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on-line viterbi algorithm and its relationship to random walks

0704.0062

in this paper, we introduce the on-line viterbi algorithm for decoding hiddenmarkov models (hmms) in much smaller than linear space. our analysis ontwo-state hmms suggests that the expected maximum memory used to decodesequence of length $n$ with $m$-state hmm can be as low as $\theta(m\log n)$,without a significant slow-down compared to the classical viterbi algorithm.classical viterbi algorithm requires $o(mn)$ space, which is impractical foranalysis of long dna sequences (such as complete human genome chromosomes) andfor continuous data streams. we also experimentally demonstrate the performanceof the on-line viterbi algorithm on a simple hmm for gene finding on bothsimulated and real dna sequences.

cs.ds

10.1007/978-3-540-74126-8_23

['šrámek', 'brejová', 'vinař']

https://arxiv.org/abs/0704.0062

capacity of a multiple-antenna fading channel with a quantized precoding matrix

0704.0217

given a multiple-input multiple-output (mimo) channel, feedback from thereceiver can be used to specify a transmit precoding matrix, which selectivelyactivates the strongest channel modes. here we analyze the performance ofrandom vector quantization (rvq), in which the precoding matrix is selectedfrom a random codebook containing independent, isotropically distributedentries. we assume that channel elements are i.i.d. and known to the receiver,which relays the optimal (rate-maximizing) precoder codebook index to thetransmitter using b bits. we first derive the large system capacity ofbeamforming (rank-one precoding matrix) as a function of b, where large systemrefers to the limit as b and the number of transmit and receive antennas all goto infinity with fixed ratios. with beamforming rvq is asymptotically optimal,i.e., no other quantization scheme can achieve a larger asymptotic rate. theperformance of rvq is also compared with that of a simpler reduced-rank scalarquantization scheme in which the beamformer is constrained to lie in a randomsubspace. we subsequently consider a precoding matrix with arbitrary rank, andapproximate the asymptotic rvq performance with optimal and linear receivers(matched filter and minimum mean squared error (mmse)). numerical examples showthat these approximations accurately predict the performance of finite-sizesystems of interest. given a target spectral efficiency, numerical examplesshow that the amount of feedback required by the linear mmse receiver is onlyslightly more than that required by the optimal receiver, whereas the matchedfilter can require significantly more feedback.

cs.it math.it

10.1109/tit.2008.2011437

['santipach', 'honig']

https://arxiv.org/abs/0704.0217

refuting the pseudo attack on the reesse1+ cryptosystem

0704.0492

we illustrate through example 1 and 2 that the condition at theorem 1 in [8]dissatisfies necessity, and the converse proposition of fact 1.1 in [8] doesnot hold, namely the condition z/m - l/ak < 1/(2 ak^2) is not sufficient forf(i) + f(j) = f(k). illuminate through an analysis and ex.3 that there is alogic error during deduction of fact 1.2, which causes each of fact 1.2, 1.3, 4to be invalid. demonstrate through ex.4 and 5 that each or the combination ofqu+1 > qu * d at fact 4 and table 1 at fact 2.2 is not sufficient for f(i) +f(j) = f(k), property 1, 2, 3, 4, 5 each are invalid, and alg.1 based on fact 4and alg.2 based on table 1 are disordered and wrong logically. further,manifest through a repeated experiment and ex.5 that the data at table 2 isfalsified, and the example in [8] is woven elaborately. we explain why cx = ax* w^f(x) (% m) is changed to cx = (ax * w^f(x))^d (% m) in reesse1+ v2.1. tothe signature fraud, we point out that [8] misunderstands the existence of t^-1and q^-1 % (m-1), and forging of q can be easily avoided through moving h.therefore, the conclusion of [8] that reesse1+ is not secure at all (whichconnotes that [8] can extract a related private key from any public key inreesse1+) is fully incorrect, and as long as the parameter omega is fitlyselected, reesse1+ with cx = ax * w^f(x) (% m) is secure.

cs.cr

nan

['su', 'lu']

https://arxiv.org/abs/0704.0492

optimal routing for decode-and-forward based cooperation in wireless networks

0704.0499

we investigate cooperative wireless relay networks in which the nodes canhelp each other in data transmission. we study different coding strategies inthe single-source single-destination network with many relay nodes. given themyriad of ways in which nodes can cooperate, there is a natural routingproblem, i.e., determining an ordered set of nodes to relay the data from thesource to the destination. we find that for a given route, thedecode-and-forward strategy, which is an information theoretic cooperativecoding strategy, achieves rates significantly higher than that achievable bythe usual multi-hop coding strategy, which is a point-to-point non-cooperativecoding strategy. we construct an algorithm to find an optimal route (in termsof rate maximizing) for the decode-and-forward strategy. since the algorithmruns in factorial time in the worst case, we propose a heuristic algorithm thatruns in polynomial time. the heuristic algorithm outputs an optimal route whenthe nodes transmit independent codewords. we implement these coding strategiesusing practical low density parity check codes to compare the performance ofthe strategies on different routes.

cs.it math.it

10.1109/sahcn.2007.4292845

['ong', 'motani']

https://arxiv.org/abs/0704.0499

on the kolmogorov-chaitin complexity for short sequences

0704.1043

a drawback of kolmogorov-chaitin complexity (k) as a function from s to theshortest program producing s is its noncomputability which limits its range ofapplicability. moreover, when strings are short, the dependence of k on aparticular universal turing machine u can be arbitrary. in practice one canapproximate it by computable compression methods. however, such compressionmethods do not always provide meaningful approximations--for strings shorter,for example, than typical compiler lengths. in this paper we suggest anempirical approach to overcome this difficulty and to obtain a stabledefinition of the kolmogorov-chaitin complexity for short sequences.additionally, a correlation in terms of distribution frequencies was foundacross the output of two models of abstract machines, namely unidimensionalcellular automata and deterministic turing machine.

cs.cc cs.it math.it

nan

['delahaye', 'zenil']

https://arxiv.org/abs/0704.1043

optimal routing for the gaussian multiple-relay channel with decode-and-forward

0704.2926

in this paper, we study a routing problem on the gaussian multiple relaychannel, in which nodes employ a decode-and-forward coding strategy. we areinterested in routes for the information flow through the relays that achievethe highest df rate. we first construct an algorithm that provably findsoptimal df routes. as the algorithm runs in factorial time in the worst case,we propose a polynomial time heuristic algorithm that finds an optimal routewith high probability. we demonstrate that that the optimal (and near optimal)df routes are good in practice by simulating a distributed df coding schemeusing low density parity check codes with puncturing and incrementalredundancy.

cs.it math.it

10.1109/isit.2007.4557364

['ong', 'motani']

https://arxiv.org/abs/0704.2926

general-purpose computing on a semantic network substrate

0704.3395

this article presents a model of general-purpose computing on a semanticnetwork substrate. the concepts presented are applicable to any semanticnetwork representation. however, due to the standards and technologicalinfrastructure devoted to the semantic web effort, this article is presentedfrom this point of view. in the proposed model of computing, the applicationprogramming interface, the run-time program, and the state of the computingvirtual machine are all represented in the resource description framework(rdf). the implementation of the concepts presented provides a practicalcomputing paradigm that leverages the highly-distributed and standardizedrepresentational-layer of the semantic web.

cs.ai cs.pl

nan

['rodriguez']

https://arxiv.org/abs/0704.3395

wdm and directed star arboricity

0705.0315

a digraph is $m$-labelled if every arc is labelled by an integer in $\{1,\dots,m\}$. motivated by wavelength assignment for multicasts in opticalnetworks, we introduce and study $n$-fibre colourings of labelled digraphs.these are colourings of the arcs of $d$ such that at each vertex $v$, and foreach colour $\alpha$, $in(v,\alpha)+out(v,\alpha)\leq n$ with $in(v,\alpha)$the number of arcs coloured $\alpha$ entering $v$ and $out(v,\alpha)$ thenumber of labels $l$ such that there is at least one arc of label $l$ leaving$v$ and coloured with $\alpha$. the problem is to find the minimum number ofcolours $\lambda_n(d)$ such that the $m$-labelled digraph $d$ has an $n$-fibrecolouring. in the particular case when $d$ is $1$-labelled, $\lambda_1(d)$ iscalled the directed star arboricity of $d$, and is denoted by $dst(d)$. wefirst show that $dst(d)\leq 2\delta^-(d)+1$, and conjecture that if$\delta^-(d)\geq 2$, then $dst(d)\leq 2\delta^-(d)$. we also prove that for asubcubic digraph $d$, then $dst(d)\leq 3$, and that if $\delta^+(d),\delta^-(d)\leq 2$, then $dst(d)\leq 4$. finally, we study$\lambda_n(m,k)=\max\{\lambda_n(d) \tq d \mbox{is $m$-labelled} \et\delta^-(d)\leq k\}$. we show that if $m\geq n$, then $\ds\left\lceil\frac{m}{n}\left\lceil \frac{k}{n}\right\rceil + \frac{k}{n}\right\rceil\leq \lambda_n(m,k) \leq\left\lceil\frac{m}{n}\left\lceil\frac{k}{n}\right\rceil + \frac{k}{n} \right\rceil + c \frac{m^2\log k}{n}$ forsome constant $c$. we conjecture that the lower bound should be the right valueof $\lambda_n(m,k)$.

cs.ni math.co

nan

['amini', 'havet', 'huc', 'thomasse']

https://arxiv.org/abs/0705.0315

soft constraint abstraction based on semiring homomorphism

0705.0734

the semiring-based constraint satisfaction problems (semiring csps), proposedby bistarelli, montanari and rossi \cite{bmr97}, is a very general framework ofsoft constraints. in this paper we propose an abstraction scheme for softconstraints that uses semiring homomorphism. to find optimal solutions of theconcrete problem, the idea is, first working in the abstract problem andfinding its optimal solutions, then using them to solve the concrete problem. in particular, we show that a mapping preserves optimal solutions if and onlyif it is an order-reflecting semiring homomorphism. moreover, for a semiringhomomorphism $\alpha$ and a problem $p$ over $s$, if $t$ is optimal in$\alpha(p)$, then there is an optimal solution $\bar{t}$ of $p$ such that$\bar{t}$ has the same value as $t$ in $\alpha(p)$.

cs.ai

10.1016/j.tcs.2008.03.029

['li', 'ying']

https://arxiv.org/abs/0705.0734

block locally optimal preconditioned eigenvalue xolvers (blopex) in hypre and petsc

0705.2626

we describe our software package block locally optimal preconditionedeigenvalue xolvers (blopex) publicly released recently. blopex is available asa stand-alone serial library, as an external package to petsc (``portable,extensible toolkit for scientific computation'', a general purpose suite oftools for the scalable solution of partial differential equations and relatedproblems developed by argonne national laboratory), and is also built into {\ithypre} (``high performance preconditioners'', scalable linear solvers packagedeveloped by lawrence livermore national laboratory). the present blopexrelease includes only one solver--the locally optimal block preconditionedconjugate gradient (lobpcg) method for symmetric eigenvalue problems. {\ithypre} provides users with advanced high-quality parallel preconditioners forlinear systems, in particular, with domain decomposition and multigridpreconditioners. with blopex, the same preconditioners can now be efficientlyused for symmetric eigenvalue problems. petsc facilitates the integration ofindependently developed application modules with strict attention to componentinteroperability, and makes blopex extremely easy to compile and use withpreconditioners that are available via petsc. we present the lobpcg algorithmin blopex for {\it hypre} and petsc. we demonstrate numerically the scalabilityof blopex by testing it on a number of distributed and shared memory parallelsystems, including a beowulf system, sun fire 880, an amd dual-core opteronworkstation, and ibm bluegene/l supercomputer, using petsc domain decompositionand {\it hypre} multigrid preconditioning. we test blopex on a model problem,the standard 7-point finite-difference approximation of the 3-d laplacian, withthe problem size in the range $10^5-10^8$.

