-fMRI datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The results suggest that the proposed NOTEARS-PFL yields superior effectiveness and accuracy than the comparable methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 1 Introduction Major depressive disorder (MDD) is one of the most prevalent, costly, and disabling mental disorders worldwide [Cassano and Fava, 2002, Jia et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2010].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It is often characterized by persistent sadness, worthlessness, hopelessness, anxiety, and cognitive impairments [Fu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2008].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The negative psychology of MDD can lead to severe consequences, including suicide [Jia et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2015].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The ∗Department of Information Systems and Intelligent Business, School of Management, Xi’an Jiaotong University;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' email: hljliushuai@stu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='xjtu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='cn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' †Corresponding author: Center for Modern Statistics, School of Mathematics, Northwest University;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' email: xiaoguo@nwu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='cn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ‡Key Laboratory of Biomedical Information Engineering of Ministry of Education, Institute of Health and Rehabilitation Science, School of Life Science and Technology, Xi’an Jiaotong University;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' email: qishun@xjtu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='cn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' §Department of Psychiatry, Xijing Hospital, Air Force Medical University;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' email: xskzhu@fmmu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='cn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ¶Center for Intelligent Decision-Making and Machine Learning, School of Management, Xi’an Jiaotong University;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' email: xiangyuchang@xjtu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='edu.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='cn.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 1 arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02423v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='LG] 6 Jan 2023 productivity loss and disability due to MDD also pose a severe burden to society and affected families [Vos et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Therefore, understanding the pathogenesis of MDD is crucial for effective intervention, diagnosis, and treatment [Belmaker and Agam, 2008].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Diagnostic neuroimaging has been shown to be an effective modality to understand the underlying pathological mechanisms and cognitive information of brain diseases [Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2016, 2017], and has been used for early identification of MDD [Smith et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2013].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Resting-state functional magnetic resonance imaging (rs- fMRI) is one of the most widely used imaging modes for MDD identification [Hamilton et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2011, Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2013, Lin et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2016].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It can detect abnormal brain functional connectivity in MDD patients, allowing non-invasive investigation of the disease [Ye et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2015].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Functional connectivity (FC), an essential biomarker in neurological disorders, is traditionally defined as the Pearson correlation between different regions of interest (ROIs) [Ryali et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2012].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, this association still does not truly determine the direction of interactions between ROIs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' An accurate understanding of this directional information is critical to understanding the brain functional integration of MDD [Price et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To further investigate FC with rs-fMRI data, a number of approaches beyond the Pearson correlation are proposed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For example, Kandilarova et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2018] used a dynamic causal modeling (DCM) method to reveal differences of FC in anterior insula between healthy control (HC) participants and MDD patients.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Hamilton et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2011] used Granger causality (GC) analysis method to investigate the aberrant patterns of FC in MDD, and identify the limbic inhibition of dorsal cortex as a key biomarker for MDD diagnosis .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Nevertheless, these methods are not robust for analyzing specific individuals or large-scale ROIs [Molenaar, 2004, Friston et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2011].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Bayesian network (BN), an approach for studying the conditional dependencies between variables in a system via a directed acyclic graph (DAG), has been used for detecting abnormal brain FC in MDD patients [Koller and Friedman, 2009, Ide et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2014, Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Compared with DCM and GC methods, BN benefits from utilizing more samples to improve the robustness and stability of the resulting FC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Note that the amount of rs-fMRI data collected at a single imaging site is limited due to the difficult and expensive data acquisition in practice.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Therefore, it is difficult to provide enough data from a single site to make a good BN estimate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Fortunately, multiple rs-fMRI datasets from different sites provide the possibility for enhancing the quality of learned BNs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, multi-site data are often subject to inter-site heterogeneity and data-sharing policies [Li et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2020, Tong et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' How to learn more helpful heterogeneous information from multi-site data with considering data-sharing policies is still one of the research hotspots of BN learning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In this paper, we consider the problem of learning BN structures using multiple datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Our initial interest arises from discovering noninvasive biomarkers inherent in multi-site rs-fMRI data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Generally, data collected at multiple imaging sites have a common disease of interest (such as MDD), which results in that they may share similar disease-induced connectivity abnormalities.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Therefore, we consider leveraging data from multi-site to learn multiple BNs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We are committed to addressing the three challenges: (1) computational inefficiency of the structural learning algorithms of BNs, which partially comes from the DAG constraint and the resulting combinatorial optimization problem;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (2) large heterogeneity of multi-site rs-fMRI data, which is caused by inter-site variation in scanners, image acquisition protocols, and patient populations across sites [Wang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022];' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (3) data sharing barriers, that is, patients worry that sharing their medical data will lead to personal information disclosure [Li et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2020].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The government is likely to promulgate some privacy protection regulations and inflict severe penalties for medical data breach events [Jin et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2019].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To address the above issues, we propose a federated joint estimator for the simultaneous learning of multiple BNs with continuous optimization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In pursuit of computational efficiency, we convert the 2 traditional combinatorial BN structure learning problem into a continuous numerical optimization problem inspired by the NOTEARS method [Zheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To capture the heterogeneity, we learn multiple BNs from multi-site data but with similar structures by introducing the group fused lasso penalty instead of learning a single BN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To lighten the data-sharing barriers, we study the structure learning of multiple BNs in the federated learning (FL) setting, which is a natural method to tackle the data-sharing problem [Pfitzner et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2021].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We refer to the proposed NOTEARS-based Personalized Federated Learning framework of learning multiple BNs’ structures as NOTEARS-PFL, whose whole protocol is shown in Figure 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Figure 1: Illustration of the learning framework of NOTEARS-PFL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Each site stores and processes rs-fMRI data locally.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In the t-th iteration, each site estimates the local weighted adjacency matrix W k (t) through the local update step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, each site transmits the estimated local matrix to the center.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Center updates the global weighted adjacency matrices ˜Z(t) through the global update step based on the received ˜ W(t) = {W 1 (t), .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , W K (t)}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Finally, the center transmits the estimated global matrix to each site for the (t + 1)-th iteration update.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 3 Center Global model: Z(t) ← argmin [L, (W(t),z,O(t-1)) ①(t) ←[W(t),Z(t), O(t-1)) Wh () Z2 02 1),0h W(t) 1) Local model: W() arg win [L, (wK, z(-1), (-1)) +2 data data data rs-fMRI preprocessing rs-fMRI preprocessing preprocessing rs-fMRI scan scan scan Site K Site 1 Site 2The merits of the proposed NOTEARS-PFL are multi-fold.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' NOTEARS-PFL is capable of learning site-specific BNs from multi-site rs-fMRI data, which makes full use of the multi-site data while still being flexible enough to capture the site-specific BN structures.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' NOTEARS-PFL is subtly fitted in an FL framework without sharing and exchanging the original data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' NOTEARS-PFL overcomes the computational intractability of traditional BNs by transforming the discrete combinatorial optimization to continuous numerical optimization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' NOTEARS-PFL can effectively detect the common abnormal FC in MDD patients among multiple sites, especially the connectivity between the insula, thalamus cortex, and middle temporal gyrus.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Meanwhile, NOTEARS-PFL can also identify the site-specific abnormal FC due to the differences in scanners, protocols, and patient populations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The paper is organized as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In Section 2, we briefly review directed FC estimation methods for rs-fMRI data and BN structure learning with continuous optimization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We present the formulation and optimization approach of NOTEARS-PFL in Section 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We conduct simulation experiments to validate NOTEARS-PFL in Section 4, and analyze the real-world multi-site rs-fMRI data in Section 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Finally, we conclude this paper in Section 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 2 Related Work 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Directed FC Estimation Methods for rs-fMRI Data The directed FC, also known as effective FC, helps depict the abnormalities or dysfunction of the brain connectivity network [Smith, 2012] and shows how information flows in the brain connectivity network [Henry and Gates, 2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Based on rs-fMRI data, many directed FC estimation methods have been developed, including the following four types.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (1) Granger causality (GC).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' GC establishes a model in the framework of vector autoregression (VAR) and determines the edges to be added after considering the autoregressive effect of each region [Granger, 1969, Liao et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2009].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' GC is applied to detect the effects of psychostimulants on youths with attention deficit hyperactivity disorder (ADHD) [Peterson et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2009].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, when GC is applied to analyze specific individuals, heterogeneity across individuals may lead to spurious results [Molenaar, 2004].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (2) Dynamic Causal Modeling (DCM).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' DCM is a method to capture nonlinear relationships between brain regions that may be affected by different stimuli during scanning [Friston et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2003], and has been used to detect the propagation of epileptic seizures [Murta et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2012].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The limitation of DCM is that it cannot handle large amounts of ROIs or analysis group rs-fMRI data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [Friston et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2011].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (3) Constraint-based methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Constraint-based methods estimate directed edges by conditional independence tests.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Common constraint-based methods include Peter Spirtes, and Clark Glymour (PC) algorithm [Spirtes and Glymour, 1991], conservative PC (CPC) [Ramsey et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2006], fast causal inference (FCI) [Spirtes, 2001], and cyclic causal discovery (CCD) [Richardson, 1996].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The PC algorithm can obtain reliable networks on data aggregated across individuals [Smith et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2011].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 4 However, according to results from Smith et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2011], PC can detect the existence of edges but can not accurately determine the directions at the individual level.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (4) Score-based methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Score-based methods define a score function that measures how well the BN structure fits the observed data and searches for the best network structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Standard score-based methods include greedy equivalent search (GES) [Chickering, 2002], independent multiple-sample greedy equivalent search (IMaGES) [Ramsey et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2010], and group iterative multiple model Estimation (GIMME) [Gates and Molenaar, 2012].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Score-based methods typically require large samples to identify edges and directions, which limits the utility of these methods when using rs-fMRI data for individual-level analysis [Mumford and Ramsey, 2014].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Meanwhile, the performance of score-based methods is poor on data with a large number of ROIs, which makes it difficult to analyze the complete parcellation of the brain.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Due to the combinatorial acyclicity constraint of DAG, it is often hard to find BN with the optimal score.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' And its scalability is also limited [Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 BN Structure Learning with Continuous Optimization In this work, we focus on BN learning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' BN is a probabilistic graphical model that captures dependencies among a collection of random variables.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Each model is associated with a directed network G = (V, E), where the vertex set V corresponds to the random variables and the edge set E corresponds to the set of conditional independence [Drton and Maathuis, 2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' BN models the conditional independence among random variables via Markov properties [Cowell, 1998, Marrelec et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2004].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Denote X = (X1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , Xd)⊤ that satisfies the local Markov property with respect to a DAG G if Xv⊥XndG(v)\\paG(v) | XpaG(v), where paG(v) = {w ∈ V : {w, v} ∈ E} denotes the parents of node v in G, ndG(v) = V \\deG(v) denotes the non-descendants of v in G with deG(v) = {w ∈ V : w = v or v → .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' → w in G} representing the descendants of v in G.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Alternatively, if X is a continuous random vector and it has a density P(X) with respect to a product measure, then the local Markov property is equivalent to the following factorization property [Verma and Pearl, 1990], P(X) = d � v=1 P � Xv | XpaG(v) � .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (1) The structure learning of BN is to estimate the DAG G using the observations from the density P(X).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Score-based methods seek the optimal G by minimizing the score function S(W) with respect to the corresponding weighted adjacency matrix W ∈ Rd×d, subject to that the induced graph g(W ) is a DAG;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' see the LHS of equation (2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The DAG constraint initiates a combinatorial optimization problem, which is computationally costly when d is large.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Recently, Zheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2018] proposed a NOTEARS method which enforces the acyclicity via setting a smooth function h(W ) exactly at zero;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' see the RHS of equation (2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' By this novel characterization of acyclicity, the resulting optimization problem can be solved efficiently using standard algorithms.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' minW ∈Rd×d S(W ), minW ∈Rd×d S(W ), s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' g(W ) ∈ DAGs, s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' h(W ) = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (2) 5 Currently, NOTEARS has been extended to handle problems in many situations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For example, DAG Graph Neural Network (DAG-GNN) extends NOTEARS to solve nonlinear cases by incor- porating neural networks [Yu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2019].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Graph AutoEncoder (GAE) extends NOTEARS and DAG-GNN into a graph autoencoder model, facilitating vector-valued variables [Ng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2019].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Pamfil et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2020] proposed DYNOTEARS method to learn dynamic BNs from time-series data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Huang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2020] used reinforcement learning to find the optimal DAGs from incomplete data based on NOTEARS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To the best of our knowledge, few studies have focused on using NOTEARS to learn personalized BNs from fMRI data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Zhang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2022] proposed a joint BN estimation model to detect abnormal directed FC in schizophrenia (SZ) patients.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, the joint estimation model proposed by Zhang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2022] is not applicable for the FL setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Ng and Zhang [2022] proposed NOTEARS-ADMM model to estimate the structure of BN in FL setting.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' However, they did not consider the data heterogeneity, which can lead to model bias [Zhao et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018, Jiang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Compared with Zhang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2022] and Ng and Zhang [2022], the proposed NOTEARS-PFL is powerful because it captures the data heterogeneity, overcomes the data sharing barriers, and attains computational efficiency, simultaneously.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 3 NOTEARS-based Personalized Federated Learning Framework 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Preliminary The BN associated with a DAG G can also be thought of as a structural equation model [Bollen, 1989] Xi = fi(W T i X) + Zi, i = 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , d, (3) where W = (W1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , Wd) ∈ Rd×d denotes the weighted adjacency matrix whose nonzero coefficients correspond to the directed edges in G, fi’s are functions related to the conditional distributions of Xi’s, and Zi’s are jointly independent random noises.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Equation (3) is equivalent to the local Markov property and factorization property introduced in Section 2 [Drton and Maathuis, 2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We consider the linear structural equation model Xi = W T i X + Zi, i = 1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (4) Actually, the multivariate Gaussian distribution can be modeled as equation (4) with Zi’s being independent Gaussian noises.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Let the data matrix x ∈ Rn×d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Zheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2018] formulates the structure learning of BNs as min W ∈Rd×d 1 2n ∥x − xW ∥2 F + λ∥W ∥1, s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' h(W ) = 0, (5) where h(W ) := tr � eW ⊙W � − d = 0, (6) ⊙ denotes the Hadamard product, eA = �∞ k=0 1 k!' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='Ak denotes the the matrix exponential operator [Leonard, 1996], ∥A∥F denotes the Frobenius norm, ∥A∥1 refers to the entry-wise ℓ1 norm and the tuning parameter λ > 0 controls the amount of sparsity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 6 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 Problem Formulation We now proceed to formulate our NOTEARS-PFL method, which can efficiently learn multiple heterogeneous BNs without sharing data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We consider the setting in which there is a fixed set of K sites in total, and each site has its own local dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The k-th site holds nk i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' samples, denoted by xk = � xk i �nk i=1 ∈ Rnk×d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Let D = {x1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , xK} be the K overall observational datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The goal is to infer the K weighted adjacency matrices ˜ W0 = {W 1 0 , .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , W K 0 } (correspond to the BN structures) using D.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To incorporate the heterogeneity among K sites, we consider the following optimization problem: min ˜ W K � k=1 1 2nk ���xk − xkW k��� 2 F + R( ˜ W ), s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' h(W k) = 0, k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K, (7) where h(W k) is defined in the same way as equation (6) and R( ˜ W ) is a penalty function for inducing the similarity and sparsity within ˜ W .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' With the data sharing constraint, we formulate equation (7) into the framework of ADMM, which is a natural solution to distributed learning and FL [Ng and Zhang, 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Define a set of consensus variables ˜Z = {Z1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , ZK}, which can be thought of as the global weighted adjacency matrices, in contrast to the local weighted adjacency matrices ˜ W .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then we rewrite equation (7) as min ˜ W , ˜ Z K � k=1 L(W k, xk) + R( ˜Z), s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='t.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' h(Zk) = 0, W k = Zk, k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K, (8) where L(W k, xk) := 1 2nk ���xk − xkW k��� 2 F , (9) h(Zk) is defined in the same way as equation (6), and R( ˜Z) is defined by R( ˜Z) := λ1 K � k=1 ∥Zk∥1 + λ2 K−1 � k=1 ∥Zk+1 − Zk∥F , (10) where λ1 > 0 controls the sparsity of Zk and λ2 > 0 controls the similarity within ˜Z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The general optimization procedure can be summarized as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' First, each site estimates the local weighted adjacency matrix W k by using local dataset xk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, instead of transmitting the original data, each site only transmits its local weighted adjacency matrix to the center.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' After that, the center updates the global weighted adjacency matrices ˜Z0 = {Z1 0, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , ZK 0 }, based on received ˜ W0, Finally, the center transmits the updated ˜Z to each site, which performs the next update locally based W k = Zk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In the next subsection, we provide the computational details of NOTEARS-PFL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 7 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Optimization Algorithm By applying the augmented Lagrangian method [Bertsekas, 2014], the equation (8) can be written as L � ˜ W , ˜Z, Θ � = K � k=1 L(W k, xk) + R( ˜Z) + K � k=1 αkh(Zk) + ρ1 2 K � k=1 |h(Zk)|2 + K � k=1 tr(βk(W k − Zk)⊤) + ρ2 2 K � k=1 ���W k − Zk��� 2 F , (11) where ˜Θ = {ρ1, ρ2, α1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , αK, β1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , βK}, ρ1, ρ2 are the penalty coefficients, α1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , αK and β1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , βK are the Lagrange multiplies.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' At the t-th iteration, we can solve equation (11) as follows: (1) Local update: ˜ W(t) ← arg min ˜ W � L � ˜ W , ˜Z(t−1), ˜Θ(t−1) �� .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (12) (2) Global update: ˜Z(t) ← arg min ˜ Z � L � ˜ W(t), ˜Z, ˜Θ(t−1) �� .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (13) (3) Global update: ˜Θ(t) ← � ˜ W(t), ˜Z(t), ˜Θ(t−1) � .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (14) 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Federated Local Update of ˜ W Taking the derivative of equation (11) with respect to ˜ W , we can update each W k (t) of ˜ W(t) as W k (t) := arg min W k (L(W k, xk) + ρ2,(t−1) 2 ���W k − Zk (t−1) ��� 2 F + tr(βk,(t−1)(W k − Zk (t−1))⊤)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (15) Let U k = 1 nk (xk)⊤xk and assume U k + ρ2I is invertible.