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| creation_date
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|---|---|---|---|---|
1203.0965
|
The XMM-Newton Slew view of IGRJ17361-4441: a transient in the globular cluster NGC 6388
|
IGRJ17361-4441 is a hard transient recently observed by the INTEGRAL satellite. The source, close to the center of gravity of the globular cluster NGC 6388, quickly became the target of follow-up observations conducted by the Chandra, Swift/XRT and RXTE observatories. Here, we concentrate in particular on a set of observations conducted by the XMM-Newton satellite during two slews, in order to get the spectral information of the source and search for spectral variations. The spectral parameters determined by the recent XMM-Newton slew observations were compared to the previously known results. The maximum unabsorbed $X$-ray flux in the 0.5-10 keV band as detected by the XMM-Newton slew observations is $\simeq 4.5\times 10^{-11}$ erg cm$^{-2}$ s$^{-1}$, i.e. consistent with that observed by the Swift/XRT satellite 15 days earlier. The spectrum seems to be marginally consistent ($\Gamma\simeq 0.93-1.63$) with that derived from the previous high energy observation.
|
[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2012-03-05T16:42:33Z |
2101.04355
|
Neural Contract Element Extraction Revisited: Letters from Sesame Street
|
We investigate contract element extraction. We show that LSTM-based encoders perform better than dilated CNNs, Transformers, and BERT in this task. We also find that domain-specific WORD2VEC embeddings outperform generic pre-trained GLOVE embeddings. Morpho-syntactic features in the form of POS tag and token shape embeddings, as well as context-aware ELMO embeddings do not improve performance. Several of these observations contradict choices or findings of previous work on contract element extraction and generic sequence labeling tasks, indicating that contract element extraction requires careful task-specific choices. Analyzing the results of (i) plain TRANSFORMER-based and (ii) BERT-based models, we find that in the examined task, where the entities are highly context-sensitive, the lack of recurrency in TRANSFORMERs greatly affects their performance.
|
[
"Computer Science Archive->cs.CL"
] | 2021-01-12T09:02:22Z |
1808.08106
|
The Shift from Processor Power Consumption to Performance Variations: Fundamental Implications at Scale
|
The Intel Haswell-EP processor generation introduces several major advancements of power control and energy-efficiency features. For computationally intense applications using advanced vector extension (AVX) instructions, the processor cannot continuously operate at full speed but instead reduces its frequency below the nominal frequency to maintain operations within thermal design power (TDP) limitations. Moreover, the running average power limitation (RAPL) mechanism to enforce the TDP limitation has changed from a modeling to a measurement approach. The combination of these two novelties have significant implications. Through measurements on an Intel Sandy Bridge-EP cluster, we show that previous generations have sustained homogeneous performance across multiple CPUs and compensated for hardware manufacturing variability through varying power consumption. In contrast, our measurements on a Petaflop Haswell system show that this generation exhibits rather homogeneous power consumption limited by the TDP and capped by the improved RAPL while providing inhomogeneous performance under full load. Since all of these controls are transparent to the user, this behavior is likely to complicate performance analysis tasks and impact tightly coupled parallel applications.
|
[
"Computer Science Archive->cs.DC"
] | 2018-08-24T12:40:03Z |
2110.03145
|
Distribution-free and Model-free Multivariate Feature Screening via Multivariate Rank Distance Correlation
|
Feature screening approaches are effective in selecting active features from data with ultrahigh dimensionality and increasing complexity; however, the majority of existing feature screening approaches are either restricted to a univariate response or rely on some distribution or model assumptions. In this article, we propose a novel sure independence screening approach based on the multivariate rank distance correlation (MrDc-SIS). The MrDc-SIS achieves multiple desirable properties such as being distribution-free, completely nonparametric, scale-free, robust for outliers or heavy tails, and sensitive for hidden structures. Moreover, the MrDc-SIS can be used to screen either univariate or multivariate responses and either one dimensional or multi-dimensional predictors. We establish the asymptotic sure screening consistency property of the MrDc-SIS under a mild condition by lifting previous assumptions about the finite moments. Simulation studies demonstrate that MrDc-SIS outperforms three other closely relevant approaches under various settings. We also apply the MrDc-SIS approach to a multi-omics ovarian carcinoma data downloaded from The Cancer Genome Atlas (TCGA).