cs.ms cs.na

10.1137/060661624

['knyazev', 'argentati', 'lashuk', 'ovtchinnikov']

https://arxiv.org/abs/0705.2626

maximizing maximal angles for plane straight-line graphs

0705.3820

let $g=(s, e)$ be a plane straight-line graph on a finite point set$s\subset\r^2$ in general position. the incident angles of a vertex $p \in s$of $g$ are the angles between any two edges of $g$ that appear consecutively inthe circular order of the edges incident to $p$. a plane straight-line graph is called $\phi$-open if each vertex has anincident angle of size at least $\phi$. in this paper we study the followingtype of question: what is the maximum angle $\phi$ such that for any finite set$s\subset\r^2$ of points in general position we can find a graph from a certainclass of graphs on $s$ that is $\phi$-open? in particular, we consider theclasses of triangulations, spanning trees, and paths on $s$ and give tightbounds in most cases.

cs.cg cs.dm math.co

10.1007/978-3-540-73951-7_40

['aichholzer', 'hackl', 'hoffmann', 'huemer', 'por', 'santos', 'speckmann', 'vogtenhuber']

https://arxiv.org/abs/0705.3820

mixed membership stochastic blockmodels

0705.4485

observations consisting of measurements on relationships for pairs of objectsarise in many settings, such as protein interaction and gene regulatorynetworks, collections of author-recipient email, and social networks. analyzingsuch data with probabilisic models can be delicate because the simpleexchangeability assumptions underlying many boilerplate models no longer hold.in this paper, we describe a latent variable model of such data called themixed membership stochastic blockmodel. this model extends blockmodels forrelational data to ones which capture mixed membership latent relationalstructure, thus providing an object-specific low-dimensional representation. wedevelop a general variational inference algorithm for fast approximateposterior inference. we explore applications to social and protein interactionnetworks.

stat.me cs.lg math.st physics.soc-ph stat.ml stat.th

nan

['airoldi', 'blei', 'fienberg', 'xing']

https://arxiv.org/abs/0705.4485

sampling colourings of the triangular lattice

0706.0489

we show that the glauber dynamics on proper 9-colourings of the triangularlattice is rapidly mixing, which allows for efficient sampling. consequently,there is a fully polynomial randomised approximation scheme (fpras) forcounting proper 9-colourings of the triangular lattice. proper colouringscorrespond to configurations in the zero-temperature anti-ferromagnetic pottsmodel. we show that the spin system consisting of proper 9-colourings of thetriangular lattice has strong spatial mixing. this implies that there is aunique infinite-volume gibbs distribution, which is an important propertystudied in statistical physics. our results build on previous work by goldberg,martin and paterson, who showed similar results for 10 colours on thetriangular lattice. their work was preceded by salas and sokal's 11-colourresult. both proofs rely on computational assistance, and so does our 9-colourproof. we have used a randomised heuristic to guide us towards rigourousresults.

math-ph cs.dm cs.ds math.mp

nan

['jalsenius']

https://arxiv.org/abs/0706.0489

tropical implicitization and mixed fiber polytopes

0706.0564

the software trim offers implementations of tropical implicitization andtropical elimination, as developed by tevelev and the authors. given apolynomial map with generic coefficients, trim computes the tropical variety ofthe image. when the image is a hypersurface, the output is the newton polytopeof the defining polynomial. trim can thus be used to compute mixed fiberpolytopes, including secondary polytopes.

cs.sc math.ag math.co

nan

['sturmfels', 'yu']

https://arxiv.org/abs/0706.0564

getting started in probabilistic graphical models

0706.2040

probabilistic graphical models (pgms) have become a popular tool forcomputational analysis of biological data in a variety of domains. but, whatexactly are they and how do they work? how can we use pgms to discover patternsthat are biologically relevant? and to what extent can pgms help us formulatenew hypotheses that are testable at the bench? this note sketches out someanswers and illustrates the main ideas behind the statistical approach tobiological pattern discovery.

q-bio.qm cs.lg physics.soc-ph stat.me stat.ml

10.1371/journal.pcbi.0030252

['airoldi']

https://arxiv.org/abs/0706.2040

stability of boundary measures

0706.2153

we introduce the boundary measure at scale r of a compact subset of then-dimensional euclidean space. we show how it can be computed for point cloudsand suggest these measures can be used for feature detection. the maincontribution of this work is the proof a quantitative stability theorem forboundary measures using tools of convex analysis and geometric measure theory.as a corollary we obtain a stability result for federer's curvature measures ofa compact, allowing to compute them from point-cloud approximations of thecompact.

cs.cg math.ca math.mg

10.1007/s10208-009-9056-2

['chazal', 'cohen-steiner', 'mérigot']

https://arxiv.org/abs/0706.2153

interference and outage in clustered wireless ad hoc networks

0706.2434

in the analysis of large random wireless networks, the underlying nodedistribution is almost ubiquitously assumed to be the homogeneous poisson pointprocess. in this paper, the node locations are assumed to form a poissonclustered process on the plane. we derive the distributional properties of theinterference and provide upper and lower bounds for its ccdf. we consider theprobability of successful transmission in an interference limited channel whenfading is modeled as rayleigh. we provide a numerically integrable expressionfor the outage probability and closed-form upper and lower bounds.we show thatwhen the transmitter-receiver distance is large, the success probability isgreater than that of a poisson arrangement. these results characterize theperformance of the system under geographical or mac-induced clustering. weobtain the maximum intensity of transmitting nodes for a given outageconstraint, i.e., the transmission capacity (of this spatial arrangement) andshow that it is equal to that of a poisson arrangement of nodes. for theanalysis, techniques from stochastic geometry are used, in particular theprobability generating functional of poisson cluster processes, the palmcharacterization of poisson cluster processes and the campbell-mecke theorem.

cs.it math.it

10.1109/tit.2009.2025543

['ganti', 'haenggi']

https://arxiv.org/abs/0706.2434

approximations of lovasz extensions and their induced interaction index

0706.3856

the lovasz extension of a pseudo-boolean function $f : \{0,1\}^n \to r$ isdefined on each simplex of the standard triangulation of $[0,1]^n$ as theunique affine function $\hat f : [0,1]^n \to r$ that interpolates $f$ at the$n+1$ vertices of the simplex. its degree is that of the unique multilinearpolynomial that expresses $f$. in this paper we investigate the least squaresapproximation problem of an arbitrary lovasz extension $\hat f$ by lovaszextensions of (at most) a specified degree. we derive explicit expressions ofthese approximations. the corresponding approximation problem forpseudo-boolean functions was investigated by hammer and holzman (1992) and thensolved explicitly by grabisch, marichal, and roubens (2000), giving rise to analternative definition of banzhaf interaction index. similarly we introduce anew interaction index from approximations of $\hat f$ and we present some ofits properties. it turns out that its corresponding power index identifies withthe power index introduced by grabisch and labreuche (2001).

math.co cs.dm

nan

['marichal', 'mathonet']

https://arxiv.org/abs/0706.3856

determinacy in a synchronous pi-calculus

0707.0556

the s-pi-calculus is a synchronous pi-calculus which is based on the slmodel. the latter is a relaxation of the esterel model where the reaction tothe absence of a signal within an instant can only happen at the next instant.in the present work, we present and characterise a compositional semantics ofthe s-pi-calculus based on suitable notions of labelled transition system andbisimulation. based on this semantic framework, we explore the notion ofdeterminacy and the related one of (local) confluence.

cs.lo

nan

['amadio', 'dogguy']

https://arxiv.org/abs/0707.0556

the cyborg astrobiologist: porting from a wearable computer to the astrobiology phone-cam

0707.0808

we have used a simple camera phone to significantly improve an `explorationsystem' for astrobiology and geology. this camera phone will make it mucheasier to develop and test computer-vision algorithms for future planetaryexploration. we envision that the `astrobiology phone-cam' exploration systemcan be fruitfully used in other problem domains as well.

cs.cv astro-ph cs.ai cs.ce cs.hc cs.ni cs.ro cs.se

10.1017/s1473550407003862

['bartolo', 'mcguire', 'camilleri', 'spiteri', 'borg', 'farrugia', 'ormo', 'gomez-elvira', 'rodriguez-manfredi', 'diaz-martinez', 'ritter', 'haschke', 'oesker', 'ontrup']

https://arxiv.org/abs/0707.0808

p-adic modelling of the genome and the genetic code

0707.3043

the present paper is devoted to foundations of p-adic modelling in genomics.considering nucleotides, codons, dna and rna sequences, amino acids, andproteins as information systems, we have formulated the corresponding p-adicformalisms for their investigations. each of these systems has itscharacteristic prime number used for construction of the related informationspace. relevance of this approach is illustrated by some examples. inparticular, it is shown that degeneration of the genetic code is a p-adicphenomenon. we have also put forward a hypothesis on evolution of the geneticcode assuming that primitive code was based on single nucleotides andchronologically first four amino acids. this formalism of p-adic genomicinformation systems can be implemented in computer programs and applied tovarious concrete cases.

q-bio.ot cs.it math.it physics.bio-ph

10.1093/comjnl/bxm083

['dragovich', 'dragovich']

https://arxiv.org/abs/0707.3043

separable and low-rank continuous games

0707.3462

in this paper, we study nonzero-sum separable games, which are continuousgames whose payoffs take a sum-of-products form. included in this subclass areall finite games and polynomial games. we investigate the structure ofequilibria in separable games. we show that these games admit finitelysupported nash equilibria. motivated by the bounds on the supports of mixedequilibria in two-player finite games in terms of the ranks of the payoffmatrices, we define the notion of the rank of an n-player continuous game anduse this to provide bounds on the cardinality of the support of equilibriumstrategies. we present a general characterization theorem that states that acontinuous game has finite rank if and only if it is separable. using our rankresults, we present an efficient algorithm for computing approximate equilibriaof two-player separable games with fixed strategy spaces in time polynomial inthe rank of the game.

cs.gt math.oc

10.1007/s00182-008-0129-2

['stein', 'ozdaglar', 'parrilo']

https://arxiv.org/abs/0707.3462

mumford dendrograms

0707.3540

an effective $p$-adic encoding of dendrograms is presented through anexplicit embedding into the bruhat-tits tree for a $p$-adic number field. thisfield depends on the number of children of a vertex and is a finite extensionof the field of $p$-adic numbers. it is shown that fixing $p$-adicrepresentatives of the residue field allows a natural way of encoding stringsby identifying a given alphabet with such representatives. a simple $p$-adichierarchic classification algorithm is derived for $p$-adic numbers, and isapplied to strings over finite alphabets. examples of dna coding are presentedand discussed. finally, new geometric and combinatorial invariants of timeseries of $p$-adic dendrograms are developped.