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Equation (15) has a closed form expression W k (t) = (U k + ρ2,(t−1)I)−1(ρ2,(t−1)Zk (t−1) − βk,(t−1) + U k), (16) where the details of the derivation are given in Appendix A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 Federated Global Update of ˜Z Similar to equation (15), we can update each Zk (t) of ˜Z(t) as Zk (t) := arg min Zk {L( ˜Z) + R( ˜Z)}, (17) 8 Algorithm 1 Dykstra-like iterative proximal algorithm (DIPA) Input: K: Number of site;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ˜Z: global adjacency matrices;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ˜ W : local adjacency matrices;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' N: The number of iterations;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ϵ: Tolerance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Output: ˜Z: The result of equation (19).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 1: ∇Lk � Zk� = equation (20).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 2: for k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K do 3: U k = Zk − 1 C ∇L � Zk� .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 4: end for 5: ¯U ← Transform (U k).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 6: Set A0 = ¯U, Mn = 0, Qn = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 7: for n = 0, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , N do 8: V(n) ← proxR2 � A(n) + M(n) � , see equation (28).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 9: M(n+1) ← A(n) + M(n) − V(n).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 10: A(n+1) ← proxR1 � V(n) + Q(n) � , see equation (25).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 11: Q(n+1) ← V(n) + Q(n) − A(n+1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 12: Break: if ��A(n+1) − A(n) �� F < ϵ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 13: end for 14: ¯U ← A(N+1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 15: ˜Z ← Inverse-Transform ( ¯U).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 16: return ˜Z.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' where L( ˜Z) := K � k=1 αk,(t−1)h(Zk) + ρ1,(t−1) 2 K � k=1 |h(Zk)|2 + ρ2,(t−1) 2 K � k=1 ���W k (t) − Zk��� 2 F ) + K � k=1 tr(βk,(t−1)(W k (t) − Zk)⊤).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Due to the acyclicity term h(Zk), we are not able to derive a closed-form solution for equation (17).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To tackle this issue, we utilize a proximal gradient method which constructs a quadratic approximation of L( ˜Z) at ˜Z(t−1), and updates ˜Z(t) by ˜Z(t) = arg min ˜ Z {L( ˜Z(t−1)) + K � k=1 � Zk − Zk (t−1), ∇Lk(Zk (t−1)) � + C 2 K � k=1 ���Zk − Zk (t−1) ��� 2 F + R( ˜Z)}, (18) where ∇Lk(·) is the gradient of Lk(·), C > 0 is the Lipschitz constant of ∇Lk(·).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' After some simple 9 manipulations of equation (18), e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', ignoring constant terms of Zk (t−1), we have ˜Z(t) = arg min ˜ Z {C 2 K � k=1 ����Zk − � Zk (t−1) − 1 L∇Lk � Zk t−1 ������ 2 F + R( ˜Z)}, = proxCR � K � k=1 � Zk (t−1) − 1 L∇Lk � Zk (t−1) ��� , (19) where ∇Lk � Zk (t−1) � = αk,(t−1)∇h(Zk (t−1))+ρ1,(t−1)h(Zk (t−1))∇h(Zk (t−1))−βk,(t−1)+ρ2,(t−1)(Zk (t−1)−W k), (20) and proxg(v) = arg min x ( 1 2∥x − v∥2 F + g(x)) denotes the proximal operator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Unlike the calculation of W k, we cannot separate the equation (19) by k because of the grouped constraint R( ˜Z).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Instead, we must estimate the whole set of matrices ˜Z(t) jointly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Inspired by Gibberd and Nelson [2017], we use the following iterative proximal projection step to solve.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Let U k = Zk (t−1) − 1 C ∇Lk � Zk (t−1) � , and perform transform procedure (see AppendixB) for U k → ¯U.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, equation (19) can be re-written as min ¯ Z 1 2 �� ¯Z − ¯U ��2 F � �� � L( ¯ Z) + λ1∥ ¯Z∥1 � �� � R1( ¯ Z) + λ2∥D ¯Z∥2,1 � �� � R2( ¯ Z) , (21) where D ∈ R(K−1)×K is a backwards difference matrix of the form Di,i = −1, Di,i+1 = 1 for i = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K − 1, and ∥A∥2,1 := � k ∥Ak,·∥2 denotes the group ℓ2,1 norm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Actually, equation (21) is equivalent to the Group-Fused Lasso Signal Approximator (GFLSA) defined by Gibberd and Nelson [2017].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We denote the objective in equation (21) by f � ¯U;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' λ1, λ2 � = proxR1+R2 � ¯U � .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, we adopt the Dykstra-like iterative proximal algorithm (DIPA) [Combettes and Pesquet, 2011] to handle proxR1+R2 � ¯U � and find a feasible solution for both the group fused lasso penalty and the lasso penalty.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We summarize the details of iteration in Algorithm 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Federated Global Update of ˜Θ The update of ˜Θ follows the following iterative steps βk,t := βk,t−1 + ρ2,t−1 � W k (t) − Zk (t) � , αk,t := αk,t−1 + ρ1,t−1h � Zk (t) � , ρ1,t := γ1ρ1,t−1, ρ2,t := γ2ρ2,t−1, (22) where γ1, γ1 ∈ R are hyperparameters that respectively control the increasing speeds of the coefficients ρ1, ρ2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The overall ADMM algorithm of NOTEARS-PFL is thereby given in Algorithm 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 10 Algorithm 2 ADMM of NOTEARS-PFL Input: K: Number of site;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' xk: Original data;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ˜Z(0): Initial global adjacency matrices;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ρ1,0, ρ2,0, α1,0, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , αK,0, β1,0, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , βK,0: Initial parameters;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' T: The maximum of iterations;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ϵ: Tolerance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Output: ˆ Zk: Estimated adjacency matrix.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' for iterations t = 1 to T do Local update step: for site k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K do Update W k (t) according to equation (16).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' end for Global update step: for variables ˜Z(t−1), Θ(t−1) in the center do Zk (t) ← DIPA (W k (t), Zk (t−1)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Update ˜Θ(t−1) according to equation (22).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' end for Break: if K � k=1 ���Zk (t) − Zk (t−1) ��� F ���Zk (t) ��� 2 < ϵ.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' end for return ˜Z = (Z1 (T), .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', ZK (T)).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 11 4 Simulations 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Simulation Design of Synthetic Data We simulate synthetic data according to equation (4).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' First, we generate a random graph Gtruth based on Erdös–Rényi (ER) model [Erdös et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 1960].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To obtain a set of related graphs, we apply perturbations to Gtruth to create K similar but different graphs ˜G = {G1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , GK}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The details of the definition of perturbation are shown in Appendix C, and we denote the perturbation level as pl.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Given ˜G, we assign uniformly random edge weights to obtain K weights matrices ˜ W = {W 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , W K}, where the non-zero entries are sampled uniformly at random form [−2, −0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5]∪[0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5, 2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Given ˜ W , we generate the datasets D = {x1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , xK} based on equation (4) with standard Gaussian noise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To evaluate and compare the performance of the proposed method, we apply the NOTEARS [Zheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018] method to estimate each network independently from each site’s local data (NOTEARS-SIG for short), and apply the NOTEARS method to learn a common network structure for all contexts (NOTEARS-AVG for short), i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', an “average” network that treats all site’s data as samples in one dataset.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We also compare the performance between NOTEARS-ADMM [Ng and Zhang, 2022] and the proposed method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We use the following four metrics to evaluate the learning performance of different methods (see Appendix C for a detailed definition of metrics).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Edge arrowhead error: Error = FP + FN TP + TN + FP + FN .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (23) Edge arrowhead precision: Precision = TP TP + FP .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Edge arrowhead F-score: F-score = 2 · Precision · Recall Precision + Recall , where Recall = TP/(TP + FN).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Edge arrowhead structural Hamming distance (SHD): Given two structures, this measure is the minimum number of edges needed to convert the learned graph into the true one.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We compare the performance of the proposed NOTEARS-PFL, NOTEARS-SIG, NOTEARS- AVG, and NOTEARS-ADMM on the following three aspects.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Performance vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' the number of variable: We fix the number of sites K = 10, perturbation level pl = 10%, set the total sample size nt = �K k=1 nk equals to three times the number of variable d (nt = 3d, nk = 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3d), and compare the model performance of network structure learning for different variable number d = 10, 20, 30, 40, 50, 60, 70, 80.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 12 Performance vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' the number of site: We fix the number of variable d = 50, perturbation level pl = 10%.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We set the total sample size nt = 256, and distributed evenly across the number of site K = 2, 4, 8, 16, 32, 64.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Performance vs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' perturbation level: We fix the number of site K = 10, the number of variable d = 30, sample size nt = 3d, and vary the perturbation level pl = 5%, 10%, 15%, 20%, 30%.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The evaluation metrics for one simulation run are averaged over the K sites’ dataset, and we repeat each experiment 10 times.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The final evaluation metrics are thereby averaged over the ten simulation runs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (a) (b) (d) (c) Figure 2: Simulation results for synthetic data under different variable numbers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (a) Average edge arrowhead error (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (b) Average edge arrowhead SHD (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (c) Average edge arrowhead precision (higher is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (d) Average edge arrowhead F-score (higher is better).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In the synthetic data experiment, we first evaluate the effect of the number of variables d on the performance of each compared method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The results are shown in Figure 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It is clear that NOTEARS-PFL performs the best among all the methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The average arrowhead adjacency error of NOTEARS-PFL has a relatively low level ranging from 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 to 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In contrast, for NOTEARS-SIG, the average arrowhead adjacency error is far larger than NOTEARS-PFL, ranging from 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 to 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' This may be because the sample size of a single dataset is too small for NOTEARS-SIG to give a satisfactory estimate.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The same result is observed in the average arrowhead SHD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For the other two metrics, NOTEARS-PFL consistently results in higher average arrowhead precision and F-score than the other three methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Compared with NOTEARS-SIG and NOTEARS-AVG, the average arrowhead precision of NOTEARS-PFL is also more stable with respect to different variable numbers, indicating that it can successfully identify most of the edges in high-dimensional settings.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We also test the effect of the number of sites K on the performance of each method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The results are shown in Figure 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Clearly, NOTEARS-PFL performs better than NOTEARS-SIG, NOTEARS-AVG, and NOTEARS-ADMM for all the tested cases.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' As K increases, the performance 13 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 100 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 - 80 - SHD 60 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 40 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 - 20 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 - 0 20 50 10 30 40 60 70 80 10 20 30 40 50 60 70 80 Number of variables Number of variables 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0- 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='7 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6 ion 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 Preci 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 10 20 30 40 50 80 60 70 10 20 30 40 50 60 70 80 Number of variables Number of variables NOTEARS-PFL NOTEARS-SIG NOTEARS-AVG NOTEARS-ADMM(a) (b) (d) (c) Figure 3: Simulation results for synthetic data under different site numbers.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (a) Average edge arrowhead error (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (b) Average edge arrowhead SHD (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (c) Average edge arrowhead precision (higher is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (d) Average edge arrowhead F-score (higher is better).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (a) (b) (d) (c) Figure 4: Simulation results for synthetic data under different perturbation levels (a) Average edge arrowhead error (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (b) Average edge arrowhead SHD (lower is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (c) Average edge arrowhead precision (higher is better);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (d) Average edge arrowhead F-score (higher is better).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 14 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='10 120 100: 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 80 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 SHD 60 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 40 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 20 - 0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='00 10 20 50 60 0 10 20 30 40 50 60 0 30 40 Number of sites Number of sites 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6 Precisic 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 - 0 10 20 30 40 50 60 0 10 20 30 50 60 40 Number of sites Number of sites NOTEARS-PFL NOTEARS-SIG NOTEARS-AVG NOTEARS-ADMM0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08: 35 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 30 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 - 25 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='05 D 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 15- 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='03 10 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 5 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='01 5% 10% 15% 20% 30% 5% 10% 15% 20% 30% Perturbation levels Perturbation levels 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='00 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='90 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='7 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 ision core 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='80 Precis 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6 S F 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='75 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='70 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='60 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 5% 10% 15% 20% 30% 5% 10% 15% 20% 30% Perturbation levels Perturbation levels NOTEARS-PFL NOTEARS-SIG NOTEARS-AVG NOTEARS-ADMMof NOTEARS-SIG, NOTEARS-AVG decline rapidly.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Although the performance of NOTEARS-PFL also decreases with the increase of K, it still provides a relatively stable and satisfying performance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' As expected, NOTEARS-SIG does not perform better at larger K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' A possible reason is that NOTEARS-SIG only utilizes the information of a single dataset whose sample size decreases with the increase of K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' On the contrary, NOTEARS-PFL works well in the setting with a large site number because information can be exchanged during optimization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' These results are also consistent with the existing literature [Ng and Zhang, 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Finally, we examine the effect of the perturbation level pl on the performance of each method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The results are shown in Figure 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It is clear that NOTEARS-PFL significantly outperforms the other three methods.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It can be seen that with the increase of perturbation level, average arrowhead error and SHD increase significantly, while average arrowhead precision and F-score decrease.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' When the perturbation level is relatively low, the difference between the four methods is relatively small, but when the perturbation level is relatively large, the advantage of NOTEARS-PFL is more significant.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5 Application to Real-world rs-fMRI Data 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Data and Preprocessing (1) Data acquisition: The multi-site rs-fMRI datasets in this study were obtained from the DecNef Project Brain Data Repository1, collected as part of the Japanese Strategic Research Program for the Promotion of Brain Science (SRPBS) database project [Tanaka et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2021].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' This dataset consists of 255 MDD patients (135 men versus 120 women) and 791 HC participants (426 men versus 365 women) from 8 sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Some samples were discarded as some sites only have rs-fMRI data on HC participants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' As a result, 238 MDD patients and 475 HC participants from 5 sites were used in this study (see Table 3).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The demographic characteristics of all subjects in both datasets are summarized in Table 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (2) Data preprocessing : Each subject of the data underwent a single rs-fMRI session and a structural MRI session.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' During the fMRI scan, participants were asked to relax, stay awake and think about anything in particular.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Detailed imaging parameters of rs-fMRI and T1-weighted (T1w) structural MRI at each site are shown in Table 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We applied the following preprocessing steps to the data by using DPARSF [Yan and Zang, 2010] software2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For each participant, we removed the first 10 MRI volumes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Slice-time correction and head motion were corrected on the remaining images.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The T1-weighted images were unified segment segmentation and diffeomorphic anatomical registration.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The rs-fMRI data were smoothed with a 6mm full-width at half-maximum Gaussian kernel and the Friston 24-parameter model was used to regress head motion effects further.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, all the time series were filtered by linear detrending and a temporal band-pass filter (0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='01 - 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 Hz).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (3) Feature extraction: After preprocessing, we estimated the time series of 116 ROIs based on the automated anatomical labeling (AAL) template [Tzourio-Mazoyer et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2002].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Details of cortical and subcortical regions of interest (ROIs) defined in the AAL template are presented in Table 6 and Table 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We selected 56 ROIs from 116 ROIs because these regions are considered to be related to MDD in the literature.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The names of the selected ROIs are shown in bold in Table 6 and Table 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The voxel-wise fMRI time courses were averaged into one regional average time course within each ROI.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The data for each participant was then in the form of an X× 56 matrix (X 1https://bicr-resource.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='atr.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='jp/srpbsopen/ 2http://www.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='rfmri.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='org/DPARSF 15 sampling points in each regional average fMRI time course and 56 selected ROIs).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 Experimental Setup We randomly select 70% of MDD patients and HC participants from each site and aggregate their rs-fMRI data into the MDD discovery dataset and HC discovery dataset for that site, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Similarly, we aggregate the remaining 30% into the MDD validation dataset and HC validation dataset for that site, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We analyze the 5 sites’ discovery datasets of MDD patients, which are regarded as 5 related tasks.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then we can obtain a brain connection network of MDD for each site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To study the differences in brain FC, the brain connection networks of HC for five sites, which are viewed as another set of related tasks, are also obtained using the proposed NOTEARS-PFL method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' According to the estimated BN structures, we analyze the abnormal FC in MDD by the following aspects.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Important Nodes Identification By identifying important nodes, we reveal the aberrant nodal characteristics of the brain functional connectivity networks of MDD from multi-site datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 Overlapping Connections Identification By identifying overlapping connections, we obtain the common functional connections for MDD patients from multiple sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' By comparing with the overlapping connections of HC participants, we further investigate the altered functional connections in MDD patients, which provide the potential biomarkers for clinic treatment of MDD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Site-specific Connections Identification By identifying the site-specific connections in different sites, we investigate the specific FC alterations in MDD at each site due to the differences in image acquisition protocols and patient populations at different sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 Comparison with Other Methods We randomly select 5 MDD patients and 5 HC participants from each site’s MDD validation dataset and HC validation dataset and repeat such selection 10 times.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We then have 10 datasets containing MDD data and HC data from the 5 sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Based on these datasets, we compare NOTEARS-PFL with NOTEARS-SIG and existing standard analysis methods of rs-fMRI data: GES [Chickering, 2002], PC [Spirtes and Glymour, 1991], and GC [Granger, 1969].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To further test whether NOTEARS-PFL is able to learn the differences between MDD patients and HC participants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Experimental Results In this section, we use NOTEARS-PFL method to analyze the multi-site rs-fMRI data from 5 sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We can obtain the brain functional connection network of MDD patients for each site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To study the differences in brain FC, we also obtain the brain functional connection network of HC participants for each site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 16 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 Results of Important Nodes To better understand the differences in brain FC between MDD patients and HC participants through the estimated directed brain networks from multi-site rs-fMRI data, we further use the connection degree to identify some important nodes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The connection degree (including in and out degree) is a commonly used measure of functional connectivity [Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' More specifically, it represents the amount of directed functional connections.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The greater the connection degree, the higher the effective FC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Identifying important nodes further helps to discover the nodes associated with the disease.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Table 1 shows the differences in total connection degrees between MDD patients and HC participants at 5 sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The total out connection degrees in Table 1 are 657 for MDD and 478 for HC, indicating that MDD has 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4% effective FC than HC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Similarly, MDD also has 23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4% more effective FC than HC, with a total in connection degrees of 516 and 418, respectively.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The rise of FC is an apparent robust biomarker of MDD disease [Zamoscik et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2014], which can also be found in our results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Table 1: The top 10 out and in connection degrees of MDD patients and HC participants Index ROI Abbreviation Degree Index ROI Abbreviation Degree MDD (Out) 77 Thalamus THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 75 HC (Out) 55 Fusiform gyrus FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 58 29 Insula INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 74 37 Hippocampus HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 57 35 Cingulate gyurs, posterior part PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 72 31 Cingulate gyrus, anterior part ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 55 33 Cingulate gyrus, mid part DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 68 38 Hippocampus HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 49 34 Cingulate gyrus, mid part DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 67 9 Middle frontal gyrus, orbital HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 47 31 Cingulate gyrus, anterior part ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 63 29 Insula INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 46 72 Caudate CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 62 77 Thalamus THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 45 71 Caudate CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 61 33 Cingulate gyrus, mid part DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 43 55 Fusiform gyrus FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 58 56 Fusiform gyrus FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 40 79 Heschl gyrus HES.