|
[
"Statistics Archive->stat.ME"
] | 2021-10-07T02:35:26Z |
cond-mat/0210218
|
Theory of spin relaxation in magnetic resonance force microscopy
|
We study relaxation of a spin in magnetic resonance force microscopy (MRFM) experiments. We evaluate the relaxation rate for the spin caused by high-frequency mechanical noise of the cantilever under the conditions of adiabatic spin inversion. We find qualitative agreement between the obtained relaxation time and the experimental results of Stipe {\it et al.} [Phys. Rev. Lett. 87, 277602 (2001)]. Based on our analysis, we propose a method for improving the MRFM sensitivity by engineering cantilevers with reduced tip positional fluctuations.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2002-10-09T21:42:33Z |
astro-ph/0410666
|
Cosmic abundances: The impact of stellar duplicity
|
The mass-transfer scenario links chemical peculiarities with stellar duplicity for an increasing number of stellar classes (classical and dwarf barium stars, subgiant and giant CH stars, S stars without technetium, yellow symbiotic stars, WIRRING stars, Abell-35-like nuclei of planetary nebulae...). Despite these successes, the mass-transfer scenario still faces several problems: What is the mass-transfer mode? Why orbital elements of dwarf barium stars do not fully match those of the classical barium stars? What is the origin of the few non-binary stars among dwarf barium stars? The paper reviews these open questions.
|
[
"Physics Archive->astro-ph"
] | 2004-10-27T15:25:17Z |
cond-mat/0509099
|
Modelling and Simulation of Charging and Discharging Processes in Nanocrystal Flash Memories During Program and Erase Operations
|
This work is focused on the understanding of charging and discharging processes in silicon nanocrystal flash memories during program and erase operations through time-dependent numerical simulations. Time dependent simulations of the program and erase operations are based on a description of the nanocrystal memory dynamics in terms of a master equation. The related transition rates are computed with a one dimensional Poisson-Schroedinger solver which allows the computation of the tunnelling currents and of generation and recombination rates between the outer reservoir and localized states in the dielectric layer. Comparison between simulations and experiments available in the literature provides useful insights of the storing mechanisms. In particular, simulations allow us to rule out that electrons are stored in confined states in the conduction band of silicon nanocrystals, whereas they suggest that electrons are actually trapped in localized states in the silicon gap at an energy close to the silicon valence band edge, and located at the interface between the nanocrystals and the surrounding silicon oxide.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2005-09-05T09:53:21Z |
physics/9903009
|
Symplectic algorithm for constant-pressure molecular dynamics using a Nose-Poincare thermostat
|
We present a new algorithm for isothermal-isobaric molecular-dynamics simulation. The method uses an extended Hamiltonian with an Andersen piston combined with the Nos'e-Poincar'e thermostat, recently developed by Bond, Leimkuhler and Laird [J. Comp. Phys., 151, (1999)]. This Nos'e-Poincar'e-Andersen (NPA) formulation has advantages over the Nos'e-Hoover-Andersen approach in that the NPA is Hamiltonian and can take advantage of symplectic integration schemes, which lead to enhanced stability for long-time simulations. The equations of motion are integrated using a Generalized Leapfrog Algorithm and the method is easy to implement, symplectic, explicit and time reversible. To demonstrate the stability of the method we show results for test simulations using a model for aluminum.
|
[
"Physics Archive->physics->physics.chem-ph"
] | 1999-03-04T16:32:23Z |
1110.0867
|
Emergent spacetime, and a model for unitary gravitational collapse in AdS
|
We propose a CFT unitary description of the gravitational collapse. The starting point is the model of a black hole in AdS proposed by Maldacena in arXiv: 0106112 [hep-th]. We show that by proposing a two-copies version of the AdS/CFT conjecture, the process of formation of black holes so as other spacetimes with horizons may be described as an unitary process in the dual field theory. In doing this, we construct a well defined framework to describe general spacetimes as entangled states, in terms of the spectrum of states on the exact Anti-de-Sitter background. As application, we show how the description of the Hawking-Page transition results simplified in this formalism and some novel aspects may be observed. Finally, a simplified analysis based on weakly coupled bulk fields is discussed.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2011-10-04T23:25:28Z |
2207.12033
|
Contrastive Learning for Interactive Recommendation in Fashion
|
Recommender systems and search are both indispensable in facilitating personalization and ease of browsing in online fashion platforms. However, the two tools often operate independently, failing to combine the strengths of recommender systems to accurately capture user tastes with search systems' ability to process user queries. We propose a novel remedy to this problem by automatically recommending personalized fashion items based on a user-provided text request. Our proposed model, WhisperLite, uses contrastive learning to capture user intent from natural language text and improves the recommendation quality of fashion products. WhisperLite combines the strength of CLIP embeddings with additional neural network layers for personalization, and is trained using a composite loss function based on binary cross entropy and contrastive loss. The model demonstrates a significant improvement in offline recommendation retrieval metrics when tested on a real-world dataset collected from an online retail fashion store, as well as widely used open-source datasets in different e-commerce domains, such as restaurants, movies and TV shows, clothing and shoe reviews. We additionally conduct a user study that captures user judgements on the relevance of the model's recommended items, confirming the relevancy of WhisperLite's recommendations in an online setting.