cs.dm

10.1093/comjnl/bxm088

['bradley']

https://arxiv.org/abs/0707.3540

complexity of propositional proofs under a promise

0707.4255

we study -- within the framework of propositional proof complexity -- theproblem of certifying unsatisfiability of cnf formulas under the promise thatany satisfiable formula has many satisfying assignments, where ``many'' standsfor an explicitly specified function $\lam$ in the number of variables $n$. tothis end, we develop propositional proof systems under different measures ofpromises (that is, different $\lam$) as extensions of resolution. this is doneby augmenting resolution with axioms that, roughly, can eliminate sets of truthassignments defined by boolean circuits. we then investigate the complexity ofsuch systems, obtaining an exponential separation in the average-case betweenresolution under different size promises: 1. resolution has polynomial-size refutations for all unsatisfiable 3cnfformulas when the promise is $\eps\cd2^n$, for any constant $0<\eps<1$. 2. there are no sub-exponential size resolution refutations for random 3cnfformulas, when the promise is $2^{\delta n}$ (and the number of clauses is$o(n^{3/2})$), for any constant $0<\delta<1$.

cs.cc cs.lo

nan

['dershowitz', 'tzameret']

https://arxiv.org/abs/0707.4255

efficient divide-and-conquer implementations of symmetric fsas

0708.0580

a deterministic finite-state automaton (fsa) is an abstract sequentialmachine that reads the symbols comprising an input word one at a time. an fsais symmetric if its output is independent of the order in which the inputsymbols are read, i.e., if the output is invariant under permutations of theinput. we show how to convert a symmetric fsa a into an automaton-likedivide-and-conquer process whose intermediate results are no larger than thesize of a's memory. in comparison, a similar result for general fsa's has beenlong known via functional composition, but entails an exponential increase inmemory size. the new result has applications to parallel processing andsymmetric fsa networks.

cs.fl cs.dm

nan

['pritchard']

https://arxiv.org/abs/0708.0580

on perfect, amicable, and sociable chains

0708.1491

let $x = (x_0,...,x_{n-1})$ be an n-chain, i.e., an n-tuple of non-negativeintegers $< n$. consider the operator $s: x \mapsto x' = (x'_0,...,x'_{n-1})$,where x'_j represents the number of $j$'s appearing among the components of x.an n-chain x is said to be perfect if $s(x) = x$. for example, (2,1,2,0,0) is aperfect 5-chain. analogously to the theory of perfect, amicable, and sociablenumbers, one can define from the operator s the concepts of amicable pair andsociable group of chains. in this paper we give an exhaustive list of all theperfect, amicable, and sociable chains.

math.co cs.dm math.nt

nan

['marichal']

https://arxiv.org/abs/0708.1491

resolution over linear equations and multilinear proofs

0708.1529

we develop and study the complexity of propositional proof systems of varyingstrength extending resolution by allowing it to operate with disjunctions oflinear equations instead of clauses. we demonstrate polynomial-size refutationsfor hard tautologies like the pigeonhole principle, tseitin graph tautologiesand the clique-coloring tautologies in these proof systems. using the(monotone) interpolation by a communication game technique we establish anexponential-size lower bound on refutations in a certain, considerably strong,fragment of resolution over linear equations, as well as a general polynomialupper bound on (non-monotone) interpolants in this fragment. we then apply these results to extend and improve previous results onmultilinear proofs (over fields of characteristic 0), as studied in[raztzameret06]. specifically, we show the following: 1. proofs operating with depth-3 multilinear formulas polynomially simulate acertain, considerably strong, fragment of resolution over linear equations. 2. proofs operating with depth-3 multilinear formulas admit polynomial-sizerefutations of the pigeonhole principle and tseitin graph tautologies. theformer improve over a previous result that established small multilinear proofsonly for the \emph{functional} pigeonhole principle. the latter are differentthan previous proofs, and apply to multilinear proofs of tseitin mod p graphtautologies over any field of characteristic 0. we conclude by connecting resolution over linear equations with extensions ofthe cutting planes proof system.

cs.cc cs.lo

10.1016/j.apal.2008.04.001

['raz', 'tzameret']

https://arxiv.org/abs/0708.1529

optimal causal inference: estimating stored information and approximating causal architecture

0708.1580

we introduce an approach to inferring the causal architecture of stochasticdynamical systems that extends rate distortion theory to use causalshielding---a natural principle of learning. we study two distinct cases ofcausal inference: optimal causal filtering and optimal causal estimation. filtering corresponds to the ideal case in which the probability distributionof measurement sequences is known, giving a principled method to approximate asystem's causal structure at a desired level of representation. we show that,in the limit in which a model complexity constraint is relaxed, filtering findsthe exact causal architecture of a stochastic dynamical system, known as thecausal-state partition. from this, one can estimate the amount of historicalinformation the process stores. more generally, causal filtering finds a gradedmodel-complexity hierarchy of approximations to the causal architecture. abruptchanges in the hierarchy, as a function of approximation, capture distinctscales of structural organization. for nonideal cases with finite data, we show how the correct number ofunderlying causal states can be found by optimal causal estimation. apreviously derived model complexity control term allows us to correct for theeffect of statistical fluctuations in probability estimates and thereby avoidover-fitting.

cs.it cond-mat.stat-mech cs.lg math.it math.st stat.th

nan

['still', 'crutchfield', 'ellison']

https://arxiv.org/abs/0708.1580

obstructions to genericity in study of parametric problems in control theory

0708.2078

we investigate systems of equations, involving parameters from the point ofview of both control theory and computer algebra. the equations might involvelinear operators such as partial (q-)differentiation, (q-)shift, (q-)differenceas well as more complicated ones, which act trivially on the parameters. such asystem can be identified algebraically with a certain left module over anon-commutative algebra, where the operators commute with the parameters. wedevelop, implement and use in practice the algorithm for revealing all theexpressions in parameters, for which e.g. homological properties of a systemdiffer from the generic properties. we use groebner bases and groebner basicsin rings of solvable type as main tools. in particular, we demonstrate anoptimized algorithm for computing the left inverse of a matrix over a ring ofsolvable type. we illustrate the article with interesting examples. inparticular, we provide a complete solution to the "two pendula, mounted on acart" problem from the classical book of polderman and willems, including thecase, where the friction at the joints is essential . to the best of ourknowledge, the latter example has not been solved before in a complete way.

math.oc cs.sc math.ra

nan

['levandovskyy', 'zerz']

https://arxiv.org/abs/0708.2078

a dichotomy theorem for general minimum cost homomorphism problem

0708.3226

in the constraint satisfaction problem ($csp$), the aim is to find anassignment of values to a set of variables subject to specified constraints. inthe minimum cost homomorphism problem ($minhom$), one is additionally givenweights $c_{va}$ for every variable $v$ and value $a$, and the aim is to findan assignment $f$ to the variables that minimizes $\sum_{v} c_{vf(v)}$. let$minhom(\gamma)$ denote the $minhom$ problem parameterized by the set ofpredicates allowed for constraints. $minhom(\gamma)$ is related to manywell-studied combinatorial optimization problems, and concrete applications canbe found in, for instance, defence logistics and machine learning. we show that$minhom(\gamma)$ can be studied by using algebraic methods similar to thoseused for csps. with the aid of algebraic techniques, we classify thecomputational complexity of $minhom(\gamma)$ for all choices of $\gamma$. ourresult settles a general dichotomy conjecture previously resolved only forcertain classes of directed graphs, [gutin, hell, rafiey, yeo, european j. ofcombinatorics, 2008].

cs.lg cs.cc

nan

['takhanov']

https://arxiv.org/abs/0708.3226

bounding the betti numbers and computing the euler-poincar\'e characteristic of semi-algebraic sets defined by partly quadratic systems of polynomials

0708.3522

let $\r$ be a real closed field, $ {\mathcal q} \subset\r[y_1,...,y_\ell,x_1,...,x_k], $ with $ \deg_{y}(q) \leq 2, \deg_{x}(q) \leqd, q \in {\mathcal q}, #({\mathcal q})=m,$ and $ {\mathcal p} \subset\r[x_1,...,x_k] $ with $\deg_{x}(p) \leq d, p \in {\mathcal p}, #({\mathcalp})=s$, and $s \subset \r^{\ell+k}$ a semi-algebraic set defined by a booleanformula without negations, with atoms $p=0, p \geq 0, p \leq 0, p \in {\mathcalp} \cup {\mathcal q}$. we prove that the sum of the betti numbers of $s$ isbounded by \[ \ell^2 (o(s+\ell+m)\ell d)^{k+2m}. \] this is a commongeneralization of previous results on bounding the betti numbers of closedsemi-algebraic sets defined by polynomials of degree $d$ and 2, respectively. we also describe an algorithm for computing the euler-poincar\'echaracteristic of such sets, generalizing similar algorithms known before. thecomplexity of the algorithm is bounded by $(\ell s m d)^{o(m(m+k))}$.

math.ag cs.sc math.at math.gt

10.1137/070711141

['basu', 'pasechnik', 'roy']

https://arxiv.org/abs/0708.3522

convolutional entanglement distillation

0708.3699

we develop a theory of entanglement distillation that exploits aconvolutional coding structure. we provide a method for converting an arbitraryclassical binary or quaternary convolutional code into a convolutionalentanglement distillation protocol. the imported classical convolutional codedoes not have to be dual-containing or self-orthogonal. the yield anderror-correcting properties of such a protocol depend respectively on the rateand error-correcting properties of the imported classical convolutional code. aconvolutional entanglement distillation protocol has several other benefits.two parties sharing noisy ebits can distill noiseless ebits ``online'' as theyacquire more noisy ebits. distillation yield is high and decoding complexity issimple for a convolutional entanglement distillation protocol. our theory ofconvolutional entanglement distillation reduces the problem of finding a goodconvolutional entanglement distillation protocol to the well-establishedproblem of finding a good classical convolutional code.

quant-ph cs.it math.it

10.1109/isit.2010.5513666

['wilde', 'krovi', 'brun']

https://arxiv.org/abs/0708.3699

conjugates of characteristic sturmian words generated by morphisms

0708.4387

this article is concerned with characteristic sturmian words of slope$\alpha$ and $1-\alpha$ (denoted by $c_\alpha$ and $c_{1-\alpha}$respectively), where $\alpha \in (0,1)$ is an irrational number such that$\alpha = [0;1+d_1,\bar{d_2,...,d_n}]$ with $d_n \geq d_1 \geq 1$. it is knownthat both $c_\alpha$ and $c_{1-\alpha}$ are fixed points of non-trivial(standard) morphisms $\sigma$ and $\hat{\sigma}$, respectively, if and only if$\alpha$ has a continued fraction expansion as above. accordingly, such words$c_\alpha$ and $c_{1-\alpha}$ are generated by the respective morphisms$\sigma$ and $\hat{\sigma}$. for the particular case when $\alpha =[0;2,\bar{r}]$ ($r\geq1$), we give a decomposition of each conjugate of$c_\alpha$ (and hence $c_{1-\alpha}$) into generalized adjoining singularwords, by considering conjugates of powers of the standard morphism $\sigma$ bywhich it is generated. this extends a recent result of lev\'{e} and s\ee boldon conjugates of the infinite fibonacci word.