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 57 79 Heschl gyrus HES.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 38 Total 657 Total 478 MDD (In) 24 Superior frontal gyrus, medial SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 79 HC (In) 3 Superior frontal gyrus, dorsolateral SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 55 90 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 62 9 Middle frontal gyrus, orbital ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 48 26 Superior frontal gyrus, medial orbital ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 59 26 Superior frontal gyrus, medial orbital ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 45 89 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 54 90 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 44 3 Superior frontal gyrus, dorsolateral SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 48 10 Middle frontal gyrus, orbital ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 41 46 Cuneus CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 46 14 Inferior frontal gyrus, triangular IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 40 11 Inferior frontal gyrus, opercular IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 45 24 Superior frontal gyrus, medial SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 39 25 Superior frontal gyrus, medial orbital ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 42 1 Precentral gyrus PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 38 41 Amygdala AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 41 89 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 36 32 Cingulate gyrus, anterior part ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 40 6 Superior frontal gyrus, orbital ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 32 Total 516 Total 418 From Table 1, we can find some ROI nodes with high connection degrees, such as THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (thalamus), INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (insula), SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (superior frontal gyrus, medial) in MDD, and FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (fusiform gyrus) and HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (hippocampus) in HC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Specifically, THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L and INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L have more outgoing connections in MDD than in HC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It indicates that THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L and INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L of MDD have a higher essential impact on other ROI nodes than HC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The result from NOTEARS-PFL is in line with literature [Kang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018, Avery et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2014, Porta-Casteràs et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2021].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' According to Kang et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' [2018], emerging evidence indicates that the enhanced thalamus FC is an important feature of the underlying pathophysiology of MDD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' This abnormal FC is related to the core clinical symptoms of MDD, such as anxiety, memory, and attention.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Our result further implies that the impaired FC of the hippocampus is potentially an important biomarker of MDD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Compared to HC, the bilateral hippocampus in MDD lack FC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' As the core region of the limbic system, the hippocampus plays an important role in regulating motivation and emotion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The mode of emotion regulation in MDD may be related to the decreased FC of the hippocampus [Cao et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2012].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (superior frontal gyrus, medial) and ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (inferior temporal gyrus) have more incoming connections than outgoing connections, which indicates that SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R and ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R are mainly affected by other ROI nodes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' These findings are also consistent with the physiological discoveries of MDD disease [Porta-Casteràs et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2021].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 17 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 Results of Overlapping Connections Figure 5 depicts the overlapping connections between the directed networks of 5 sites of MDD patients and HC participants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The overlapping connection refers to the connection shared by five sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We can use it to study the universal connection between MDD and compare the differences between MDD and HC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' From Figure 5, we can find some abnormal functional connections in MDD: INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (insula) → ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (middle frontal gyrus, orbital), INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (insula) → INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (insula), INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (insula) → ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (cingulate gyrus, anterior part), PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (cingulate gyurs, posterior part) → PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (cingulate gyurs, posterior part), THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (thalamus) → CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (caudate), STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (superior temporal gyrus) → MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R (middle temporal gyrus).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Three common functional connections are associated with the insula, which further demonstrates the important role of the insula in identifying abnormal functional connections in MDD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The insula has been shown to be a potential primary biomarker for the diagnosis of MDD [McGrath et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2013].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In MDD patients, the insula show increased FC with other limbic or paralimbic structures, particularly with the ventromedial prefrontal cortex (vmPFC) and orbitofrontal cortex (OFC) [Avery et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2014, Drevets et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2008], which is also illustrated in our results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Figure 5: The overlapping connections between the directed networks of 5 sites of MDD patients and HC participants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In addition to the abnormal insula structure in MDD patients, we also observe the abnormalities of FC in posterior cingulate gyurs, thalamus, inferior temporal gyrus, and middle temporal gyrus, which are also consistent with findings in the works of literature [Khundakar and Thomas, 2009, Zhao et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2014].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' These cortices belong to the default mode network (DMN) and are considered to contribute greatly to MDD [Gong and He, 2015].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The abnormalities of FC in DMN have been reported in many MDD studies [Vasudev et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018], especially the frontal lobe and temporal lobe.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' These lobes are suggested to be closely associated to the cognitive and information-processing abilities of MDD patients [Brzezicka, 2013].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 18 R L R L SFGdo MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R CG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 R 14 1 13 11 9 14 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' ACGL ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 3 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 3 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 、PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 3 % HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 41 39 37 PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 40 PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 42 Temporal 41 CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 4 Occipital Pariental Subcortial region 5 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 18 5 LL 6L T8 TVHL 58 Z8 68 06 88 98 STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L (a) MDD patients (b) HC participantsFigure 6: The site-specific connections between the directed networks of 5 sites of MDD patients.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Site 1: Center of Innovation in Hiroshima (COI), Site 2: Kyoto University (KUT), Site 3: University of Tokyo (UTO), Site 4: Hiroshima Kajikawa Hospital (HKH), Site 5: Hiroshima University Hospital (HUH).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Results of Site-specific Connections In this study, we are also interested in the connections specific to a site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' A site-specific connection is a connection that only exists on one site.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' By identifying the site-specific connections in different sites, we can better understand the specificity of FC in MDD patients due to the differences in image acquisition protocols and patient populations at different sites.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The site-specific connections of 5 sites of MDD patients are visualized in Figure 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In the results of site 1, we can find the increased functional connection from frontal to pariental and from frontal to temporal, especially the increased afferent connections to precuneus.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The precuneus is considered one of the hubs of DMN, which is generally associated with the rumination of negative and sad thoughts in MDD [Cheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2018].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' It has been shown to play a key role in identifying MDD [Peng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2015].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' A study of effective FC in MDD has shown a significant increase in forward connectivity from the middle and inferior temporal cortical areas to the precuneus [Öngür et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2003], which is consistent with our study (the connections IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L → PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R, IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L → PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Similarly, in site 2, we find the enhanced FC within the frontal cortex, particularly the connections associated with the orbitofrontal cortex (the connections ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L → ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L, MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L → ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R, AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L → ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The increased FC in the orbitofrontal cortex in MDD patients is associated with emotionally negative self-perception [Cheng et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2016].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The orbitofrontal cortex is also a part of the brain’s affective network (AN), and the increased functional connections of the orbitofrontal cortex in MDD have been consistently reported [Townsend et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2010].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The different effective FC patterns of the orbitofrontal cortex can also be used to reveal different pathophysiological mechanisms of different depression types or groups.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 19 Sitel Site4 Site2 Site5 Site3Table 2: Two-sample proportion tests for published overlapped connections.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Connection NOTEARS-PFL NOTEARS-SIG GES PC GC INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R→INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0002 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0016 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0022 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0512 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0057 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R→ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0012 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0029 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0055 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0234 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0133 THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L →CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0016 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0040 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0126 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1636 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0264 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L→PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R 0.' 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metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0126 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0283 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0264 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1556 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1018 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 Comparison Results with Other Methods To further test whether NOTEARS-PFL is able to learn the differences between MDD patients and HC participants, we use different methods to learn the BN structures from the test validation dataset established in Section 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Based on the learned BN structures, we perform a two-sample proportion test for each published overlapping connection of MDD in Figure 5, and report the p-values in Table 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The smaller p value indicates that NOTEARS-PFL recognizes the connection more easily in MDD group than in HC group.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We also included test results for NOTEARS-SIG, GES, PC, and GS for comparison.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' In order to ensure the consistency of measurement standards, we control these methods to learn the same sparsity network structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 6 Conclusion In this work, we focus on learning the heterogeneous brain functional connectivity in MDD patients using multi-site data efficiently and with the data sharing constraint.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To this end, we developed a toolbox called NOTEARS-PFL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' To achieve the model heterogeneity and computational efficiency, NOTEARS-PFL is formulated as minimizing a group fused lasso penalized score function with a continuous constraint for DAG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Considering the data-sharing barriers, the objective is solved in a federated learning framework using the ADMM, where original data is not exchanged during the optimization process.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The algorithm is fast because the local update step has a closed-form expression, and the global update step can be solved using an efficient iterative proximal projection method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Extensive experiments on synthetic data and real-world multi-site rs-fMRI datasets with MDD demonstrate the excellent performance of the proposed method.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We highlight the usefulness of NOTERAS-PFL in analyzing multi-site rs-fMRI data and facilitating the study of MDD.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' References Jason A Avery, Wayne C Drevets, Scott E Moseman, Jerzy Bodurka, Joel C Barcalow, and W Kyle Simmons.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Major depressive disorder is associated with abnormal interoceptive activity and functional connectivity in the insula.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Biological Psychiatry, 76(3):258–266, 2014.' metadata={'source': 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9(12):2034–2040, 2014.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Gemeng Zhang, Biao Cai, Aiying Zhang, Zhuozhuo Tu, Li Xiao, Julia M Stephen, Tony W Wilson, Vince D Calhoun, and Yu-Ping Wang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Detecting abnormal connectivity in schizophrenia via a joint directed acyclic graph estimation model.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' NeuroImage, 260, 2022.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Y-J Zhao, M-Y Du, X-Q Huang, S Lui, Z-Q Chen, J Liu, Y Luo, X-L Wang, GJ Kemp, and Q-Y Gong.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Brain grey matter abnormalities in medication-free patients with major depressive disorder: a meta-analysis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Psychological Medicine, 44(14):2927–2937, 2014.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Yue Zhao, Meng Li, Liangzhen Lai, Naveen Suda, Damon Civin, and Vikas Chandra.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Federated learning with non-iid data.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' arXiv preprint arXiv:1806.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='00582, 2018.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Xun Zheng, Bryon Aragam, Pradeep K Ravikumar, and Eric P Xing.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Dags with no tears: Continuous optimization for structure learning.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Advances in Neural Information Processing Systems, 31, 2018.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 26 Supplementary Materials A Derivation of Federated Local Update Step To solve the subproblem as shown in equation (15), we first drop the subscript t to lighten the notation, which leads to min W k f(W k) := L(W k, xk) + tr(βk(W k − Zk)⊤) + ρ2 2 ���W k − Zk��� 2 F .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (24) Let U k = 1 nk (xk)⊤xk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The first term of the equation (24) can be written as L(W k, xk) = 1 2nk ���xk − xkW k��� 2 F , = 1 2nk tr((xk − xkW k)⊤(xk − xkW k)), = 1 2nk tr((xk)⊤xk − (W k)⊤(xk)⊤xk − (xk)⊤xkW k + (W k)⊤(xk)⊤xkW k), = 1 2 tr � U k − (W k)⊤U k − U kW k + (W k)⊤U kW k� , = 1 2 tr � U k − 2(W k)⊤U k + (W k)⊤U kW k� .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Similarly, the third term of equation (24) can be written as ρ2 2 ∥W k − Zk∥2 F = ρ2 2 tr �� W k − Zk�⊤ � W k − Zk�� , = ρ2 2 tr � (W k)⊤W k − 2(W k)⊤Zk + (Zk)⊤Zk� .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Therefore, we have f(W k) = 1 2 tr(U k − 2(W k)⊤U k + (W k)⊤U kW k) + tr(βk(W k)⊤ − βk(Zk)⊤) + ρ2 2 tr((W k)⊤W k − 2(W k)⊤Zk + (Zk)⊤Zk), = 1 2 tr(−2(W k)⊤U k + (W k)⊤U kW k) + tr(βk(W k)⊤)ρ2 2 tr((W k)⊤W k − 2(W k)⊤Zk + c, and its derivative is given by ∇W kf � W k� = 1 2(−2U k + ((U k)⊤ + U k)W k) + βk + ρ2 2 (2W k − 2Zk), = −U k + U kW k + βk + ρ2W k − ρ2Zk, = (U k + ρ2I)W k − U k + βk − ρ2Zk.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Assuming U k + ρ2I is invertible, solving ∇W kf � W k� = 0 yields the solution W k = (U k + ρ2I)−1(ρ2Zk − βk + U k).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 27 B Details on the Federated Global Update Step We provide details of the DIPA algorithm in the federated global update step.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For convenience, we introduce the following procedures and discuss how to transform K matrices into one matrix, so that we can re-write equation (19) into vector form.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Transform: Given K matrices ˜ M = {M1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , MK}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For each k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K, Mk ∈ Rd×d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Transform Mk into vector form, denote as mk = � Mk i,j | for i, j = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , d �⊤ .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, construct a matrix ¯ M = � m1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , mK�⊤ ∈ RK×d2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Inverse-Transform: The inverse-transform reverses the steps of the transform, which to transform the matrix ¯ M ∈ RK×d2 to K matrices ˜ M = {M1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , MK}.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The core of DIPA algorithm is to compute the separate proximal operators for R1 and R2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' And then the iterative projection can be used to find a feasible point.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The proximal operator for the ℓ1 term proxR1 � ¯U � is given by the soft-thresholding operator [Tibshirani, 1996].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' proxR1 � ¯U;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' λ1 � = arg min ¯ Z 1 2 �� ¯Z − ¯U ��2 F + λ1∥ ¯Z∥1, = sign( ¯U) ⊙ max � | ¯U| − λ1, 0 � .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (25) where the max and sign functions act in an element-wise manner and ⊙ denotes element-wise multiplication.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The calculation of group-fused lasso proximal operator proxR2 � ¯U � is more complex, and there is no obvious closed-form solution.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We tackle this through a block-coordinate descent approach [Bleakley and Vert, 2011].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then, the proximal operator for the group smoothing aspect of the regularizer can be written as: proxR2 � ¯U;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' λ2 � = arg min ¯ Z 1 2 �� ¯Z − ¯U ��2 F + λ2∥D ¯Z∥2,1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (26) Let A = D ¯Z and construct ¯Z as a sum of differences via Zk,• = a+�K−1 i=1 Ai,•, ( where a = Z1,•).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then we can interpret the proximal operator as a group lasso probem [Bleakley and Vert, 2011].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' A := arg min A 1 2∥ ¯Ucen − ¯RcenA∥2 F + λ2∥A∥2,1, (27) where Xcen denotes a column centered matrix and R ∈ RK×(K−1) is a matrix with entries Ri,j = 1 for i > j and 0 otherwise.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The problem above can be solved through a block-coordinate descent strategy, sequentially updating the solution for each block Ak,• for k = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , K − 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We can then construct a solution for ¯Z by summing the differences.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' And the optimal value for a is given by a = 11,T (U − RA).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Correspondingly, the proximal operator for R2 is proxR2 � ¯U;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' λ2 � = � �a⊤, (a + A1,•)⊤ , .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , � a + K−1 � i=1 Ai,• �⊤� � ⊤ .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' (28) C Details of the Synthetic Data Generating We followed the similar synthetic data generate procedure as in [Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=', 2022].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The key is how to create similar but different graphs by applying perturbations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 28 Perturbation level: Denote the adjacency matrix of Gtruth as At = (at ij) ∈ Rd×d, where at ij = 1 if there is an edge from node i to node j, and at ij = 0 otherwise, i, j = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , d.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Then the generated BN, denoted by Ggen, is constructed in the following way.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Let Ag be the adjacency matrix of Ggen, and define the perturbation level as the ratio of the number of changed edges in Ag to the number of all possible edges.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For example, if the perturbation level is 10%, we first set Ag = At, and then randomly select 10% of the off-diagonal elements at ij(i ̸= j) in At.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' For each selected element at ij, if at ij = 0, then we set ag ij = 1 (adding edge);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' if at ij = 1, then with probability 1/2 we set ag ij = 0 (deleting edge), otherwise let ag ji = 1 (reversing edge).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' We generate K graphs ˜G = {G1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , GK} by such a perturbation scheme.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Evaluation metric: Let {G1 output, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' , GK output} represent the K BN structures obtained from NOTEARS-PFL, NOTEARS-SIG, NOTEARS-AVG, NOTEARS-ADMM.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' The four basic statistics in the evaluation metrics are defined as follows: true positives (TP), the number of edges that are both in G1 output and G1;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' false positives (FP), the number of edges that are present in G1 output but not in G1;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' false negatives (FN), the number of edges that are present in G1 but not in G1 output;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' and true negatives (TN), the number of vertex pairs that are neither edges in G1 nor in G1 output.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 29 D Supplementary Tables Table 3: Data summary of the datasets used in this study.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Center of Innovation in Hiroshima (COI) Kyoto University (KUT) University of Tokyo (UTO) Hiroshima Kajikawa Hospital (HKH) Hiroshima University Hospital (HUH) Total Subject 194 175 158 62 124 MDD Subject 70 16 62 33 57 HC Subject 124 159 96 29 67 MDD Percentage 36% 9% 39% 53% 46% rs-fMRI Frames 240 240 240 107 143 Table 4: Demographic characteristics of participants in multi-site datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Site Number Male/Female Age BDI MDD COI 70 31/39 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 ± 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 26.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 ± 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 KUT 16 10 6 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='79±10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='82 27.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='7 ± 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 UTO 62 36/26 38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='74 ±11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='62 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5±11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 HKH 33 20/13 44.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8±11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5±8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='7 HUH 57 32/25 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3±12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9±9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 HC COI 124 46/78 51.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 ± 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 ± 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 KUT 159 93/66 36.