|
[
"Computer Science Archive->cs.IR"
] | 2022-07-25T10:15:56Z |
1810.13359
|
Selecting competent referees to assess research projects proposals: a study of referees' registers
|
The selection of referees for evaluation of research projects under competitive financing appears particularly critical: the greater the competence of the referee concerning the core topic, the more their judgment is trustworthy and the more the financing of the best proposals is probable. The current work analyzes registers of experts used to select referees for the evaluation of research proposals in public programs with competitive funding. The work has the objective to present a methodology to verify the degree of "coverage" of the register compared to the spectrum of competencies necessary for the evaluation of such wide-ranging national programs; and to evaluate the level of scientific performance of the register's referees in the hard sciences, compared to the their national colleagues from the same fields.
|
[
"Computer Science Archive->cs.DL"
] | 2018-10-31T15:52:55Z |
1012.1638
|
Ontology and Knowledge Management System on Epilepsy and Epileptic Seizures
|
A Knowledge Management System developed for supporting creation, capture, storage and dissemination of information about Epilepsy and Epileptic Seizures is presented. We present an Ontology on Epilepsy and a Web-based prototype that together create the KMS.
|
[
"Computer Science Archive->cs.DL"
] | 2010-12-07T23:20:15Z |
2103.14238
|
FRITL: A Hybrid Method for Causal Discovery in the Presence of Latent Confounders
|
We consider the problem of estimating a particular type of linear non-Gaussian model. Without resorting to the overcomplete Independent Component Analysis (ICA), we show that under some mild assumptions, the model is uniquely identified by a hybrid method. Our method leverages the advantages of constraint-based methods and independent noise-based methods to handle both confounded and unconfounded situations. The first step of our method uses the FCI procedure, which allows confounders and is able to produce asymptotically correct results. The results, unfortunately, usually determine very few unconfounded direct causal relations, because whenever it is possible to have a confounder, it will indicate it. The second step of our procedure finds the unconfounded causal edges between observed variables among only those adjacent pairs informed by the FCI results. By making use of the so-called Triad condition, the third step is able to find confounders and their causal relations with other variables. Afterward, we apply ICA on a notably smaller set of graphs to identify remaining causal relationships if needed. Extensive experiments on simulated data and real-world data validate the correctness and effectiveness of the proposed method.
|
[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2021-03-26T03:12:14Z |
1711.10628
|
Coexistence of superconductivity and charge-density wave in the quasi-one-dimensional material HfTe3
|
We present the first experimental evidence for metallicity, superconductivity (SC) and the co-existence of charge density waves (CDW) in the quasi-one-dimensional material HfTe3. The existence of such phenomena is a typical characteristic of the transition metal chalcogenides however, without the application of hydrostatic pressure/chemical doping, it is rare for a material to exhibit the co-existence of both states. Materials such as HfTe3 can therefore provide us with a unique insight into the relationship between these multiple ordered states. By improving on the original synthesis conditions, we have successfully synthesised single phase HfTe3 and confirmed the resultant structure by performing Rietveld refinement. Using low temperature resistivity measurements, we provide the first experimental evidence of SC at ~1.4 K as well as a resistive anomaly indicative of a CDW formation at ~82 K. By the application of hydrostatic-pressure, the resistivity anomaly shifts to higher temperature. The results show that HfTe3 is a promising new material to help study the relationship between SC and CDW.
