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|---|---|---|---|---|
1011.2022
|
Observation of exchange Coulomb interactions in the quantum Hall state at nu=3
|
Coulomb exchange interactions of electrons in the nu=3 quantum Hall state are determined from two inter-Landau level spin-flip excitations measured by resonant inelastic light scattering. The two coupled collective excitations are linked to inter-Landau level spin-flip transitions arising from the N=0 and N=1 Landau levels. The strong repulsion between the two spin-flip modes in the long-wave limit is clearly manifested in spectra displaying Coulomb exchange contributions that are comparable to the exchange energy for the quantum Hall state at nu=1. Theoretical calculations within the Hartree-Fock approximation are in a good agreement with measured energies of spin-flip collective excitations.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2010-11-09T10:10:59Z |
gr-qc/0107059
|
The Graviton Production in a Hot Homogeneous Isotropic Universe
|
It is shown that the RTG predicts an opportunity of the intensive production of gravitons at the early stage of evolution of the homogeneous isotropic Universe. A hypothesis is suggested that the produced gas of gravitons could be just the ``dark matter'' which presently manifests itself as a ``missing mass'' in our Universe.
|
[
"Physics Archive->gr-qc"
] | 2001-07-17T08:47:59Z |
1508.07225
|
Calibration of the Cherenkov Telescope Array
|
The construction of the Cherenkov Telescope Array is expected to start soon. We will present the baseline methods and their extensions currently foreseen to calibrate the observatory. These are bound to achieve the strong requirements on allowed systematic uncertainties for the reconstructed gamma-ray energy and flux scales, as well as on the pointing resolution, and on the overall duty cycle of the observatory. Onsite calibration activities are designed to include a robust and efficient calibration of the telescope cameras, and various methods and instruments to achieve calibration of the overall optical throughput of each telescope, leading to both inter-telescope calibration and an absolute calibration of the entire observatory. One important aspect of the onsite calibration is a correct understanding of the atmosphere above the telescopes, which constitutes the calorimeter of this detection technique. It is planned to be constantly monitored with state-of-the-art instruments to obtain a full molecular and aerosol profile up to the stratosphere. In order to guarantee the best use of the observation time, in terms of usable data, an intelligent scheduling system is required, which gives preference to those sources and observation programs that can cope with the given atmospheric conditions, especially if the sky is partially covered by clouds, or slightly contaminated by dust. Ceilometers in combination with all-sky-cameras are plannned to provide the observatory with a fast, online and full-sky knowledge of the expected conditions for each pointing direction. For a precise characterization of the adopted observing direction, wide-field optical telescopes and Raman Lidars are planned to provide information about the height-resolved and wavelength-dependent atmospheric extinction, throughout the field-of-view of the cameras.
|
[
"Physics Archive->astro-ph->astro-ph.IM"
] | 2015-08-28T14:22:28Z |
hep-th/0310200
|
Stochastic inflation on the brane
|
Chaotic inflation on the brane is considered in the context of stochastic inflation. It is found that there is a regime in which eternal inflation on the brane takes place. The corresponding probability distributions are found in certain cases. The stationary probability distribution over a comoving volume and the creation probability of a de Sitter braneworld yield the same exponential behaviour. Finally, nonperturbative effects are briefly discussed.
|
[
"Physics Archive->astro-ph",
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2003-10-21T12:54:09Z |
2307.10282
|
The manifestly gauge-invariant spectrum of the Minimal Supersymmetric Standard Model
|
Formal field theory requires, even in the presence of a Brout-Englert-Higgs effect, to maintain manifest non-perturbative gauge invariance. The Fr\"ohlich-Morchio-Strocchi mechanism allows nonetheless an augmented perturbative treatment. We perform such an augmented tree-level analysis for the minimal supersymmetric standard model. We find that, as for the standard model, corrections to standard perturbation theory are only sub-leading.
|
[
"Physics Archive->hep->hep-ph"
] | 2023-07-18T11:01:32Z |
quant-ph/0308115
|
Measuring Controlled-NOT and two-qubit gate operation
|
Accurate characterisation of two-qubit gates will be critical for any realisation of quantum computation. We discuss a range of measurements aimed at characterising a two-qubit gate, specifically the CNOT gate. These measurements are architecture-independent, and range from simple truth table measurements, to single figure measures such as the fringe visibility, parity, fidelity, and entanglement witnesses, through to whole-state and whole-gate measures achieved respectively via quantum state and process tomography. In doing so, we examine critical differences between classical and quantum gate operation.
|
[
"Physics Archive->quant-ph"
] | 2003-08-22T01:22:52Z |
2307.15237
|
Weather Sensitive High Spatio-Temporal Resolution Transportation Electric Load Profiles For Multiple Decarbonization Pathways
|
Electrification of transport compounded with climate change will transform hourly load profiles and their response to weather. Power system operators and EV charging stakeholders require such high-resolution load profiles for their planning studies. However, such profiles accounting whole transportation sector is lacking. Thus, we present a novel approach to generating hourly electric load profiles that considers charging strategies and evolving sensitivity to temperature. The approach consists of downscaling annual state-scale sectoral load projections from the multi-sectoral Global Change Analysis Model (GCAM) into hourly electric load profiles leveraging high resolution climate and population datasets. Profiles are developed and evaluated at the Balancing Authority scale, with a 5-year increment until 2050 over the Western U.S. Interconnect for multiple decarbonization pathways and climate scenarios. The datasets are readily available for production cost model analysis. Our open source approach is transferable to other regions.
|
[
"Computer Science Archive->cs.SY",
"Electrical Engineering and Systems Science Archive->eess.SY"
] | 2023-07-28T00:03:35Z |
1909.08977
|
SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE
|
We present SCUBA-2 850-$\mu$m observations of 13 candidate starbursting protoclusters selected using Planck and Herschel data. The cumulative number counts of the 850-$\mu$m sources in 9/13 of these candidate protoclusters show significant overdensities compared to the field, with the probability $<$10$^{-2}$ assuming the sources are randomly distributed in the sky. Using the 250-, 350-, 500- and 850-$\mu$m flux densities, we estimate the photometric redshifts of individual SCUBA-2 sources by fitting spectral energy distribution (SED) templates with an MCMC method. The photometric redshift distribution, peaking at $2<z<3$, is consistent with that of known $z>2$ protoclusters and the peak of the cosmic star-formation rate density (SFRD). We find that the 850-$\mu$m sources in our candidate protoclusters have infrared luminosities of $L_{\mathrm{IR}}\gtrsim$10$^{12}L_{\odot}$ and star-formation rates of SFR=(500-1,500)$M_{\odot}$yr$^{-1}$. By comparing with results in the literature considering only Herschel photometry, we conclude that our 13 candidate protoclusters can be categorised into four groups: six of them being high-redshift starbursting protoclusters, one being a lower-redshift cluster/protocluster, three being protoclusters that contain lensed DSFG(s) or are rich in 850-$\mu$m sources, and three regions without significant Herschel or SCUBA-2 source overdensities. The total SFRs of the candidate protoclusters are found to be comparable or higher than those of known protoclusters, suggesting our sample contains some of the most extreme protocluster population. We infer that cross-matching Planck and Herschel data is a robust method for selecting candidate protoclusters with overdensities of 850-$\mu$m sources.
|
[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2019-09-19T13:26:27Z |
1305.1573
|
Multi-Scale Codes in the Nervous System: The Problem of Noise Correlations and the Ambiguity of Periodic Scales
|
Encoding information about continuous variables using noisy computational units is a challenge; nonetheless, asymptotic theory shows that combining multiple periodic scales for coding can be highly precise despite the corrupting influence of noise (Mathis et al., Phys. Rev. Lett. 2012). Indeed, cortex seems to use such stochastic multi-scale periodic `grid codes' to represent position accurately. We show here how these codes can be read out without taking the asymptotic limit; even on short time scales, the precision of neuronal grid codes scales exponentially in the number N of neurons. Does this finding also hold for neurons that are not statistically independent? To assess the extent to which biological grid codes are subject to statistical dependencies, we analyze the noise correlations between pairs of grid code neurons in behaving rodents. We find that if the grids of the two neurons align and have the same length scale, the noise correlations between the neurons can reach 0.8. For increasing mismatches between the grids of the two neurons, the noise correlations fall rapidly. Incorporating such correlations into a population coding model reveals that the correlations lessen the resolution, but the exponential scaling of resolution with N is unaffected.
|
[
"Quantitative Biology Archive->q-bio.NC"
] | 2013-05-07T16:24:41Z |
0912.4467
|
Cd-doping effects in Ce2MIn8 (M = Rh and Ir) heavy fermion compounds
|
Low temperature magnetic properties of Cd-doped Ce2MIn8 (M = Rh and Ir) single crystals are investigated. Experiments of temperature dependent magnetic susceptibility, heat capacity and electrical resistivity measurements revealed that Cd-doping enhances the antiferromagnetic (AFM) ordering temperature from TN = 2.8 K (x = 0) to TN = 4.8 K (x = 0.21) for Ce2RhIn8-xCdx and induces long range AFM ordering with TN = 3.8 K (x = 0.21) for Ce2IrIn8-xCdx. Additionally, X-ray and neutron magnetic scattering studies showed that Cd-doped samples present below TN a commensurate antiferromagnetic structure with a propagation vector (1/2,1/2,0). The resolved magnetic structures for both compounds indicate that the Cd-doping tends to rotate the direction of the ordered magnetic moments toward the ab-plane. This result suggests that the Cd-doping affects the Ce3+ ground state single ion anisotropy modifying the crystalline electrical field (CEF) parameters at the Ce3+ site. Indications of CEF evolution induced by Cd-doping were also found in the electrical resistivity measurements. Comparisons between our results and the general effects of Cd-doping on the related compounds CeMIn5 (M = Co, Rh and Ir) confirms the claims that the Cd-doping induced electronic tuning is the main effect favoring AFM ordering in these compounds.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2009-12-22T17:42:41Z |
1209.0161
|
On Hexagonal Structures in Higher Dimensional Theories
|
We analyze the geometrical background under which many Lie groups relevant to particle physics are endowed with a (possibly multiple) hexagonal structure. There are several groups appearing, either as special holonomy groups on the compactification process from higher dimensions, or as dynamical string gauge groups; this includes groups like SU(2),SU(3), G_2, Spin(7), SO(8) as well as E_8 and SO(32). We emphasize also the relation of these hexagonal structures with the octonion division algebra, as we expect as well eventually some role for octonions in the interpretation of symmetries in High Energy Physics.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->hep->hep-th",
"Physics Archive->math-ph"
] | 2012-09-02T09:40:15Z |
1802.07256
|
Hampering G\"{o}rtler vortices via optimal control in the framework of nonlinear boundary region equations
|
The control of stream-wise vortices in high Reynolds number boundary layer flows often aims at reducing the vortex energy as a means of mitigating the growth of secondary instabilities, which eventually delay the transition from laminar to turbulent flow. In this paper, we aim at utilizing such an energy reduction strategy using optimal control theory to limit the growth of G\"{o}rtler vortices developing in an incompressible laminar boundary layer flow over a concave wall, and excited by a row of roughness elements with span-wise separation in the same order of magnitude as the boundary layer thickness. Commensurate with control theory formalism, we transform a constrained optimization problem into an unconstrained one by applying the method of Lagrange multipliers. A high Reynolds number asymptotic framework is utilized, wherein the Navier-Stokes equations are reduced to the boundary region equations (BRE), in which wall deformations enter the problem through an appropriate Prandtl transformation. In the optimal control strategy, the wall displacement or the wall transpiration velocity serve as control variables, while the cost functional is defined in terms of the wall shear stress. Our numerical results indicate, among other things, that the optimal control algorithm is very effective in reducing the amplitude of the G\"{o}rtler vortices, especially for the control based on wall displacement.
|
[
"Physics Archive->physics->physics.flu-dyn"
] | 2018-02-19T21:22:43Z |
1309.3564
|
Lepton flavor violation in the Higgs sector and the role of hadronic tau-lepton decays
|
It has been pointed out recently that current low-energy constraints still allow for sizable flavor-changing decay rates of the 125 GeV boson into leptons, h -> tau ell (ell= e, mu). In this work we discuss the role of hadronic tau-lepton decays in probing lepton flavor violating couplings in the Higgs sector. At low energy, the effective Higgs coupling to gluons induced by heavy quarks contributes to hadronic tau decays, establishing a direct connection with the relevant process at the LHC, pp (gg)-> h -> tau ell. Semileptonic transitions like tau -> ell pi pi are sensitive to flavor-changing scalar couplings while decays such as tau -> ell eta(') probe pseudoscalar couplings, thus providing a useful low-energy handle to disentangle possible Higgs flavor violating signals at the LHC. As part of our analysis, we provide an appropriate description of all the relevant hadronic matrix elements needed to describe Higgs-mediated tau -> ell pi pi transitions, improving over previous treatments in the literature.