math.co cs.dm

10.1016/j.ejc.2003.12.012

['glen']

https://arxiv.org/abs/0708.4387

occurrences of palindromes in characteristic sturmian words

0708.4389

this paper is concerned with palindromes occurring in characteristic sturmianwords $c_\alpha$ of slope $\alpha$, where $\alpha \in (0,1)$ is an irrational.as $c_\alpha$ is a uniformly recurrent infinite word, any (palindromic) factorof $c_\alpha$ occurs infinitely many times in $c_\alpha$ with bounded gaps. ouraim is to completely describe where palindromes occur in $c_\alpha$. inparticular, given any palindromic factor $u$ of $c_\alpha$, we shall establisha decomposition of $c_\alpha$ with respect to the occurrences of $u$. such adecomposition shows precisely where $u$ occurs in $c_\alpha$, and this isdirectly related to the continued fraction expansion of $\alpha$.

math.co cs.dm

10.1016/j.tcs.2005.09.075

['glen']

https://arxiv.org/abs/0708.4389

powers in a class of a-strict standard episturmian words

0708.4400

this paper concerns a specific class of strict standard episturmian wordswhose directive words resemble those of characteristic sturmian words. inparticular, we explicitly determine all integer powers occurring in suchinfinite words, extending recent results of damanik and lenz (2003), whostudied powers in sturmian words. the key tools in our analysis are canonicaldecompositions and a generalization of singular words, which were originallydefined for the ubiquitous fibonacci word. our main results are demonstratedvia some examples, including the $k$-bonacci word: a generalization of thefibonacci word to a $k$-letter alphabet ($k\geq2$).

math.co cs.dm

10.1016/j.tcs.2007.03.023

['glen']

https://arxiv.org/abs/0708.4400

a characterization of fine words over a finite alphabet

0708.4406

to any infinite word w over a finite alphabet a we can associate two infinitewords min(w) and max(w) such that any prefix of min(w) (resp. max(w)) is thelexicographically smallest (resp. greatest) amongst the factors of w of thesame length. we say that an infinite word w over a is "fine" if there exists aninfinite word u such that, for any lexicographic order, min(w) = au where a =min(a). in this paper, we characterize fine words; specifically, we prove thatan infinite word w is fine if and only if w is either a "strict episturmianword" or a strict "skew episturmian word''. this characterization generalizes arecent result of g. pirillo, who proved that a fine word over a 2-letteralphabet is either an (aperiodic) sturmian word, or an ultimately periodic (butnot periodic) infinite word, all of whose factors are (finite) sturmian.

math.co cs.dm

10.1016/j.tcs.2007.10.029

['glen']

https://arxiv.org/abs/0708.4406

characterizations of finite and infinite episturmian words via lexicographic orderings

0708.4409

in this paper, we characterize by lexicographic order all finite sturmian andepisturmian words, i.e., all (finite) factors of such infinite words.consequently, we obtain a characterization of infinite episturmian words in a"wide sense" (episturmian and episkew infinite words). that is, we characterizethe set of all infinite words whose factors are (finite) episturmian.similarly, we characterize by lexicographic order all balanced infinite wordsover a 2-letter alphabet; in other words, all sturmian and skew infinite words,the factors of which are (finite) sturmian.

math.co cs.dm

10.1016/j.ejc.2007.01.002

['glen', 'justin', 'pirillo']

https://arxiv.org/abs/0708.4409

a new distributed topology control algorithm for wireless environments with non-uniform path loss and multipath propagation

0709.0961

each node in a wireless multi-hop network can adjust the power level at whichit transmits and thus change the topology of the network to save energy bychoosing the neighbors with which it directly communicates. many previousalgorithms for distributed topology control have assumed an ability at eachnode to deduce some location-based information such as the direction and thedistance of its neighbor nodes with respect to itself. such a deduction oflocation-based information, however, cannot be relied upon in real environmentswhere the path loss exponents vary greatly leading to significant errors indistance estimates. also, multipath effects may result in different signalpaths with different loss characteristics, and none of these paths may beline-of-sight, making it difficult to estimate the direction of a neighboringnode. in this paper, we present step topology control (stc), a simpledistributed topology control algorithm which reduces energy consumption whilepreserving the connectivity of a heterogeneous sensor network without use ofany location-based information. we show that the stc algorithm achieves thesame or better order of communication and computational complexity whencompared to other known algorithms that also preserve connectivity without theuse of location-based information. we also present a detailed simulation-basedcomparative analysis of the energy savings and interference reduction achievedby the algorithms. the results show that, in spite of not incurring a highercommunication or computational complexity, the stc algorithm performs betterthan other algorithms in uniform wireless environments and especially betterwhen path loss characteristics are non-uniform.

cs.ni

nan

['sethu', 'gerety']

https://arxiv.org/abs/0709.0961

the graver complexity of integer programming

0709.1500

in this article we establish an exponential lower bound on the gravercomplexity of integer programs. this provides new type of evidence supportingthe presumable intractability of integer programming. specifically, we showthat the graver complexity of the incidence matrix of the complete bipartitegraph $k_{3,m}$ satisfies $g(m)=\omega(2^m)$, with $g(m)\geq 17\cdot 2^{m-3}-7$for every $m>3$ .

math.co cs.cc cs.dm math.ac

nan

['berstein', 'onn']

https://arxiv.org/abs/0709.1500

toward psycho-robots

0709.2065

we try to perform geometrization of psychology by representing mental states,<<ideas>>, by points of a metric space, <<mental space>>. evolution of ideas isdescribed by dynamical systems in metric mental space. we apply the mentalspace approach for modeling of flows of unconscious and conscious informationin the human brain. in a series of models, models 1-4, we consider cognitivesystems with increasing complexity of psychological behavior determined bystructure of flows of ideas. since our models are in fact models of theai-type, one immediately recognizes that they can be used for creation ofai-systems, which we call psycho-robots, exhibiting important elements of humanpsyche. creation of such psycho-robots may be useful improvement of domesticrobots. at the moment domestic robots are merely simple working devices (e.g.vacuum cleaners or lawn mowers) . however, in future one can expect demand insystems which be able not only perform simple work tasks, but would haveelements of human self-developing psyche. such ai-psyche could play animportant role both in relations between psycho-robots and their owners as wellas between psycho-robots. since the presence of a huge numbers ofpsycho-complexes is an essential characteristic of human psychology, it wouldbe interesting to model them in the ai-framework.

cs.ai

10.2478/s13230-010-0014-0

['khrennikov']

https://arxiv.org/abs/0709.2065

algebraic characterization of logically defined tree languages

0709.2962

we give an algebraic characterization of the tree languages that are definedby logical formulas using certain lindstr\"om quantifiers. an importantinstance of our result concerns first-order definable tree languages. ourcharacterization relies on the usage of preclones, an algebraic structureintroduced by the authors in a previous paper, and of the block productoperation on preclones. our results generalize analogous results on finite wordlanguages, but it must be noted that, as they stand, they do not yield analgorithm to decide whether a given regular tree language is first-orderdefinable.

cs.lo math.lo

nan

['esik', 'weil']

https://arxiv.org/abs/0709.2962

the extended edit distance metric

0709.4669

similarity search is an important problem in information retrieval. thissimilarity is based on a distance. symbolic representation of time series hasattracted many researchers recently, since it reduces the dimensionality ofthese high dimensional data objects. we propose a new distance metric that isapplied to symbolic data objects and we test it on time series data bases in aclassification task. we compare it to other distances that are well known inthe literature for symbolic data objects. we also prove, mathematically, thatour distance is metric.

cs.ir

10.1109/cbmi.2008.4564953

['fuad', 'marteau']

https://arxiv.org/abs/0709.4669

faster least squares approximation

0710.1435

least squares approximation is a technique to find an approximate solution toa system of linear equations that has no exact solution. in a typical setting,one lets $n$ be the number of constraints and $d$ be the number of variables,with $n \gg d$. then, existing exact methods find a solution vector in$o(nd^2)$ time. we present two randomized algorithms that provide very accuraterelative-error approximations to the optimal value and the solution vector of aleast squares approximation problem more rapidly than existing exactalgorithms. both of our algorithms preprocess the data with the randomizedhadamard transform. one then uniformly randomly samples constraints and solvesthe smaller problem on those constraints, and the other performs a sparserandom projection and solves the smaller problem on those projectedcoordinates. in both cases, solving the smaller problem provides relative-errorapproximations, and, if $n$ is sufficiently larger than $d$, the approximatesolution can be computed in $o(nd \log d)$ time.

cs.ds

nan

['drineas', 'mahoney', 'muthukrishnan', 'sarlos']

https://arxiv.org/abs/0710.1435

a polynomial bound for untangling geometric planar graphs

0710.1641

to untangle a geometric graph means to move some of the vertices so that theresulting geometric graph has no crossings. pach and tardos [discrete comput.geom., 2002] asked if every n-vertex geometric planar graph can be untangledwhile keeping at least n^\epsilon vertices fixed. we answer this question inthe affirmative with \epsilon=1/4. the previous best known bound was\omega((\log n / \log\log n)^{1/2}). we also consider untangling geometrictrees. it is known that every n-vertex geometric tree can be untangled whilekeeping at least (n/3)^{1/2} vertices fixed, while the best upper bound waso(n\log n)^{2/3}. we answer a question of spillner and wolff [arxiv:0709.01702007] by closing this gap for untangling trees. in particular, we show that forinfinitely many values of n, there is an n-vertex geometric tree that cannot beuntangled while keeping more than 3(n^{1/2}-1) vertices fixed. moreover, weimprove the lower bound to (n/2)^{1/2}.

cs.cg cs.dm math.co

10.1007/s00454-008-9125-3

['bose', 'dujmovic', 'hurtado', 'langerman', 'morin', 'wood']

https://arxiv.org/abs/0710.1641

analyzing covert social network foundation behind terrorism disaster

0710.4231

this paper addresses a method to analyze the covert social network foundationhidden behind the terrorism disaster. it is to solve a node discovery problem,which means to discover a node, which functions relevantly in a social network,but escaped from monitoring on the presence and mutual relationship of nodes.the method aims at integrating the expert investigator's prior understanding,insight on the terrorists' social network nature derived from the complex graphtheory, and computational data processing. the social network responsible forthe 9/11 attack in 2001 is used to execute simulation experiment to evaluatethe performance of the method.

cs.ai

10.1504/ijssci.2009.024936

['maeno', 'ohsawa']

https://arxiv.org/abs/0710.4231

a multi-level blocking distinct degree factorization algorithm

0710.4410

we give a new algorithm for performing the distinct-degree factorization of apolynomial p(x) over gf(2), using a multi-level blocking strategy. the coarsestlevel of blocking replaces gcd computations by multiplications, as suggested bypollard (1975), von zur gathen and shoup (1992), and others. the novelty of ourapproach is that a finer level of blocking replaces multiplications bysquarings, which speeds up the computation in gf(2)[x]/p(x) of certain intervalpolynomials when p(x) is sparse. as an application we give a fast algorithm tosearch for all irreducible trinomials x^r + x^s + 1 of degree r over gf(2),while producing a certificate that can be checked in less time than the fullsearch. naive algorithms cost o(r^2) per trinomial, thus o(r^3) to search overall trinomials of given degree r. under a plausible assumption about thedistribution of factors of trinomials, the new algorithm has complexity o(r^2(log r)^{3/2}(log log r)^{1/2}) for the search over all trinomials of degree r.our implementation achieves a speedup of greater than a factor of 560 over thenaive algorithm in the case r = 24036583 (a mersenne exponent). using ourprogram, we have found two new primitive trinomials of degree 24036583 overgf(2) (the previous record degree was 6972593).