|
[
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2017-11-29T00:37:26Z |
1808.10230
|
Collisions involving antiprotons and antihydrogen: an overview
|
I give an overview of experimental and theoretical results for antiproton and antihydrogen scattering with atoms and molecules (in particular H, He). At low energies ($\lesssim1$~keV) there are practically no experimental data available. Instead I compare the results from different theoretical calculations, of various degrees of sophistication. At energies up to a few 10:s of eV, I focus on simple approximations that give reasonably accurate results, as these allow quick estimates of collision rates without embarking on a research project.
|
[
"Physics Archive->physics->physics.atom-ph"
] | 2018-08-30T11:31:02Z |
chao-dyn/9303005
|
Global Solutions of the Equations of Elastodynamics of Incompressible Neo-Hookean Materials
|
We prove that the initial-value problem for the motion of a certain type of elastic body has a solution for all time if the initial data are sufficiently small. The body must fill all of three space, obey a ``neo-Hookean'' stress-strain law, and be incompressible. The proof takes advantage of the delayed singularity formation which occurs for solutions of quasi-linear hyperbolic equations in more than one space dimension. It turns out that the curl of the displacement of the body obeys such an equation. Thus using Klainerman's inequality, one derives the necessary estimates to gaurantee that solutions persist for all time.
|
[
"Physics Archive->nlin->nlin.CD"
] | 1993-03-18T20:10:17Z |
0708.0683
|
Persistence and Memory in Patchwork Dynamics for Glassy Models
|
Slow dynamics in disordered materials prohibits direct simulation of their rich nonequilibrium behavior at large scales. "Patchwork dynamics" is introduced to mimic relaxation over a very broad range of time scales by equilibrating or optimizing directly on successive length scales. This dynamics is used to study coarsening and to replicate memory effects for spin glasses and random ferromagnets. It is also used to find, with high confidence, exact ground states in large or toroidal samples.
|
[
"Physics Archive->cond-mat->cond-mat.dis-nn",
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2007-08-05T21:39:32Z |
2308.01096
|
Learning Fourier-Constrained Diffusion Bridges for MRI Reconstruction
|
Recent years have witnessed a surge in deep generative models for accelerated MRI reconstruction. Diffusion priors in particular have gained traction with their superior representational fidelity and diversity. Instead of the target transformation from undersampled to fully-sampled data, common diffusion priors are trained to learn a multi-step transformation from Gaussian noise onto fully-sampled data. During inference, data-fidelity projections are injected in between reverse diffusion steps to reach a compromise solution within the span of both the diffusion prior and the imaging operator. Unfortunately, suboptimal solutions can arise as the normality assumption of the diffusion prior causes divergence between learned and target transformations. To address this limitation, here we introduce the first diffusion bridge for accelerated MRI reconstruction. The proposed Fourier-constrained diffusion bridge (FDB) leverages a generalized process to transform between undersampled and fully-sampled data via random noise addition and random frequency removal as degradation operators. Unlike common diffusion priors that use an asymptotic endpoint based on Gaussian noise, FDB captures a transformation between finite endpoints where the initial endpoint is based on moderate degradation of fully-sampled data. Demonstrations on brain MRI indicate that FDB outperforms state-of-the-art reconstruction methods including conventional diffusion priors.
|
[
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2023-08-02T12:04:07Z |
1801.09049
|
Covariance-based Dissimilarity Measures Applied to Clustering Wide-sense Stationary Ergodic Processes
|
We introduce a new unsupervised learning problem: clustering wide-sense stationary ergodic stochastic processes. A covariance-based dissimilarity measure together with asymptotically consistent algorithms is designed for clustering offline and online datasets, respectively. We also suggest a formal criterion on the efficiency of dissimilarity measures, and discuss of some approach to improve the efficiency of our clustering algorithms, when they are applied to cluster particular type of processes, such as self-similar processes with wide-sense stationary ergodic increments. Clustering synthetic data and real-world data are provided as examples of applications.
|
[
"Statistics Archive->stat.ML"
] | 2018-01-27T07:37:41Z |
hep-ph/0007180
|
Two-Fermion Production in Electron-Positron Collisions
|
This report summarizes the results of the two-fermion working group of the LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the theoretical calculations of the two fermion production process in the electron-positron collision at LEP2 center of the mass energies are reported. The Bhabha process and the production of muon, tau, neutrino and quark pairs is covered. On the basis of comparison of various calculations, theoretical uncertainties are estimated and compared with those needed for the final LEP2 data analysis. The subjects for the further studies are identified.