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='51± 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 ± 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 UTO 96 33/63 46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65±15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='54 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6 ± 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 HKH 29 12 17 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4±9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1±4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6 HUH 67 30/37 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6±9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='6±4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 Table 5: Imaging protocols for rs-fMRI and structural MRI in multi-site datasets.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' COI KUT UTO HKH HUH rs-fMRI MRI scanner Siemens Verio Siemens TimTrio GE MR750w Siemens Spectra GE Sigma HDxt Magnetic field strength 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0T 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0T 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0T 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0T 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0T Number of channels per coil 12 32 24 12 8 FoV (mm) 212 212 212 192 256 Matrix 64 x 64 64 x 64 64 x 64 64 x 64 64 x 64 Number of slices 40 40 40 38 32 Number of volumes 240 240 240 107 143 In-plane resolution (mm) 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 x 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3125 X 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3125 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 x 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='3 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 x 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 x 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='0 Slice thickness (mm) 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 3 4 Slice gap (mm) 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 0 0 TR (ms) 2500 2500 2500 2700 2000 TE (ms) 30 30 30 31 27 Flip angel (deg) 80 80 80 90 90 Slice acquisition order Ascending Ascending Ascending Ascending Ascending Total scan time 10 min + 10s (dummy) 10 min + 10s (dummy) 10 min + 10s (dummy) 4 min.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 46s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' + 14s (dummy) 4 min.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' 46s.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' + 14s (dummy) Eye closed/fixate Fixate Fixate Fixate Fixate Fixate Structural MRI FoV (mm) 256 225x 240 240 256 256 Matrix 256 x 256 240 x 256 256 x 256 256 x 256 256 x 256 Voxel size mm3 1 x 1x 1 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9375 x 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9375 x 1 1 x 1x 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 1 x 1x 1 1 x 1x 1 TR (ms) 2300 2000 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='7 1900 6812 TE (ms) 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='38 1986 TI (ms) 900 990 400 900 450 Flip angel (deg) 9 8 11 10 20 30 Table 6: Description of ROIs in AAL template and their Montreal Neurological Institute (MNI) coordinates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Index Region name Abbreviation Lobe x y z 1 Precentral gyrus PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 -5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='68 50.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='94 2 Precentral gyrus PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='37 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='21 52.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='09 3 Superior frontal gyrus, dorsolateral SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='45 34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='81 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='20 4 Superior frontal gyrus, dorsolateral SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='90 31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='12 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='82 5 Superior frontal gyrus, orbital ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='56 47.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 -13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='31 6 Superior frontal gyrus, orbital ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='49 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='10 -14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 7 Middle frontal gyrus MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='73 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 8 Middle frontal gyrus MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 9 Middle frontal gyrus, orbital ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 50.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='62 10 Middle frontal gyrus, orbital ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 52.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 -10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='73 11 Inferior frontal gyrus, opercular IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='73 19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 12 Inferior frontal gyrus, opercular IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 50.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='20 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='41 13 Inferior frontal gyrus, triangular IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='58 29.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='91 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='99 14 Inferior frontal gyrus, triangular IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 50.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='33 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 15 Inferior frontal gyrus, orbital ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='71 -12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='11 16 Inferior frontal gyrus, orbital ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 -11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='91 17 Rolandic operculum ROL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 47.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 -8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='48 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 18 Rolandic operculum ROL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 52.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='25 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='63 19 Supplementary motor area SMA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 61.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='38 20 Supplementary motor area SMA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='62 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 61.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 21 Olfactory cortex OLF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='05 -11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 22 Olfactory cortex OLF.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='91 -11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='26 23 Superior frontal gyrus, medial SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='80 49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='89 24 Superior frontal gyrus, medial SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='10 50.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='84 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 25 Superior frontal gyrus, medial orbital ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 54.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='40 26 Superior frontal gyrus, medial orbital ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 51.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='67 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 27 Gyrus rectus REC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 -18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 28 Gyrus rectus REC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='35 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='64 -18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 29 Insula INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri -35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='44 30 Insula INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='25 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 31 Cingulate gyrus, anterior part ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri -4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='04 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='40 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 32 Cingulate gyrus, anterior part ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='01 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='84 33 Cingulate gyrus, mid part DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri -5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='48 -14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='92 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='57 34 Cingulate gyrus, mid part DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='83 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='79 35 Cingulate gyurs, posterior part PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri -4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 -42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='92 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='67 36 Cingulate gyurs, posterior part PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='44 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='81 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='87 37 Hippocampus HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='03 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='74 -10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 38 Hippocampus HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 29.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 -19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='78 -10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='33 39 Parahippocampus PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 -15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='70 40 Parahippocampus PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='38 -15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='47 41 Amygdala AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='27 -0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='67 -17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 42 Amygdala AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 27.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='64 17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='50 43 Calcarine fissure and surrounding cortex CAL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 -78.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='67 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='44 44 Calcarine fissure and surrounding cortex CAL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='99 -73.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='40 45 Cuneus CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 -80.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 27.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 46 Cuneus CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='51 -79.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 47 Lingual gyrus LING.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='62 -67.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='56 -4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='63 48 Lingual gyrus LING.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='29 -66.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 -3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='87 49 Superior occipital lobe SOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='54 -84.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='26 28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 50 Superior occipital lobe SOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='29 -80.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 51 Middle occipital lobe MOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='39 -80.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='73 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='11 52 Middle occipital lobe MOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='39 -79.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='70 19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='42 53 Inferior occipital lobe IOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 36.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 -78.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='29 -7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='84 54 Inferior occipital lobe IOG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 -81.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='99 -7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='61 55 Fusiform gyrus FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 -40.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='30 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 56 Fusiform gyrus FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='97 -39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='10 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 57 Postcentral gyrus PoCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 -22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='63 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='92 58 Postcentral gyrus PoCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 -25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='49 52.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='55 59 Superior pariental gyrus SPG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='45 -59.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='56 58.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='96 60 Superior pariental gyrus SPG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 26.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='11 -59.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 62.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 61 Inferior pariental gyrus IPL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='80 -45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='82 46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='74 62 Inferior pariental gyrus IPL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 -46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='29 49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='54 63 Supramarginal gyrus SMG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 55.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='79 -33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='64 30.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='45 31 Table 7: Continue table: Description of ROIs in AAL template and their Montreal Neurological Institute (MNI) coordinates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' Index Region name Abbreviation Lobe x y z 64 Supramarginal gyrus SMG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 57.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='61 -31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='50 34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='48 65 Angular gyrus ANG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 44.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 -60.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='82 35.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 66 Angular gyrus ANG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='51 -59.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='63 67 Precuneus PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='24 -56.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='01 68 Precuneus PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 56.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='05 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='77 69 Paracentral lobule PCL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='63 -25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 70.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 70 Paracentral lobule PCL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='48 31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 68.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='09 71 Caudate CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region -11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='00 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='24 72 Caudate CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Subcortial region 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='84 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='42 73 Putamen PUT.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region -23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='91 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='86 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='40 74 Putamen PUT.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Subcortial region 27.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='78 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='91 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 75 Pallidum PAL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region -17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='75 -0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='03 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='21 76 Pallidum PAL.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Subcortial region 21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='20 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 77 Thalamus THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region -10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='85 -17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='56 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 78 Thalamus THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 13.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='00 -17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='55 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='09 79 Heschl gyrus HES.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='99 -18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='88 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='98 80 Heschl gyrus HES.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='86 -17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='41 81 Superior temporal gyrus STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 53.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='16 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='68 7.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 82 Superior temporal gyrus STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 58.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 -21.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='78 6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='80 83 Temporal pole: superior temporal gyrus TPOsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='88 15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 84 Temporal pole: superior temporal gyrus TPOsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='25 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='75 -16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='86 85 Middle temporal gyrus MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 55.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='52 -33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='80 -2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='20 86 Middle temporal gyrus MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 57.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='47 -37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 -1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='47 87 Temporal pole: middle temporal gyrus TPOmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 36.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='59 -34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 88 Temporal pole: middle temporal gyrus TPOmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 44.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 14.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='55 -32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='23 89 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='77 -28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='05 -23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='17 90 Inferior temporal gyrus ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 53.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='69 -31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 -22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 91 Cerebellum crus 1 CRBLCrus1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 36.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='07 -66.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='72 -28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 92 Cerebellum crus 1 CRBLCrus1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 -67.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 -29.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='55 93 Cerebellum crus 2 CRBLCrus2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 28.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='64 -73.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='26 -38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 94 Cerebellum crus 2 CRBLCrus2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 -69.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='02 -39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 95 Cerebellum 3 CRBL3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 37.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 -18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='58 96 Cerebellum 3 CRBL3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 12.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 -34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='47 -19.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='39 97 Cerebellum 4 CRBL45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 15 43.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='49 -16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 98 Cerebellum 4 CRBL45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 17.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='2 42.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='86 -18.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 99 Cerebellum 6 CRBL6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='24 -59.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='1 -22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='13 100 Cerebellum 6 CRBL6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 24.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='69 -58.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='32 -23.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='65 101 Cerebellum 7 CRBL7b.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 32.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 -59.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='82 -45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='45 102 Cerebellum 7 CRBL7b.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 -63.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='18 -48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 103 Cerebellum 8 CRBL8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='75 -54.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='52 -47.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='68 104 Cerebellum 8 CRBL8.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 -56.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='34 -49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='47 105 Cerebellum 9 CRBL9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 -48.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='95 -45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 106 Cerebellum 9 CRBL9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 9.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='46 49.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='5 -46.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='33 107 Cerebellum 10 CRBL10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Posterior Fossa 22.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='61 -33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 -41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='76 108 Cerebellum 10 CRBL10.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Posterior Fossa 25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='99 -33.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='84 -41.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='35 109 Vermis12 Vermis12 Posterior Fossa 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='76 38.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='79 -20.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='05 110 Vermis3 Vermis3 Posterior Fossa 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='38 39.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 -11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='4 111 Vermis45 Vermis45 Posterior Fossa 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='22 52.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 -6.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='11 112 Vermis6 Vermis6 Posterior Fossa 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 67.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='06 -15.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='12 113 Vermis7 Vermis7 Posterior Fossa 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 71.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='93 -25.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='14 114 Vermis8 Vermis8 Posterior Fossa 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='15 64.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='43 -34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='08 115 Vermis9 Vermis9 Posterior Fossa 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='86 54.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='87 -34.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='9 116 Vermis10 Vermis10 Posterior Fossa 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='36 45.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='8 -31.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='68 32 Table 8: The overlapping connections between the directed networks of 5 sites of MDD patients and HC participants.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' From To Index ROI Lobe Index ROI Lobe MDD 10 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 6 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 24 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 33 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 30 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 10 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 30 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 29 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 30 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 32 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 33 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 3 SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 35 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 36 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 46 CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 45 CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Occipital 56 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 11 IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 68 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 46 CUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Occipital 68 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 26 ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 71 CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region 6 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 77 THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region 72 CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Subcortial region 82 STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 86 MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 85 MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 10 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 89 ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal HC 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 26 ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 8 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 9 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 23 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 24 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 31 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 23 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 34 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 67 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 38 HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 39 PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 40 PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 3 SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 82 STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 8 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 86 MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 89 ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 33 Table 9: The site-specific connections between the directed networks of 5 sites of MDD patients.