cs.ds

nan

['brent', 'zimmermann']

https://arxiv.org/abs/0710.4410

a numerical algorithm for zero counting. i: complexity and accuracy

0710.4508

we describe an algorithm to count the number of distinct real zeros of apolynomial (square) system f. the algorithm performs o(n d kappa(f)) iterationswhere n is the number of polynomials (as well as the dimension of the ambientspace), d is a bound on the polynomials' degree, and kappa(f) is a conditionnumber for the system. each iteration uses an exponential number of operations.the algorithm uses finite-precision arithmetic and a polynomial bound for theprecision required to ensure the returned output is correct is exhibited. thisbound is a major feature of our algorithm since it is in contrast with theexponential precision required by the existing (symbolic) algorithms forcounting real zeros. the algorithm parallelizes well in the sense that eachiteration can be computed in parallel polynomial time with an exponentialnumber of processors.

cs.cc cs.na cs.sc math.na

10.1016/j.jco.2008.03.001

['cucker', 'krick', 'malajovich', 'wschebor']

https://arxiv.org/abs/0710.4508

on compositions of numbers and graphs

0710.4965

the main purpose of this note is to pose a couple of problems which areeasily formulated thought some seem to be not yet solved. these problems are ofgeneral interest for discrete mathematics including a new twig of a bough oftheory of graphs i.e. a given graph compositions. the problems result from andare served in the entourage of series of exercises with hints basedpredominantly on the second reference and other related recent papers.

math.co cs.dm

nan

['kwasniewski']

https://arxiv.org/abs/0710.4965

node discovery problem for a social network

0710.4975

methods to solve a node discovery problem for a social network are presented.covert nodes refer to the nodes which are not observable directly. theytransmit the influence and affect the resulting collaborative activities amongthe persons in a social network, but do not appear in the surveillance logswhich record the participants of the collaborative activities. discovering thecovert nodes is identifying the suspicious logs where the covert nodes wouldappear if the covert nodes became overt. the performance of the methods isdemonstrated with a test dataset generated from computationally synthesizednetworks and a real organization.

cs.ai

nan

['maeno']

https://arxiv.org/abs/0710.4975

analog chaos-based secure communications and cryptanalysis: a brief survey

0710.5455

a large number of analog chaos-based secure communication systems have beenproposed since the early 1990s exploiting the technique of chaossynchronization. a brief survey of these chaos-based cryptosystems and ofrelated cryptanalytic results is given. some recently proposed countermeasuresagainst known attacks are also introduced.

nlin.cd cs.cr

nan

['li', 'alvarez', 'li', 'halang']

https://arxiv.org/abs/0710.5455

cryptanalysis of an image encryption scheme based on a new total shuffling algorithm

0710.5465

chaotic systems have been broadly exploited through the last two decades tobuild encryption methods. recently, two new image encryption schemes have beenproposed, where the encryption process involves a permutation operation and anxor-like transformation of the shuffled pixels, which are controlled by threechaotic systems. this paper discusses some defects of the schemes and how tobreak them with a chosen-plaintext attack.

nlin.cd cs.cr cs.mm

10.1016/j.chaos.2008.09.051

['arroyo', 'li', 'li', 'alvarez', 'halang']

https://arxiv.org/abs/0710.5465

an interface group for process components

0711.0834

we take a process component as a pair of an interface and a behaviour. westudy the composition of interacting process components in the setting ofprocess algebra. we formalize the interfaces of interacting process componentsby means of an interface group. an interesting feature of the interface groupis that it allows for distinguishing between expectations and promises ininterfaces of process components. this distinction comes into play in casecomponents with both client and server behaviour are involved.

cs.lo

10.3233/fi-2010-254

['bergstra', 'middelburg']

https://arxiv.org/abs/0711.0834

on the operating unit size of load/store architectures

0711.0838

we introduce a strict version of the concept of a load/store instruction setarchitecture in the setting of maurer machines. we take the view thattransformations on the states of a maurer machine are achieved by applyingthreads as considered in thread algebra to the maurer machine. we study how thetransformations on the states of the main memory of a strict load/storeinstruction set architecture that can be achieved by applying threads depend onthe operating unit size, the cardinality of the instruction set, and themaximal number of states of the threads.

cs.ar

10.1017/s0960129509990314

['bergstra', 'middelburg']

https://arxiv.org/abs/0711.0838

a thread calculus with molecular dynamics

0711.0840

we present a theory of threads, interleaving of threads, and interactionbetween threads and services with features of molecular dynamics, a model ofcomputation that bears on computations in which dynamic data structures areinvolved. threads can interact with services of which the states consist ofstructured data objects and computations take place by means of actions whichmay change the structure of the data objects. the features introduced includerestriction of the scope of names used in threads to refer to data objects.because that feature makes it troublesome to provide a model based onstructural operational semantics and bisimulation, we construct a projectivelimit model for the theory.

cs.lo

10.1016/j.ic.2010.01.004

['bergstra', 'middelburg']

https://arxiv.org/abs/0711.0840

predicting relevant empty spots in social interaction

0711.1466

an empty spot refers to an empty hard-to-fill space which can be found in therecords of the social interaction, and is the clue to the persons in theunderlying social network who do not appear in the records. this contributionaddresses a problem to predict relevant empty spots in social interaction.homogeneous and inhomogeneous networks are studied as a model underlying thesocial interaction. a heuristic predictor function approach is presented as anew method to address the problem. simulation experiment is demonstrated over ahomogeneous network. a test data in the form of baskets is generated from thesimulated communication. precision to predict the empty spots is calculated todemonstrate the performance of the presented approach.

cs.ai

nan

['maeno', 'ohsawa']

https://arxiv.org/abs/0711.1466

asymptotic capacity of wireless ad hoc networks with realistic links under a honey comb topology

0711.1605

we consider the effects of rayleigh fading and lognormal shadowing in thephysical interference model for all the successful transmissions of trafficacross the network. new bounds are derived for the capacity of a given randomad hoc wireless network that reflect packet drop or capture probability of thetransmission links. these bounds are based on a simplified network topologytermed as honey-comb topology under a given routing and scheduling scheme.

cs.it math.it

nan

['asnani', 'karandikar']

https://arxiv.org/abs/0711.1605

natural realizations of sparsity matroids

0711.3013

a hypergraph g with n vertices and m hyperedges with d endpoints each is(k,l)-sparse if for all sub-hypergraphs g' on n' vertices and m' edges, m'\lekn'-l. for integers k and l satisfying 0\le l\le dk-1, this is known to be alinearly representable matroidal family. motivated by problems in rigidity theory, we give a new linear representationtheorem for the (k,l)-sparse hypergraphs that is natural; i.e., therepresenting matrix captures the vertex-edge incidence structure of theunderlying hypergraph g.

math.co cs.cg math.ag math.mg

nan

['streinu', 'theran']

https://arxiv.org/abs/0711.3013

an estimation of distribution algorithm with intelligent local search for rule-based nurse rostering

0711.3591

this paper proposes a new memetic evolutionary algorithm to achieve explicitlearning in rule-based nurse rostering, which involves applying a set ofheuristic rules for each nurse's assignment. the main framework of thealgorithm is an estimation of distribution algorithm, in which an ant-minermethodology improves the individual solutions produced in each generation.unlike our previous work (where learning is implicit), the learning in thememetic estimation of distribution algorithm is explicit, i.e. we are able toidentify building blocks directly. the overall approach learns by building aprobabilistic model, i.e. an estimation of the probability distribution ofindividual nurse-rule pairs that are used to construct schedules. the localsearch processor (i.e. the ant-miner) reinforces nurse-rule pairs that receivehigher rewards. a challenging real world nurse rostering problem is used as thetest problem. computational results show that the proposed approach outperformsmost existing approaches. it is suggested that the learning methodologiessuggested in this paper may be applied to other scheduling problems whereschedules are built systematically according to specific rules

cs.ne cs.ce

10.1057/palgrave.jors.2602308

['aickelin', 'burke', 'li']

https://arxiv.org/abs/0711.3591

instruction sequences with dynamically instantiated instructions

0711.4217

we study sequential programs that are instruction sequences with dynamicallyinstantiated instructions. we define the meaning of such programs in twodifferent ways. in either case, we give a translation by which each programwith dynamically instantiated instructions is turned into a program withoutthem that exhibits on execution the same behaviour by interaction with someservice. the complexity of the translations differ considerably, whereas theservices concerned are equally simple. however, the service concerned in thecase of the simpler translation is far more powerful than the service concernedin the other case.

cs.pl

10.3233/fi-2009-165

['bergstra', 'middelburg']

https://arxiv.org/abs/0711.4217

evolving localizations in reaction-diffusion cellular automata

0712.0836

we consider hexagonal cellular automata with immediate cell neighbourhood andthree cell-states. every cell calculates its next state depending on theintegral representation of states in its neighbourhood, i.e. how manyneighbours are in each one state. we employ evolutionary algorithms to breedlocal transition functions that support mobile localizations (gliders), andcharacterize sets of the functions selected in terms of quasi-chemical systems.analysis of the set of functions evolved allows to speculate that mobilelocalizations are likely to emerge in the quasi-chemical systems with limiteddiffusion of one reagent, a small number of molecules is required foramplification of travelling localizations, and reactions leading to stationarylocalizations involve relatively equal amount of quasi-chemical species.techniques developed can be applied in cascading signals in nature-inspiredspatially extended computing devices, and phenomenological studies andclassification of non-linear discrete systems.

cs.ai

10.1142/s0129183108012376

['adamatzky', 'bull', 'collet', 'sapin']

https://arxiv.org/abs/0712.0836

reconstruction of markov random fields from samples: some easy observations and algorithms

0712.1402

markov random fields are used to model high dimensional distributions in anumber of applied areas. much recent interest has been devoted to thereconstruction of the dependency structure from independent samples from themarkov random fields. we analyze a simple algorithm for reconstructing theunderlying graph defining a markov random field on $n$ nodes and maximum degree$d$ given observations. we show that under mild non-degeneracy conditions itreconstructs the generating graph with high probability using $\theta(d\epsilon^{-2}\delta^{-4} \log n)$ samples where $\epsilon,\delta$ depend on thelocal interactions. for most local interaction $\eps,\delta$ are of order$\exp(-o(d))$. our results are optimal as a function of $n$ up to a multiplicative constantdepending on $d$ and the strength of the local interactions. our results seemto be the first results for general models that guarantee that {\em the}generating model is reconstructed. furthermore, we provide explicit $o(n^{d+2}\epsilon^{-2}\delta^{-4} \log n)$ running time bound. in cases where themeasure on the graph has correlation decay, the running time is $o(n^2 \log n)$for all fixed $d$. we also discuss the effect of observing noisy samples andshow that as long as the noise level is low, our algorithm is effective. on theother hand, we construct an example where large noise impliesnon-identifiability even for generic noise and interactions. finally, webriefly show that in some simple cases, models with hidden nodes can also berecovered.

cs.cc cs.lg

nan

['bresler', 'mossel', 'sly']

https://arxiv.org/abs/0712.1402

two-connected graphs with prescribed three-connected components

0712.1869

we adapt the classical 3-decomposition of any 2-connected graph to the caseof simple graphs (no loops or multiple edges). by analogy with theblock-cutpoint tree of a connected graph, we deduce from this decomposition abicolored tree tc(g) associated with any 2-connected graph g, whose whitevertices are the 3-components of g (3-connected components or polygons) andwhose black vertices are bonds linking together these 3-components, arisingfrom separating pairs of vertices of g. two fundamental relationships on graphsand networks follow from this construction. the first one is a dissymmetrytheorem which leads to the expression of the class b=b(f) of 2-connectedgraphs, all of whose 3-connected components belong to a given class f of3-connected graphs, in terms of various rootings of b. the second one is afunctional equation which characterizes the corresponding class r=r(f) oftwo-pole networks all of whose 3-connected components are in f. all therootings of b are then expressed in terms of f and r. there followcorresponding identities for all the associated series, in particular the edgeindex series. numerous enumerative consequences are discussed.