|
[
"Physics Archive->hep->hep-ph"
] | 2013-09-13T20:00:05Z |
1506.00741
|
An Efficient Inexact Symmetric Gauss-Seidel Based Majorized ADMM for High-Dimensional Convex Composite Conic Programming
|
In this paper, we propose an inexact multi-block ADMM-type first-order method for solving a class of high-dimensional convex composite conic optimization problems to moderate accuracy. The design of this method combines an inexact 2-block majorized semi-proximal ADMM and the recent advances in the inexact symmetric Gauss-Seidel (sGS) technique for solving a multi-block convex composite quadratic programming whose objective contains a nonsmooth term involving only the first block-variable. One distinctive feature of our proposed method (the sGS-imsPADMM) is that it only needs one cycle of an inexact sGS method, instead of an unknown number of cycles, to solve each of the subproblems involved.With some simple and implementable error tolerance criteria, the cost for solving the subproblems can be greatly reduced, and many steps in the forward sweep of each sGS cycle can often be skipped, which further contributes to the efficiency of the proposed method. Global convergence as well as the iteration complexity in the non-ergodic sense is established.Preliminary numerical experiments on some high-dimensional linear and convex quadratic SDP problems with a large number of linear equality and inequality constraints are also provided. The results show that for the vast majority of the tested problems, the sGS-imsPADMM is 2 to 3 times faster than the directly extended multi-block ADMM with the aggressive step-length of 1.618, which is currently the benchmark among first-order methods for solving multi-block linear and quadratic SDP problems though its convergence is not guaranteed.
|
[
"Mathematics Archive->math.OC"
] | 2015-06-02T03:35:34Z |
2201.03161
|
Holographic Einstein Ring of a Charged AdS Black Hole
|
Taking into account that the real quantum materials are engineered generically at a finite chemical potential, we investigate the Einstein ring structure for the lensed response of the complex scalar field as a probe wave on the charged AdS black hole in the context of AdS/CFT. On the one hand, we find that the resulting Einstein ring radius has no variation with the chemical potential, which is similar to the behavior for the weakly interacting quantum system. On the other hand, not only can such a ring exist well within the screen, but also the temperature dependence of its radius exhibits a distinct feature in the sense that it displays an appreciable increase at low temperatures while the ring keeps unchanged right at the edge of the screen for the weakly interacting system. Note that such a Einstein ring emerges in the large frequencies and can be well captured by the photon sphere away from the black hole horizon in the geometric optics approximation, thus such a distinct feature may be regarded as a universal behavior associated with the high energy modes of the strongly coupled system which has a gravity dual.
|
[
"Physics Archive->hep->hep-th"
] | 2022-01-10T05:02:16Z |
2205.11925
|
Robust 3D Object Detection in Cold Weather Conditions
|
Adverse weather conditions can negatively affect LiDAR-based object detectors. In this work, we focus on the phenomenon of vehicle gas exhaust condensation in cold weather conditions. This everyday effect can influence the estimation of object sizes, orientations and introduce ghost object detections, compromising the reliability of the state of the art object detectors. We propose to solve this problem by using data augmentation and a novel training loss term. To effectively train deep neural networks, a large set of labeled data is needed. In case of adverse weather conditions, this process can be extremely laborious and expensive. We address this issue in two steps: First, we present a gas exhaust data generation method based on 3D surface reconstruction and sampling which allows us to generate large sets of gas exhaust clouds from a small pool of labeled data. Second, we introduce a point cloud augmentation process that can be used to add gas exhaust to datasets recorded in good weather conditions. Finally, we formulate a new training loss term that leverages the augmented point cloud to increase object detection robustness by penalizing predictions that include noise. In contrast to other works, our method can be used with both grid-based and point-based detectors. Moreover, since our approach does not require any network architecture changes, inference times remain unchanged. Experimental results on real data show that our proposed method greatly increases robustness to gas exhaust and noisy data.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.CV"
] | 2022-05-24T09:37:07Z |
astro-ph/0306014
|
Non coeval young multiple systems? On the pairing of protostars and T Tauri stars
|
We summarize here the observed properties of ``infrared companions'' to T Tauri stars and argue that their observational properties are identical to those of Class I sources. They may therefore be embedded protostars in a much earlier evolutionary phase than T Tauri stars, in which case these multiple systems are significantly non-coeval as opposed to the majority of young binary systems. They would have formed through a different mechanism than core fragmentation. The only distinction between IRCs and Class I sources is that they lie within a few tens of AU of a T Tauri star, and so they cannot be at the center of a vast optically thick envelope as is believed to be the case for protostars. We discuss whether systems with an IRC are really candidates for non-coeval multiple systems.
|
[
"Physics Archive->astro-ph"
] | 2003-05-31T20:58:24Z |
1704.06087
|
Explicit Solution and Fine Asymptotics for a Critical Growth-Fragmentation Equation
|
We give here an explicit formula for the following critical case of the growth-fragmentation equation $$\frac{\partial}{\partial t} u(t, x) + \frac{\partial}{\partial x} (gxu(t, x)) + bu(t, x) = b\alpha^2 u(t, \alpha x), \qquad u(0, x) = u\_0 (x),$$ for some constants $g > 0$, $b > 0$ and $\alpha > 1$ - the case $\alpha = 2$ being the emblematic binary fission case. We discuss the links between this formula and the asymptotic ones previously obtained in (Doumic, Escobedo, Kin. Rel. Mod., 2016), and use them to clarify how periodicity may appear asymptotically.
|
[
"Mathematics Archive->math.AP"
] | 2017-04-20T11:19:29Z |
1202.0807
|
Seesaw Scale in the Minimal Renormalizable SO(10) Grand Unification
|
Simple SO(10) Higgs models with the adjoint representation triggering the grand-unified symmetry breaking, discarded a long ago due to inherent tree-level tachyonic instabilities in the physically interesting scenarios, have been recently brought back to life by quantum effects. In this work we focus on the variant with 45_H+126_H in the Higgs sector and show that there are several regions in the parameter space of this model that can support stable unifying configurations with the B-L breaking scale as high as 10^14 GeV, well above the previous generic estimates based on the minimal survival hypothesis. This admits for a renormalizable implementation of the canonical seesaw and makes the simplest potentially realistic scenario of this kind a good candidate for a minimal SO(10) grand unification. Last, but not least, this setting is likely to be extensively testable at future large-volume facilities such as Hyper-Kamiokande.
|
[
"Physics Archive->hep->hep-ph"
] | 2012-02-03T20:03:33Z |
math/0612213
|
Cluster-Cyclic Quivers with three Vertices and the Markov Equation
|
Acyclic cluster algebras have an interpretation in terms of tilting objects in a Calabi-Yau category defined by some hereditary algebra. For a given quiver $Q$ it is thus desirable to decide if the cluster algebra defined by $Q$ is acyclic. We call $Q$ cluster-acyclic in this case, otherwise cluster-cyclic. In this note we classify the cluster-cyclic quivers with three vertices using a Diophantine equation studied by Markov.
|
[
"Mathematics Archive->math.RA",
"Mathematics Archive->math.RT"
] | 2006-12-08T11:53:03Z |
1209.2535
|
Search for high-mass resonances decaying to dilepton final states in pp collisions at a center-of-mass energy of 7 TeV with the ATLAS detector
|
The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z' gauge bosons, Randall-Sundrum gravitons, Z* bosons, techni-mesons, Kaluza-Klein Z/gamma bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9/fb in the dielectron channel and 5.0/fb in the dimuon channel. A Z' boson with Standard Model-like couplings is excluded at 95 percent confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/Mbar = 0.1 is excluded at 95 percent confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z' Models.
|
[
"Physics Archive->hep->hep-ex"
] | 2012-09-12T09:33:50Z |
1807.02996
|
Dynamic Objects Segmentation for Visual Localization in Urban Environments
|
Visual localization and mapping is a crucial capability to address many challenges in mobile robotics. It constitutes a robust, accurate and cost-effective approach for local and global pose estimation within prior maps. Yet, in highly dynamic environments, like crowded city streets, problems arise as major parts of the image can be covered by dynamic objects. Consequently, visual odometry pipelines often diverge and the localization systems malfunction as detected features are not consistent with the precomputed 3D model. In this work, we present an approach to automatically detect dynamic object instances to improve the robustness of vision-based localization and mapping in crowded environments. By training a convolutional neural network model with a combination of synthetic and real-world data, dynamic object instance masks are learned in a semi-supervised way. The real-world data can be collected with a standard camera and requires minimal further post-processing. Our experiments show that a wide range of dynamic objects can be reliably detected using the presented method. Promising performance is demonstrated on our own and also publicly available datasets, which also shows the generalization capabilities of this approach.
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.RO"
] | 2018-07-09T09:17:59Z |
0810.1250
|
Unstructured intermediate states in single protein force experiments
|
Recent single-molecule force measurements on single-domain proteins have highlighted a three-state folding mechanism where a stabilized intermediate state (I) is observed on the folding trajectory between the stretched state and the native state. Here we investigate on-lattice protein-like heteropolymer models that lead to a three-state mechanism and show that force experiments can be useful to determine the structure of I. We have mostly found that I is composed of a core stabilized by a high number of native contacts, plus an unstructured extended chain. The lifetime of I is shown to be sensitive to modifications of the protein that spoil the core. We then propose three types of modifications--point mutations, cuts, and circular permutations--aiming at: (1) confirming the presence of the core and (2) determining its location, within one amino acid accuracy, along the polypeptide chain. We also propose force jump protocols aiming to probe the on/off-pathway nature of I.
|
[
"Physics Archive->physics->physics.bio-ph"
] | 2008-10-07T17:35:56Z |
1902.06578
|
Effects and side-effects of plasmonic photothermal therapy in brain tissue
|
Heat generated from plasmonic nanoparticles can be utilized in plasmonic photothermal therapy. A combination of near-infrared laser and metallic nanoparticles are compelling for the treatment of brain cancer, due to their efficient light-to-heat conversion and bio-compatibility. However, one of the challenges of plasmonic photothermal therapy is to minimize the damage of the surrounding brain tissue. The adjacent tissue can be damaged as the results of either absorption of laser light, thermal conductivity, nanoparticles diffusing from the tumor, or a combination hereof. Hence, we still lack the full understanding about the light-tissue interaction and, in particular, the thermal response. We tested the temperature change in three different porcine cerebral tissues, i.e., the stem, the cerebrum, and the cerebellum, under laser treatment. We find that the different tissues have differential optical and thermal properties and confirm the enhancement of heating from adding plasmonic nanoparticles. Furthermore, we measure the loss of laser intensity through the different cerebral tissues and stress the importance of correct analysis of the local environment of a brain tumor.
|
[
"Physics Archive->physics->physics.med-ph"
] | 2019-02-18T14:08:40Z |
2310.08343
|
Bootstrapping Deconfined Quantum Tricriticality
|
The paradigmatic example of deconfined quantum criticality is the Neel-VBS phase transition. The continuum description of this transition is the $N=2$ case of the $CP^{N-1}$ model, which is a field theory of $N$ complex scalars in 3d coupled to an Abelian gauge field with $SU(N)\times U(1)$ global symmetry. Lattice studies and duality arguments suggest the global symmetry of the $CP^1$ model is enhanced to $SO(5)$. We perform a conformal bootstrap study of $SO(5)$ invariant fixed points with one relevant $SO(5)$ singlet operator, which would correspond to two relevant $SU(2)\times U(1)$ singlets, i.e. a tricritical point. We find that the bootstrap bounds are saturated by four different predictions from the large $N$ computation of monopole operator scaling dimensions, which were recently shown to be very accurate even for small $N$. This suggests that the Neel-VBS phase transition is described by this bootstrap bound, which predicts that the second relevant singlet has dimension $\approx 2.34$.