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content=' From To Index ROI Lobe Index ROI Lobe Site 1 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 10 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 67 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 2 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 67 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 5 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 39 PHG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 6 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 78 THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 7 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 71 CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region 8 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 82 STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 11 IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 68 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 13 IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 67 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 16 ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 56 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 24 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 72 CAU.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Subcortial region 26 ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 42 AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 29 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 8 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 42 AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 87 TPOmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 55 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 68 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 77 THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region 31 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 90 ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 56 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal Site2 3 SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 7 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 4 SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 5 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 25 ORBsupmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 7 MFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 10 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 15 ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 11 IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 24 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 3 SFGdor.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 29 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 9 ORBmid.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 29 INS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 16 ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 31 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 5 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 77 THA.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Subcortial region 13 IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 81 STG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 24 SFGmed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 85 MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 14 IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 33 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 35 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 37 HIP.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 12 IFGoperc.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 89 ITG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Temporal 42 AMYG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 56 FFG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 35 PCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 86 MTG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Temporal 5 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal Site3 1 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 14 IFGtriang.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 2 PreCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 57 PoCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Pariental 5 ORBsup.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 26 ORBsupmed.' metadata={'source': 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'/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Frontal 31 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='L Insula and Cingulate Gyri 16 ORBinf.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Frontal 32 ACG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 68 PCUN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Pariental 34 DCG.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/EtE0T4oBgHgl3EQfgwHQ/content/2301.02423v1.pdf'} +page_content='R Insula and Cingulate Gyri 5 ORBsup.' metadata={'source': 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can improve communication rates even when the relay cannot decode +the source signal. Efficient implementation of CF is a topic of contemporary interest, in part because +of its potential impact on wireless technologies such as cloud-RAN. There exists a gap between +the performance of CF implementations in the high spectral efficiency regime and the corresponding +information theoretic achievable rates. We begin by re-framing a dilemma causing this gap, and propose +an approach for its mitigation. We utilize trellis coded quantization (TCQ) at the relay together with +multi-level coding at the source and relay, in a manner that facilitates the calculation of bit LLRs at +the destination for joint decoding. The contributions of this work include designing TCQ for end-to- +end relay performance, since a distortion-minimizing TCQ is suboptimum. The reported improvements +include a 1dB gain over prior results for PSK modulation. +Index Terms +Compress-forward relay, coded modulation, multilevel coding, trellis coded quantization +I. INTRODUCTION +This paper addresses compress-forward (CF) relaying under high-spectral efficiency (coded +modulation), where implementations of CF show a performance gap to the best known (informa- +tion theoretic) achievable rates. The nature of the difficulties is succinctly explained as follows. +This work of H. Wan and A. Nosratinia was supported by the grant 1711689 from the National Science Foundation. The +work of A. Host-Madsen was supported by the grant 1923751 from the National Science Foundation. +H. Wan and A. Nosratinia are with the Department of Electrical Engineering, The University of Texas at Dallas, Richardson, +TX, USA,Email: Heping.Wan@utdallas.edu, aria@utdallas.edu A. Host-Madsen is with the Department of Electrical Engineering, +University of Hawaii, Manoa, Honolulu, HI, USA Email: ahm@hawaii.edu +DRAFT + +2 +The best theoretical achievable rates employ either Wyner-Ziv compression at the relay, or joint +decoding at the destination [1], [2]. Since practical Wyner-Ziv coding implementations have had +some difficulty in approaching the theoretical limits, joint decoding at the destination has been +pursued [3], [4] via iterative decoding. Iterative decoding requires bit-level LLRs, which are +easy to obtain under scalar quantization but difficult with Vector Quantization (VQ). Thus, joint +decoding approaches so far have utilized scalar quantization and given up on the shaping gain +that is only provided by vector quantization. The current paper addresses this issue and, via a +new approach, improves the performance of CF implementations. +We begin with a brief survey of literature. In [5] the relay quantizes soft information of +received values followed by a multi-level coding with convolutional codes for each level, which +serves as both Slepian-Wolf compression as well as error protection. The works [6]–[8], feature +half-duplex relay, Wyner-Ziv coding, and successive decoding at destination. [6], [7] employ +LDPC codes at the source and irregular-repeat accumulation (IRA) codes at the relay. [8] uses +a nested construction of polar codes at the relay. Liu et al. [9] implements Wyner-Ziv coding +via a superposition structure. +An alternative strategy maps the quantized sequence to a relay codeword without Wyner- +Ziv encoding [1], [2], [10], but with joint decoding at destination. This strategy has the same +achievable rate as Wyner-Ziv encoding with successive cancellation decoding. The following +works utilized scalar quantization and joint decoding. Chakrabarti et al. [11] designed quantizers +by maximizing the mutual information between the source and the quantizer output instead of +minimizing the distortion. Nagpal et al. [3] used LDPC codes, and Nagpal et al. [4] used Low +Density Generator Matrix (LDGM) codes to map the scalar quantized symbols to codewords. +These binary modulations were extended to coded modulation via bit-interleaved coded mod- +ulation (BICM). The present authors employed this approach in [12] with scalar quantization, +multilevel coding, and LDPC codes, and joint decoding. +As mentioned earlier, scalar quantization is easier to manage in soft decoding, but sacrifices +the shaping gain. A general vector quantizer (VQ) captures the shaping gain in principle, but +makes the calculation of bit LLRs intractable. To resolve this tension, we utilize trellis coded +quantization (TCQ) [13]. In this technique, trellis coding captures shaping gain while likelihood +exchange is enabled by the BCJR algorithm [14]. +We utilize this technique for the design of coded modulation for full-duplex compress-forward +relays in the AWGN channel. We employ multilevel coding (MLC) [15] as a convenient and +DRAFT + +3 +flexible method for the implementation of coded modulation in this multi-node network. We +analyze the proper assignment of rates to the component level-wise binary codes for near- +optimal error protection; this is in contrast with [3], [4] which were limited to the same rate +at all levels. Part of the contribution of this work is a practical design of the TCQ that targets +end-to-end relay performance, since a distortion-minimizing TCQ proved insufficient. Quantizer +optimization, and the related computation of input-output distributions for the soft decoding +of TCQ, are elucidated. We use LDPC codes for error protection at the source, and map the +quantized sequence at the relay to a codeword whose parity bits are transmitted. A joint iterative +decoding graphical model and corresponding information exchange algorithm are described for +the joint decoding at the destination. +In summary, contributions of this letter include: TCQ for the CF relay to achieve shaping +gain while allowing LLR exchange at the iterative decoder, MLC per-level rate analysis for CF +relaying, iterative joint decoding, and demonstrating the gains of the proposed approach. +II. SETUP, NOTATION, AND PRELIMINARIES1 +In the point-to-point channel, MLC is implemented by splitting the data stream into m bit- +streams for a 2m-ary constellation. Each sub-stream i ∈ {1, 2, ..., m} is encoded independently. +At each time instance, the outputs of the (binary) encoders are combined to construct vector +[A1, A2, ...Am] which is then mapped to a constellation point X and transmitted. At the desti- +nation, Y is observed. The channel is described by conditional distribution p(y|x). The mutual +information between the input and output is given by +I(X; Y ) = I(A1, A2, ..., Am; Y ) = +m +� +i=1 +I(Ai; Y |Ai−1), +(1) +where Ai−1 ≜ [A1, A2, ..., Ai−1] with A0 representing a constant, and the chain rule for the +mutual information and a one-to-one relationship between X and [A1, A2, ..., Am] are used. +Equation (1) suggests a multistage decoding, and the original channel is decomposed into m +levels where the information bits of level i is recovered using channel observations and the +output of decoders of preceding levels. Therefore, the rate assigned to level i should be less than +or equal to I(Ai; Y |Ai−1). +1This section appears here for completeness and follows [12] in its entirety. +DRAFT + +4 +Fig. 1. Full-duplex Gaussian relay channel +The three-node AWGN full-duplex relay channel is shown in Fig. 1. The source transmits +X1 ∈ A satisfying power constraint Ps to the destination and relay. The relay transmits X2 ∈ B +satisfying power constraint Pr to the destination. A and B denote the constellation alphabets +of X1 and X2. n2 and n3 are AWGN with zero mean and variance N2 and N3. The received +signals at the relay and destination are +Y2 = H12X1 + n2, +(2) +Y3 = H13X1 + H23X2 + n3, +(3) +where H13, H12 and H23 are channel coefficients as illustrated in Fig. 1. +In block t, the source maps one of 2nR messages to a length-n codeword X(t) +1 , and emits X(t) +1 +to the destination and relay. Due to causality, the relay quantizes the sequence received in block +t − 1. ˜Y(t−1) +2 +of length n denotes the quantized binning of Y(t−1) +2 +. Then ˜Y(t−1) +2 +is mapped to +a length-n codeword X(t−1) +2 +and transmitted to the destination. The destination uses the joint +decoding to recover the source message sent at block t − 1. The achievable rate is [16, Section +16.7] +R < max I(X1; ˜Y2, Y3|X2), +(4) +subject to +I(Y2; ˜Y2|X2, Y3) ≤ I(X2; Y3), where the maximum is over joint distributions +p(x1)p(x2)p(˜y2|x2, y2). +When MLC is implemented in the CF relaying under 2m-QAM/PSK modulation for both +source and relay, the data stream at the source and the quantized binning at the relay are split +into m bit-streams. Each of m binary bit-streams at the source/relay is encoded independently. +Due to one-to-one relationships between X1 ↔ [A1, A2, ..., Am], ˜Y2 ↔ [B1, B2, ..., Bm], and +DRAFT + +5 +X2 ↔ [C1, C2, ..., Cm], multistage decoding will induce a decomposition of the original channel, +and the achievable rate in (4) can be expressed as +R ≤ max +m +� +i=1 +I(Ai; Bm, Y3|Cm, Ai−1). +(5) +subject to the constraint: +m +� +i=1 +I(Y2; Bi|Cm, Y3, Bi−1) ≤ +m +� +i=1 +I(Ci; Y3|Ci−1) . +(6) +The rate assigned to each level is denoted Ri, requiring +Ri ≤ I(Ai; Bm, Y3|Cm, Ai−1) +(7) +III. MULTILEVEL REALIZATION OF CF RELAYING +The message to be transmitted is partitioned into m bit-streams. Each bit-stream is indepen- +dently encoded with binary LDPC code of rate Ri, i = 1, . . . , m, where Ri should satisfy (7). +At each time instance, binary vector [A1, A2, ...Am] is mapped to a symbol of the transmitted +sequence X1 by a 2m-QAM/PSK modulator. At the relay, the quantized binning ˜Y2 is split into +m bit-streams. Each bit-stream is encoded through a systematic rate-1/2 binary LDPC code. +The parity bits of the codeword are combined via a 2m-QAM/PSK modulator, to construct X2 +which is transmitted to the destination at the next block. +A. Quantization at the Relay +The key impediment to CF performance has been the implementation of compression at the +relay. Wyner-Ziv implementations have not approached fundamental limits, and joint decoding +has concentrated on scalar quantization to facilitate LLR calculation, thus losing shaping gain +of the quantizer at the relay. We provide a new solution via TCQ that reconciles this issue by +providing shaping gain as well as feasible LLR calculation for joint decoding. +Trellis source coding aims to compress a sequence y = [y1, y2, . . . , yn] sampled from a +memoryless source with marginal distribution p(y) to ˜y = [˜y1, ˜y2, . . . , ˜yn] at a rate of ˜R. The +reconstruction values are ˆy ∈ ˆY. Trellis source coding is to find a path determined by ˜y which +generates a reconstruction sequence ˆy with minimum distortion. +TCQ [13] is a practical implementation of trellis source coding that was inspired by trellis +coded modulation (TCM) [17]. In TCM, to send m information bits in each signaling interval, +the traditional 2m- point signal constellation is expanded to 2m+1 points and partitioned into 2m +DRAFT + +6 +subsets according to Ungerboeck’s set partitioning idea. m input bits are passed through a rate +m/(m + 1) trellis encoder among which m − 1 bits are used to select the set partition, and the +remaining bit determines the symbol from the set partition. +B. Obtaining p(ˆy2|y2) and Quantizer Optimization +For iterative decoding at the destination, one needs a soft version of TCQ, for which a +logical candidate is the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm. To implement the BCJR, +the (marginal) conditional distribution p(ˆy2|y2) is needed [14], where ˆy2 ∈ ˆY2 represents re- +construction value and | ˆY2| = 2m+1. Unfortunately, this distribution is not readily available and +its calculation is not straight forward. In this subsection, we highlight the different approaches +for calculating this value, and present the technique that we utilized, which to our experience +produces the best results. +Rate-distortion theory [18] suggests an optimal source encoder coming from the solution of +the following minimization +R(D) = +min +p(ˆy|y):E{d(y,ˆy)}≤DI(Y, ˆY ), +where the minimization is over all conditional distributions p(ˆy|y) for which the joint distribution +p(ˆy, y) = p(y)p(ˆy|y) satisfies the expected distortion constraint D, and d(y, ˆy) is the distortion +measure function. p(ˆy|y) can be interpreted as the probability that a given source value y is +represented by a reconstruction value ˆy. +With the resulting p(ˆy|y) obtained from the above optimization, the encoding procedure is +equivalent to finding a ˆy(n) that maximizes p(ˆy(n), y). For trellis source coding, the BCJR algo- +rithm [14] can be used to find the reconstruction sequence ˆy and the corresponding compressed +bitstream ˜y. +However, minimizing distortion is not necessarily a good strategy for CF relaying, because the +ultimate goal is for relaying to give maximal help in decoding at destination. Counterintuitively, +this is not always the same as low distortion, which only preserves the fidelity of a reconstruction +of y2. Our simulations indicate that Lloyd-Max reconstruction values and p(ˆy2|y2) obtained +from rate-distortion optimization together produce mediocre performance.2 This seems to suggest +jointly designing p(ˆy2|y2) and the trellis structure, but this is too unwieldy for practical quantizer +2This issue has also been pointed out by others, e.g., Chakrabarti et al. [11] produced a comparison in which a quantizer with +worse mean-squared distortion resulted in better relay performance. +DRAFT + +7 +design. Our results are obtained by choosing a good trellis from the literature and determining +quantizer boundaries by maximizing the CF (end-to-end) achievable rate expression, which +is related to the quantization boundaries through the conditional distribution p(ˆy2|y2). The +boundaries were determined via a simple discrete search that maintained the symmetry of the +quantizer and utilized the trellis and the reconstruction values in Fig. 4. +C. Decoding +As mentioned earlier, the destination decodes the source signal as well as the quantized signal +at the relay; information theory arguments show that this joint decoding permits the relay to avoid +dirty-paper type encoding without a rate penalty. The joint decoder is implemented iteratively via +a graphical model for the exchange of information within, and between, the component LDPC +tanner graphs. +The desination begins by seeking a codeword x1 according to maximum a posteriori proba- +bility p(x1|y3); this search is performed via a bit-wise MAP decoder with decoding rule: +ˆx1,j = arg max +x1,j∈A +� +∼x1,j +p(x1|y3), +for all j = 1, ..., n,. Recall that ˆy2 are the quantized values while ˜y2 is the compressed bit +sequence. These two representations are equivalent given the quantization strategy, however, +˜y2 is a more convenient representation for the relay’s channel encoder as well as for iterative +decoding at destination. p(x1|y3) can be decomposed as follows: +p(x1|y3) = +1 +p(y3) +� +˜y2,x2 +p(x1, x2, ˜y2, y3), +(8) +where +p(x1, x2, ˜y2, y3) = p(y3|x1, x2, ˜y2)p(x1, x2, ˜y2), +(9) +(a) += p(y3|x1, x2)p(x1, x2, ˜y2), +(10) += p(y3|x1, x2)p(x2|x1, ˜y2)p(˜y2|x1)p(x1), +(11) +(b)= p(y3|x1, x2)p(x2|˜y2)p(˜y2|x1)p(x1), +(12) +(c) +∝ p(y3|x1, x2)1{x2 = CR(˜y2)}p(˜y2|x1)1{x1 ∈ CS}, +(13) +where (a) follows because y3 is only dependent on x1, x2, (b) is due to Markov x1 ↔ ˜y2 ↔ x2, +and (c) is due to p(x1) = +1{x1∈CS} +2nR +being a uniform distribution over the elements of the source +DRAFT + +8 +codebook CS, and p(x2|˜y2) = +1{x2 = CR(˜y2)}, i.e., the output of error-control coding at the +relay CR being a deterministic function of its input. +Fig. 2. The simplified destination part of the channel model +During block t, the destination receives a version of X(t−1) +2 +that is contaminated with noise +and interference, which carries information about X(t−1) +1 +, which is independent of X(t) +1 . This +independence allows successive interference cancellation, simplifying the channel model at des- +tination [3]: +Y23 = H23X2 + n′ +3, +(14) +Y13 = H13X1 + n3, +(15) +which is shown in Fig. 2. At block t, the destination jointly decodes X(t−1) +1 +and X(t−1) +2 +on the +basis of Y(t) +23 and Y(t−1) +13 +where the processing of Y(t) +23 treats X(t) +1 +as zero-mean Gaussian noise +with power H2 +12Ps, and Y(t−1) +13 +is processed by subtracting X(t−2) +2 +decoded during block t−1 from +Y(t−1) +3 +. This operation can decompose Y3 to two links Y13 and Y23 with independent additive +white Gaussian noise n′ +3 of variance N3 + H2 +12Ps and n3 of variance N3. Using p(y3|x1.x2) = +p(y31|x1)p(y32|x2), for LLR calculation at destination, (13) can be rewritten as +n +� +j=1 +p(y13,j|x1,j) +n +� +k=1 +p(y23,k|x2,k) +· +1{x1 ∈ CS}p(˜y2|x1)1{x2 = CR(˜y2)}, +(16) +Enabled by this decomposition, joint decoding can be performed by a repeated application +of two LDPC decoders whose cost function is based on p(y13|x1) and p(y23|x2), as well as +enforcing the relationship between x1 and x2 through the term p(˜y2|x1) together with the relay +LPDC coding x2 = CR(˜y2). Using the destination observations y13 and y23 (after successive in- +terference cancellation) a three-way iterative decoding is performed whose information exchange +is described by Fig. 3, where each LDPC decoder block represents a Tanner graph. +DRAFT + +9 +Fig. 3. The joint iterative decoding graphical model +The two LDPC decoder components follow well-known principles, therefore their internal +structure is omitted in Fig. 3 for simplicity. The iterative decoding also needs propagating soft in- +formation through p(˜y2|x1), which is not straight forward, therefore we break it into two compo- +nents. Considering the Markov chain x1 ↔ ˆy2 ↔ ˜y2, we have p(˜y2|x1) = � +ˆy2 +p(˜y2|ˆy2)p(ˆy2|x1). +The information exchange across the trellis, shown by p(˜y2|ˆy2), is calculated using the BCJR +algorithm. The information exchange between x1 and ˆy2 is through p(ˆy2|x1). This marginal +distribution of quantized values is described as a weighted sum since TCQ employs several +scalar quantizers, whose number we denote with K. The quantizer choice at each sample has a +probability P(Qi|x1). The overall marginal distribution is given by: +p(ˆy2|x1) = +K +� +i=1 +P(Qi|x1) +� +ˆy2=Qi(y2) +p(y2|x1) dy2 +(17) +The probability P(Qi|x1) at each sample is driven by the contamination of x1 with noise prior to +quantization, as well as the action of the trellis. The overall effect is difficult to model, therefore +we obtain an empirical estimate for P(Qi|x1) by a monte carlo simulation of the channel x1 → y2, +applying the TCQ, and collecting the empirical frequency of occurrence of each quantizer Qi +conditioned on x1. +The destination begins by initializing p(y13) and p(y23) according to channel observations. +Then, we update the soft estimate of x1 at the destination, via executing the sum-product +algorithm for CS. From this, an updated soft estimate for ˆy2 is obtained via +(17). Then, the +DRAFT + +10 +BCJR algorithm, induced by the compression trellis, is used to update the soft estimate of ˜y2. +Then, another sum-product is executed utilizing the observation y23 and the structure of the +relay-destination LDPC code, to update ˜y2. We then repeat backward, updating ˆy2 and x1, and +then another sum-product iteration on x1. +To summarize, the process consists of two sum-product algorithms operating on the source +LDPC code and the relay LDPC code, and information being exchanged between them via +the method mentioned above. Our algorithm performs one bit-to-check and one check-to-bit +operation in each sum-product before propagating the information to the other LDPC decoder. +At the end of the process, we perform a multistage hard decoding of the MLC. +IV. SIMULATIONS +This section presents simulation results supporting the findings of this letter. The following +values underlie the simulations: N3 = 1, N2 = 8, H13 = 1, H12 = 2, and H23 = 11. Furthermore, +in all experiments the source and the relay transmitters emit the same power. The reported SNRs +for simulations are generated by fixing the noise power and varying the power of the source/relay. +Error control coding is achieved via DVB-S2 LDPC codes with block length 64,800. At the +relay, the first 32,400 quantized bits are encoded by a rate-1/2 DVB-S2 code, and the remaining +quantized bits are encoded with a second, similar, DVB-S2 code. The parity bits of these two +encoders are then concatenated for transmission. +Our experiments involve 16-QAM at the normalized rate of 3.4 bits/s/Hz and 16-PSK at the +rate of 3.27 bits/s/Hz. Each modulation is attached to a 4-level multi-level code, which in the +case of 16-QAM have rates 0.9, 0.8, 0.9, and 0.8, and in the case of 16-PSK have rates 0.9, 0.9, +0.8, and 2/3. +The relay utilizes a TCQ with an 8-state trellis whose generator matrix is: + + +1 +0 +0 +0 +0 +0 +1 +0 +0 +0 +0 +0 +D +1 +0 +0 +0 +1 +D2 +D + + +. +The quantizer reconstruction values, shown in Fig. 4, have a cardinality that is twice the size +of the 16-QAM/PSK constellation used for source/relay modulation. For the 16-QAM example, +extending to a standard 32AMPM would present inconvenient cell boundaries, therefore we +experimented with the shown 32-point extension as well as a symmetric extension with 64 +DRAFT + +11 +Fig. 4. The reconstruction values for CF relaying using 16-QAM (a), and 16-PSK (b), where the circles represent 16-QAM/PSK +constellation. +points, finding the latter produces negligible gains over the former. The design of quantizer bin +boundaries is according to the optimization mentioned in Section III-B. +We compare our results with that of bit-interleaved coded modulation (BICM) [3], [4], where +the component LDPC codes in the sub-channels have the same rate by definition. Since the +granularity of available DVB-2 codes are limited, we simulated BICM at the closest rate possible +with available codes. A rate-5/6 DVB-S2 code is used for 16-QAM BICM, resulting in an overall +rate of 3.33 bits/s/Hz, and a rate-0.8 DVB-S2 code was used for 16-PSK resulting in overall rate +of 3.2 bits/s/Hz. In addition to the BICM results, we also display the results of a preliminary +version of this work from [12] which uses only scalar quantization. In addition, rates are carefully +chosen to avoid any unfair advantage to the method of this letter in reporting error rates. +Simulation results are displayed in Fig. 5. The observations and insights arising from these +simulations are as follows: +• The proposed method outperforms the error rate of BICM under 16-QAM and 16-PSK, +even though the simulated BICM rates were slightly advantageous. +• Superior performance of MLC over BICM was known in point-to-point channels, but is +affirmed in this letter for the end-to-end performance of a CF relaying. +• It is also established that TCQ can outperform scalar quantization in CF relaying. Although +at first sight this may seem a natural outcome, past work [11] implies that utilizing vector +quantization in the context of CF has been remarkably difficult. In that sense, the result +reported herein has significant practical novelty. +DRAFT + +12 +9 +10 +11 +12 +13 +14 +15 +10-8 +10-7 +10-6 +10-5 +10-4 +10-3 +10-2 +10-1 +BER +16-QAM, TCQ +16-QAM, scalar +16-QAM, BICM +16-PSK, TCQ +16-PSK, scalar +16-PSK, BICM +Fig. 5. 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Rec., pp. 142–163, Mar. +1959. +DRAFT + diff --git a/HdE1T4oBgHgl3EQfXgSr/content/tmp_files/load_file.txt b/HdE1T4oBgHgl3EQfXgSr/content/tmp_files/load_file.txt new file mode 100644 index 0000000000000000000000000000000000000000..6f599553659f854bf019b5bda63267a895511127 --- /dev/null +++ b/HdE1T4oBgHgl3EQfXgSr/content/tmp_files/load_file.txt @@ -0,0 +1,458 @@ +filepath=/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf,len=457 +page_content='arXiv:2301.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='03128v1 [cs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='IT] 9 Jan 2023 1 Compress-and-Forward via Multilevel Coding and Trellis Coded Quantization Heping Wan, Anders Høst-Madsen, Fellow, IEEE, and Aria Nosratinia, Fellow, IEEE Abstract Compress-forward (CF) relays can improve communication rates even when the relay cannot decode the source signal.