math.co cs.dm

10.1016/j.aam.2009.01.002

['gagarin', 'labelle', 'leroux', 'walsh']

https://arxiv.org/abs/0712.1869

entanglement-assisted quantum convolutional coding

0712.2223

we show how to protect a stream of quantum information from decoherenceinduced by a noisy quantum communication channel. we exploit presharedentanglement and a convolutional coding structure to develop a theory ofentanglement-assisted quantum convolutional coding. our construction produces acalderbank-shor-steane (css) entanglement-assisted quantum convolutional codefrom two arbitrary classical binary convolutional codes. the rate anderror-correcting properties of the classical convolutional codes directlydetermine the corresponding properties of the resulting entanglement-assistedquantum convolutional code. we explain how to encode our cssentanglement-assisted quantum convolutional codes starting from a stream ofinformation qubits, ancilla qubits, and shared entangled bits.

quant-ph cs.it math.it

10.1103/physreva.81.042333

['wilde', 'brun']

https://arxiv.org/abs/0712.2223

distinguishing short quantum computations

0712.2595

distinguishing logarithmic depth quantum circuits on mixed states is shown tobe complete for qip, the class of problems having quantum interactive proofsystems. circuits in this model can represent arbitrary quantum processes, andthus this result has implications for the verification of implementations ofquantum algorithms. the distinguishability problem is also complete for qip onconstant depth circuits containing the unbounded fan-out gate. these resultsare shown by reducing a qip-complete problem to a logarithmic depth version ofitself using a parallelization technique.

quant-ph cs.cc

10.4230/lipics.stacs.2008.1322

['rosgen']

https://arxiv.org/abs/0712.2595

algorithmic permutation of part of the torah

0712.2606

a small part of the torah is arranged into a two dimensional array. thecharacters are then permuted using a simple recursive deterministic algorithm.the various permutations are then passed through three stochastic filters andone deterministic filter to identify the permutations which most closelyapproximate readable biblical hebrew. of the 15 billion sequences available atthe second level of recursion, 800 pass the a priori thresholds set for eachfilter. the resulting "biblical hebrew" text is available for inspection andthe generation of further material continues.

cs.cr

nan

['croll']

https://arxiv.org/abs/0712.2606

on the monotonicity of the generalized marcum and nuttall q-functions

0712.4103

monotonicity criteria are established for the generalized marcum q-function,$\emph{q}_{m}$, the standard nuttall q-function, $\emph{q}_{m,n}$, and thenormalized nuttall q-function, $\mathcal{q}_{m,n}$, with respect to their realorder indices m,n. besides, closed-form expressions are derived for thecomputation of the standard and normalized nuttall q-functions for the casewhen m,n are odd multiples of 0.5 and $m\geq n$. by exploiting these results,novel upper and lower bounds for $\emph{q}_{m,n}$ and $\mathcal{q}_{m,n}$ areproposed. furthermore, specific tight upper and lower bounds for$\emph{q}_{m}$, previously reported in the literature, are extended for realvalues of m. the offered theoretical results can be efficiently applied in thestudy of digital communications over fading channels, in theinformation-theoretic analysis of multiple-input multiple-output systems and inthe description of stochastic processes in probability theory, among others.

cs.it math.it

10.1109/tit.2009.2023710

['kapinas', 'mihos', 'karagiannidis']

https://arxiv.org/abs/0712.4103

on the maximum span of fixed-angle chains

0801.0258

soss proved that it is np-hard to find the maximum 2d span of a fixed-anglepolygonal chain: the largest distance achievable between the endpoints in aplanar embedding. these fixed-angle chains can serve as models of proteinbackbones. the corresponding problem in 3d is open. we show that three specialcases of particular relevance to the protein model are solvable in polynomialtime. when all link lengths and all angles are equal, the maximum 3d span isachieved in a flat configuration and can be computed in constant time. when allangles are equal and the chain is simple (non-self-crossing), the maximum flatspan can be found in linear time. in 3d, when all angles are equal to 90 deg(but the link lengths arbitrary), the maximum 3d span is in general nonplanarbut can be found in quadratic time.

cs.cg

nan

['benbernou', "o'rourke"]

https://arxiv.org/abs/0801.0258

episturmian words: a survey

0801.1655

in this paper, we survey the rich theory of infinite episturmian words whichgeneralize to any finite alphabet, in a rather resembling way, the well-knownfamily of sturmian words on two letters. after recalling definitions and basicproperties, we consider episturmian morphisms that allow for a deeper study ofthese words. some properties of factors are described, including factorcomplexity, palindromes, fractional powers, frequencies, and return words. wealso consider lexicographical properties of episturmian words, as well as theirconnection to the balance property, and related notions such as finiteepisturmian words, arnoux-rauzy sequences, and "episkew words" that generalizethe skew words of morse and hedlund.

math.co cs.dm

10.1051/ita/2009003

['glen', 'justin']

https://arxiv.org/abs/0801.1655

palindromic richness

0801.1656

in this paper, we study combinatorial and structural properties of a newclass of finite and infinite words that are 'rich' in palindromes in the utmostsense. a characteristic property of so-called "rich words" is that all completereturns to any palindromic factor are themselves palindromes. these wordsencompass the well-known episturmian words, originally introduced by the secondauthor together with x. droubay and g. pirillo in 2001. other examples of richwords have appeared in many different contexts. here we present the firstunified approach to the study of this intriguing family of words. amongst our main results, we give an explicit description of the periodicrich infinite words and show that the recurrent balanced rich infinite wordscoincide with the balanced episturmian words. we also consider two widerclasses of infinite words, namely "weakly rich words" and almost rich words(both strictly contain all rich words, but neither one is contained in theother). in particular, we classify all recurrent balanced weakly rich words. asa consequence, we show that any such word on at least three letters isnecessarily episturmian; hence weakly rich words obey fraenkel's conjecture.likewise, we prove that a certain class of almost rich words obeys fraenkel'sconjecture by showing that the recurrent balanced ones are episturmian orcontain at least two distinct letters with the same frequency. lastly, we study the action of morphisms on (almost) rich words withparticular interest in morphisms that preserve (almost) richness. suchmorphisms belong to the class of "p-morphisms" that was introduced by a. hof,o. knill, and b. simon in 1995.

math.co cs.dm

10.1016/j.ejc.2008.04.006

['glen', 'justin', 'widmer', 'zamboni']

https://arxiv.org/abs/0801.1656

computational approach to the emergence and evolution of language - evolutionary naming game model

0801.1658

computational modelling with multi-agent systems is becoming an importanttechnique of studying language evolution. we present a brief introduction intothis rapidly developing field, as well as our own contributions that include ananalysis of the evolutionary naming-game model. in this model communicatingagents, that try to establish a common vocabulary, are equipped with anevolutionarily selected learning ability. such a coupling of biological andlinguistic ingredients results in an abrupt transition: upon a small change ofthe model control parameter a poorly communicating group of linguisticallyunskilled agents transforms into almost perfectly communicating group withlarge learning abilities. genetic imprinting of the learning abilities proceedsvia baldwin effect: initially unskilled communicating agents learn a languageand that creates a niche in which there is an evolutionary pressure for theincrease of learning ability. under the assumption that communication intensityincreases continuously with finite speed, the transition is split into severaltransition-like changes. it shows that the speed of cultural changes, that setsan additional characteristic timescale, might be yet another factor affectingthe evolution of language. in our opinion, this model shows that linguistic andbiological processes have a strong influence on each other and this effectcertainly has contributed to an explosive development of our species.

physics.soc-ph cs.cl cs.ma

nan

['lipowski', 'lipowska']

https://arxiv.org/abs/0801.1658

an algorithm for road coloring

0801.2838

a coloring of edges of a finite directed graph turns the graph intofinite-state automaton. the synchronizing word of a deterministic automaton isa word in the alphabet of colors (considered as letters) of its edges that mapsthe automaton to a single state. a coloring of edges of a directed graph ofuniform outdegree (constant outdegree of any vertex) is synchronizing if thecoloring turns the graph into a deterministic finite automaton possessing asynchronizing word. the road coloring problem is the problem of synchronizingcoloring of a directed finite strongly connected graph of uniform outdegree ifthe greatest common divisor of the lengths of all its cycles is one. theproblem posed in 1970 had evoked a noticeable interest among the specialists inthe theory of graphs, automata, codes, symbolic dynamics as well as among thewide mathematical community. a polynomial time algorithm of $o(n^3)$ complexityin the most worst case and quadratic in majority of studied cases for the roadcoloring of the considered graph is presented below. the work is based onrecent positive solution of the road coloring problem. the algorithm wasimplemented in the package testas

cs.dm

nan

['trahtman']

https://arxiv.org/abs/0801.2838

a pyramidal evolutionary algorithm with different inter-agent partnering strategies for scheduling problems

0801.3209

this paper combines the idea of a hierarchical distributed genetic algorithmwith different inter-agent partnering strategies. cascading clusters ofsub-populations are built from bottom up, with higher-level sub-populationsoptimising larger parts of the problem. hence higher-level sub-populationssearch a larger search space with a lower resolution whilst lower-levelsub-populations search a smaller search space with a higher resolution. theeffects of different partner selection schemes amongst the agents on solutionquality are examined for two multiple-choice optimisation problems. it is shownthat partnering strategies that exploit problem-specific knowledge are superiorand can counter inappropriate (sub-) fitness measurements.

cs.ne cs.ce

nan

['aickelin']

https://arxiv.org/abs/0801.3209

on the effects of idiotypic interactions for recommendation communities in artificial immune systems

0801.3539

it has previously been shown that a recommender based on immune systemidiotypic principles can out perform one based on correlation alone. this paperreports the results of work in progress, where we undertake some investigationsinto the nature of this beneficial effect. the initial findings are that theimmune system recommender tends to produce different neighbourhoods, and thatthe superior performance of this recommender is due partly to the differentneighbourhoods, and partly to the way that the idiotypic effect is used toweight each neighbours recommendations.

cs.ne cs.ai

nan

['cayzer', 'aickelin']

https://arxiv.org/abs/0801.3539

a recommender system based on the immune network

0801.3547

the immune system is a complex biological system with a highly distributed,adaptive and self-organising nature. this paper presents an artificial immunesystem (ais) that exploits some of these characteristics and is applied to thetask of film recommendation by collaborative filtering (cf). natural evolutionand in particular the immune system have not been designed for classicaloptimisation. however, for this problem, we are not interested in finding asingle optimum. rather we intend to identify a sub-set of good matches on whichrecommendations can be based. it is our hypothesis that an ais built on twocentral aspects of the biological immune system will be an ideal candidate toachieve this: antigen - antibody interaction for matching and antibody -antibody interaction for diversity. computational results are presented insupport of this conjecture and compared to those found by other cf techniques.