|
[
"Physics Archive->hep->hep-th"
] | 2023-10-12T14:05:55Z |
1312.2629
|
Sense, Model and Identify the Load Signatures of HVAC Systems in Metro Stations
|
The HVAC systems in subway stations are energy consuming giants, each of which may consume over 10, 000 Kilowatts per day for cooling and ventilation. To save energy for the HVAC systems, it is critically important to firstly know the "load signatures" of the HVAC system, i.e., the quantity of heat imported from the outdoor environments and by the passengers respectively in different periods of a day, which will significantly benefit the design of control policies. In this paper, we present a novel sensing and learning approach to identify the load signature of the HVAC system in the subway stations. In particular, sensors and smart meters were deployed to monitor the indoor, outdoor temperatures, and the energy consumptions of the HVAC system in real-time. The number of passengers was counted by the ticket checking system. At the same time, the cooling supply provided by the HVAC system was inferred via the energy consumption logs of the HVAC system. Since the indoor temperature variations are driven by the difference of the loads and the cooling supply, linear regression model was proposed for the load signature, whose coefficients are derived via a proposed algorithm . We collected real sensing data and energy log data from HaiDianHuangZhuang Subway station, which is in line 4 of Beijing from the duration of July 2012 to Sept. 2012. The data was used to evaluate the coefficients of the regression model. The experiment results show typical variation signatures of the loads from the passengers and from the outdoor environments respectively, which provide important contexts for smart control policies.
|
[
"Computer Science Archive->cs.SY"
] | 2013-12-10T00:11:50Z |
2002.01720
|
Dynamics of resonantly excited excitons in MoSe$_2$ and WS$_2$ single-layers monitored with four-wave mixing
|
We investigate dynamics of resonantly excited excitons in single-layers of MoSe$_2$ and WS$_2$ down to 4.5 K. To this end, we measure the delay dependence of the heterodyne four-wave mixing (FWM) amplitude induced by three, short laser pulses. This signal depends not only on the population of optically active excitons, which affects the absorption of the probe, but also on the population of optically inactive states, by interaction-induced energy shift, influencing the refractive index experienced by the probe. As such, it offers insight into density dynamics of excitons which do not directly couple to photons. Reproducing the coherent signal detected in amplitude and phase, the FWM delay dependence is modeled by a coherent superposition of several exponential decay components, with characteristic time constants from 0.1 picosecond up to 1 nanosecond. With increasing excitation intensity and/or temperature, we observe strong interference effects in the FWM field amplitude, resulting in progressively more complex and nonintuitive signal dynamics. We attribute this behaviour to increasingly populated exciton dark states, which change the FWM field phase by the relative effect on absorption and refractive index. We observe that exciton recombination occurs on a significantly longer timescale in WS$_2$ with respect to MoSe$_2$, which is attributed to the dark character of exciton ground state in the former and the bright in the latter.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2020-02-05T10:48:35Z |
math/0610293
|
Open-closed field algebras
|
We introduce the notions of open-closed field algebra and open-closed field algebra over a vertex operator algebra V. In the case that V satisfies certain finiteness and reductivity conditions, we show that an open-closed field algebra over V canonically gives an algebra over a $\C$-extension of the Swiss-cheese partial operad. We also give a tensor categorical formulation and categorical constructions of open-closed field algebras over V.
|
[
"Mathematics Archive->math.QA",
"Physics Archive->hep->hep-th"
] | 2006-10-09T16:39:59Z |
1510.07758
|
Fast Compatibility Testing for Rooted Phylogenetic Trees
|
We consider the following basic problem in phylogenetic tree construction. Let $\mathcal{P} = \{T_1, \ldots, T_k\}$ be a collection of rooted phylogenetic trees over various subsets of a set of species. The tree compatibility problem asks whether there is a tree $T$ with the following property: for each $i \in \{1, \dots, k\}$, $T_i$ can be obtained from the restriction of $T$ to the species set of $T_i$ by contracting zero or more edges. If such a tree $T$ exists, we say that $\mathcal{P}$ is compatible. We give a $\tilde{O}(M_\mathcal{P})$ algorithm for the tree compatibility problem, where $M_\mathcal{P}$ is the total number of nodes and edges in $\mathcal{P}$. Unlike previous algorithms for this problem, the running time of our method does not depend on the degrees of the nodes in the input trees. Thus, it is equally fast on highly resolved and highly unresolved trees.
|
[
"Computer Science Archive->cs.DS"
] | 2015-10-27T02:59:29Z |
1207.4596
|
The Construction of Spin Foam Vertex Amplitudes
|
Spin foam vertex amplitudes are the key ingredient of spin foam models for quantum gravity. These fall into the realm of discretized path integral, and can be seen as generalized lattice gauge theories. They can be seen as an attempt at a 4-dimensional generalization of the Ponzano-Regge model for 3d quantum gravity. We motivate and review the construction of the vertex amplitudes of recent spin foam models, giving two different and complementary perspectives of this construction. The first proceeds by extracting geometric configurations from a topological theory of the BF type, and can be seen to be in the tradition of the work of Barrett, Crane, Freidel and Krasnov. The second keeps closer contact to the structure of Loop Quantum Gravity and tries to identify an appropriate set of constraints to define a Lorentz-invariant interaction of its quanta of space. This approach is in the tradition of the work of Smolin, Markopoulous, Engle, Pereira, Rovelli and Livine.
|
[
"Physics Archive->gr-qc"
] | 2012-07-19T09:46:32Z |
1204.4391
|
Where are the Walls?
|
The reported spatial variation in the fine-structure constant at high redshift, if physical, could be due to the presence of dilatonic domains, and one or more domain walls inside our horizon. An absorption spectrum of an object in a different domain from our own would be characterized by a different value of alpha. We show that while a single wall solution is statically comparable to a dipole fit, and is a big improvement over a weighted mean (despite adding 3 parameters), a two-wall solution is a far better fit (despite adding 3 parameters over the single wall solution). We derive a simple model accounting for the two-domain wall solution. The goodness of these fits is however dependent on the extra random error which was argued to account for the large scatter in most of the data. When this error is omitted, all the above solutions are poor fits to the data. When included, the solutions that exhibit a spatial dependence agree with the data much more significantly than the Standard Model; however, the Standard Model itself is not a terrible fit to the data, having a p-value of ~ 20 %.
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th"
] | 2012-04-19T15:57:54Z |
cond-mat/0311374
|
Berezinskii-Kosterlitz-Thouless transition and BCS-Bose crossover in the two-dimensional attractive Hubbard model
|
We study the two-dimensional attractive Hubbard model using the mapping onto the half-filled repulsive Hubbard model in a uniform magnetic field coupled to the fermion spins. The low-energy effective action for charge and pairing fluctuations is obtained in the hydrodynamic regime. We recover the action of a Bose superfluid where half the fermion density is identified as the conjugate variable of the phase of the superconducting order parameter. By integrating out charge fluctuations, we obtain a phase-only action. In the zero-temperature superconducting state, this action describes a collective phase mode smoothly evolving from the Anderson-Bogoliubov mode at weak coupling to the Bogoliubov mode of a Bose superfluid at strong coupling. At finite temperature, the phase-only action can be used to extract an effective XY model and thus obtain the Berezinskii-Kosterlitz-Thouless (BKT) phase transition temperature. We also identify a renormalized classical regime of superconducting fluctuations above the BKT phase transition, and a regime of incoherent pairs at higher temperature. Special care is devoted to the nearly half-filled case where the symmetry of the order parameter is enlarged to SO(3) due to strong ${\bf q}=(\pi,\pi)$ charge fluctuations. The low-energy effective action is then an SO(3) non-linear sigma model with a (symmetry breaking) magnetic field proportional to the doping. In the strong-coupling limit, the attractive Hubbard model can be mapped onto the Heisenberg model, from which we recover the Gross-Pitaevskii equation in the low-density limit.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2003-11-17T09:39:21Z |
1310.8422
|
Recurrence statistics for the space of Interval Exchange maps and the Teichm\"uller flow on the space of translation surfaces
|
In this note we show that the transfer operator of a Rauzy-Veech-Zorich renormalization map acting on a space of quasi-H\"older functions is quasicompact and derive certain statistical recurrence properties for this map and its associated Teichm\"uller flow. We establish Borel-Cantelli lemmas, Extreme Value statistics and return time statistics for the map and flow. Previous results have established quasicompactness in H\"older or analytic function spaces, for example the work of M. Pollicott and T. Morita. The quasi-H\"older function space is particularly useful for investigating return time statistics. In particular we establish the shrinking target property for nested balls in the setting of Teichm\"uller flow. Our point of view, approach and terminology derives from the work of M. Pollicott augmented by that of M. Viana.
|
[
"Mathematics Archive->math.DS"
] | 2013-10-31T08:42:03Z |
2203.08552
|
Multilingual Pre-training with Language and Task Adaptation for Multilingual Text Style Transfer
|
We exploit the pre-trained seq2seq model mBART for multilingual text style transfer. Using machine translated data as well as gold aligned English sentences yields state-of-the-art results in the three target languages we consider. Besides, in view of the general scarcity of parallel data, we propose a modular approach for multilingual formality transfer, which consists of two training strategies that target adaptation to both language and task. Our approach achieves competitive performance without monolingual task-specific parallel data and can be applied to other style transfer tasks as well as to other languages.
|
[
"Computer Science Archive->cs.CL"
] | 2022-03-16T11:27:48Z |
1512.06687
|
Radiative Neutrino Model with Inert Triplet Scalar
|
We study a one-loop induced radiative neutrino model with an inert isospin triplet scalar field, in which we discuss current neutrino oscillation data, lepton flavor violations, muon anomalous magnetic moment, and a dark matter candidate. We show global analysis combining all the constraints, and briefly mention another possibility.
|
[
"Physics Archive->hep->hep-ph"
] | 2015-12-21T16:38:43Z |
1801.04004
|
Short arc orbit determination and imminent impactors in the Gaia era
|
Short-arc orbit determination is crucial when an asteroid is first discovered. In these cases usually the observations are so few that the differential correction procedure may not converge. We have developed an initial orbit computation method, based on the systematic ranging, an orbit determination techniques which systematically explores a raster in the topocentric range and range-rate space region inside the admissible region. We obtain a fully rigorous computation of the probability for the asteroid that could impact the Earth within few days from the discovery, without any a priori assumption. We test our method on the two past impactors 2008 TC3 and 2014 AA, on some very well known cases, and on two particular objects observed by the ESA Gaia mission.
|
[
"Physics Archive->astro-ph->astro-ph.EP"
] | 2018-01-11T22:07:14Z |
0911.2928
|
New observables in topological instantonic field theories
|
Instantonic theories are quantum field theories where all correlators are determined by integrals over the finite-dimensional space (space of generalized instantons). We consider novel geometrical observables in instantonic topological quantum mechanics that are strikingly different from standard evaluation observables. These observables allow jumps of special type of the trajectory (at the point of insertion of such observables). They do not (anti)commute with evaluation observables and raise the dimension of the space of allowed configurations, while the evaluation observables lower this dimension. We study these observables in geometric and operator formalisms. Simple examples are explicitly computed; they depend on linking of the points. The new "arbitrary jump" observables may be used to construct correlation functions computing e.g. the linking numbers of cycles, as we illustrate on Hopf fibration.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->hep->hep-th",
"Physics Archive->math-ph"
] | 2009-11-16T20:29:20Z |
2202.02443
|
Machine Learning Method for Functional Assessment of Retinal Models
|
Challenges in the field of retinal prostheses motivate the development of retinal models to accurately simulate Retinal Ganglion Cells (RGCs) responses. The goal of retinal prostheses is to enable blind individuals to solve complex, reallife visual tasks. In this paper, we introduce the functional assessment (FA) of retinal models, which describes the concept of evaluating the performance of retinal models on visual understanding tasks. We present a machine learning method for FA: we feed traditional machine learning classifiers with RGC responses generated by retinal models, to solve object and digit recognition tasks (CIFAR-10, MNIST, Fashion MNIST, Imagenette). We examined critical FA aspects, including how the performance of FA depends on the task, how to optimally feed RGC responses to the classifiers and how the number of output neurons correlates with the model's accuracy. To increase the number of output neurons, we manipulated input images - by splitting and then feeding them to the retinal model and we found that image splitting does not significantly improve the model's accuracy. We also show that differences in the structure of datasets result in largely divergent performance of the retinal model (MNIST and Fashion MNIST exceeded 80% accuracy, while CIFAR-10 and Imagenette achieved ~40%). Furthermore, retinal models which perform better in standard evaluation, i.e. more accurately predict RGC response, perform better in FA as well. However, unlike standard evaluation, FA results can be straightforwardly interpreted in the context of comparing the quality of visual perception.