|
[
"Physics Archive->hep->hep-ph"
] | 2000-07-17T19:15:00Z |
2202.03692
|
The factorization method and Capon's method for random source identification in experimental aeroacoustics
|
Experimental aeroacoustics is concerned with the estimation of acoustic source power distributions, which are for instance caused by fluid structure interactions on scaled aircraft models inside a wind tunnel, from microphone array measurements of associated sound pressure fluctuations. In the frequency domain aeroacoustic sound propagation can be modelled as a random source problem for a convected Helmholtz equation. This article is concerned with the inverse random source problem to recover the support of an uncorrelated aeroacoustic source from correlations of observed pressure signals. We show that a variant of the factorization method from inverse scattering theory can be used for this purpose. We also discuss a surprising relation between the factorization method and a commonly used beamforming algorithm from experimental aeroacoustics, which is known as Capon's method or as the minimum variance method. Numerical examples illustrate our theoretical findings.
|
[
"Computer Science Archive->cs.NA",
"Mathematics Archive->math.NA"
] | 2022-02-08T07:29:15Z |
1902.00824
|
Joint User Selection, Power Allocation, and Precoding Design with Imperfect CSIT for Multi-Cell MU-MIMO Downlink Systems
|
In this paper, a new optimization framework is presented for the joint design of user selection, power allocation, and precoding in multi-cell multi-user multiple-input multiple-output (MU-MIMO) systems when imperfect channel state information at transmitter (CSIT) is available. By representing the joint optimization variables in a higher-dimensional space, the weighted sum-spectral efficiency maximization is formulated as the maximization of the product of Rayleigh quotients. Although this is still a non-convex problem, a computationally efficient algorithm, referred to as generalized power iteration precoding (GPIP), is proposed. The algorithm converges to a stationary point (local maximum) of the objective function and therefore it guarantees the first-order optimality of the solution. By adjusting the weights in the weighted sum-spectral efficiency, the GPIP yields a joint solution for user selection, power allocation, and downlink precoding. The GPIP is also extended to a multi-cell scenario, where cooperative base stations perform joint user selection and design their precoding vectors by sharing global yet imperfect CSIT within the cooperative BSs. System-level simulations show the gains of the proposed approach with respect to conventional user selection and linear downlink precoding.
|
[
"Computer Science Archive->cs.IT",
"Mathematics Archive->math.IT"
] | 2019-02-03T01:01:32Z |
1512.01042
|
Finite volume methods for elasticity with weak symmetry
|
We introduce a new cell-centered finite volume discretization for elasticity with weakly enforced symmetry of the stress tensor. The method is motivated by the need for robust discretization methods for deformation and flow in porous media, and falls in the category of multi-point stress approximations (MPSA). By enforcing symmetry weakly, the resulting method has additional flexibility beyond previous MPSA methods. This allows for a construction of a method which is applicable to all grid types, and in particular the method amends a crucial shortcoming in previous MPSA methods for simplex grids. By formulating the method as a discrete variational problem, we prove convergence of the new method for a wide range of problems, with conditions that can be verified at the time of discretization. We present the first set of comprehensive numerical tests for the MPSA methods in three dimensions, covering Cartesian and simplex grids, with both heterogeneous and nearly incompressible media. The tests show that the new method consistently is second order convergent in displacement, despite being lowest order, with a rate that mostly is between 1 and 2 for stresses. The results further show that the new method is more robust and computationally cheaper than previous MPSA methods.
|
[
"Mathematics Archive->math.NA"
] | 2015-12-03T11:28:30Z |
0906.3037
|
On the density of the sum of two independent Student t-random vectors
|
In this paper, we find an expression for the density of the sum of two independent $d-$dimensional Student $t-$random vectors $\mathbf{X}$ and $\mathbf{Y}$ with arbitrary degrees of freedom. As a byproduct we also obtain an expression for the density of the sum $\mathbf{N}+\mathbf{X}$, where $\mathbf{N}$ is normal and $\mathbf{X}$ is an independent Student $t-$vector. In both cases the density is given as an infinite series \[ \sum_{n=0}^{\infty} c_{n}f_{n} \] where $f_{n}$ is a sequence of probability densities on $\mathbb{R}^{d}$ and $(c_{n} )$ is a sequence of positive numbers of sum 1, i.e. the distribution of a non-negative integer-valued random variable $C$, which turns out to be infinitely divisible for $d=1$ and $d=2.$ When $d=1$ and the degrees of freedom of the Student variables are equal, we recover an old result of Ruben.