cs.ne cs.ai

nan

['cazyer', 'aickelin']

https://arxiv.org/abs/0801.3547

the danger theory and its application to artificial immune systems

0801.3549

over the last decade, a new idea challenging the classical self-non-selfviewpoint has become popular amongst immunologists. it is called the dangertheory. in this conceptual paper, we look at this theory from the perspectiveof artificial immune system practitioners. an overview of the danger theory ispresented with particular emphasis on analogies in the artificial immunesystems world. a number of potential application areas are then used to providea framing for a critical assessment of the concept, and its relevance forartificial immune systems.

cs.ne cs.ai cs.cr

nan

['aickelin', 'cayzer']

https://arxiv.org/abs/0801.3549

partnering strategies for fitness evaluation in a pyramidal evolutionary algorithm

0801.3550

this paper combines the idea of a hierarchical distributed genetic algorithmwith different inter-agent partnering strategies. cascading clusters ofsub-populations are built from bottom up, with higher-level sub-populationsoptimising larger parts of the problem. hence higher-level sub-populationssearch a larger search space with a lower resolution whilst lower-levelsub-populations search a smaller search space with a higher resolution. theeffects of different partner selection schemes for (sub-)fitness evaluationpurposes are examined for two multiple-choice optimisation problems. it isshown that random partnering strategies perform best by providing bettersampling and more diversity.

cs.ne cs.ai

nan

['aickelin', 'bull']

https://arxiv.org/abs/0801.3550

on minimality of convolutional ring encoders

0801.3703

convolutional codes are considered with code sequences modelled assemi-infinite laurent series. it is wellknown that a convolutional code c overa finite group g has a minimal trellis representation that can be derived fromcode sequences. it is also wellknown that, for the case that g is a finitefield, any polynomial encoder of c can be algebraically manipulated to yield aminimal polynomial encoder whose controller canonical realization is a minimaltrellis. in this paper we seek to extend this result to the finite ring case g= z_{p^r} by introducing a socalled "p-encoder". we show how to manipulate apolynomial encoding of a noncatastrophic convolutional code over z_{p^r} toproduce a particular type of p-encoder ("minimal p-encoder") whose controllercanonical realization is a minimal trellis with nonlinear features. the minimumnumber of trellis states is then expressed as p^gamma, where gamma is the sumof the row degrees of the minimal p-encoder. in particular, we show that anyconvolutional code over z_{p^r} admits a delay-free p-encoder which implies thenovel result that delay-freeness is not a property of the code but of theencoder, just as in the field case. we conjecture that a similar result holdswith respect to catastrophicity, i.e., any catastrophic convolutional code overz_{p^r} admits a noncatastrophic p-encoder.

cs.it math.it

nan

['kuijper', 'pinto']

https://arxiv.org/abs/0801.3703

a bayesian optimisation algorithm for the nurse scheduling problem

0801.3971

a bayesian optimization algorithm for the nurse scheduling problem ispresented, which involves choosing a suitable scheduling rule from a set foreach nurses assignment. unlike our previous work that used gas to implementimplicit learning, the learning in the proposed algorithm is explicit, ie.eventually, we will be able to identify and mix building blocks directly. thebayesian optimization algorithm is applied to implement such explicit learningby building a bayesian network of the joint distribution of solutions. theconditional probability of each variable in the network is computed accordingto an initial set of promising solutions. subsequently, each new instance foreach variable is generated, ie in our case, a new rule string has beenobtained. another set of rule strings will be generated in this way, some ofwhich will replace previous strings based on fitness selection. if stoppingconditions are not met, the conditional probabilities for all nodes in thebayesian network are updated again using the current set of promising rulestrings. computational results from 52 real data instances demonstrate thesuccess of this approach. it is also suggested that the learning mechanism inthe proposed approach might be suitable for other scheduling problems.

cs.ne cs.ce

nan

['li', 'aickelin']

https://arxiv.org/abs/0801.3971

strategic alert throttling for intrusion detection systems

0801.4119

network intrusion detection systems are themselves becoming targets ofattackers. alert flood attacks may be used to conceal malicious activity byhiding it among a deluge of false alerts sent by the attacker. although thesetypes of attacks are very hard to stop completely, our aim is to presenttechniques that improve alert throughput and capacity to such an extent thatthe resources required to successfully mount the attack become prohibitive. thekey idea presented is to combine a token bucket filter with a realtimecorrelation algorithm. the proposed algorithm throttles alert output from theids when an attack is detected. the attack graph used in the correlationalgorithm is used to make sure that alerts crucial to forming strategies arenot discarded by throttling.

cs.ne cs.cr

nan

['tedesco', 'aickelin']

https://arxiv.org/abs/0801.4119

movie recommendation systems using an artificial immune system

0801.4287

we apply the artificial immune system (ais) technology to the collaborativefiltering (cf) technology when we build the movie recommendation system. twodifferent affinity measure algorithms of ais, kendall tau and weighted kappa,are used to calculate the correlation coefficients for this movierecommendation system. from the testing we think that weighted kappa is moresuitable than kendall tau for movie problems.

cs.ne cs.ai

nan

['chen', 'aickelin']

https://arxiv.org/abs/0801.4287

investigating artificial immune systems for job shop rescheduling in changing environments

0801.4312

artificial immune system can be used to generate schedules in changingenvironments and it has been proven to be more robust than schedules developedusing a genetic algorithm. good schedules can be produced especially when thenumber of the antigens is increased. however, an increase in the range of theantigens had somehow affected the fitness of the immune system. in thisresearch, we are trying to improve the result of the system by rescheduling thesame problem using the same method while at the same time maintaining therobustness of the schedules.

cs.ne cs.ce

nan

['aickelin', 'burke', 'din']

https://arxiv.org/abs/0801.4312

artificial immune systems (ais) - a new paradigm for heuristic decision making

0801.4314

over the last few years, more and more heuristic decision making techniqueshave been inspired by nature, e.g. evolutionary algorithms, ant colonyoptimisation and simulated annealing. more recently, a novel computationalintelligence technique inspired by immunology has emerged, called artificialimmune systems (ais). this immune system inspired technique has already beenuseful in solving some computational problems. in this keynote, we will verybriefly describe the immune system metaphors that are relevant to ais. we willthen give some illustrative real-world problems suitable for ais use and show astep-by-step algorithm walkthrough. a comparison of ais to other well-knownalgorithms and areas for future work will round this keynote off. it should benoted that as ais is still a young and evolving field, there is not yet a fixedalgorithm template and hence actual implementations might differ somewhat fromthe examples given here.

cs.ne cs.ai

nan

['aickelin']

https://arxiv.org/abs/0801.4314

mimo networks: the effects of interference

0802.0738

multiple-input/multiple-output (mimo) systems promise enormous capacityincrease and are being considered as one of the key technologies for futurewireless networks. however, the decrease in capacity due to the presence ofinterferers in mimo networks is not well understood. in this paper, we developan analytical framework to characterize the capacity of mimo communicationsystems in the presence of multiple mimo co-channel interferers and noise. weconsider the situation in which transmitters have no information about thechannel and all links undergo rayleigh fading. we first generalize the knowndeterminant representation of hypergeometric functions with matrix arguments tothe case when the argument matrices have eigenvalues of arbitrary multiplicity.this enables the derivation of the distribution of the eigenvalues of gaussianquadratic forms and wishart matrices with arbitrary correlation, withapplication to both single user and multiuser mimo systems. in particular, wederive the ergodic mutual information for mimo systems in the presence ofmultiple mimo interferers. our analysis is valid for any number of interferers,each with arbitrary number of antennas having possibly unequal power levels.this framework, therefore, accommodates the study of distributed mimo systemsand accounts for different positions of the mimo interferers.

cs.it math.it

10.1109/tit.2009.2034810

['chiani', 'win', 'shin']

https://arxiv.org/abs/0802.0738

doubly-generalized ldpc codes: stability bound over the bec

0802.0823

the iterative decoding threshold of low-density parity-check (ldpc) codesover the binary erasure channel (bec) fulfills an upper bound depending only onthe variable and check nodes with minimum distance 2. this bound is aconsequence of the stability condition, and is here referred to as stabilitybound. in this paper, a stability bound over the bec is developed fordoubly-generalized ldpc codes, where the variable and the check nodes can begeneric linear block codes, assuming maximum a posteriori erasure correction ateach node. it is proved that in this generalized context as well the bounddepends only on the variable and check component codes with minimum distance 2.a condition is also developed, namely the derivative matching condition, underwhich the bound is achieved with equality.

cs.it math.it

10.1109/tit.2008.2011446

['paolini', 'fossorier', 'chiani']

https://arxiv.org/abs/0802.0823

a connection between palindromic and factor complexity using return words

0802.1332

in this paper we prove that for any infinite word w whose set of factors isclosed under reversal, the following conditions are equivalent: (i) all complete returns to palindromes are palindromes; (ii) p(n) + p(n+1) = c(n+1) - c(n) + 2 for all n, where p (resp. c) denotesthe palindromic complexity (resp. factor complexity) function of w, whichcounts the number of distinct palindromic factors (resp. factors) of eachlength in w.

math.co cs.dm

10.1016/j.aam.2008.03.005

['bucci', 'de luca', 'glen', 'zamboni']

https://arxiv.org/abs/0802.1332

new type stirling like numbers - an email style letter

0802.1382

the notion of the fibonacci cobweb poset from [1] has been naturally extendedto any admissible sequence $f$ in [2] where it was also recognized that thecelebrated prefab notion of bender and goldman [3] - (see also [4,5]) - admitssuch an extension so as to encompass the new type combinatorial objects from[2] as leading examples. recently the present author had introduced also [6]two natural partial orders in there: one $\leq$ in grading-natural subsets ofcobweb`s prefabs sets [2] and in the second proposal one endows the set sums ofthe so called "prefabiants" with such another partial order that one arrives atbell-like numbers including fibonacci triad sequences introduced by the presentauthor in [7]. here we quote the basic observations concerning the new typestirling like numbers as they appear in [6]. for more on notation, stirlinglike numbers of the first kind and for proofs - see [6].

math.co cs.dm

nan

['kwasniewski']

https://arxiv.org/abs/0802.1382

exploiting problem structure in a genetic algorithm approach to a nurse rostering problem

0802.2001

there is considerable interest in the use of genetic algorithms to solveproblems arising in the areas of scheduling and timetabling. however, theclassical genetic algorithm paradigm is not well equipped to handle theconflict between objectives and constraints that typically occurs in suchproblems. in order to overcome this, successful implementations frequently makeuse of problem specific knowledge. this paper is concerned with the developmentof a ga for a nurse rostering problem at a major uk hospital. the structure ofthe constraints is used as the basis for a co-evolutionary strategy usingco-operating sub-populations. problem specific knowledge is also used to definea system of incentives and disincentives, and a complementary mutationoperator. empirical results based on 52 weeks of live data show how thesefeatures are able to improve an unsuccessful canonical ga to the point where itis able to provide a practical solution to the problem

cs.ne cs.ce

10.1002/(sici)1099-1425(200005/06)3:3<139::aid-jos41>3.0.co;2-2

['aickelin', 'dowsland']

https://arxiv.org/abs/0802.2001

well-centered triangulation

0802.2108

meshes composed of well-centered simplices have nice orthogonal dual meshes(the dual voronoi diagram). this is useful for certain numerical algorithmsthat prefer such primal-dual mesh pairs. we prove that well-centered meshesalso have optimality properties and relationships to delaunay and minmax angletriangulations. we present an iterative algorithm that seeks to transform agiven triangulation in two or three dimensions into a well-centered one byminimizing a cost function and moving the interior vertices while keeping themesh connectivity and boundary vertices fixed. the cost function is a directresult of a new characterization of well-centeredness in arbitrary dimensionsthat we present. ours is the first optimization-based heuristic forwell-centeredness, and the first one that applies in both two and threedimensions. we show the results of applying our algorithm to small and largetwo-dimensional meshes, some with a complex boundary, and obtain awell-centered tetrahedralization of the cube. we also show numerical evidencethat our algorithm preserves gradation and that it improves the maximum andminimum angles of acute triangulations created by the best known previousmethod.