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Efficient implementation of CF is a topic of contemporary interest, in part because of its potential impact on wireless technologies such as cloud-RAN.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' There exists a gap between the performance of CF implementations in the high spectral efficiency regime and the corresponding information theoretic achievable rates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We begin by re-framing a dilemma causing this gap, and propose an approach for its mitigation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We utilize trellis coded quantization (TCQ) at the relay together with multi-level coding at the source and relay, in a manner that facilitates the calculation of bit LLRs at the destination for joint decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The contributions of this work include designing TCQ for end-to- end relay performance, since a distortion-minimizing TCQ is suboptimum.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The reported improvements include a 1dB gain over prior results for PSK modulation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Index Terms Compress-forward relay, coded modulation, multilevel coding, trellis coded quantization I.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' INTRODUCTION This paper addresses compress-forward (CF) relaying under high-spectral efficiency (coded modulation), where implementations of CF show a performance gap to the best known (informa- tion theoretic) achievable rates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The nature of the difficulties is succinctly explained as follows.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' This work of H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Wan and A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Nosratinia was supported by the grant 1711689 from the National Science Foundation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The work of A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Host-Madsen was supported by the grant 1923751 from the National Science Foundation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' H.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Wan and A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Nosratinia are with the Department of Electrical Engineering, The University of Texas at Dallas, Richardson, TX, USA,Email: Heping.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='Wan@utdallas.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='edu, aria@utdallas.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='edu A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Host-Madsen is with the Department of Electrical Engineering, University of Hawaii, Manoa, Honolulu, HI, USA Email: ahm@hawaii.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='edu DRAFT 2 The best theoretical achievable rates employ either Wyner-Ziv compression at the relay, or joint decoding at the destination [1], [2].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Since practical Wyner-Ziv coding implementations have had some difficulty in approaching the theoretical limits, joint decoding at the destination has been pursued [3], [4] via iterative decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Iterative decoding requires bit-level LLRs, which are easy to obtain under scalar quantization but difficult with Vector Quantization (VQ).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Thus, joint decoding approaches so far have utilized scalar quantization and given up on the shaping gain that is only provided by vector quantization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The current paper addresses this issue and, via a new approach, improves the performance of CF implementations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We begin with a brief survey of literature.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In [5] the relay quantizes soft information of received values followed by a multi-level coding with convolutional codes for each level, which serves as both Slepian-Wolf compression as well as error protection.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The works [6]–[8], feature half-duplex relay, Wyner-Ziv coding, and successive decoding at destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [6], [7] employ LDPC codes at the source and irregular-repeat accumulation (IRA) codes at the relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [8] uses a nested construction of polar codes at the relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Liu et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [9] implements Wyner-Ziv coding via a superposition structure.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' An alternative strategy maps the quantized sequence to a relay codeword without Wyner- Ziv encoding [1], [2], [10], but with joint decoding at destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' This strategy has the same achievable rate as Wyner-Ziv encoding with successive cancellation decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The following works utilized scalar quantization and joint decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Chakrabarti et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [11] designed quantizers by maximizing the mutual information between the source and the quantizer output instead of minimizing the distortion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Nagpal et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [3] used LDPC codes, and Nagpal et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [4] used Low Density Generator Matrix (LDGM) codes to map the scalar quantized symbols to codewords.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' These binary modulations were extended to coded modulation via bit-interleaved coded mod- ulation (BICM).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The present authors employed this approach in [12] with scalar quantization, multilevel coding, and LDPC codes, and joint decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' As mentioned earlier, scalar quantization is easier to manage in soft decoding, but sacrifices the shaping gain.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' A general vector quantizer (VQ) captures the shaping gain in principle, but makes the calculation of bit LLRs intractable.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' To resolve this tension, we utilize trellis coded quantization (TCQ) [13].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In this technique, trellis coding captures shaping gain while likelihood exchange is enabled by the BCJR algorithm [14].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We utilize this technique for the design of coded modulation for full-duplex compress-forward relays in the AWGN channel.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We employ multilevel coding (MLC) [15] as a convenient and DRAFT 3 flexible method for the implementation of coded modulation in this multi-node network.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We analyze the proper assignment of rates to the component level-wise binary codes for near- optimal error protection;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' this is in contrast with [3], [4] which were limited to the same rate at all levels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Part of the contribution of this work is a practical design of the TCQ that targets end-to-end relay performance, since a distortion-minimizing TCQ proved insufficient.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Quantizer optimization, and the related computation of input-output distributions for the soft decoding of TCQ, are elucidated.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We use LDPC codes for error protection at the source, and map the quantized sequence at the relay to a codeword whose parity bits are transmitted.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' A joint iterative decoding graphical model and corresponding information exchange algorithm are described for the joint decoding at the destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In summary, contributions of this letter include: TCQ for the CF relay to achieve shaping gain while allowing LLR exchange at the iterative decoder, MLC per-level rate analysis for CF relaying, iterative joint decoding, and demonstrating the gains of the proposed approach.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' II.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' SETUP, NOTATION, AND PRELIMINARIES1 In the point-to-point channel, MLC is implemented by splitting the data stream into m bit- streams for a 2m-ary constellation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Each sub-stream i ∈ {1, 2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', m} is encoded independently.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At each time instance, the outputs of the (binary) encoders are combined to construct vector [A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='Am] which is then mapped to a constellation point X and transmitted.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At the desti- nation, Y is observed.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The channel is described by conditional distribution p(y|x).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The mutual information between the input and output is given by I(X;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y ) = I(A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Am;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y ) = m � i=1 I(Ai;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y |Ai−1), (1) where Ai−1 ≜ [A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Ai−1] with A0 representing a constant, and the chain rule for the mutual information and a one-to-one relationship between X and [A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Am] are used.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Equation (1) suggests a multistage decoding, and the original channel is decomposed into m levels where the information bits of level i is recovered using channel observations and the output of decoders of preceding levels.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Therefore, the rate assigned to level i should be less than or equal to I(Ai;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y |Ai−1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 1This section appears here for completeness and follows [12] in its entirety.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' DRAFT 4 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Full-duplex Gaussian relay channel The three-node AWGN full-duplex relay channel is shown in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The source transmits X1 ∈ A satisfying power constraint Ps to the destination and relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The relay transmits X2 ∈ B satisfying power constraint Pr to the destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' A and B denote the constellation alphabets of X1 and X2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' n2 and n3 are AWGN with zero mean and variance N2 and N3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The received signals at the relay and destination are Y2 = H12X1 + n2, (2) Y3 = H13X1 + H23X2 + n3, (3) where H13, H12 and H23 are channel coefficients as illustrated in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In block t, the source maps one of 2nR messages to a length-n codeword X(t) 1 , and emits X(t) 1 to the destination and relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Due to causality, the relay quantizes the sequence received in block t − 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜Y(t−1) 2 of length n denotes the quantized binning of Y(t−1) 2 .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Then ˜Y(t−1) 2 is mapped to a length-n codeword X(t−1) 2 and transmitted to the destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The destination uses the joint decoding to recover the source message sent at block t − 1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The achievable rate is [16, Section 16.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='7] R < max I(X1;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜Y2, Y3|X2), (4) subject to I(Y2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜Y2|X2, Y3) ≤ I(X2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y3), where the maximum is over joint distributions p(x1)p(x2)p(˜y2|x2, y2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' When MLC is implemented in the CF relaying under 2m-QAM/PSK modulation for both source and relay, the data stream at the source and the quantized binning at the relay are split into m bit-streams.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Each of m binary bit-streams at the source/relay is encoded independently.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Due to one-to-one relationships between X1 ↔ [A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Am], ˜Y2 ↔ [B1, B2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Bm], and DRAFT 5 X2 ↔ [C1, C2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Cm], multistage decoding will induce a decomposition of the original channel, and the achievable rate in (4) can be expressed as R ≤ max m � i=1 I(Ai;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Bm, Y3|Cm, Ai−1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (5) subject to the constraint: m � i=1 I(Y2;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Bi|Cm, Y3, Bi−1) ≤ m � i=1 I(Ci;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Y3|Ci−1) .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (6) The rate assigned to each level is denoted Ri, requiring Ri ≤ I(Ai;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Bm, Y3|Cm, Ai−1) (7) III.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' MULTILEVEL REALIZATION OF CF RELAYING The message to be transmitted is partitioned into m bit-streams.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Each bit-stream is indepen- dently encoded with binary LDPC code of rate Ri, i = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' , m, where Ri should satisfy (7).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At each time instance, binary vector [A1, A2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='Am] is mapped to a symbol of the transmitted sequence X1 by a 2m-QAM/PSK modulator.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At the relay, the quantized binning ˜Y2 is split into m bit-streams.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Each bit-stream is encoded through a systematic rate-1/2 binary LDPC code.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The parity bits of the codeword are combined via a 2m-QAM/PSK modulator, to construct X2 which is transmitted to the destination at the next block.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' A.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Quantization at the Relay The key impediment to CF performance has been the implementation of compression at the relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Wyner-Ziv implementations have not approached fundamental limits, and joint decoding has concentrated on scalar quantization to facilitate LLR calculation, thus losing shaping gain of the quantizer at the relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We provide a new solution via TCQ that reconciles this issue by providing shaping gain as well as feasible LLR calculation for joint decoding.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Trellis source coding aims to compress a sequence y = [y1, y2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' , yn] sampled from a memoryless source with marginal distribution p(y) to ˜y = [˜y1, ˜y2, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' , ˜yn] at a rate of ˜R.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The reconstruction values are ˆy ∈ ˆY.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Trellis source coding is to find a path determined by ˜y which generates a reconstruction sequence ˆy with minimum distortion.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' TCQ [13] is a practical implementation of trellis source coding that was inspired by trellis coded modulation (TCM) [17].' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In TCM, to send m information bits in each signaling interval, the traditional 2m- point signal constellation is expanded to 2m+1 points and partitioned into 2m DRAFT 6 subsets according to Ungerboeck’s set partitioning idea.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' m input bits are passed through a rate m/(m + 1) trellis encoder among which m − 1 bits are used to select the set partition, and the remaining bit determines the symbol from the set partition.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' B.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Obtaining p(ˆy2|y2) and Quantizer Optimization For iterative decoding at the destination, one needs a soft version of TCQ, for which a logical candidate is the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' To implement the BCJR, the (marginal) conditional distribution p(ˆy2|y2) is needed [14], where ˆy2 ∈ ˆY2 represents re- construction value and | ˆY2| = 2m+1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Unfortunately, this distribution is not readily available and its calculation is not straight forward.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In this subsection, we highlight the different approaches for calculating this value, and present the technique that we utilized, which to our experience produces the best results.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Rate-distortion theory [18] suggests an optimal source encoder coming from the solution of the following minimization R(D) = min p(ˆy|y):E{d(y,ˆy)}≤DI(Y, ˆY ), where the minimization is over all conditional distributions p(ˆy|y) for which the joint distribution p(ˆy, y) = p(y)p(ˆy|y) satisfies the expected distortion constraint D, and d(y, ˆy) is the distortion measure function.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' p(ˆy|y) can be interpreted as the probability that a given source value y is represented by a reconstruction value ˆy.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' With the resulting p(ˆy|y) obtained from the above optimization, the encoding procedure is equivalent to finding a ˆy(n) that maximizes p(ˆy(n), y).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' For trellis source coding, the BCJR algo- rithm [14] can be used to find the reconstruction sequence ˆy and the corresponding compressed bitstream ˜y.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' However, minimizing distortion is not necessarily a good strategy for CF relaying, because the ultimate goal is for relaying to give maximal help in decoding at destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Counterintuitively, this is not always the same as low distortion, which only preserves the fidelity of a reconstruction of y2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Our simulations indicate that Lloyd-Max reconstruction values and p(ˆy2|y2) obtained from rate-distortion optimization together produce mediocre performance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='2 This seems to suggest jointly designing p(ˆy2|y2) and the trellis structure, but this is too unwieldy for practical quantizer 2This issue has also been pointed out by others, e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='g.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', Chakrabarti et al.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' [11] produced a comparison in which a quantizer with worse mean-squared distortion resulted in better relay performance.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' DRAFT 7 design.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Our results are obtained by choosing a good trellis from the literature and determining quantizer boundaries by maximizing the CF (end-to-end) achievable rate expression, which is related to the quantization boundaries through the conditional distribution p(ˆy2|y2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The boundaries were determined via a simple discrete search that maintained the symmetry of the quantizer and utilized the trellis and the reconstruction values in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' C.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Decoding As mentioned earlier, the destination decodes the source signal as well as the quantized signal at the relay;' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' information theory arguments show that this joint decoding permits the relay to avoid dirty-paper type encoding without a rate penalty.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The joint decoder is implemented iteratively via a graphical model for the exchange of information within, and between, the component LDPC tanner graphs.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The desination begins by seeking a codeword x1 according to maximum a posteriori proba- bility p(x1|y3);' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' this search is performed via a bit-wise MAP decoder with decoding rule: ˆx1,j = arg max x1,j∈A � ∼x1,j p(x1|y3), for all j = 1, .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='..' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', n,.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Recall that ˆy2 are the quantized values while ˜y2 is the compressed bit sequence.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' These two representations are equivalent given the quantization strategy, however, ˜y2 is a more convenient representation for the relay’s channel encoder as well as for iterative decoding at destination.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' p(x1|y3) can be decomposed as follows: p(x1|y3) = 1 p(y3) � ˜y2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='x2 p(x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' y3),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (8) where p(x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' y3) = p(y3|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2)p(x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (9) (a) = p(y3|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2)p(x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (10) = p(y3|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2)p(x2|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' ˜y2)p(˜y2|x1)p(x1),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (11) (b)= p(y3|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2)p(x2|˜y2)p(˜y2|x1)p(x1),' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (12) (c) ∝ p(y3|x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2)1{x2 = CR(˜y2)}p(˜y2|x1)1{x1 ∈ CS},' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (13) where (a) follows because y3 is only dependent on x1,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' (b) is due to Markov x1 ↔ ˜y2 ↔ x2,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' and (c) is due to p(x1) = 1{x1∈CS} 2nR being a uniform distribution over the elements of the source DRAFT 8 codebook CS,' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' and p(x2|˜y2) = 1{x2 = CR(˜y2)},' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' i.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='e.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=', the output of error-control coding at the relay CR being a deterministic function of its input.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The simplified destination part of the channel model During block t, the destination receives a version of X(t−1) 2 that is contaminated with noise and interference, which carries information about X(t−1) 1 , which is independent of X(t) 1 .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' This independence allows successive interference cancellation, simplifying the channel model at des- tination [3]: Y23 = H23X2 + n′ 3, (14) Y13 = H13X1 + n3, (15) which is shown in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At block t, the destination jointly decodes X(t−1) 1 and X(t−1) 2 on the basis of Y(t) 23 and Y(t−1) 13 where the processing of Y(t) 23 treats X(t) 1 as zero-mean Gaussian noise with power H2 12Ps, and Y(t−1) 13 is processed by subtracting X(t−2) 2 decoded during block t−1 from Y(t−1) 3 .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' This operation can decompose Y3 to two links Y13 and Y23 with independent additive white Gaussian noise n′ 3 of variance N3 + H2 12Ps and n3 of variance N3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Using p(y3|x1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='x2) = p(y31|x1)p(y32|x2), for LLR calculation at destination, (13) can be rewritten as n � j=1 p(y13,j|x1,j) n � k=1 p(y23,k|x2,k) 1{x1 ∈ CS}p(˜y2|x1)1{x2 = CR(˜y2)}, (16) Enabled by this decomposition, joint decoding can be performed by a repeated application of two LDPC decoders whose cost function is based on p(y13|x1) and p(y23|x2), as well as enforcing the relationship between x1 and x2 through the term p(˜y2|x1) together with the relay LPDC coding x2 = CR(˜y2).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Using the destination observations y13 and y23 (after successive in- terference cancellation) a three-way iterative decoding is performed whose information exchange is described by Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 3, where each LDPC decoder block represents a Tanner graph.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' DRAFT 9 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The joint iterative decoding graphical model The two LDPC decoder components follow well-known principles, therefore their internal structure is omitted in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 3 for simplicity.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The iterative decoding also needs propagating soft in- formation through p(˜y2|x1), which is not straight forward, therefore we break it into two compo- nents.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Considering the Markov chain x1 ↔ ˆy2 ↔ ˜y2, we have p(˜y2|x1) = � ˆy2 p(˜y2|ˆy2)p(ˆy2|x1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The information exchange across the trellis, shown by p(˜y2|ˆy2), is calculated using the BCJR algorithm.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The information exchange between x1 and ˆy2 is through p(ˆy2|x1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' This marginal distribution of quantized values is described as a weighted sum since TCQ employs several scalar quantizers, whose number we denote with K.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The quantizer choice at each sample has a probability P(Qi|x1).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The overall marginal distribution is given by: p(ˆy2|x1) = K � i=1 P(Qi|x1) � ˆy2=Qi(y2) p(y2|x1) dy2 (17) The probability P(Qi|x1) at each sample is driven by the contamination of x1 with noise prior to quantization, as well as the action of the trellis.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The overall effect is difficult to model, therefore we obtain an empirical estimate for P(Qi|x1) by a monte carlo simulation of the channel x1 → y2, applying the TCQ, and collecting the empirical frequency of occurrence of each quantizer Qi conditioned on x1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The destination begins by initializing p(y13) and p(y23) according to channel observations.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Then, we update the soft estimate of x1 at the destination, via executing the sum-product algorithm for CS.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' From this, an updated soft estimate for ˆy2 is obtained via (17).' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Then, the DRAFT 10 BCJR algorithm, induced by the compression trellis, is used to update the soft estimate of ˜y2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Then, another sum-product is executed utilizing the observation y23 and the structure of the relay-destination LDPC code, to update ˜y2.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We then repeat backward, updating ˆy2 and x1, and then another sum-product iteration on x1.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' To summarize, the process consists of two sum-product algorithms operating on the source LDPC code and the relay LDPC code, and information being exchanged between them via the method mentioned above.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Our algorithm performs one bit-to-check and one check-to-bit operation in each sum-product before propagating the information to the other LDPC decoder.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At the end of the process, we perform a multistage hard decoding of the MLC.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' IV.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' SIMULATIONS This section presents simulation results supporting the findings of this letter.