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG",
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2022-02-05T00:35:38Z |
2210.05530
|
Variance-Based Sensitivity Analysis of $\Lambda$-type Quantum Memory
|
The storage and retrieval of photonic quantum states, quantum memory, is a key resource for a wide range of quantum applications. Here we investigate the sensitivity of $\Lambda$-type quantum memory to experimental fluctuations and drift. We use a variance-based approach, focusing on the effects of fluctuations and drift on memory efficiency. We consider shot-to-shot fluctuations of the memory parameters, and separately we consider longer timescale drift of the control field parameters. We find the parameters that a quantum memory is most sensitive to depend on the quantum memory protocol being employed, where the observed sensitivity agrees with physical interpretation of the protocols. We also present a general framework that is applicable to other figures of merit beyond memory efficiency. These results have practical ramifications for quantum memory experiments.
|
[
"Physics Archive->physics->physics.optics",
"Physics Archive->quant-ph"
] | 2022-10-11T15:18:24Z |
1809.09825
|
Robust Tube-based Model Predictive Control for Time-constrained Robot Navigation
|
This paper deals with the problem of time-constrained navigation of a robot modeled by uncertain nonlinear non-affine dynamics in a bounded workspace of $\mathbb{R}^n$. Initially, we provide a novel class of robust feedback controllers that drive the robot between Regions of Interest (RoI) of the workspace. The control laws consists of two parts: an on-line controller which is the outcome of a Finite Horizon Optimal Control Problem (FHOCP); and a backstepping feedback law which is tuned off-line and guarantees that the real trajectory always remains in a bounded hyper-tube centered along the nominal trajectory of the robot. The proposed controller falls within the so-called tube-based Nonlinear Model Predictive control (NMPC) methodology. Then, given a desired high-level specification for the robot in Metric Interval Temporal Logic (MITL), by utilizing the aforementioned controllers, a framework that provably guarantees the satisfaction of the formula is provided. The proposed framework can handle the rich expressiveness of MITL in both safety and reachability specifications. Finally, the proposed framework is validated by numerical simulations.
|
[
"Computer Science Archive->cs.SY",
"Mathematics Archive->math.OC"
] | 2018-09-26T06:57:59Z |
1905.08057
|
Projection factors and generalized real and complex Pythagorean theorems
|
Projection factors describe the contraction of Lebesgue measures in orthogonal projections between subspaces of a real or complex inner product space. They are connected to Grassmann's exterior algebra and the Grassmann angle between subspaces, and lead to generalized Pythagorean theorems, relating measures of subsets of real or complex subspaces and their orthogonal projections on certain families of subspaces. The complex Pythagorean theorems differ from the real ones in that the measures are not squared, and this may have important implications for quantum theory. Projection factors of the complex line of a quantum state with the eigenspaces of an observable give the corresponding quantum probabilities. The complex Pythagorean theorem for lines corresponds to the condition of unit total probability, and may provide a way to solve the probability problem of Everettian quantum mechanics.
|
[
"Mathematics Archive->math.GM"
] | 2019-05-16T19:15:24Z |
2302.00157
|
Eigenstate Thermalization Hypothesis for Generalized Wigner Matrices
|
In this paper, we extend results of Eigenvector Thermalization to the case of generalized Wigner matrices. Analytically, the central quantity of interest here are multiresolvent traces, such as $\Lambda_A:= \frac{1}{N} \text{Tr }{ GAGA}$. In the case of Wigner matrices, as in \cite{cipolloni-erdos-schroder-2021}, one can form a self-consistent equation for a single $\Lambda_A$. There are multiple difficulties extending this logic to the case of general covariances. The correlation structure prevents us from deriving a self-consistent equation for a single matrix $A$; this is due to the introduction of new terms that are quite distinct from the form of $\Lambda_A$. We find a way around this by carefully splitting these new terms and writing them as sums of $\Lambda_B$, for matrices $B$ obtained by modifying $A$ using the covariance matrix. The result is a system of self-consistent equations relating families of deterministic matrices. Our main effort in this work is to derive and analyze this system of self-consistent equations.
|
[
"Mathematics Archive->math.MP",
"Mathematics Archive->math.PR",
"Physics Archive->math-ph"
] | 2023-02-01T00:35:21Z |
2003.12802
|
Extension of elementary $p$-groups and its application in classification of groups of prime exponent
|
Let $p$ be a prime number and $\mathbb{Z}_p=\mathbb{Z}/p\mathbb{Z}$. We study finite groups with abelian derived subgroup and exponent $p$ in terms of group extension data and their matrix presentations. We show a one-to-one correspondence between the following two sets: (i) the isoclasses of class 2 groups of exponent $p$ and order $p^{m+n}$ and with derived subgroup $\mathbb{Z}_p^n$, and (ii) the set $\text{Gr}(n,\text{AS}_m(\mathbb{Z}_p))/\text{GL}_m(\mathbb{Z}_p)$ of orbits of $\text{Gr}(n,\text{AS}_m(\mathbb{Z}_p))$ under the congruence action by $\text{GL}_m(\mathbb{Z}_p)$, where $\text{Gr}(n,\text{AS}_m(\mathbb{Z}_p))$ is the set of $n$-dimensional subspaces of anti-symmetric matrices of order $m$ over $\mathbb{Z}_p$. We give a description of the orbit spaces $\text{Gr}(2, \text{AS}_m(\mathbb{Z}_p))/\text{GL}_m(\mathbb{Z}_p)$ for all $m$ and $p$ by applying the theory of pencils of anti-symmetric matrices. Based on this, we show complete sets of representatives of orbits of $\text{Gr}(3,\text{AS}_4(\mathbb{Z}_3))/\text{GL}_4(\mathbb{Z}_3)$, $\text{Gr}(4, \text{AS}_4(\mathbb{Z}_3))/\text{GL}_4(\mathbb{Z}_3)$ and $\text{Gr}(3, \text{AS}_5(\mathbb{Z}_3))/\text{GL}_5(\mathbb{Z}_3)$. As a consequence, we obtain a classification of corresponding class 2 groups of exponent $p$. In particular, we recover the classification of groups with exponent 3 and order $\le 3^8$.
|
[
"Mathematics Archive->math.GR"
] | 2020-03-28T14:52:10Z |
2305.14046
|
Towards Automated Security Analysis of Smart Contracts based on Execution Property Graph
|
Identifying and mitigating vulnerabilities in smart contracts is crucial, especially considering the rapid growth and increasing complexity of Decentralized Finance (DeFi) platforms. To address the challenges associated with securing these contracts, we introduce a versatile dynamic analysis framework specifically designed for the Ethereum Virtual Machine (EVM). This comprehensive framework focuses on tracking contract executions, capturing valuable runtime information, while introducing and employing the Execution Property Graph (EPG) to propose a unique graph traversal technique that swiftly detects potential smart contract attacks. Our approach showcases its efficacy with rapid average graph traversal time per transaction and high true positive rates. The successful identification of a zero-day vulnerability affecting Uniswap highlights the framework's potential to effectively uncover smart contract vulnerabilities in complex DeFi systems.
|
[
"Computer Science Archive->cs.CR"
] | 2023-05-23T13:16:42Z |
2010.14343
|
Learning to Infer Unseen Attribute-Object Compositions
|
The composition recognition of unseen attribute-object is critical to make machines learn to decompose and compose complex concepts like people. Most of the existing methods are limited to the composition recognition of single-attribute-object, and can hardly distinguish the compositions with similar appearances. In this paper, a graph-based model is proposed that can flexibly recognize both single- and multi-attribute-object compositions. The model maps the visual features of images and the attribute-object category labels represented by word embedding vectors into a latent space. Then, according to the constraints of the attribute-object semantic association, distances are calculated between visual features and the corresponding label semantic features in the latent space. During the inference, the composition that is closest to the given image feature among all compositions is used as the reasoning result. In addition, we build a large-scale Multi-Attribute Dataset (MAD) with 116,099 images and 8,030 composition categories. Experiments on MAD and two other single-attribute-object benchmark datasets demonstrate the effectiveness of our approach.
|
[
"Computer Science Archive->cs.CV"
] | 2020-10-27T14:57:35Z |
2301.07187
|
Artificial Neuronal Ensembles with Learned Context Dependent Gating
|
Biological neural networks are capable of recruiting different sets of neurons to encode different memories. However, when training artificial neural networks on a set of tasks, typically, no mechanism is employed for selectively producing anything analogous to these neuronal ensembles. Further, artificial neural networks suffer from catastrophic forgetting, where the network's performance rapidly deteriorates as tasks are learned sequentially. By contrast, sequential learning is possible for a range of biological organisms. We introduce Learned Context Dependent Gating (LXDG), a method to flexibly allocate and recall `artificial neuronal ensembles', using a particular network structure and a new set of regularization terms. Activities in the hidden layers of the network are modulated by gates, which are dynamically produced during training. The gates are outputs of networks themselves, trained with a sigmoid output activation. The regularization terms we have introduced correspond to properties exhibited by biological neuronal ensembles. The first term penalizes low gate sparsity, ensuring that only a specified fraction of the network is used. The second term ensures that previously learned gates are recalled when the network is presented with input from previously learned tasks. Finally, there is a regularization term responsible for ensuring that new tasks are encoded in gates that are as orthogonal as possible from previously used ones. We demonstrate the ability of this method to alleviate catastrophic forgetting on continual learning benchmarks. When the new regularization terms are included in the model along with Elastic Weight Consolidation (EWC) it achieves better performance on the benchmark `permuted MNIST' than with EWC alone. The benchmark `rotated MNIST' demonstrates how similar tasks recruit similar neurons to the artificial neuronal ensemble.
|
[
"Computer Science Archive->cs.LG"
] | 2023-01-17T20:52:48Z |
1512.07807
|
Visualizations Relevant to The User By Multi-View Latent Variable Factorization
|
A main goal of data visualization is to find, from among all the available alternatives, mappings to the 2D/3D display which are relevant to the user. Assuming user interaction data, or other auxiliary data about the items or their relationships, the goal is to identify which aspects in the primary data support the user\'s input and, equally importantly, which aspects of the user\'s potentially noisy input have support in the primary data. For solving the problem, we introduce a multi-view embedding in which a latent factorization identifies which aspects in the two data views (primary data and user data) are related and which are specific to only one of them. The factorization is a generative model in which the display is parameterized as a part of the factorization and the other factors explain away the aspects not expressible in a two-dimensional display. Functioning of the model is demonstrated on several data sets.
|
[
"Computer Science Archive->cs.IR",
"Computer Science Archive->cs.LG"
] | 2015-12-24T12:53:39Z |
1903.04418
|
Localisation in a growth model with interaction. Arbitrary graphs
|
This paper concerns the long term behaviour of a growth model describing a random sequential deposition of particles on a finite graph. The probability of allocating a particle at a vertex is proportional to a log-linear function of numbers of existing particles in a neighbourhood of a vertex. When this function depends only on the number of particles in the vertex, the model becomes a special case of the generalised Polya urn model. In this special case all but finitely many particles are allocated at a single random vertex almost surely. In our model interaction leads to the fact that, with probability one, all but finitely many particles are allocated at vertices of a clique.
|
[
"Mathematics Archive->math.PR"
] | 2019-03-11T16:29:42Z |
0806.4635
|
Distance to NGC 281 in a Galactic Fragmenting Superbubble: Parallax Measurements with VERA
|
We have used the Japanese VLBI array VERA to perform high-precision astrometry of an H2O maser source in the Galactic star-forming region NGC 281 West, which has been considered to be part of a 300-pc superbubble. We successfully detected a trigonometric parallax of 0.355+/-0.030 mas, corresponding to a source distance of 2.82+/-0.24 kpc. Our direct distance determination of NGC 281 has resolved the large distance discrepancy between previous photometric and kinematic studies; likely NGC 281 is in the far side of the Perseus spiral arm. The source distance as well as the absolute proper motions were used to demonstrate the 3D structure and expansion of the NGC 281 superbubble, ~650 pc in size parallel to the Galactic disk and with a shape slightly elongated along the disk or spherical, but not vertically elongated, indicating the superbubble expansion may be confined to the disk. We estimate the expansion velocity of the superbubble as ~20 km/s both perpendicular to and parallel to the Galactic disk with a consistent timescale of ~20 Myr.