cs.cg cs.na

10.1137/090748214

['vanderzee', 'hirani', 'guoy', 'ramos']

https://arxiv.org/abs/0802.2108

essential variables and positions in terms

0802.2385

the paper deals with $\sigma-$composition of terms, which allows us to extendthe derivation rules in formal deduction of identities. the concept of essential variables and essential positions of terms withrespect to a set of identities is a key step in the simplification of theprocess of formal deduction. $\sigma-$composition of terms is defined asreplacement between $\sigma$-equal terms. this composition induces $\sigmar-$deductively closed sets of identities. in analogy to balanced identities weintroduce and investigate $\sigma-$balanced identities for a given set ofidentities $\sigma$.

math.gm cs.it math.it

nan

['shtrakov']

https://arxiv.org/abs/0802.2385

fixed point and aperiodic tilings

0802.2432

an aperiodic tile set was first constructed by r.berger while proving theundecidability of the domino problem. it turned out that aperiodic tile setsappear in many topics ranging from logic (the entscheidungsproblem) to physics(quasicrystals) we present a new construction of an aperiodic tile set that isbased on kleene's fixed-point construction instead of geometric arguments. thisconstruction is similar to j. von neumann self-reproducing automata; similarideas were also used by p. gacs in the context of error-correctingcomputations. the flexibility of this construction allows us to construct a"robust" aperiodic tile set that does not have periodic (or close to periodic)tilings even if we allow some (sparse enough) tiling errors. this property wasnot known for any of the existing aperiodic tile sets.

cs.cc cs.dm

10.1007/978-3-540-85780-8_22

['durand', 'romashchenko', 'shen']

https://arxiv.org/abs/0802.2432

capacity of general discrete noiseless channels

0802.2451

this paper concerns the capacity of the discrete noiseless channel introducedby shannon. a sufficient condition is given for the capacity to bewell-defined. for a general discrete noiseless channel allowing non-integervalued symbol weights, it is shown that the capacity--if well-defined--can bedetermined from the radius of convergence of its generating function, from thesmallest positive pole of its generating function, or from the rightmost realsingularity of its complex generating function. a generalisation is given forpringsheim's theorem and for the exponential growth formula to generatingfunctions of combinatorial structures with non-integer valued symbol weights.

cs.it math.it

nan

['bocherer', 'junior', 'pimentel']

https://arxiv.org/abs/0802.2451

pure exploration for multi-armed bandit problems

0802.2655

we consider the framework of stochastic multi-armed bandit problems and studythe possibilities and limitations of forecasters that perform an on-lineexploration of the arms. these forecasters are assessed in terms of theirsimple regret, a regret notion that captures the fact that exploration is onlyconstrained by the number of available rounds (not necessarily known inadvance), in contrast to the case when the cumulative regret is considered andwhen exploitation needs to be performed at the same time. we believe that thisperformance criterion is suited to situations when the cost of pulling an armis expressed in terms of resources rather than rewards. we discuss the linksbetween the simple and the cumulative regret. one of the main results in thecase of a finite number of arms is a general lower bound on the simple regretof a forecaster in terms of its cumulative regret: the smaller the latter, thelarger the former. keeping this result in mind, we then exhibit upper bounds onthe simple regret of some forecasters. the paper ends with a study devoted tocontinuous-armed bandit problems; we show that the simple regret can beminimized with respect to a family of probability distributions if and only ifthe cumulative regret can be minimized for it. based on this equivalence, weare able to prove that the separable metric spaces are exactly the metricspaces on which these regrets can be minimized with respect to the family ofall probability distributions with continuous mean-payoff functions.

math.st cs.lg stat.th

nan

['bubeck', 'munos', 'stoltz']

https://arxiv.org/abs/0802.2655

wavelet and curvelet moments for image classification: application to aggregate mixture grading

0802.3528

we show the potential for classifying images of mixtures of aggregate, basedthemselves on varying, albeit well-defined, sizes and shapes, in order toprovide a far more effective approach compared to the classification ofindividual sizes and shapes. while a dominant (additive, stationary) gaussiannoise component in image data will ensure that wavelet coefficients are ofgaussian distribution, long tailed distributions (symptomatic, for example, ofextreme values) may well hold in practice for wavelet coefficients. energy (2ndorder moment) has often been used for image characterization for imagecontent-based retrieval, and higher order moments may be important also, notleast for capturing long tailed distributional behavior. in this work, weassess 2nd, 3rd and 4th order moments of multiresolution transform -- waveletand curvelet transform -- coefficients as features. as analysis methodology,taking account of image types, multiresolution transforms, and moments ofcoefficients in the scales or bands, we use correspondence analysis as well ask-nearest neighbors supervised classification.

cs.cv

nan

['murtagh', 'starck']

https://arxiv.org/abs/0802.3528

are complex systems hard to evolve?

0802.3875

evolutionary complexity is here measured by the number of trials/evaluationsneeded for evolving a logical gate in a non-linear medium. behaviouralcomplexity of the gates evolved is characterised in terms of cellular automatabehaviour. we speculate that hierarchies of behavioural and evolutionarycomplexities are isomorphic up to some degree, subject to substrate specificityof evolution and the spectrum of evolution parameters.

cs.ne

10.1002/cplx.20269

['adamatzky', 'bull']

https://arxiv.org/abs/0802.3875

rich, sturmian, and trapezoidal words

0802.3885

in this paper we explore various interconnections between rich words,sturmian words, and trapezoidal words. rich words, first introduced inarxiv:0801.1656 by the second and third authors together with j. justin and s.widmer, constitute a new class of finite and infinite words characterized byhaving the maximal number of palindromic factors. every finite sturmian word isrich, but not conversely. trapezoidal words were first introduced by the firstauthor in studying the behavior of the subword complexity of finite sturmianwords. unfortunately this property does not characterize finite sturmian words.in this note we show that the only trapezoidal palindromes are sturmian. moregenerally we show that sturmian palindromes can be characterized either interms of their subword complexity (the trapezoidal property) or in terms oftheir palindromic complexity. we also obtain a similar characterization of richpalindromes in terms of a relation between palindromic complexity and subwordcomplexity.

math.co cs.dm

10.1016/j.tcs.2008.06.009

['de luca', 'glen', 'zamboni']

https://arxiv.org/abs/0802.3885

directive words of episturmian words: equivalences and normalization

0802.3888

episturmian morphisms constitute a powerful tool to study episturmian words.indeed, any episturmian word can be infinitely decomposed over the set of pureepisturmian morphisms. thus, an episturmian word can be defined by one of itsmorphic decompositions or, equivalently, by a certain directive word. here wecharacterize pairs of words directing a common episturmian word. we alsopropose a way to uniquely define any episturmian word through a normalizationof its directive words. as a consequence of these results, we characterizeepisturmian words having a unique directive word.

cs.dm math.co

10.1051/ita:2008029

['glen', 'levé', 'richomme']

https://arxiv.org/abs/0802.3888

sensing danger: innate immunology for intrusion detection

0802.4002

the immune system provides an ideal metaphor for anomaly detection in generaland computer security in particular. based on this idea, artificial immunesystems have been used for a number of years for intrusion detection,unfortunately so far with little success. however, these previous systems werelargely based on immunological theory from the 1970s and 1980s and over thelast decade our understanding of immunological processes has vastly improved.in this paper we present two new immune inspired algorithms based on the latestimmunological discoveries, such as the behaviour of dendritic cells. theresultant algorithms are applied to real world intrusion problems and showencouraging results. overall, we believe there is a bright future for thesenext generation artificial immune algorithms.

cs.ne cs.cr

10.1016/j.istr.2007.10.003

['aickelin', 'greensmith']

https://arxiv.org/abs/0802.4002

safety alternating automata on data words

0802.4237

a data word is a sequence of pairs of a letter from a finite alphabet and anelement from an infinite set, where the latter can only be compared forequality. safety one-way alternating automata with one register on infinitedata words are considered, their nonemptiness is shown expspace-complete, andtheir inclusion decidable but not primitive recursive. the same complexitybounds are obtained for satisfiability and refinement, respectively, for thesafety fragment of linear temporal logic with freeze quantification. droppingthe safety restriction, adding past temporal operators, or adding one moreregister, each causes undecidability.

cs.lo

nan

['lazic']

https://arxiv.org/abs/0802.4237

polynomial time algorithms for bi-criteria, multi-objective and ratio problems in clustering and imaging. part i: normalized cut and ratio regions

0803.0146

partitioning and grouping of similar objects plays a fundamental role inimage segmentation and in clustering problems. in such problems a typical goalis to group together similar objects, or pixels in the case of imageprocessing. at the same time another goal is to have each group distinctlydissimilar from the rest and possibly to have the group size fairly large.these goals are often combined as a ratio optimization problem. one example ofsuch problem is the normalized cut problem, another is the ratio regionsproblem. we devise here the first polynomial time algorithms solving theseproblems optimally. the algorithms are efficient and combinatorial. thiscontrasts with the heuristic approaches used in the image segmentationliterature that formulate those problems as nonlinear optimization problems,which are then relaxed and solved with spectral techniques in real numbers.these approaches not only fail to deliver an optimal solution, but they arealso computationally expensive. the algorithms presented here use as asubroutine a minimum $s,t-cut procedure on a related graph which is ofpolynomial size. the output consists of the optimal solution to the respectiveratio problem, as well as a sequence of nested solution with respect to anyrelative weighting of the objectives of the numerator and denominator. an extension of the results here to bi-criteria and multi-criteria objectivefunctions is presented in part ii.

cs.cv cs.dm

nan

['hochbaum']

https://arxiv.org/abs/0803.0146

stream sampling for variance-optimal estimation of subset sums

0803.0473

from a high volume stream of weighted items, we want to maintain a genericsample of a certain limited size $k$ that we can later use to estimate thetotal weight of arbitrary subsets. this is the classic context of on-linereservoir sampling, thinking of the generic sample as a reservoir. we presentan efficient reservoir sampling scheme, $\varoptk$, that dominates all previousschemes in terms of estimation quality. $\varoptk$ provides {\em variance optimal unbiased estimation of subsetsums}. more precisely, if we have seen $n$ items of the stream, then for {\emany} subset size $m$, our scheme based on $k$ samples minimizes the averagevariance over all subsets of size $m$. in fact, the optimality is against anyoff-line scheme with $k$ samples tailored for the concrete set of items seen.in addition to optimal average variance, our scheme provides tighter worst-casebounds on the variance of {\em particular} subsets than previously possible. itis efficient, handling each new item of the stream in $o(\log k)$ time.finally, it is particularly well suited for combination of samples fromdifferent streams in a distributed setting.

cs.ds

nan

['cohen', 'duffield', 'kaplan', 'lund', 'thorup']

https://arxiv.org/abs/0803.0473