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The following values underlie the simulations: N3 = 1, N2 = 8, H13 = 1, H12 = 2, and H23 = 11.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Furthermore, in all experiments the source and the relay transmitters emit the same power.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The reported SNRs for simulations are generated by fixing the noise power and varying the power of the source/relay.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Error control coding is achieved via DVB-S2 LDPC codes with block length 64,800.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' At the relay, the first 32,400 quantized bits are encoded by a rate-1/2 DVB-S2 code, and the remaining quantized bits are encoded with a second, similar, DVB-S2 code.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The parity bits of these two encoders are then concatenated for transmission.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Our experiments involve 16-QAM at the normalized rate of 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='4 bits/s/Hz and 16-PSK at the rate of 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='27 bits/s/Hz.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Each modulation is attached to a 4-level multi-level code, which in the case of 16-QAM have rates 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='9, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='8, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='9, and 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='8, and in the case of 16-PSK have rates 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='9, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='9, 0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='8, and 2/3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The relay utilizes a TCQ with an 8-state trellis whose generator matrix is: \uf8ee \uf8ef\uf8ef\uf8ef\uf8ef\uf8ef\uf8f0 1 0 0 0 0 0 1 0 0 0 0 0 D 1 0 0 0 1 D2 D \uf8f9 \uf8fa\uf8fa\uf8fa\uf8fa\uf8fa\uf8fb .' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The quantizer reconstruction values, shown in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 4, have a cardinality that is twice the size of the 16-QAM/PSK constellation used for source/relay modulation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' For the 16-QAM example, extending to a standard 32AMPM would present inconvenient cell boundaries, therefore we experimented with the shown 32-point extension as well as a symmetric extension with 64 DRAFT 11 Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 4.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The reconstruction values for CF relaying using 16-QAM (a), and 16-PSK (b), where the circles represent 16-QAM/PSK constellation.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' points, finding the latter produces negligible gains over the former.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The design of quantizer bin boundaries is according to the optimization mentioned in Section III-B.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' We compare our results with that of bit-interleaved coded modulation (BICM) [3], [4], where the component LDPC codes in the sub-channels have the same rate by definition.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Since the granularity of available DVB-2 codes are limited, we simulated BICM at the closest rate possible with available codes.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' A rate-5/6 DVB-S2 code is used for 16-QAM BICM, resulting in an overall rate of 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='33 bits/s/Hz, and a rate-0.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='8 DVB-S2 code was used for 16-PSK resulting in overall rate of 3.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content='2 bits/s/Hz.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In addition to the BICM results, we also display the results of a preliminary version of this work from [12] which uses only scalar quantization.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In addition, rates are carefully chosen to avoid any unfair advantage to the method of this letter in reporting error rates.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Simulation results are displayed in Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The observations and insights arising from these simulations are as follows: The proposed method outperforms the error rate of BICM under 16-QAM and 16-PSK, even though the simulated BICM rates were slightly advantageous.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Superior performance of MLC over BICM was known in point-to-point channels, but is affirmed in this letter for the end-to-end performance of a CF relaying.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' It is also established that TCQ can outperform scalar quantization in CF relaying.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Although at first sight this may seem a natural outcome, past work [11] implies that utilizing vector quantization in the context of CF has been remarkably difficult.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' In that sense, the result reported herein has significant practical novelty.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' DRAFT 12 9 10 11 12 13 14 15 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 BER 16-QAM, TCQ 16-QAM, scalar 16-QAM, BICM 16-PSK, TCQ 16-PSK, scalar 16-PSK, BICM Fig.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' 5.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Simulation results using 16-QAM/PSK with N3 = 1, N2 = 8, H13 = 1, H12 = 2, H23 = 11, and Pr = Ps.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' Approximately 1dB improvement is observed for 16-PSK.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' The improvement for 16-QAM is more modest.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' V.' metadata={'source': '/home/zjlab/wf/langchain-ChatGLM/knowledge_base/HdE1T4oBgHgl3EQfXgSr/content/2301.03128v1.pdf'} +page_content=' DISCUSSION AND CONCLUSION This paper significantly improves known implementations of compress-forward via a combi- nation of trellis coded quantization at the relay, multi-level coding with LDPC component codes, and iterative joint decoding of the source and relay signals at the destination.' metadata={'source': 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mode 100644 index 0000000000000000000000000000000000000000..1bf7bb8430b1652d64a300d9334e9633aaf5dfc8 --- /dev/null +++ b/K9FAT4oBgHgl3EQfwR5T/content/tmp_files/2301.08680v1.pdf.txt @@ -0,0 +1,3137 @@ +arXiv:2301.08680v1 [cs.DS] 20 Jan 2023 +Online Dependent Rounding Schemes +Joseph (Seffi) Naor∗1, Aravind Srinivasan†2, and David Wajc‡3 +1Technion – Israel Institute of Technology +2University of Maryland, College Park +3Google Research +January 23, 2023 +Abstract +We study the abstract problem of rounding fractional bipartite b-matchings online. The +input to the problem is an unknown fractional bipartite b-matching, which is exposed node-by- +node on one side. The objective is to maximize the rounding ratio of the output matching M, +which is the minimum over all fractional b-matching x, and edges e, of the ratio Pr[e ∈ M]/xe. +In offline settings, dependent rounding schemes achieving a ratio of one and strong negative +correlation properties are known (e.g., Gandhi et al., FOCS’02, J.ACM’06 and Chekuri et al., +FOCS’10), and have found numerous applications. Motivated by online applications, we present +online dependent-rounding schemes (ODRSes) for b-matching. +For the basic case of a single offline node, i.e., uniform matroids (a.k.a. level sets), we achieve +an online rounding ratio of one. Moreover, we show that our ODRS yields the same distribution +as (offline) pivotal sampling (Srinivasan, FOCS’01, J.ACM’06), and so inherits the latter’s known +strong correlation properties. In arbitrary bipartite graphs, for which online rounding ratios of +one are impossible, we show that a combination of our level-set ODRS with repeated invocations +of offline contention resolution schemes (CRSes) yields a rounding ratio of 1 − 1 +e ≈ 0.632. Our +main technical contribution is an ODRS breaking this pervasive bound, yielding rounding ratios +of 0.646 and 0.652 for b-matchings and simple matchings, respectively. We obtain these results +by grouping nodes and using CRSes for negatively-correlated distributions, together with a new +method we call group discount and individual markup, analyzed using the theory of negative +association. +Extending and applying our ODRSes, we obtain a number of new results, including (directly) +the first online bipartite edge-weighted matching algorithms with ML predictions, and: +1. The first results for online edge coloring multigraphs under adversarial arrivals, adding to +the recent exciting work on online edge coloring, e.g., Kulkarni et al. (STOC’22), Bhat- +tacharya et al. (SODA’21) and Cohen et al. (FOCS’19). +2. Improved polytime online approximation of the optimum (computationally-unbounded) +online algorithm for online stochastic weighted bipartite matching, improving on recent +works of Papadimitriou et al. (EC’21) and Braverman et al. (EC’22). +3. A generalization of a result of Srinivasan (SODA’07) that improved a previous result of +Swamy and Shmoys (FOCS’05, SICOMP’12) to multi-stage stochastic multi-coverage. +∗Supported in part by Israel Science Foundation grant 2233/19 and United States - Israel Binational Science +Foundation grant 2018352. +†Supported in part by NSF award number CCF-1918749, and by research awards from Amazon and Google. +‡Part of this work done while the author was at Stanford University. + +Contents +1 +Introduction +1 +1.1 +Our Contributions +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2 +1.1.1 +Extensions and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2 +1.2 +Techniques +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +3 +1.3 +Further related work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +4 +2 +Preliminaries +5 +2.1 +Negative association and strong Rayleigh properties . . . . . . . . . . . . . . . . . . . +5 +3 +Online Level-Set Rounding +6 +3.1 +Offline level-set rounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6 +3.2 +The online level-set rounding algorithm +. . . . . . . . . . . . . . . . . . . . . . . . . +7 +3.3 +Coupling the online and offline algorithms . . . . . . . . . . . . . . . . . . . . . . . . +8 +4 +Rounding b-Matchings Online +8 +4.1 +The improved ODRS: Overview and intuition . . . . . . . . . . . . . . . . . . . . . . +9 +4.2 +The core of the improved ODRS +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . +10 +4.2.1 +The improved ODRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +11 +4.2.2 +The b-matching ODRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 +5 +Applications +16 +5.1 +Applications and extensions of the matching ODRS . . . . . . . . . . . . . . . . . . . +16 +5.1.1 +Online edge coloring (multigraphs) . . . . . . . . . . . . . . . . . . . . . . . . +16 +5.1.2 +Stochastic extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +17 +5.2 +Application of the level-set ODRS +. . . . . . . . . . . . . . . . . . . . . . . . . . . . +23 +5.2.1 +Multi-stage stochastic optimization . . . . . . . . . . . . . . . . . . . . . . . . +23 +5.2.2 +Negative association, fairness, diversity, and streaming . . . . . . . . . . . . . +24 +6 +Lower Bounds +26 +7 +Summary and Open Questions +28 +A Additional Preliminaries +28 +A.1 Contention Resolution Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +28 +A.2 Negative correlation properties +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +29 +A.3 Odds and Ends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +30 +B Deferred Proofs of Section 3 +30 +B.1 +Direct analysis of Algorithm 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +31 +B.2 +Coupling the offline and online algorithms . . . . . . . . . . . . . . . . . . . . . . . . +32 +C Deferred Proofs of Section 4 +34 +C.1 Polytime implementation +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +34 +C.2 Deferred proofs of the b-matching ODRS . . . . . . . . . . . . . . . . . . . . . . . . . +35 +D Deferred Proofs of Section 6 +36 + +1 +Introduction +Online bipartite b-matching is a prototypical online problem, tracing its origin to the seminal work +of Karp et al. [51]. Here, nodes on one side of a bipartite graph are revealed over time, and each +node v can be matched at most bv times, with arriving nodes matched immediately and irrevocably. +This influential problem has been widely studied in various settings (e.g., fractional/integral, sim- +ple/capacitated, unweighted/vertex-weighted/edge-weighted) [2, 11, 12, 29, 36, 39, 41, 50, 51, 60] +and has been a cornerstone of the online algorithms literature. +We study the abstract problem of online randomized rounding of fractional b-matchings. Here, +both online nodes and their edges’ associated fractions in a fractional b-matching are revealed online. +(The fractional matching may be provided by a online fractional algorithm, or some machine-learned +advice—see discussion in Section 1.1.1.) An online dependent rounding scheme (ODRS) must decide +immediately and irrevocably, upon a node’s arrival, which of its edges to match.1 +In offline settings, where all fractions and nodes are given upfront, numerous dependent rounding +schemes for b-matching are known with the following desirable properties: they (1) match each +edge with marginal probability equal to its fraction in the fractional b-matching (thus preserving +any linear objective, while being oblivious to this objective), and (2) guarantee strong negative +correlation properties (thus guaranteeing concentration and preservation of submodular objectives) +[19, 22, 23, 44, 66]. These dependent rounding schemes have been highly influential, and yielded +numerous applications in the approximation algorithms literature. +Unfortunately for online applications, not only are all above offline rounding schemes not imple- +mentable online, but online schemes satisfying Property (1) are provably impossible [17, 28, 29]. For +example, in recent work [17], Buchbinder et al. asked what additional constraints can be imposed +on the fractional matching to allow for Property (1) to be satisfied exactly. In this work, guided by +the observation that approximate satisfaction of Property (1) would still allow us to approximately +preserve linear objectives (with the ensuing applications), we study the natural complementary +question: How well can one approximate Property (1)? Capturing this objective, we introduce the +notion of an oblivious online rounding ratio, defined generally as follows. +Definition 1.1. An ODRS A for a maximization problem has (oblivious) rounding ratio α ∈ [0, 1] +if, when (batches of) elements e1, . . . , en are revealed online with their associated fractions x1, . . . , xn, +with ⃗x a valid fractional solution, A outputs an integral solution I satisfying +Pr[ei ∈ I] ≥ α · xi +∀i ∈ [n]. +This question has been intensely studied for matchings in the context of one algorithmic paradigm: +online (batched) contention resolution schemes (OCRSes), e.g., [37, 38, 43, 58]. There, each arriving +element ei is active independently with probability xi,2 and an OCRS outputs a feasible subset of +active elements. An ODRS can be obtained from an OCRS directly by simulating the activation +process for arriving elements. However, even for simple b-matching problems such as rank-1 uniform +matroids (selecting a single element), no rounding ratio beyond 0.5 is possible, via standard connec- +tions between OCRSes and the prophet inequality problem [38, 43, 54]. Better oblivious rounding +ratios are known (via different approaches) for simple bipartite matchings [28, 62, 65, 73], with the +current best ratio standing at 0.526 [65]. +Can we improve on the previous best oblivious rounding ratios (for b-matchings more generally)? +Can we achieve the ratio of 1 − 1 +e—ubiquitous in competitive ratios of online matching algorithms? +Can we beat this bound, at least for key special cases? +1As in the offline dependent rounding schemes of [44], the term dependent here underscores the need for random +choices to depend on each other, since independent coin tosses do not yield a valid high-value (b-)matching. +2Batched OCRSes [38] only require independence between batches of elements (e.g., edges of an arriving node). +1 + +1.1 +Our Contributions +We provide positive answers to the above questions, and give multiple applications of our new +ODRSes. We focus on the online rounding questions in this section. +One special case we consider is rounding b-matchings in a star graph with a single offline node, +also known as rounding uniform matroids, or level sets. Herein, a sequence of fractions arrive online +over time and the goal is to round them to {0, 1} while preserving their marginals and the sum of +every prefix (up to floors or ceilings). As we show later, this is a useful subroutine for rounding +b-matchings in arbitrary bipartite graphs (and other applications). +Our first contribution is an online level-set rounding algorithm breaking the ratio of 1 − 1 +e +that is best possible via (even offline) CRSes [24, 58], attaining an oblivious rounding ratio of +one. We thus provide an online counterpart to the well-known offline algorithm of Srinivasan [66]. +Indeed, as we show, our algorithm’s output distribution matches the offline algorithm’s output +distribution, together with its useful properties, including strong negative correlations (“Strong +Rayleigh" property, see Section 2) implying e.g., preservation of monotone submodular objectives. +Theorem 1.2 (Informal). There exists an online level-set rounding algorithm with rounding +ratio of one, and strong negative correlation properties. +In arbitrary bipartite graphs, an ODRS with rounding ratio of one is impossible, even for simple +matching, as discussed above. We further rule out any better than 2 +√ +2 − 2 ≈ 0.828 rounding ratio. +On the positive side, we show that combining our online level-set algorithm with the single-item +offline contention resolution scheme (CRS) of Feige and Vondrák [40] yields a simple ODRS with +rounding ratio of 1 − 1/e ≈ 0.632. Our main result breaks this ubiquitous bound. +Theorem 1.3. There exist bipartite matching (b-matching) ODRSes with rounding ratio 0.652 +(0.646). No such ODRS has rounding ratio greater than 2 +√ +2 − 2 ≈ 0.828. +1.1.1 +Extensions and Applications +Our ODRSes and the techniques underlying them have a number of applications and extensions. +We briefly discuss these here, deferring detailed discussions to Section 5. +Online edge coloring. Our ability to round fractional matchings has implications to online edge +coloring. For this problem, it is known that the greedy algorithm’s competitive ratio of 2 is tight +for graphs of low maximum degree ∆ = O(log n) [8], while better competitive ratios are known for +high-degree graphs under various arrival models, mostly for simple graphs [3, 6, 10, 27, 55, 65]. For +multigraphs, positive results (competitive ratios smaller than 2) were only known under random- +order arrivals [3]. Addressing this gap between simple graphs and multigraphs, in Section 5.1.1 we +extend known reductions from α-competitive edge coloring (α ≥ 1) to computing online matchings +that match each (in this case, parallel) edge with probability +1 +α∆ [27]. We thus show that a rounding +ratio of 1/α implies a competitive ratio of α + o(1) for edge coloring multigraphs (and is, in fact, +equivalent to it). Combined with our rounding algorithms, this yields the first positive result for +online edge-coloring in multigraphs under adversarial arrivals, achieving a competitive factor of +e/(e − 1) − Ω(1) in bipartite multigraphs, answering a question of Schrijver [28, Sec. VI]. +Stochastic optimization. Another application of our techniques concerns the online stochastic +bipartite weighted matching problem, much studied in the online Prophet-Inequality literature +[35, 38, 42, 54]. (See Section 5.1.2 for formal definition.) Recently, Papadimitriou et al. [62] initiated +2 + +the study of efficiently approximating the optimum online algorithm for this problem. They showed +that it is pspace-hard to approximate the optimum algorithm within some universal constant β < 1, +and provided a polynomial-time online algorithm that 0.51-approximates this online optimum. (In +contrast, the best competitive ratio, or approximation of the offline optimum, is 0.5 for this problem +[38].) The bound of [62] can be improved to 0.526 using ideas in [65] and was significantly improved +to 1 − 1/e ≈ 0.632 by Braverman et al. [16]. All three results are achieved via online rounding. +Extending our online rounding approach of Theorem 1.3 to such stochastic settings, we improve on +the recent bound of [16] and break the ubiquitous bound of 1 − 1/e, providing an online polytime +0.652-approximation of the optimal (computationally-unbounded) online algorithm. +Algorithms with predictions. Our ODRS of Theorem 1.3 finds a direct application in the bur- +geoning area of online algorithms with advice (see the survey [61] and site [1]). Here, an online +algorithm is equipped with machine-learned (ML) predictions concerning the input. For example, +many works show that for related problems, high-quality fractional solutions are efficiently learnable +and can guide integral algorithms, via online rounding schemes [56, 57, 59]. Our ODRS immediately +yields the first online edge-weighted bipartite matching algorithm with predictions, getting a com- +petitive ratio of (1−1/e+Ω(1)) with sufficiently good predictions. In contrast, with no predictions, +only recently was it shown how to break the barrier of 1/2 for this problem (using free disposal) +[12, 39, 45], and 1 − 1/e + Ω(1) is impossible to achieve even in unweighted graphs [51]. +Multi-Stage stochastic optimization. +In multi-stage stochastic optimization, uncertain pa- +rameters are stochastic but their distributions get refined over time: actions in earlier stages are +cheaper but perhaps less accurate due to the stochasticity, while actions in later stages are more +expensive but more accurate. (See the survey [68].) A basic example is the (hyper-)graph covering +problem, where sets (hyperedges) are revealed in k stages, and must be covered by bought elements +(nodes). Swamy and Shmoys [69] presented a 2k-approximation for this problem, later improved to +2, matching the offline hardness of the non-stochastic single-stage problem, in [67]. Building on the +framework of [67, 69], in Section 5.2.1 we generalize this result to allow for sets with muti-coverage +demands. Our algorithms have approximation ratio of 2 (and tending to one in some settings), and +these ratios hold w.h.p., building on our algorithm’s strong negative correlation properties. +Fairness and diversity in allocation. +Building on the previous sentence, an even-stronger +negative correlation property—negative association—helps our rounding guarantee that its resultant +intersectional unfairness [18] (if any) is limited. Continuing on the theme of ML advice, we prove that +our rounding algorithm produces online allocations (e.g., of vaccines as they are produced) from ML +advice such that these allocations do not impact multiple intersectional groups unfairly, with high +probability. Furthermore, our online-rounding algorithm only needs O(log n) space. In Section 5.2.2 +we leverage this and the fact that diversity/fairness models often lead to monotone submodular +objectives which work very well with our rounding scheme, in order to develop logarithmic-space +streaming algorithms that act on ML advice, in order to produce provably-diverse search results. +1.2 +Techniques +In this section we highlight some of the key ideas that allow us to achieve our main results, namely +Theorems 1.2 and 1.3, deferring detailed discussions of applications to later sections. +For level-set rounding, we provide a simple ODRS using limited memory (i.e., both online and +streaming) – only remembering how many edges/elements were matched/taken – that achieves a +rounding ratio of one. Surprisingly, we show via a coupling argument that this online algorithm’s +distribution is identical to that of (offline) pivotal sampling, a.k.a. Srinivasan sampling [66]. This +allows us to inherit this well-studied algorithm’s concentration properties [15, 31, 66]. In particular, +3 + +this implies that our online algorithm’s output distribution satisfies the Strong Rayleigh property (see +Section 2), which in turn implies a slew of negative correlation properties, useful for our applications. +For our impossibility result, we rely on a Ramsey-theoretic probabilistic lemma, whereby in any +sufficiently large set of binary variables, some (near-)positive correlation is inevitable. An extension +of this lemma (Lemma 6.3), of possible independent interest, rules out algorithmic approaches based +on guaranteeing strict negative correlation between offline nodes’ matched statuses. +ODRSes for b-matching. Our first ODRS for b-matchings more broadly is obtained by interleav- +ing our level-set algorithm with repeated invocations of the offline single-item contention resolution +scheme (CRS) of Feige and Vondrák [40]. (This is, to the best of our knowledge, the first online al- +gorithm to use offline CRSes in such a black-box manner.) Specifically, we run independent copies of +our level-set algorithm, one per offline node, thus having each offline node i “bid” for arriving online +node t independently of other offline nodes with probability xi,t, while preserving the b-matching +constraints of the offline nodes. To preserve online nodes’ matching constraints, we then use the +single-item offline CRS of [40] at each time t: this CRS guarantees for such product distributions +that t is allocated to at most one buyer, with every buyer i being allocated item t (i.e., (i, t) being +matched) with probability at least (1 − 1/e) · xi,t, thus yielding a rounding ratio of 1 − 1/e. +To improve on the above, we first note that the (1 − 1/e) · xit bound is loose if any of the xit +fractions are bounded away from 0. Indeed, this 1 − 1/e factor is of the form +� +1 − +� +j +(1 − xit) +�� � +i +xi,t ≥ 1 − 1/e, +where the inequality is loose if any xit is large. To beat this 1−1/e bound, we therefore simulate the +existence of a large xit, by grouping offline nodes via a bin-packing heuristic, and letting at most one +node per group (bin) B bid for t. The obtained distribution over biding offline nodes is no longer +a product distribution, but it is strongly negatively correlated, and even negatively associated (see +Section 2). This allows us to achieve the same 1 − 1/e bound using CRSes for negatively correlated +distributions of Bansal and Cohen [7]. Moreover, this grouping allows us to beat the 1−1/e ratio in +some cases: In a very concrete sense, it results in effectively a single aggregated offline node bidding +with large probability � +i∈B xi,t, thus allowing us to beat the bound of 1 − 1/e, if much grouping +occurs. Furthermore, thinking of bids as “costing” the offline node future matching opportunities, we +can even beat the bound of 1−1/e after giving nodes in a group a “group discount”, and having them +bid with lower probability than xi,t. This discounting then leaves offline nodes with more budget +(probability of not being matched), thus allowing us to charge these nodes more at later times: in +particular, when these offline nodes are not grouped, we charge them an “individual markup”, by +having them bid with higher probability than xi,t. This then increases the matching probability of +those t for which little grouping occurs to beyond 1 − 1 +e, and the improved rounding ratio follows. +1.3 +Further related work +A natural approach to round a feasible fractional solution ⃗x is to activate each element e indepen- +dently w.p. xe and then pick a feasible subset I of active elements, such that Pr[e ∈ I] ≥ α · xe. +The latter is obtained by contention resolution schemes (CRSes), first studied in offline settings for +single-item problems (rank-one matroids) by Feige and Vondrák [40] (see Section 2), and later for +arbitrary matroids by Chekuri et al. [22]. This approach was then extended to online settings by +Feldman et al. [43], and has since become a bedrock of stochastic online problems, from prophet +inequalities [43], secretary problems [33, 34], posted-price mechanisms [21, 52] and sequential pricing +[64], algorithmic contract design [9] and more. Unfortunately, for bipartite matching ODRSes, using +4 + +OCRSes (letting each i bid for t with probability xi,t independently of all prior bids, including i’s) is +of limited use: such OCRS-based OCRSes have rounding ratio better at most 0.5 even for rank-one +matroids, by connections to the prophet-inequality problem [38, 54]. Going beyond independent +bids for each pair (i, t) is therefore crucial to obtain high oblivious rounding ratios. +Another online matching rounding approach is provided by the recent exciting literature on +Online Correlated Selection (OCS), first introduced in the groundbreaking paper of Fahrbach et al. +[39] (and its predecessor by Huang and Tao [48]). Specifically, the OCSes of Gao et al. [45] underlie +many rounding-based online algorithms for edge-weighted matching [45], fair matching [46] and i.i.d +matching [47, 70]. This powerful machinery, however, does not