|
[
"Physics Archive->astro-ph"
] | 2008-06-27T23:51:19Z |
1604.05703
|
A large deviations analysis of certain qualitative properties of parallel tempering and infinite swapping algorithms
|
Parallel tempering, or replica exchange, is a popular method for simulating complex systems. The idea is to run parallel simulations at different temperatures, and at a given swap rate exchange configurations between the parallel simulations. From the perspective of large deviations it is optimal to let the swap rate tend to infinity and it is possible to construct a corresponding simulation scheme, known as infinite swapping. In this paper we propose a novel use of large deviations for empirical measures for a more detailed analysis of the infinite swapping limit in the setting of continuous time jump Markov processes. Using the large deviations rate function and associated stochastic control problems we consider a diagnostic based on temperature assignments, which can be easily computed during a simulation. We show that the convergence of this diagnostic to its a priori known limit is a necessary condition for the convergence of infinite swapping. The rate function is also used to investigate the impact of asymmetries in the underlying potential landscape, and where in the state space poor sampling is most likely to occur.
|
[
"Mathematics Archive->math.OC",
"Mathematics Archive->math.PR"
] | 2016-04-19T19:40:16Z |
1810.11244
|
Matrix-Monotonic Optimization Part I: Single-Variable Optimization
|
Matrix-monotonic optimization exploits the monotonic nature of positive semi-definite matrices to derive optimal diagonalizable structures for the matrix variables of matrix-variable optimization problems. Based on the optimal structures derived, the associated optimization problems can be substantially simplified and underlying physical insights can also be revealed. In our work, a comprehensive framework of the applications of matrix-monotonic optimization to multiple-input multiple-output (MIMO) transceiver design is provided for a series of specific performance metrics under various linear constraints. This framework consists of two parts, i.e., Part-I for single-variable optimization and Part-II for multi-variable optimization. In this paper, single-variable matrix-monotonic optimization is investigated under various power constraints and various types of channel state information (CSI) condition. Specifically, three cases are investigated: 1) both the transmitter and receiver have imperfect CSI; 2) perfect CSI is available at the receiver but the transmitter has no CSI; 3) perfect CSI is available at the receiver but the channel estimation error at the transmitter is norm-bounded. In all three cases, the matrix-monotonic optimization framework can be used for deriving the optimal structures of the optimal matrix variables.
|
[
"Computer Science Archive->cs.IT",
"Mathematics Archive->math.IT"
] | 2018-10-26T10:11:24Z |
2109.07455
|
Deep Bregman Divergence for Contrastive Learning of Visual Representations
|
Deep Bregman divergence measures divergence of data points using neural networks which is beyond Euclidean distance and capable of capturing divergence over distributions. In this paper, we propose deep Bregman divergences for contrastive learning of visual representation where we aim to enhance contrastive loss used in self-supervised learning by training additional networks based on functional Bregman divergence. In contrast to the conventional contrastive learning methods which are solely based on divergences between single points, our framework can capture the divergence between distributions which improves the quality of learned representation. We show the combination of conventional contrastive loss and our proposed divergence loss outperforms baseline and most of the previous methods for self-supervised and semi-supervised learning on multiple classifications and object detection tasks and datasets. Moreover, the learned representations generalize well when transferred to the other datasets and tasks. The source code and our models are available in supplementary and will be released with paper.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG"
] | 2021-09-15T17:44:40Z |
1905.05842
|
The Penetration Rate Effect of Connected and Automated Vehicles in Mixed Traffic Routing
|
We study the problem of routing Connected and Automated Vehicles (CAVs) in the presence of mixed traffic (coexistence of regular vehicles and CAVs). In this setting, we assume that all CAVs belong to the same fleet, and can be routed using a centralized controller. The routing objective is to minimize a given overall fleet traveling cost (travel time or energy consumption). We assume that regular vehicles (non-CAVs) choose their routing decisions selfishly to minimize their traveling time. We propose an algorithm that deals with the routing interaction between CAVs and regular uncontrolled vehicles. We investigate the effect of assigning system-centric routes under different penetration rates (fractions) of CAVs. To validate our method, we apply the proposed routing algorithms to the Braess Network and to a sub-network of the Eastern Massachusetts (EMA) transportation network using actual traffic data provided by the Boston Region Metropolitan Planning Organization. The results suggest that collaborative routing decisions of CAVs improve not only the cost of CAVs, but also that of the non-CAVs. Furthermore, even a small CAV penetration rate can ease congestion for the entire network.
|
[
"Computer Science Archive->cs.SY",
"Mathematics Archive->math.OC"
] | 2019-05-14T21:06:03Z |
1703.06201
|
Changing measurements or changing movements? Sampling scale and movement model identifiability across generations of biologging technology
|
1. Animal movement patterns contribute to our understanding of variation in breeding success and survival of individuals, and the implications for population dynamics. 2. Over time, sensor technology for measuring movement patterns has improved. Although older technologies may be rendered obsolete, the existing data are still valuable, especially if new and old data can be compared to test whether a behaviour has changed over time. 3. We used simulated data to assess the ability to quantify and correctly identify patterns of seabird flight lengths under observational regimes used in successive generations of tracking technology. 4. Care must be taken when comparing data collected at differing time-scales, even when using inference procedures that incorporate the observational process, as model selection and parameter estimation may be biased. In practice, comparisons may only be valid when degrading all data to match the lowest resolution in a set. 5. Changes in tracking technology that lead to aggregation of measurements at different temporal scales make comparisons challenging. We therefore urge ecologists to use synthetic data to assess whether accurate parameter estimation is possible for models comparing disparate data sets before conducting analyses such as responses to environmental changes or the assessment of management actions.
|
[
"Quantitative Biology Archive->q-bio.QM"
] | 2017-03-17T21:30:09Z |
1905.10261
|
Approximation Ratios of Graph Neural Networks for Combinatorial Problems
|
In this paper, from a theoretical perspective, we study how powerful graph neural networks (GNNs) can be for learning approximation algorithms for combinatorial problems. To this end, we first establish a new class of GNNs that can solve a strictly wider variety of problems than existing GNNs. Then, we bridge the gap between GNN theory and the theory of distributed local algorithms. We theoretically demonstrate that the most powerful GNN can learn approximation algorithms for the minimum dominating set problem and the minimum vertex cover problem with some approximation ratios with the aid of the theory of distributed local algorithms. We also show that most of the existing GNNs such as GIN, GAT, GCN, and GraphSAGE cannot perform better than with these ratios. This paper is the first to elucidate approximation ratios of GNNs for combinatorial problems. Furthermore, we prove that adding coloring or weak-coloring to each node feature improves these approximation ratios. This indicates that preprocessing and feature engineering theoretically strengthen model capabilities.
|
[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2019-05-24T14:41:17Z |
1408.1831
|
Intersubband optical absorption in InSb stepped quantum wells. Effect of spin sublevels crossing
|
We study linear and non-linear coefficients of the intersubband absorption in InSb-based stepped quantum wells subjected to an in-plane magnetic field. We consider also a transverse electric field to achieve near resonance conditions. Taking into account the two deepest conduction levels and their corresponding Zeeman spin splitting sublevels, we calculate dispersion relations by means of an improved version of Kane model. Besides the known anti-crossing between down and up spin split sublevels, we obtain an extra spin level crossing for some determined parameters. This crossing clearly modifies the absorption spectrum for transitions among the four sublevels considered. We study a low electron density case, when only the first deepest sublevel is occupied, and a high density case with only the highest sublevel empty. We find a similar behavior of the absorption spectrum in both cases.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2014-08-08T12:06:37Z |
1912.04188
|
Connection between $\nu n \rightarrow \bar{\nu} \bar{n}$ reactions and $n$-$\bar{n}$ oscillations via additional Higgs triplets
|
In this work, we investigate the connection and compatibility between $\nu n \rightarrow \bar{\nu} \bar{n}$ reactions and $n$-$\bar{n}$ oscillations based on the $SU(3)_c \times SU(2)_L \times U(1)$ symmetry model with additional Higgs triplets. We explore the possibility that the scattering process $\nu n\rightarrow \bar{\nu}\bar{n}$ produced by low-energy solar neutrinos gives rise to an unavoidable background in the measurements of $n$-$\bar{n}$ oscillations. We focus on two different scenarios, depending on whether the $(B-L)$ symmetry could be broken. We analyze the interplay of the various constraints on the two processes and their observable consequences. In the scenario where both $(B+L)$ and $(B-L)$ could be broken, we point out that if all the constraints, mainly arising from the type-II seesaw mechanism, are satisfied, the parameter space would be severely constrained. In this case, although the masses of the Higgs triplet bosons could be within the reach of a direct detection at the LHC or future high-energy experiments, the predicted $n$-$\bar{n}$ oscillation times would be completely beyond the detectable regions of the present experiments. In both scenarios, the present experiments cannot distinguish a $\nu n \rightarrow \bar{\nu} \bar{n}$ reaction event from a $n$-$\bar{n}$ oscillation event within the accessible energy range. Nevertheless, if any of the two processes is detected, there could be signal associated with new physics beyond the Standard Model.
|
[
"Physics Archive->astro-ph->astro-ph.HE",
"Physics Archive->hep->hep-ph"
] | 2019-12-09T17:11:15Z |
1306.4155
|
Symbolic-numerical Algorithm for Generating Cluster Eigenfunctions: Tunneling of Clusters Through Repulsive Barriers
|
A model for quantum tunnelling of a cluster comprising A identical particles, coupled by oscillator-type potential, through short-range repulsive potential barriers is introduced for the first time in the new symmetrized-coordinate representation and studied within the s-wave approximation. The symbolic-numerical algorithms for calculating the effective potentials of the close-coupling equations in terms of the cluster wave functions and the energy of the barrier quasistationary states are formulated and implemented using the Maple computer algebra system. The effect of quantum transparency, manifesting itself in nonmonotonic resonance-type dependence of the transmission coefficient upon the energy of the particles, the number of the particles A=2,3,4, and their symmetry type, is analyzed. It is shown that the resonance behavior of the total transmission coefficient is due to the existence of barrier quasistationary states imbedded in the continuum.
|
[
"Physics Archive->nucl->nucl-th"
] | 2013-06-18T11:45:49Z |
1601.02430
|
A posteriori error analysis for evolution nonlinear Schr\"odinger equations up to the critical exponent
|
We provide a posteriori error estimates in the $L^\infty(L^2)-$norm for relaxation time discrete and fully discrete schemes for a class of evolution nonlinear Schr\"odinger equations up to the critical exponent. In particular for the discretization in time we use the relaxation Crank-Nicolson-type scheme introduced by Besse in \cite{Besse}. For the discretization in space we use finite element spaces that are allowed to change between time steps. The estimates are obtained using the reconstruction technique. Through this technique the problem is converted to a perturbation of the original partial differential equation and this makes it possible to use nonlinear stability arguments as in the continuous problem. In particular, main ingredients we use in our analysis are the Gagliardo-Nirenberg inequality and the two conservation laws (mass and energy conservation) of the continuous problem. Numerical results illustrate that the estimates are indeed of optimal order of convergence.
|
[
"Mathematics Archive->math.NA"
] | 2016-01-11T13:02:31Z |
1305.4463
|
Fundamental diagrams for kinetic equations of traffic flow
|
In this paper we investigate the ability of some recently introduced discrete kinetic models of vehicular traffic to catch, in their large time behavior, typical features of theoretical fundamental diagrams. Specifically, we address the so-called "spatially homogeneous problem" and, in the representative case of an exploratory model, we study the qualitative properties of its solutions for a generic number of discrete microstates. This includes, in particular, asymptotic trends and equilibria, whence fundamental diagrams originate.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->math-ph"
] | 2013-05-20T08:43:07Z |
1701.00799
|
Non trivial limit distributions for transient renewal chains
|
In this work we study the asymptotic of renewal sequences associated with certain transient renewal Markov chains and enquire about the existence of limit laws in this set up.
|
[
"Mathematics Archive->math.PR"
] | 2017-01-03T19:47:10Z |
2212.10817
|
High-fidelity Direct Contrast Synthesis from Magnetic Resonance Fingerprinting
|
Magnetic Resonance Fingerprinting (MRF) is an efficient quantitative MRI technique that can extract important tissue and system parameters such as T1, T2, B0, and B1 from a single scan. This property also makes it attractive for retrospectively synthesizing contrast-weighted images. In general, contrast-weighted images like T1-weighted, T2-weighted, etc., can be synthesized directly from parameter maps through spin-dynamics simulation (i.e., Bloch or Extended Phase Graph models). However, these approaches often exhibit artifacts due to imperfections in the mapping, the sequence modeling, and the data acquisition. Here we propose a supervised learning-based method that directly synthesizes contrast-weighted images from the MRF data without going through the quantitative mapping and spin-dynamics simulation. To implement our direct contrast synthesis (DCS) method, we deploy a conditional Generative Adversarial Network (GAN) framework and propose a multi-branch U-Net as the generator. The input MRF data are used to directly synthesize T1-weighted, T2-weighted, and fluid-attenuated inversion recovery (FLAIR) images through supervised training on paired MRF and target spin echo-based contrast-weighted scans. In-vivo experiments demonstrate excellent image quality compared to simulation-based contrast synthesis and previous DCS methods, both visually as well as by quantitative metrics. We also demonstrate cases where our trained model is able to mitigate in-flow and spiral off-resonance artifacts that are typically seen in MRF reconstructions and thus more faithfully represent conventional spin echo-based contrast-weighted images.