provide oblivious rounding guaran- +tees, but rather per-offline-vertex guarantees, and so is inapplicable for our problem applications. +2 +Preliminaries +Problem Definition. In the online b-matching rounding problem, an a priori unknown bipartite +graph G = (L, R, E) is revealed online, together with fractions on the edges incident to the arriving +edge’s vertices that satisfy the b-matching constraints. In more detail, at each time t an online vertex +t ∈ L arrives, together with fractions xi,t assigned to its edges to offline neighbors i ∈ R = [n]. The +fractions xi,t ∈ [0, 1], are promised to satisfy the (fractional) b-matching constraints, namely each +vertex v ∈ (L ∪ R) has fractional degree � +e∋v xe at most bv. By splitting each online node t with +capacity bt into bt online unit-capacity nodes with identical edge sets and fractions xit/bt for each +copy of edge (i, t), we can assume WLOG that all online nodes have unit capacity. Following arrival +t, we must decide, immediately and irrevocably, which edges of t to add to the output b-matching +M, while satisfying the (integral) b-matching constraints of matching each vertex v no more than +bv times, and striving for a large oblivious rounding ratio. +Our ODRSes for b-matchings will repeatedly invoke offline contention resolution schemes (CRSes), +whose guarantees for product distributions, due to Feige and Vondrák [40], and arbitrary distribu- +tions, due to Bansal and Cohen [7], are given below. (For completeness, we provide a self-contained +proof for the general case in Appendix A.) +Lemma 2.1. Let D : 2[n] → R≥0 be a distribution over subsets of [n], with its support denoted by +supp(D) = {S ⊆ [n] | PrR∼D[R = S] ̸= 0}. Then, there exists a randomized algorithm CRS(R,⃗v) +which on input set R ∼ D and vector ⃗v ∈ Rn, outputs a subset O ⊆ R of size |O| ≤ 1 satisfying +Pr[i ∈ O] = vi · min +S⊆[n] +Pr[R ∩ S ̸= ∅] +� +i∈S vi +∀i ∈ [n]. +The algorithm runs in time polynomial in n if D is a product distribution. Otherwise, it runs in +time poly(n, T), where T ≥ |supp(D)| is the time to compute and write down the support of D. +2.1 +Negative association and strong Rayleigh properties +Definition 2.2. Random variables X1, . . . , Xn are negatively associated (NA) if for any two disjoint +index sets I, J ⊆ [n], I∩J = ∅, and two functions f : R|I| → R and g : R|J| → R both non-decreasing, +E[f(Xi : i ∈ I) · g(Xj : j ∈ J)] ≤ E[f(Xi : i ∈ I)] · E[g(Xj : j ∈ J)]. +By a simple inductive argument, negative association implies negative cylinder dependence [49]. +Lemma 2.3. For any real NA r.v.s X1, . . . , Xn and reals x1, . . . , xn, it holds that +Pr +� � +i +(Xi ≥ xi) +� +≤ +� +i +Pr[Xi ≥ xi] +and +Pr +� � +i +(Xi ≤ xi) +� +≤ +� +i +Pr[Xi ≤ xi]. +5 + +The following family of NA distributions is due to Dubhashi and Ranjan [32]. +Lemma 2.4. If X1, . . . , Xn are binary r.v.s with � +i Xi ≤ 1 always, then they are NA. +More elaborate NA distributions can be obtained via simple NA-preserving operations [49]. +Lemma 2.5. NA is closed under products and under disjoint non-decreasing function composition. +That is, if ⃗X = (X1, . . . , Xn) is NA, then: +1. if ⃗Y = (Y1, . . . , Ym) is NA and ⃗Y is independent of ⃗X, then (X1, . . . , Xn, Y1, . . . , Ym) are NA; +2. (f1(Xi : i ∈ I1), . . . , fk(Xi : i ∈ Ik)) are NA, for any concordant functions (i.e., all non- +decreasing or all non-increasing) f1, . . . , fk and disjoint sets I1, . . . , Ik ⊂ [n], Ij∩Ik = ∅ ∀j ̸= k. +Negative association implies many more useful properties, most notably the applicability of +Chernoff-Hoeffding type tail bounds [32] and submodular stochastic dominance (see Appendix A). +An even stronger negative correlation property than NA is the strong Rayleigh property (SRP) +(see Appendix A for a precise definition). This property implies NA (even under conditioning), as +well as concentration of any Lipschitz function [63], and numerous other useful properties. +3 +Online Level-Set Rounding +In this section we introduce our online level-set rounding algorithm. As its analysis will involve +coupling with the offline level-set rounding algorithm of Srinivasan [66], we first start by revisiting +this algorithm and its properties. +3.1 +Offline level-set rounding +Here we consider an offline procedure due to [66]. +This algorithm, on input ⃗x ∈ [0, 1]n with +integer sum � +i xi ∈ Z (possibly by adding a dummy value) and partial sums sj := � +i≤j xj, +outputs a set S ⊆ [n] with characteristic vector ⃗X given by Xi := 1[i ∈ S] with partial sums +Sj := � +i≤j Xi = |S ∩ [j]| satisfying the following properties for all i. +(P1) (Marginals) E[Xi] = xi. +(P2) (Rounding) Si ∈ {⌊si⌋, ⌈si⌉}. +Property (P1) and linearity of expectation imply that E[Si] = si. +Property (P2) requires that +Si always equals this expectation, “up to rounding”. In addition, we require the following strong +negative correlation property. +(P3) (Strongly Rayleigh) The joint distribution ⃗X is strongly Rayleigh (and thus, also NA). +Our objective will be to design an online algorithm satisfying the above, but for now we revisit +the offline algorithm of [66] and prove that when run with a certain specific way of choosing the key +indices i1 and i2 (see Algorithm 1), then it satisfies the above three properties. +As usual, “min(S)" in Algorithm 1 refers to the minimum element of a nonempty set S; the +index i2 in Algorithm 1 is always well-defined since � +i xi ∈ Z and, as we shall see, � +i yi = � +i xi +always. We emphasize that the algorithm of [66] allows much liberty in the choice of i1 and i2, and +that our specific choice of i1 and i2 is required to satisfy Property (P2). Also, the random choice in +each call to STEP is independent of the random choices of the past. +6 + +Algorithm 1 Offline Level-Set Rounding +1: Initialize ⃗y ← ⃗x +2: while frac(y) := {i | yi ̸∈ {0, 1}} ̸= ∅ do +3: +Let i1 ← min(frac(y)) +4: +Let i2 ← min(frac(y) \ {i1}) +5: +STEP(yi1, yi2) +6: Output S := {i | yi = 1} +Algorithm 2 STEP(A, B) +⊲ modifies inputs +1: if A + B < 1 then +2: +(A, B) ← +� +(A + B, 0) +w.p. +A +A+B +(0, A + B) +w.p. +B +A+B +3: else +⊲ A + B ∈ [1, 2) +4: +(A, B) ← +� +(1, A + B − 1) +w.p. +1−B +2−A−B +(A + B − 1, 1) +w.p. +1−A +2−A−B +That Algorithm 1 terminates and outputs a random set satisfying Property (P1) is known [66]. +Nonetheless, for completeness, we provide a proof of this fact in Appendix B. In the same appendix +we prove by induction on the number of invocations of STEP() that every prefix sum is preserved +with probability one, up to rounding, and so Algorithm 1 satisfies Property (P2). +Lemma 3.1. Let sj := � +i≤j xi and Y t +j := � +i≤j yt +i, where yt +i is the value yi after t applications of +STEP in Algorithm 1. Then, Y t +j ∈ [⌊sj⌋, ⌈sj⌉] for all j and t. +Strong negative correlation (Property (P3)) was proven in [15] as long as, e.g., we use some fixed +choice of i1 and i2 as in Algorithm 1: +Lemma 3.2. Let Xi := 1[i ∈ S] be the indicators for i being in the output set of Algorithm 1. +Then, ⃗X = (X1, X2, . . . , Xn) is a family of strongly Rayleigh random variables. +To conclude, we have the following. +Lemma 3.3. Algorithm 1 satisfies properties (P1) (P2) and (P3). +3.2 +The online level-set rounding algorithm +We now turn to providing an online counterpart to Algorithm 1. Here, the input is a sequence of +reals, x1, x2, · · · ∈ [0, 1], revealed in an online fashion. Algorithm 3 maintains a set S ⊆ N (initially +empty), and decides at time t (when xt is revealed) whether to add t to its output set S, immediately +and irrevocably. Let Xt := 1[t ∈ S], and let St := � +t′≤t Xt′ denote the cardinality of S right after +time t, i.e., St = |S ∩ [t]|. Finally, let st := � +t′≤t xt′. We will show that Algorithm 3 satisfies +properties (P1), (P2) and (P3) given by its offline counterpart, Algorithm 1. +Algorithm 3 Online Level-Set Rounding +1: Initialize S ← ∅ +2: for arrival xt (at time t ≥ 1) do +3: +add t to S with probability pt := + + + + + + + + + + + + + + + +0 +|S| = ⌈st⌉ +1 +|S| < ⌊st⌋ +xt +⌊st−1⌋+1−st−1 +|S| = ⌊st⌋ = ⌊st−1⌋ +st−⌊st⌋ +st−1−⌊st−1⌋ +|S| = ⌊st⌋ > ⌊st−1⌋ and st−1 ̸= ⌊st−1⌋ +0 +else. +4: Output S +The random bits used to make the random choice in each step of Algorithm 3 are independent +of the random bits used in the past: i.e., while pt depends on St−1, the random bits used to generate +the event of probability pt in step t, are independent of the random bits of past steps. +7 + +3.3 +Coupling the online and offline algorithms +Here we prove that Algorithm 3 satisfies properties (P1), (P2) and (P3). Proving properties (P1), +(P2) directly is not too hard (see Lemma B.2).3 +Proving Property (P3), on the other hand, is +slightly more involved; we do so now, using that the much-simpler properties (P1) and (P2) hold +for both the offline and online algorithms. To prove that the last property holds, we show that both +algorithms induce the same distribution over outputs. We outline a proof here, deferring a complete +proof to Appendix B. +Theorem 3.4. Fix a vector ⃗x ∈ [0, 1]n. Let D and D′ denote the probability distributions on {0, 1}n +induced by the online and offline algorithms run on ⃗x, respectively. Then, D = D′. +Proof (Sketch). We prove by induction on t ∈ [n] that the following holds: +∀(b1, . . . , bt−1) ∈ {0, 1}t−1, Pr +D [Xt = 1 +�� (∀i < t, Xi = bi)] = Pr +D′[Xt = 1 +�� (∀i < t, Xi = bi)]. +(1) +The (strong) inductive hypothesis, whereby Equation (1) holds for all t′ < t, clearly implies that for +all (b1, . . . , bt) ∈ {0, 1}t−1 we have that PrD[(∀i < t, Xi = bi)] = PrD′[(∀i < t, Xi = bi)]. Similarly, +Equation (1) holds for all t ≤ n iff the two distributions are equal. The proof then proceeds by +considering the different possibilities for the prefix sums st−1 and st, which for the online algorithm +directly determine the above conditional probability. These conditions also determine the offline +algorithm’s performance up to the (t − 1)st invocation of STEP(), from which a careful analysis +implies that the conditional probabilities of the offline and online algorithms are equal. +Theorem 3.4 combined with Lemma 3.3 immediately implies the desired properties of our Algo- +rithm 3, as these properties are determined by the distribution over output sets. +Lemma 3.5. Algorithm 3 is an online algorithm satisfying properties (P1), (P2) and (P3). +4 +Rounding b-Matchings Online +In this section we address the ODRS problem in bipartite b-matching instances more broadly. +We start with a simple algorithm, combining our ODRS for uniform matroids (Algorithm 3) +with repeated invocations of an offline CRS (Lemma 2.1). +Warm-up: 1 − 1/e rounding ratio. We consider the following simple algorithm: Run, for each +offline node i, an instance of Algorithm 3, applied to xi1, xi2, . . . . When the i-th copy of Algorithm 3 +fixes Xit = 1, we say that i bids for online node t. Out of the set of bidders (potential buyers) Pt, +we then pick at most one i ∈ Pt to match t to, using the offline contention resolution scheme of +Lemma 2.1, guaranteeing each node i a probability of xi,t · minS⊆[n] +Pr[S∩Pt̸=∅] +� +i∈S xi,t +of being matched. +This step runs in polytime, by independence of the bids. Since Algorithm 3 is an online algorithm, +so is the resultant algorithm. Moreover, since the output of Algorithm 3 satisfies the b-matching +constraints, and t is matched to at most one neighbor by the CRS, this algorithm’s output satisfies +the b-matching constraints. Finally, for each offline node set S ⊆ [n], by independence of the bids, +the Taylor expansion of exp(−x) and convexity (see Claim A.5), we have +Pr[S ∩ Pt ̸= ∅] = 1 − +� +i∈S +(1 − xit) ≥ 1 − +� +i∈S +exp(−xit) ≥ +� +1 − 1 +e +� +· +� +i∈S +xit. +(2) +Therefore, by Lemma 2.1, this ODRS matches each edge (i, t) with probability at least (1−1/e)·xi,t. +3In fact, Algorithm 3 can be shown to be the only online algorithm satisfying both these simple properties if we +further restrict it to only storing in memory the partial sums st−1 and St−1 at the beginning of step t. +8 + +Lemma 4.1. There exists a polytime ODRS for bipartite b-matching with rounding ratio 1 − 1/e. +One natural approach to improve the above algorithm’s rounding ratio would be to attempt to +negatively correlate the probability of different offline nodes to have previously bid, thus increasing +Pr[S ∩ Pt ̸= ∅] for all offline sets S ⊆ [n]. Unfortunately, for a sufficiently large number of offline +nodes, (near-)positive correlation is, generally, unavoidable: see Lemma 6.3 for a proof of such a +Ramsey-theoretic statement. Instead, to achieve a better rounding ratio, we explicitly negatively +correlate the bids of previously-non-bidding offline nodes when they do bid. +4.1 +The improved ODRS: Overview and intuition +In this section we outline our improved ODRS. We focus here and in most subsequent sections on +simple matchings, for clarity’s sake, deferring an extension to b-matchings to Section 4.2.2. +A bad example, and a false start. Consider a graph with a single online node t with xit = 1 +n for +all n offline nodes. In this case, under independent bids, t gets no bids with probability (1− 1 +n)n ≈ 1 +e, +and so one of the n offline nodes must get matched with probability no greater than (1− 1 +e) · 1 +n. For +this simple example a rounding ratio of one is possible, by correlating bids for t: if we pick exactly +one neighbor i to bid with probability xit, then each offline node both bids and buys (is matched +to) t with probability xit. Unfortunately, this approach is impossible to implement in general: if +we let each offline node i bid for at most one time t (recall that this is a simple matching instance) +with probability xi,t, then, for sit := � +t′ θ +�� +⊲ Bucketing high-degree nodes +8: +Ct ← ∅ +⊲ Candidates +9: +for each B ∈ Bt do +10: +U ∼ Uni[0, 1] +11: +if U ≤ � +i∈B +xi,t +1−si,t then +12: +Ct ← Ct ∪ mini +� +i ∈ [k] +���� U ≤ � +j∈B +j≤i +xj,t +1−sj,t +� +13: +Pt ← F ∩ Ct +⊲ Bidders = free candidates +14: +F ← F \ Pt +⊲ Bidders cease being free +15: +O ← CRS(Pt, {vi,t}i) +⊲ Contention Resolution +16: +if |O| = 1 then +17: +M ← M ∪ {(i, t) | i ∈ O} +18: Output M +First, we note that Algorithm 4—including the bin-packing steps that require +xi,t +1−si,t ≤ 1—is +well-defined provided � +t xi,t ≤ 1 for all i, t, since this implies that xi,t ≤ 1 − � +t′≤t xi,t′ = 1 − si,t. +Next, by construction, each offline node bids (and is thus matched) at most once, while the CRS +guarantees that each online node is matched at most once. To summarize, we have the following. +Observation 4.2. Algorithm 4 is well-defined and outputs a matching if � +t xi,t ≤ 1 ∀i ∈ [n]. +We turn to analyzing the algorithm’s rounding ratio, starting with the following lemma asserting +that if much grouping occurs, then most bins have high x-value. +Fact 4.3. For each time t, at most one bin B ∈ Bt at Line 6 has � +i∈B xi,t < 1−θ +2 . +4This algorithm maintains a sorted list of bins with each bin B containing items of overall size at most one, +� +i∈B si ≤ 1, and for each item i in order, adds i to the first (possibly newly-opened) bin that has enough room left. +10 + +Proof. A well-known property of the First-Fit bin packing heuristic is that at most one bin in the +output of this algorithm is less than 1 +2 full (see, e.g., [72, 74]). Therefore, since si,t ≤ θ for each +offline node i in a bin B ∈ Bt computed in Line 6, each such bin B (barring perhaps one) has +1 +2 ≤ +� +i∈B +xi,t +1 − si,t +≤ +� +i∈B +xi,t +1 − θ. +The following lemma, combined with Fact 4.3, provides a guarantee no worse than the independent- +proposals approach. Indeed, as we will show shortly, it implies a better rounding ratio if much +grouping of low-degree neighbors occurs. +Lemma 4.4. For any time t and set of offline nodes S ⊆ [n], Algorithm 4 satisfies +Pr[S ∩ Pt ̸= ∅] ≥ 1 − +� +B∈Bt +� +1 − +� +i∈B∩S +xit +� +. +Proof. Let Ft denote F at time t, and let Ct and Pt = Ct ∩ Ft be as in Algorithm 4. Next, let +Ci,t = 1[i ∈ Ct] indicate whether i is a candidate at time t, and define Fi,t and Pi,t similarly. +By independence of Ci,t and Fi,t and since Pr[Ci,t] = +xi,t +1−si,t and Pr[Fi,t] = 1 − si,t (provable by a +simple induction on t ≥ 0), we have that Pr[Pi,t] = xi,t. Therefore, by linearity of expectation and +� +i∈B Ci,t ≤ 1, we have that Pr[Pt ∩ S ∩ B = ∅] = 1 − � +i∈B∩S xi,t. It remains to show that the +events [Pt ∩S ∩B = ∅] for different B are negative cylinder dependent, giving the desired inequality +Pr[Pt ∩ S = ∅] = Pr +� � +B∈Bt +(Pt ∩ S ∩ B = ∅) +� +≤ +� +B∈Bt +Pr[Pt ∩ S ∩ B = ∅] = +� +B∈Bt +� +1 − +� +i∈B∩S +xi,t +� +. +To this end, we will show that the events [Pt ∩ S ∩ B = ∅] are negatively associated (NA), +which by Lemma 2.3 yields the required above inequality, and hence yields the lemma. First, by +Lemma 2.4, for any bin B′ at time t′ < t, the binary variables Ci,t′ for all nodes i ∈ B′ ∩ S, whose +sum is at most one, are NA. Moreover, the distributions over different bins and different time steps +are independent, and so by closure of NA under products (Lemma 2.5), all Ci,t′ are NA. Therefore, +the variables Fi,t = 1 − maxt′ θ. While ˆx is not a fractional matching, since online nodes t may +have � +i ˆxi,t > 1, this assignment does satisfy the fractional degree constraints of offline nodes. +Fact 4.5. For every offline node i ∈ [n] and time t, we have that ˆsi,t := � +t′ 0, there exists an nO(1/γ)-time bipartite matching ODRS with rounding +ratio of 0.652 − γ. +4.2.2 +The b-matching ODRS +In this section we extend our ODRS from matchings to b-matchings. To avoid repetition, we only +outline the changes needed in the algorithm and analysis, and defer the proofs to Appendix C. +The change to the core algorithm. As we did (implicitly) in Algorithm 4, we let the online +level-set algorithm dictate the marginal probabilities with which an offline node i should bid to t, +based on the number of times i has bid by time t, which we denote by Si,t. (This corresponds +to St in Algorithm 3 run from the perspective of the offline node i.) We process offline nodes at +different times t as follows, with the choice of probabilities guided by Algorithm 3 to guarantee that +E[Si,t+1 − Si,t] = xi,t, by Property (P1), and Si,t ∈ [⌊si,t⌋, ⌈si,t⌉], by Property (P2). +For nodes with ⌈st+1⌉ = ⌈st⌉ — whose fractional degrees both before and after time t lie in the +range [⌊si,t⌋, ⌈si,t⌉] — we group these offline nodes and have them bid (at most one bid per bin) as +in Algorithm 4, with the following changes: si,t is replaced by its fractional part, si,t − ⌊si,t⌋: this is +done both in the bidding probability, so these items have size +xi,t +1−(si,t−⌊si,t⌋) when bin packing, and +in the condition si,t ≤ θ, which are now replaced by the condition si,t − ⌊si,t⌋ ≤ θ (and similarly +for the condition si,t > θ), with θ to be chosen later. Moreover, we add a candidate offline node +i ∈ Ct to the list of potential matches Pt (the bidders) if Si,t < ⌊si,t⌋ (corresponding to i ∈ F ∩ Ct +in Algorithm 4 for simple matchings). +For all offline nodes with ⌊si,t+1⌋ = ⌊si,t⌋+1, we place these nodes in singleton bins, and we have +them bid with probability if Si,t = ⌊si,t⌋, or with probability si,t+1−⌊si,t+1⌋ +si,t−⌊si,t⌋ +if Si,t = ⌈si,t⌉ = ⌊si,t+1⌋. +Change to core ODRS’ analysis: Fact 4.3 and its proof hold unchanged for our extension of +the core ODRS. Lemma 4.4, too, holds unchanged, although the proof, deferred to Appendix C.2, +is now slightly more involved. Specifically, the key ingredient, proving that the events [Pt ∩ S ∩ B] +over different bins B are negatively associated (NA) requires a proof that the variables Si,t are NA. +Change to the improved ODRS. In our ODRS for b-matchings, since offline nodes i for which +⌊si,t+1⌋ = ⌊si,t⌋ + 1 are grouped into singelton bins, we wish to apply a markup to these nodes’ +xi,t-values, if xi,t is small. We therefore consider the following assignment, with 0 ≤ θ1 ≤ θ2 ≤ 1 +satisfying θ2 − θ1 = +δ +ǫ+δ, to be chosen shortly. +ˆxi,t = +� si,t+1 +z=si,t +(1 − ǫ) · 1 [⌊z⌋ ∈ [θ1, θ2)] + (1 + δ) · 1 [⌊z⌋ ̸∈ [θ1, θ2)] dz. +(6) +In words: this assignment decreases the part of xi,t corresponding to the parts of i’s fractional +degree that are bounded away from 0 and 1 (specifically, those in the range [θ1, θ2), and increases +the part of the fractional degree that is somewhat close to 0 or 1. Our new ODRS then runs the +modified core ODRS with inputs θ := θ2 · (1− ǫ) + θ1 · (δ + ǫ) and ˆx, x. The choice of the parameter +θ is taken to have ˆsi,t − ⌊ˆsi,t⌋ ≤ θ if and only if si,t − ⌊si,t⌋ ≤ θ2. +14 + +Change to the improved ODRS’ analysis. First, Fact 4.5 generalizes as follows, arguing that +modified fractional degrees ˆsi,t = � +t′ 1) therefore α-approximates this maximally-fair +algorithm. +With the above terminology, we can now state the reduction. +Lemma 5.2. An online α-fair matching algorithm yields an online (α + o(1))∆-edge-coloring algo- +rithm for n-node bipartite multigraphs with maximum degree ∆ = ω(log n). +We defer a brief proof sketch of the above to the end of the section, and turn to discussing its +consequences and converses. +Corollary 5.3. An ODRS with rounding ratio 1/α yields an online (α + o(1))∆-edge-coloring +algorithm for n-node multigraphs with maximum degree ∆ = ω(log n). +Proof. Consider the fractional matching x assigning value xe = κ(e) +∆ +to the simple edge e with κ(e) +parallel copies in the multigraph. +(Note that � +e∋v κ(e) ≤ ∆ by definition, so this is indeed a +fractional matching.) Applying an ODRS with rounding ratio 1/α to this fractional matching x +yields a randomized matching M that matches every (parallel) edge in the graph with probability +1 +α∆, i.e., it yields an α-fair matching. +We note that there is in fact an equivalence between α-fair matching algorithms and α-competitive +edge-coloring algorithms, as “the converse” also holds. +Observation 5.4. An online α∆-edge-coloring algorithm A for n-node multigraphs with maximum +degree ∆ yields an ODRS with rounding ratio 1/α for fractional matchings x with xe · ∆ integral +for all e. +16 + +Proof. Given a fractional matching x ∈ QE in a simple graph G = (V, E), using that xe·∆ is integral +for each edge e, we provide to A a multigraph H = (V, F) with each edge e having multiplicity +κ(e) = xe · ∆ in H, and then randomly sample one of the α∆ edge colors (matchings) M computed +by A. This yields an ODRS with rounding ratio of 1/α, since for each edge e ∈ E we have that +Pr[e ∈ M] = κ(e) · +1 +α∆ = xe +α . +By the equivalence between edge coloring multigraphs and ODRSes for matchings, together +with our (upper and lower) bounds on the rounding ratio of such ODRSes, we obtain the following +bounds on the number of colors needed to edge-color multigraphs online. +Theorem 5.5. In n-node bipartite multigraphs with maximum degree ∆ under adversarial one-sided +vertex arrivals, there exists an online 1.533∆-edge-coloring algorithm, assuming ∆ = ω(log n). In +contrast, no (1/(2 +√ +2 − 2 + ǫ))∆ ≈ (1.207 − O(ǫ))∆-edge-coloring exists even for ∆ = 2. +We note in passing that all known positive results for online edge coloring under adversarial +arrivals follow from Lemma 5.2, and indeed from Corollary 5.3 [27, 55, 65]. The reason most of +these results do not extend to multigraphs is that their ODRSes required their input fractional +matchings x to be of the form xe = 1 +∆, or more generally for xe = o(1) for each edge e (including its +multiplicities). The work of Saberi and Wajc [65] is a lone exception to this rule, and combining its +ODRS with Lemma 5.2 also yields an algorithm for multigraphs, but using as many as 1.9∆ colors. +We conclude the section with a brief proof sketch of Lemma 5.2. +Proof sketch of Lemma 5.2. We describe the algorithm in an offline setting first. Let C be such +that C = ω(log n) and C = o(∆). (Such C exist, by our necessary assumption that ∆ = ω(log n).) +Initially, the entire multigraph is uncolored. For some ∆/C many rounds, compute α · C colors +as follows: In the uncolored subgraph U, compute α · C many α-fair matchings M1, . . . , MαC, +and let these occupy the next αC colors. Since every vertex has at most αC = o(∆) many edges +colored during a round, any vertex with degree close to ∆ at the beginning of the round has degree +∆ − o(∆) by the end of the round. Therefore, since these Mi are α-fair matchings, and so match +each (parallel) edge with probability at least +1 +α·∆, by standard concentration bounds, all vertices +that have degree close to ∆ have some C · (1 − o(1)) many edges colored during a round (with +high probability). This allows us to compute a high-probability upper bound of on the resultant +uncolored multigraph at the end of the round (possibly useful to compute α-fair matchings), and +moreover implies that after ∆/C many rounds (and so with (∆/C) · α · C = α · ∆ colors used), the +uncolored multigraph has maximum degree ∆ − (∆/C) · C · (1 − o(1)) = o(∆), and can be colored +greedily using a further 2 · o(∆) = o(∆) many colors, for (α + o(1))∆ colors overall. +While the above algorithm was described in an offline setting, if one can compute an α-fair +algorithm online (possibly with information regarding the high-probability upper bound on ∆ in each +round), then the entire algorithm can be made to run online: for each (vertex/edge) arrival, perform +the next steps of the α∆ many α-fair matching algorithms outputting color classes M1, . . . , Mα∆, +where for the i-th such algorithm, we simulate only the arrival of the parts of the subgraph that +are not contained M1, . . . , Mi−1. The same approach is used to simulate the final greedy coloring +steps, using the fact that the greedy (2∆ − 1)-edge-coloring algorithm is an online algorithm. +5.1.2 +Stochastic extension +In this section, we generalize our matching ODRS and its analysis to the following stochastic online +bipartite matching problem. At each time t, an online node arrives with weight vector ⃗wt ∼ Dt, +17 + +where D1, D2, . . . are a priori known independent distributions. A simple example which we focus +on for notational simplicity (though our approach generalizes to this problem in full generality) +is as follows: each online node t arrives according to a Bernoulli event At ∼ Ber(pt), each edge +(i, t) having some intrinsic value wit, but realized weight vit = wit · At. This problem (in its full +generality) is an online Bayesian selection problem, and a number of algorithms with competitive +ratio of 1 +2 are known for it [35, 38, 42]. By the classic lower bound of Krengel and Sucheston for the +single-item prophet inequality problem [54], the above ratio is best-possible when comparing with +the offline optimum algorithm. +In [62], Papadimitriou et al. initiate the study of this problem in terms of the (polytime) approx- +imability of the optimum online algorithm. Perhaps surprisingly, they show that while for simple +cases of the problem (e.g., the single-offline-node problem), the optimum online algorithm is com- +putable using a simple poly-sized dynamic program, in general it is pspace-hard to approximate the +optimum online algorithm within some absolute constant α < 1 (say, α ≈ 0.999999), and showed +that a better-than-0.5 approximation of the optimum online algorithm can be obtained by polytime +online algorithms. This positive result was subsequently improved to 0.526 implicitly [65] and to +1 − 1/e ≈ 0.632 explicitly [16]. All these results are achieved by rounding the following LP, which +can be shown to upper bound the optimum online algorithm’s value [62, 71]. +max +� +i,t +wi,t · xi,t +(LP OPTon) +s.t. +� +t,r +xi,t ≤ 1 +∀i ∈ [n] +(9) +� +i +xi,t ≤ pt +∀t +(10) +xi,t ≤ pt · +� +1 − +� +t′ θ} +⊲ Bucketing low-degree nodes +8: +Ct ← ∅ +⊲ Candidates +9: +for each B ∈ Bt do +10: +U ∼ Uni[0, 1] +11: +if U ≤ � +i∈B +ˆxi,t +pt·(1−ˆsi,t) then +12: +Ct ← Ct ∪ mini +� +i ∈ [k] +��� U ≤ � +j∈B, j≤i +ˆxj,t +pt·(1−ˆsj,t) +� +13: +Pt ← Ct \ V (M) +⊲ Bidders = free candidates +14: +if Pt ̸= ∅ and t arrived then +15: +pick some i ∈ arg max{wi,t | i ∈ Pt} +16: +M ← M ∪ {(i, t)} +17: Output M +Fact 5.7. Algorithm 6 is well-defined. In particular, +ˆxi,t +pt·(1−ˆsi,t) ≤ 1 for every pair (i, t). +Proof. By Fact 4.5, we have that ˆsi,t = si,t · (1 − ǫ) + (si,t − θ)+ · (ǫ + δ) ≤ si,t. Therefore, by our +choice of θ = +δ +ǫ+δ and LP Constraint (11), we have that, indeed +ˆxi,t +pt · (1 − ˆsi,t) ≤ +� xi,t·(1−ǫ) +pt·(1−si,t) ≤ +xi,t +pt·(1−si,t) ≤ 1 +si,t ≤ θ +xi,t·(1+δ) +pt·(1−si,t(1+δ)+δ) = +xi,t +pt·(1−si,t)) ≤ 1 +si,t > θ. +Algorithm 6 is clearly a polytime algorithm. It remains to analyze its approximation ratio. +The following lemma makes explicit a fact implicit in the proof of the main theorem of [16]: +specifically, that a per-online-node “approximation ratio”, relating w(M(t), t)—the weight obtained +by matching t—to the LP solution’s value from t, implies a global approximation ratio of the same +value. We provide a short self-contained proof of this fact for completeness. +19 + +Lemma 5.8. If for each online node t and z ≥ 0 we have that Pr[w(M(t), t) ≥ z] ≥ � +i:wi,t≥z α·xi,t, +then the algorithm is an α-approximation of the optimum online algorithm. +Proof. Denote by wt := w(M(t), t) the weight of the matched edge of t, with wt = 0 if t is not +matched (possibly due to non-arrival). Then, the weight of the output matching M satisfies +� +t +E[wt] = +� +t +� ∞ +z=0 +Pr[wt ≥ z] dz ≥ +� +t +� ∞ +z=0 +α · +� +i:wi,t≥z +xi,t dz = α · +� +i,t +wi,t · xi,t. +The proof is then completed by Lemma 5.6, implying that the RHS upper bounds α times the value +of the optimum online algorithm’s gain. +The objective of our analysis will therefore be to lower bound Pr[w(M(t)) ≥ z] for all z ≥ 0. +In our analysis, we let Ft = [n] \ V (M) be the set of free offline nodes at time t, and let +Fi,t = 1[i ∈ Ft] = 1 − � +t′