|
[
"Computer Science Archive->cs.CV",
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2022-12-21T07:11:39Z |
hep-ph/0201091
|
Estimate of the Collins fragmentation function in a chiral invariant approach
|
We predict the features of the Collins function, which describes the fragmentation of a transversely polarized quark into an unpolarized hadron, by modeling the fragmentation process at a low energy scale. We use the chiral invariant approach of Manohar and Georgi, where constituent quarks and Goldstone bosons are considered as effective degrees of freedom in the non-perturbative regime of QCD. To test the approach we calculate the unpolarized fragmentation function and the transverse momentum distribution of a produced hadron, both of which are described reasonably well. In the case of semi-inclusive deep-inelastic scattering, our estimate of the Collins function in connection with the transversity distribution gives rise to a transverse single spin asymmetry of the order of 10%, supporting the idea of measuring the transversity distribution of the nucleon in this way. In the case of e+ e- annihilation into two hadrons, our model predicts a Collins azimuthal asymmetry of about 5%.
|
[
"Physics Archive->hep->hep-ph"
] | 2002-01-11T15:46:42Z |
2309.02947
|
MUSIC Algorithm for IRS-Assisted AOA Estimation
|
Based on the signals received across its antennas, a multi-antenna base station (BS) can apply the classic multiple signal classification (MUSIC) algorithm for estimating the angle of arrivals (AOAs) of its incident signals. This method can be leveraged to localize the users if their line-of-sight (LOS) paths to the BS are available. In this paper, we consider a more challenging AOA estimation setup in the intelligent reflecting surface (IRS) assisted integrated sensing and communication (ISAC) system, where LOS paths do not exist between the BS and the users, while the users' signals can be transmitted to the BS merely via their LOS paths to the IRS as well as the LOS path from the IRS to the BS. Specifically, we treat the IRS as the anchor and are interested in estimating the AOAs of the incident signals from the users to the IRS. Note that we have to achieve the above goal based on the signals received by the BS, because the passive IRS cannot process its received signals. However, the signals received across different antennas of the BS only contain AOA information of its incident signals via the LOS path from the IRS to the BS. To tackle this challenge arising from the spatial-domain received signals, we propose an innovative approach to create temporal-domain multi-dimension received signals for estimating the AOAs of the paths from the users to the IRS. Specifically, via a proper design of the user message pattern and the IRS reflecting pattern, we manage to show that our designed temporal-domain multi-dimension signals can be surprisingly expressed as a function of the virtual steering vectors of the IRS towards the users. This amazing result implies that the classic MUSIC algorithm can be applied to our designed temporal-domain multi-dimension signals for accurately estimating the AOAs of the signals from the users to the IRS.
|
[
"Computer Science Archive->cs.IT",
"Electrical Engineering and Systems Science Archive->eess.SP",
"Mathematics Archive->math.IT"
] | 2023-09-06T12:25:57Z |
0811.0164
|
A strict non-standard inequality .999... < 1
|
Is .999... equal to 1? Lightstone's decimal expansions yield an infinity of numbers in [0,1] whose expansion starts with an unbounded number of digits "9". We present some non-standard thoughts on the ambiguity of an ellipsis, modeling the cognitive concept of generic limit of B. Cornu and D. Tall. A choice of a non-standard hyperinteger H specifies an H-infinite extended decimal string of 9s, corresponding to an infinitesimally diminished hyperreal value. In our model, the student resistance to the unital evaluation of .999... is directed against an unspoken and unacknowledged application of the standard part function, namely the stripping away of a ghost of an infinitesimal, to echo George Berkeley. So long as the number system has not been specified, the students' hunch that .999... can fall infinitesimally short of 1, can be justified in a mathematically rigorous fashion.
|
[
"Mathematics Archive->math.HO"
] | 2008-11-02T14:33:51Z |
1807.09237
|
Hierarchical infinite factor model for improving the prediction of surgical complications for geriatric patients
|
We develop a hierarchical infinite latent factor model (HIFM) to appropriately account for the covariance structure across subpopulations in data. We propose a novel Hierarchical Dirichlet Process shrinkage prior on the loadings matrix that flexibly captures the underlying structure of our data across subpopulations while sharing information to improve inference and prediction. The stick-breaking construction of the prior assumes infinite number of factors and allows for each subpopulation to utilize different subsets of the factor space and select the number of factors needed to best explain the variation. Theoretical results are provided to show support of the prior. We develop the model into a latent factor regression method that excels at prediction and inference of regression coefficients. Simulations are used to validate this strong performance compared to baseline methods. We apply this work to the problem of predicting surgical complications using electronic health record data for geriatric patients at Duke University Health System (DUHS). We utilize additional surgical encounters at DUHS to enhance learning for the targeted patients. Using HIFM to identify high risk patients improves the sensitivity of predicting death to 91% from 35% based on the currently used heuristic.
|
[
"Statistics Archive->stat.AP"
] | 2018-07-24T17:15:01Z |
2106.06431
|
Offline Reinforcement Learning as Anti-Exploration
|
Offline Reinforcement Learning (RL) aims at learning an optimal control from a fixed dataset, without interactions with the system. An agent in this setting should avoid selecting actions whose consequences cannot be predicted from the data. This is the converse of exploration in RL, which favors such actions. We thus take inspiration from the literature on bonus-based exploration to design a new offline RL agent. The core idea is to subtract a prediction-based exploration bonus from the reward, instead of adding it for exploration. This allows the policy to stay close to the support of the dataset. We connect this approach to a more common regularization of the learned policy towards the data. Instantiated with a bonus based on the prediction error of a variational autoencoder, we show that our agent is competitive with the state of the art on a set of continuous control locomotion and manipulation tasks.
|
[
"Computer Science Archive->cs.LG"
] | 2021-06-11T14:41:30Z |
1001.2627
|
Stellar Mass Estimation Based on IRAC Photometry for Spitzer SWIRE-field Galaxies
|
We analyze the feasibility to estimate the stellar mass of galaxies by mid-infrared luminosities based on a large sample of galaxies cross-identified from $Spitzer$ SWIRE fields and SDSS spectrographic survey. We derived the formulae to calculate the stellar mass by using IRAC 3.6$\mu$m and 4.5$\mu$m luminosities. The mass-to-luminosity ratios of IRAC 3.6$\mu$m and 4.5$\mu$m luminosities are more sensitive to star formation history of galaxies than other factors, such as the intrinsic extinction, metallicity and star formation rate. To remove the affection from star formation history, we used g-r color to recalibrate the formulae and obtain a better result. It must be more careful to estimate the stellar mass of low metallicity galaxies using our formulae. Due to the emission from dust heated by hottest young stars, luminous infrared galaxies present higher IRAC 4.5 $\mu$m luminosity compared to IRAC 3.6 $\mu$m luminosity. For most of type-II AGNs, the nuclear activity can not enhance 3.6$\mu$m and 4.5$\mu$m luminosities compared with normal galaxies. The star formation in our AGN-hosting galaxies is also very weak, almost all of which are early-type galaxies.
|
[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2010-01-15T07:08:23Z |
2202.04955
|
Water flow in single-wall nanotubes: Oxygen makes it slip, hydrogen makes it stick
|
Experimental measurements have reported ultra-fast and radius-dependent water transport in carbon nanotubes which are absent in boron nitride nanotubes. Despite considerable effort, the origin of this contrasting (and fascinating) behaviour is not understood. Here, with the aid of machine learning-based molecular dynamics simulations that deliver first-principles accuracy, we investigate water transport in single-wall carbon and boron nitride nanotubes. Our simulations reveal a large, radius-dependent hydrodynamic slippage on both materials with water experiencing indeed a $\approx 5$ times lower friction on carbon surfaces compared to boron nitride. Analysis of the diffusion mechanisms across the two materials reveals that the fast water transport on carbon is governed by facile oxygen motion, whereas the higher friction on boron nitride arises from specific hydrogen-nitrogen interactions. This work not only delivers a clear reference of unprecedented accuracy for water flow in single-wall nanotubes, but also provides detailed mechanistic insight into its radius and material dependence for future technological application.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->physics->physics.chem-ph"
] | 2022-02-10T11:14:06Z |
gr-qc/0110053
|
Network sensitivity to geographical configuration
|
Gravitational wave astronomy will require the coordinated analysis of data from the global network of gravitational wave observatories. Questions of how to optimally configure the global network arise in this context. We have elsewhere proposed a formalism which is employed here to compare different configurations of the network, using both the coincident network analysis method and the coherent network analysis method. We have constructed a network model to compute a figure-of-merit based on the detection rate for a population of standard-candle binary inspirals. We find that this measure of network quality is very sensitive to the geographic location of component detectors under a coincident network analysis, but comparatively insensitive under a coherent network analysis.
|
[
"Physics Archive->gr-qc"
] | 2001-10-10T00:33:31Z |
1508.03916
|
Asteroseismology of a $\delta$ Scuti star CoRoT 102749568
|
For $\delta$ Scuti star CoRoT 102749568, 52 independent frequencies were obtained by Papar$\acute{o}$ et al. 2013. We find that there are 4 multiplets and 8 doublets with nearly equal split caused by rotation. Differential rotation is suggested instead of rigid body rotation to explain the equal split phenomenon. Grids of models are computed with MESA to fit observational frequencies of CoRoT 102749568. After rejecting modes of $m\neq0$ in multiplets and doublets, we identify 31 modes of $m = 0$ and 3 modes of $m\neq0$, including 4 modes of $l = 0$, 9 modes of $l=1$, 11 modes of $l=2$, and 10 modes of $l=3$. The mean error is 0.447$\mu$Hz for the best-fitting model, and the physical parameters of the corresponding model are as followings: $M=1.95$ $\rm M_{\odot}$, $Z=0.025$, $T_{\rm eff}=7096$ K, log$g=3.727$, $L=22.77$ $\rm L_{\odot}$, $Age=1.113$ Gyr.
|
[
"Physics Archive->astro-ph->astro-ph.SR"
] | 2015-08-17T03:16:45Z |
1610.05330
|
Cosmology with a light ghost
|
We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose power spectrum appears to coincide with that of single-field inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in the Universe. For all ghost masses allowed by laboratory constraints ghosts should have "overclosed" the Universe at temperatures higher than that of primordial nucleosynthesis. Thus, the model with the light Weyl ghost is ruled out.
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th"
] | 2016-10-17T20:07:22Z |
2008.11289
|
Robust Character Labeling in Movie Videos: Data Resources and Self-supervised Feature Adaptation
|
Robust face clustering is a vital step in enabling computational understanding of visual character portrayal in media. Face clustering for long-form content is challenging because of variations in appearance and lack of supporting large-scale labeled data. Our work in this paper focuses on two key aspects of this problem: the lack of domain-specific training or benchmark datasets, and adapting face embeddings learned on web images to long-form content, specifically movies. First, we present a dataset of over 169,000 face tracks curated from 240 Hollywood movies with weak labels on whether a pair of face tracks belong to the same or a different character. We propose an offline algorithm based on nearest-neighbor search in the embedding space to mine hard-examples from these tracks. We then investigate triplet-loss and multiview correlation-based methods for adapting face embeddings to hard-examples. Our experimental results highlight the usefulness of weakly labeled data for domain-specific feature adaptation. Overall, we find that multiview correlation-based adaptation yields more discriminative and robust face embeddings. Its performance on downstream face verification and clustering tasks is comparable to that of the state-of-the-art results in this domain. We also present the SAIL-Movie Character Benchmark corpus developed to augment existing benchmarks. It consists of racially diverse actors and provides face-quality labels for subsequent error analysis. We hope that the large-scale datasets developed in this work can further advance automatic character labeling in videos. All resources are available freely at https://sail.usc.edu/~ccmi/multiface.
|
[
"Computer Science Archive->cs.CV",
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2020-08-25T22:07:41Z |
1803.02808
|
OntoWind: An Improved and Extended Wind Energy Ontology
|
Ontologies are critical sources of semantic information for many application domains. Hence, there are ontologies proposed and utilized for domains such as medicine, chemical engineering, and electrical energy. In this paper, we present an improved and extended version of a wind energy ontology previously proposed. First, the ontology is restructured to increase its understandability and coverage. Secondly, it is enriched with new concepts, crisp/fuzzy attributes, and instances to increase its usability in semantic applications regarding wind energy. The ultimate ontology is utilized within a Web-based semantic portal application for wind energy, in order to showcase its contribution in a genuine application. Hence, the current study is a significant to wind and thereby renewable energy informatics, with the presented publicly-available wind energy ontology and the implemented proof-of-concept system.
|
[
"Computer Science Archive->cs.AI"
] | 2018-03-07T18:34:44Z |
2012.10307
|
Results on Competitiveness of Online Shortest Remaining Processing Time(SRPT) Scheduling with Special Classes of Inputs
|
Shortest Remaining Processing Time (SRPT) is a well known preemptive scheduling algorithm for uniprocessor and multiprocessor systems. SRPT finds applications in the emerging areas such as scheduling of client's requests that are submitted to a web server for accessing static web pages, managing the access requests to files in multiuser database systems and routing of packets across several links as per bandwidth availability in data communications. SRPT has been proved to be optimal for the settings, where the objective is to minimize the mean response time of a list of jobs. According to our knowledge, there is less attention on the study of online SRPT with respect to the minimization of makespan as a performance criterion. In this paper, we study the SRPT algorithm for online scheduling in multiprocessor systems with makespan minimization as an objective. We obtain improved constant competitiveness results for algorithm SRPT for special classes of online job sequences based on practical real life applications.
|
[
"Computer Science Archive->cs.DS"
] | 2020-12-18T15:52:31Z |
1908.08177
|
New magicity $N=32$ and $34$ triggered by strong couplings between Dirac inversion partners
|
Inspired by recent experiments, the successive new magicity $N = 32$ and $34$ in Ca isotopes are studied within the relativistic density functional theory. It is illustrated that the strong couplings between the $s_{1/2}$ and neutron ($\nu$) $\nu2p_{1/2}$ orbits, here referred as "Dirac inversion partners" (DIPs), play a key role in opening both subshells $N = 32$ and $34$. Such strong couplings originate from the inversion similarity between the DIPs, that the upper component of the Dirac spinor of one partner shares the same orbital angular momentum as the lower component of the other, and vice versa. Following the revealed mechanism, it is predicted that the magicity $N = 32$ is reserved until $^{48}$S, but vanishes in $^{46}$Si.
|
[
"Physics Archive->nucl->nucl-th"
] | 2019-08-22T02:58:05Z |
1304.1146
|
Analysis in HUGIN of Data Conflict
|
After a brief introduction to causal probabilistic networks and the HUGIN approach, the problem of conflicting data is discussed. A measure of conflict is defined, and it is used in the medical diagnostic system MUNIN. Finally, it is discussed how to distinguish between conflicting data and a rare case.
|
[
"Computer Science Archive->cs.AI"
] | 2013-03-27T14:00:40Z |
1903.02193
|
Robust Lane Detection from Continuous Driving Scenes Using Deep Neural Networks
|
Lane detection in driving scenes is an important module for autonomous vehicles and advanced driver assistance systems. In recent years, many sophisticated lane detection methods have been proposed. However, most methods focus on detecting the lane from one single image, and often lead to unsatisfactory performance in handling some extremely-bad situations such as heavy shadow, severe mark degradation, serious vehicle occlusion, and so on. In fact, lanes are continuous line structures on the road. Consequently, the lane that cannot be accurately detected in one current frame may potentially be inferred out by incorporating information of previous frames. To this end, we investigate lane detection by using multiple frames of a continuous driving scene, and propose a hybrid deep architecture by combining the convolutional neural network (CNN) and the recurrent neural network (RNN). Specifically, information of each frame is abstracted by a CNN block, and the CNN features of multiple continuous frames, holding the property of time-series, are then fed into the RNN block for feature learning and lane prediction. Extensive experiments on two large-scale datasets demonstrate that, the proposed method outperforms the competing methods in lane detection, especially in handling difficult situations.
|
[
"Computer Science Archive->cs.CV"
] | 2019-03-06T06:29:18Z |
1504.07130
|
Coupling-Deformed Pointer Observables and Weak Values
|
While the novel applications of weak values have recently attracted wide attention, weak measurement, the usual way to extract weak values, suffers from risky approximations and severe quantum noises. In this paper, we show that the weak-value information can be obtained exactly in strong measurement with postselections, via measuring the coupling-deformed pointer observables, i.e., the observables selected according to the coupling strength. With this approach, we keep all the advantages claimed by weak-measurement schemes and at the same time solve some widely criticized problems thereof, such as the questionable universality, systematical bias, and drastic inefficiency.
|
[
"Physics Archive->quant-ph"
] | 2015-04-27T15:28:09Z |
0903.0499
|
Statistical inference for semiparametric varying-coefficient partially linear models with error-prone linear covariates
|
We study semiparametric varying-coefficient partially linear models when some linear covariates are not observed, but ancillary variables are available. Semiparametric profile least-square based estimation procedures are developed for parametric and nonparametric components after we calibrate the error-prone covariates. Asymptotic properties of the proposed estimators are established. We also propose the profile least-square based ratio test and Wald test to identify significant parametric and nonparametric components. To improve accuracy of the proposed tests for small or moderate sample sizes, a wild bootstrap version is also proposed to calculate the critical values. Intensive simulation experiments are conducted to illustrate the proposed approaches.
|
[
"Mathematics Archive->math.ST",
"Statistics Archive->stat.TH"
] | 2009-03-03T11:38:07Z |
2206.01696
|
Deep Learning Prediction of Severe Health Risks for Pediatric COVID-19 Patients with a Large Feature Set in 2021 BARDA Data Challenge
|
Most children infected with COVID-19 have no or mild symptoms and can recover automatically by themselves, but some pediatric COVID-19 patients need to be hospitalized or even to receive intensive medical care (e.g., invasive mechanical ventilation or cardiovascular support) to recover from the illnesses. Therefore, it is critical to predict the severe health risk that COVID-19 infection poses to children to provide precise and timely medical care for vulnerable pediatric COVID-19 patients. However, predicting the severe health risk for COVID-19 patients including children remains a significant challenge because many underlying medical factors affecting the risk are still largely unknown. In this work, instead of searching for a small number of most useful features to make prediction, we design a novel large-scale bag-of-words like method to represent various medical conditions and measurements of COVID-19 patients. After some simple feature filtering based on logistical regression, the large set of features is used with a deep learning method to predict both the hospitalization risk for COVID-19 infected children and the severe complication risk for the hospitalized pediatric COVID-19 patients. The method was trained and tested the datasets of the Biomedical Advanced Research and Development Authority (BARDA) Pediatric COVID-19 Data Challenge held from Sept. 15 to Dec. 17, 2021. The results show that the approach can rather accurately predict the risk of hospitalization and severe complication for pediatric COVID-19 patients and deep learning is more accurate than other machine learning methods.
|
[
"Computer Science Archive->cs.LG"
] | 2022-06-03T17:14:53Z |
1107.0931
|
The Thermodynamics of a 5D Gravity-Dilaton-Tachyon Solution
|
We propose a finite-temperature holographic model with a soft-wall geometry that incorporates two scalar fields, dual to the gluon and chiral operators. A series solution is presented as the dynamical, black-hole solution to Einstein's equations. We use the solution to calculate the thermal properties of the corresponding 4D gauge theory. Gluon and chiral thermal condensates contribute leading-order terms that affect the speed of sound through and entropy of the 4D thermal medium. At a temperature $T_c\sim 900$ MeV, we find a phase transition, which is much higher than lattice QCD calculations. However, the transition only exists with nonzero thermal condensates.
|
[
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th",
"Physics Archive->nucl->nucl-th"
] | 2011-07-05T18:03:23Z |
2201.00973
|
A Trust Region Method for the Optimization of Noisy Functions
|
Classical trust region methods were designed to solve problems in which function and gradient information are exact. This paper considers the case when there are bounded errors (or noise) in the above computations and proposes a simple modification of the trust region method to cope with these errors. The new algorithm only requires information about the size of the errors in the function evaluations and incurs no additional computational expense. It is shown that, when applied to a smooth (but not necessarily convex) objective function, the iterates of the algorithm visit a neighborhood of stationarity infinitely often, and that the rest of the sequence cannot stray too far away, as measured by function values. Numerical results illustrate how the classical trust region algorithm may fail in the presence of noise, and how the proposed algorithm ensures steady progress towards stationarity in these cases.
|
[
"Mathematics Archive->math.OC"
] | 2022-01-04T04:35:13Z |
1302.4887
|
Limit theorems for the pre-averaged Hayashi-Yoshida estimator with random sampling
|
We will focus on estimating the integrated covariance of two diffusion processes observed in a nonsynchronous manner. The observation data is contaminated by some noise, which is possibly correlated with the returns of the diffusion processes, while the sampling times also possibly depend on the observed processes. In a high-frequency setting, we consider a modified version of the pre-averaged Hayashi-Yoshida estimator, and we show that such a kind of estimators has the consistency and the asymptotic mixed normality, and attains the optimal rate of convergence.
|
[
"Mathematics Archive->math.ST",
"Statistics Archive->stat.TH"
] | 2013-02-20T12:35:21Z |
1904.00677
|
Hochschild cohomology related to graded down-up algebras with weights $(1,n)$
|
Let $A=A(\alpha, \beta)$ be a graded down-up algebra with $({\rm deg}\,x, {\rm deg}\,y)=(1,n)$ and $\beta \neq 0$, and let $\nabla A$ be the Beilinson algebra of $A$. If $n=1$, then a description of the Hochschild cohomology group of $\nabla A$ is known. In this paper, we calculate the Hochschild cohomology group of $\nabla A$ for the case $n \geq 2$. As an application, we see that the structure of the bounded derived category of the noncommutative projective scheme of $A$ is different depending on whether $\left(\begin{smallmatrix} 1&0 \end{smallmatrix}\right)\left(\begin{smallmatrix} \alpha &1 \\ \beta &0 \end{smallmatrix}\right)^n\left(\begin{smallmatrix} 1 \\ 0 \end{smallmatrix}\right)$ is zero or not. Moreover, it turns out that there is a difference between the cases $n=2$ and $n\geq 3$ in the context of Grothendieck groups.
|
[
"Mathematics Archive->math.RA",
"Mathematics Archive->math.RT"
] | 2019-04-01T09:57:56Z |
2310.04394
|
Direct Photon Scattering by Plasmons in BiTeI
|
We use polarization resolved Raman spectroscopy to show that for 3D giant Rashba system the bulk plasmon collective mode directly couples to the Raman response even in the long wavelength $\mathbf q \rightarrow 0$ limit although the standard theory predicts that the plasmon spectral weight should scale as the square of its quasi-momentum and hence be negligibly weak in the Raman spectra. Such plasmon coupling to the Raman response at $\mathbf q \rightarrow 0$ arises for a polar system with spin-orbit coupling when the incoming photon excitation is turned to a resonance with Rashba-split intermediates states involved in the resonant Raman process. As an example, we identify special features of BiTeI's chiral band structure that enable the appearance of plasmon mode in the Raman spectrum.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2023-10-06T17:38:28Z |
0711.0396
|
Realistic Yukawa Textures and SUSY Spectra from Intersecting Branes
|
We study the possible phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in Type IIA string theory on the T^6/(Z2 x Z2) orientifold with some desirable semi-realistic features. In the model, tree-level gauge coupling unification is achieved automatically at the string scale, and the gauge symmetry may be broken to the Standard Model (SM) close to the string scale. The small number of extra chiral exotic states in the model may be decoupled via the Higgs mechanism and strong dynamics. We calculate the possible supersymmetry breaking soft terms and the corresponding low-energy supersymmetric particle spectra which may potentially be tested at the Large Hadron Collider (LHC). We find that for the viable regions of the parameter space the lightest CP-even Higgs boson mass usually satisfies m_H < 120 GeV, and the observed dark matter density may be generated. Finally, we find that it is possible to obtain correct SM quark masses and mixings, and the tau lepton mass at the unification scale. Additionally, neutrino masses and mixings may be generated via the seesaw mechanism. Mechanisms to stabilize the open and closed-string moduli, which are necessary for the model to be truly viable and to make definite predictions are discussed.
|
[
"Physics Archive->astro-ph",
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th"
] | 2007-11-05T20:23:46Z |
1206.0777
|
The SED of Low-Luminosity AGNs at high-spatial resolution
|
The inner structure of AGNs is expected to change below a certain luminosity limit. The big blue bump, footprint of the accretion disk, is absent for the majority of low-luminosity AGNs (LLAGNs). Moreover, recent simulations suggest that the torus, a keystone in the Unified Model, vanishes for nuclei with L_bol < 10^42 erg/s. However, the study of LLAGN is a complex task due to the contribution of the host galaxy, which light swamps these faint nuclei. This is specially critical in the IR range, at the maximum of the torus emission, due to the contribution of the old stellar population and/or dust in the nuclear region. Adaptive optics imaging in the NIR (VLT/NaCo) together with diffraction limited imaging in the mid-IR (VLT/VISIR) permit us to isolate the nuclear emission for some of the nearest LLAGNs in the Southern Hemisphere. These data were extended to the optical/UV range (HST), radio (VLA, VLBI) and X-rays (Chandra, XMM-Newton, Integral), in order to build a genuine spectral energy distribution (SED) for each AGN with a consistent spatial resolution (< 0.5") across the whole spectral range. From the individual SEDs, we construct an average SED for LLAGNs sampled in all the wavebands mentioned before. Compared with previous multiwavelength studies of LLAGNs, this work covers the mid-IR and NIR ranges with high-spatial resolution data. The LLAGNs in the sample present a large diversity in terms of SED shapes. Some of them are very well described by a self-absorbed synchrotron (e.g. NGC 1052), while some other present a thermal-like bump at ~1 micron (NGC 4594). All of them are significantly different when compared with bright Seyferts and quasars, suggesting that the inner structure of AGNs (i.e. the torus and the accretion disk) suffers intrinsic changes at low luminosities.
|
[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2012-06-04T21:47:16Z |
2109.12379
|
TEMGNet: Deep Transformer-based Decoding of Upperlimb sEMG for Hand Gestures Recognition
|
There has been a surge of recent interest in Machine Learning (ML), particularly Deep Neural Network (DNN)-based models, to decode muscle activities from surface Electromyography (sEMG) signals for myoelectric control of neurorobotic systems. DNN-based models, however, require large training sets and, typically, have high structural complexity, i.e., they depend on a large number of trainable parameters. To address these issues, we developed a framework based on the Transformer architecture for processing sEMG signals. We propose a novel Vision Transformer (ViT)-based neural network architecture (referred to as the TEMGNet) to classify and recognize upperlimb hand gestures from sEMG to be used for myocontrol of prostheses. The proposed TEMGNet architecture is trained with a small dataset without the need for pre-training or fine-tuning. To evaluate the efficacy, following the-recent literature, the second subset (exercise B) of the NinaPro DB2 dataset was utilized, where the proposed TEMGNet framework achieved a recognition accuracy of 82.93% and 82.05% for window sizes of 300ms and 200ms, respectively, outperforming its state-of-the-art counterparts. Moreover, the proposed TEMGNet framework is superior in terms of structural capacity while having seven times fewer trainable parameters. These characteristics and the high performance make DNN-based models promising approaches for myoelectric control of neurorobots.
|
[
"Computer Science Archive->cs.LG",
"Electrical Engineering and Systems Science Archive->eess.SP"
] | 2021-09-25T15:03:22Z |
1901.00033
|
Collision of Ionization Waves in Long Discharge Tubes
|
This research focuses on interaction of ionization waves (IW) generated in long discharge tubes (1 m length and 1.5 cm in diameter) filled with neon or argon under pressure about 1 Torr and, in particular, on simplest case of such interference which is collision of the opposite directed IW of positive polarity. The waves were triggered from two electrodes of the tube by simultaneous application of the same high voltage pulse and propagated toward the tube center until their collision. Space and time stability of the collisions was achieved via decreasing time delay of the initial breakdowns which trigger IW by employment of both memory effect and photo-desorption of wall surface electrons. Significant memory effect occurred for the pulse repetition rate over 100Hz. Multiple IW transition from the electrode forms specific one-electrode discharge; as a result the problem of IW collision was transformed into the observation of two opposite one-electrode discharges interaction. Patterns of IW interfering were registered via deviation of their kinematic characteristics (x-t diagrams) from ones for non-collided wave. This method shows that two ionization waves travel toward each other with decreasing speeds and subsequent degradation of the emission. An area near the tube center where IWs emission was not detected was considered as the IW suppression zone. The zone width depends on voltage amplitude, gas type and pressure.
|
[
"Physics Archive->physics->physics.plasm-ph"
] | 2018-12-31T20:05:38Z |
1206.2148
|
Sumsets in primes containing almost all even positive integers
|
Let $A$ be a subset of primes up to $x$. If we assume $A$ is well-distributed (in the Siegel-Walfisz sense) in any arithmetic progressions to moduli $q\leqslant(\log x)^c$ for any $c>0$, then the sumset $A+A$ has density 1/2 in the natural numbers as $x$ tends to infinity, which also yields almost all even positive integers could be represented as the sums of two primes in $A$ as $x$ tends to infinity. This result, improving the previous results in such special case, could be compared with the classical estimation for the exceptional set of binary Goldbach problem.
|
[
"Mathematics Archive->math.CO",
"Mathematics Archive->math.NT"
] | 2012-06-11T09:51:08Z |
hep-th/9503062
|
Hamiltonian BRST Quantization of the Conformal Spinning String
|
The Hamiltonian BRST quantization of the null spinning string for different number of supersymmetries is given. A null spinning string with manifest space-time conformal invariance is constructed. Its Brst quantization gives negative critical dimension for $N\neq 0$ and reproduces previous results for $N=0$.
|
[
"Physics Archive->hep->hep-th"
] | 1995-03-09T17:48:53Z |
1008.0513
|
On the splitting-up method for rough (partial) differential equations
|
This article introduces the splitting method to systems responding to rough paths as external stimuli. The focus is on nonlinear partial differential equations with rough noise but we also cover rough differential equations. Applications to stochastic partial differential equations arising in control theory and nonlinear filtering are given.
|
[
"Mathematics Archive->math.AP",
"Mathematics Archive->math.PR"
] | 2010-08-03T10:46:20Z |
1710.06073
|
Incremental Subgradient Methods for Minimizing The Sum of Quasi-convex Functions
|
The sum of ratios problem has a variety of important applications in economics and management science, but it is difficult to globally solve this problem. In this paper, we consider the minimization problem of a sum of a number of nondifferentiable quasi-convex component functions over a closed and convex set, which includes the sum of ratios problem as a special case. The sum of quasi-convex component functions is not necessarily to be quasi-convex, and so, this study goes beyond quasi-convex optimization. Exploiting the structure of the sum-minimization problem, we propose a new incremental subgradient method for this problem and investigate its convergence properties to a global optimal solution when using the constant, diminishing or dynamic stepsize rules and under a homogeneous assumption and the H\"{o}lder condition of order $p$. To economize on the computation cost of subgradients of a large number of component functions, we further propose a randomized incremental subgradient method, in which only one component function is randomly selected to construct the subgradient direction at each iteration. The convergence properties are obtained in terms of function values and distances of iterates from the optimal solution set with probability 1. The proposed incremental subgradient methods are applied to solve the sum of ratios problem, as well as the multiple Cobb-Douglas productions efficiency problem, and the numerical results show that the proposed methods are efficient for solving the large sum of ratios problem.
|
[
"Mathematics Archive->math.OC"
] | 2017-10-17T03:32:11Z |
astro-ph/0108105
|
Hot Outflowing Gas from the X-ray Binary Hercules X-1
|
We present a unified picture of outflowing gas from the X-ray binary system Hercules X-1/HZ Herculis. We suggest that the outflowing gas (a wind) causes UV emission seen in mid-eclipse, narrow UV absorption lines, and broad UV P Cygni lines. Observations with the FOS and STIS spectrographs on the Hubble Space Telescope (HST) show UV emission lines in the middle of X-ray eclipse, when the X-ray heated atmosphere of the normal star and accretion disk should be entirely hidden from view. Narrow absorption lines (FWHM~50 km/s) blueshifted by 500 km/s during observations in 1998 and by 400 km/s during observations in 1999 were seen from phi=0.0-0.3. The line velocity was constant to within 20 km/s. The P Cygni profiles from Hercules~X-1 have optical depths tau<1 with a maximum expansion velocity of 600 km/s, and are seen in the resonance lines N V 1238.8,1242.8, Si IV 1393.7,1402.8, and C IV 1548.2, 1550.8. We discuss whether this wind originates in the accretion disk or on the companion star, and how the relevant ions can survive X-ray ionization by the neutron star.
|
[
"Physics Archive->astro-ph"
] | 2001-08-07T02:01:24Z |
2004.03013
|
The radius of comparison of the tensor product of a C*-algebra with $C (X)$
|
Let $X$ be a compact metric space, let $A$ be a unital AH algebra with large matrix sizes, and let $B$ be a stably finite unital C*-algebra. Then we give a lower bound for the radius of comparison of $C(X) \otimes B$ and prove that the dimension-rank ratio satisfies $\operatorname{drr} (A) = \operatorname{drr} \left(C(X)\otimes A\right)$. We also give a class of unital AH algebras $A$ with $\operatorname{rc} \left(C(X) \otimes A\right) = \operatorname{rc} (A)$. We further give a class of stably finite exact $\mathcal{Z}$-stable unital C*-algebras with nonzero radius of comparison.
|
[
"Mathematics Archive->math.OA"
] | 2020-04-06T21:53:56Z |
1703.08300
|
Extreme events in Fitzhugh-Nagumo oscillators coupled with two time delays
|
We study two identical FitzHugh-Nagumo oscillators which are coupled with one or two different time delays. If only a single delay coupling is used, the length of the delay determines whether the synchronization manifold is transversally stable or unstable, exhibiting mixed mode or chaotic oscillations in which the small amplitude oscillations are always in-phase but the large amplitude oscillations are in-phase or out-of-phase respectively. For two delays we find an intricate dynamics which comprises an irregular alteration of small amplitude oscillations, in-phase and out-of-phase large amplitude oscillations, also called events. This transient chaotic dynamics is sandwiched between a bubbling transition and a blowout bifurcation.
|
[
"Physics Archive->nlin->nlin.CD"
] | 2017-03-24T07:34:30Z |
2301.03572
|
Non-oscillating Early Dark Energy and Quintessence from Alpha-Attractors
|
Early dark energy (EDE) is one of the most promising possibilities in order to resolve the Hubble tension: the discrepancy between early and late-Universe measurements of the Hubble constant. In this paper we propose a model of a scalar field which can explain both EDE and late Dark Energy (DE) in a joined manner without additional fine-tuning. The field features kinetic poles as with alpha-attractors. Our model provides an injection of EDE near matter-radiation equality, and redshifts away shortly after via free-fall, later refreezing to become late-time DE at the present day. Using reasonable estimates of the current constraints on EDE from the literature, we find that the parameter space is narrow but viable. As such our model is readily falsifiable. In contrast to other work in EDE, our model is non-oscillatory, which causes its decay to be faster than that of the usual oscillatory EDE, thereby achieving better agreement with observations.
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th"
] | 2023-01-09T18:50:02Z |
2305.01734
|
Spectrum of Massive and Massless Ambitwistor Strings
|
Inspired by recent work arXiv:2301.11227 on massive ambitwistor strings this paper examines the spectrum of such models using oscillator expansions. The spectrum depends heavily on the constant related to the normal ordering of the zero mode operator ${L_0}$ of the Virasoro algebra. The supergravity model is investigated in more detail, and two anomaly-free variations are presented, both with a rich spectrum and with tree scattering amplitudes that include a kinematic Parke-Taylor factor for particles other than gravitons without a need for an external current algebra. The spectrum of some of the models can also be interpreted as containing three generations of the Pati-Salam model.
|
[
"Physics Archive->hep->hep-th"
] | 2023-05-02T19:06:04Z |
nucl-th/0010091
|
Elastic p-3He and n-3H scattering with two- and three-body forces
|
We report on a microscopic calculation of n-3H and p-3He scattering employing the Argonne v_{18} and v_8' nucleon-nucleon potentials with and without additional three-nucleon force. An R-matrix analysis of the p-3He and n-3H scattering data is presented. Comparisons are made for the phase shifts and a selection of measurements in both scattering systems. Differences between our calculation and the R-matrix results or the experimental data can be attributed to only two partial waves (3P0 and 3P2). We find the effect of the Urbana IX and the Texas-Los Alamos three-nucleon forces on the phase shifts to be negligible.
|
[
"Physics Archive->nucl->nucl-th"
] | 2000-10-27T08:25:48Z |
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