|
[
"Mathematics Archive->math.PR"
] | 2009-06-16T22:33:12Z |
2107.13897
|
Decoherence Effects in a Three-Level System under Gaussian Process
|
When subjected to a classical fluctuating field characterized by a Gaussian process, we examine the {purity} and coherence protection in a three-level quantum system. This symmetry of the three-level system is examined when the local random field is investigated further in the noiseless and noisy regimes. In~particular, we consider fractional Gaussian, Gaussian, Ornstein--Uhlenbeck, and~power law noisy regimes. We show that the destructive nature of the Ornstein--Uhlenbeck noise toward the symmetry of the qutrit to preserve encoded {purity and coherence} remains large. Our findings suggest that properly adjusting the noisy parameters to specifically provided values can facilitate optimal extended {purity and coherence} survival. Non-vanishing terms appear in the final density matrix of the single qutrit system, indicating that it is in a strong coherence regime. Because~of all of the Gaussian noises, monotonic decay with no revivals has been observed in the single qutrit system. In~terms of coherence and information preservation, we find that the current qutrit system outperforms systems with multiple qubits or qutrits using purity and von Neumann entropy. A~comparison of noisy and noiseless situations shows that the fluctuating nature of the local random fields is ultimately lost when influenced using the classical Gaussian noises
|
[
"Physics Archive->quant-ph"
] | 2021-07-29T11:13:13Z |
0904.0210
|
A new model for evolution in a spatial continuum
|
We investigate a new model for populations evolving in a spatial continuum. This model can be thought of as a spatial version of the Lambda-Fleming-Viot process. It explicitly incorporates both small scale reproduction events and large scale extinction-recolonisation events. The lineages ancestral to a sample from a population evolving according to this model can be described in terms of a spatial version of the Lambda-coalescent. Using a technique of Evans(1997), we prove existence and uniqueness in law for the model. We then investigate the asymptotic behaviour of the genealogy of a finite number of individuals sampled uniformly at random (or more generally `far enough apart') from a two-dimensional torus of side L as L tends to infinity. Under appropriate conditions (and on a suitable timescale), we can obtain as limiting genealogical processes a Kingman coalescent, a more general Lambda-coalescent or a system of coalescing Brownian motions (with a non-local coalescence mechanism).
|
[
"Mathematics Archive->math.PR"
] | 2009-04-01T18:32:00Z |
0901.2692
|
Dehn twists and invariant classes
|
A degeneration of compact Kaehler manifolds gives rise to a monodromy action on Betti moduli space H^1(X, G) = Hom(\pi_1(X),G)/G over smooth fibres with a complex algebraic structure group G being either abelian or reductive. Assume that the singularities of the central fibre is of normal crossing. When G = C, the invariant cohomology classes arise from the global classes. This is no longer true in general. In this paper, we produce large families of locally invariant classes that do not arise from global ones for reductive G. These examples exist even when G is abelian, as long as G contains multiple torsion points. Finally, for general G, we make a new conjecture on local invariant classes and produce some suggestive examples.
|
[
"Mathematics Archive->math.AG",
"Mathematics Archive->math.CV"
] | 2009-01-18T10:30:57Z |
1901.09261
|
Topological classification of Liouville foliations for the Kovalevskaya integrable case on the Lie algebra so(4)
|
Topology of Liouville foliations for an analogue of the Kovalevskaya integrable case on Lie algebra so(4) is discussed. Fomenko-Zieschang invariants (i.e. marked molecules) were calculated for these foliations on every regular isoenergy submanifold. The corresponding stratification of the three-dimensional space of parameters of these manifolds is described in details.
|
[
"Mathematics Archive->math.DS"
] | 2019-01-26T18:31:39Z |
2003.01001
|
From the Hartree to the Vlasov dynamics: conditional strong convergence
|
We review the recent results [45, 46] concerning the semiclassical limit from the Hartree dynamics to the Vlasov equation with singular potentials and extend them to the case of more general radial interactions. We prove that, at positive temperature, the Hartree dynamics converges in trace norm to the Vlasov one, for a particular class of initial states.
|
[
"Mathematics Archive->math.AP",
"Mathematics Archive->math.MP",
"Physics Archive->math-ph"
] | 2020-03-02T16:31:08Z |
hep-th/0201051
|
Thick de Sitter 3-Branes, Dynamic Black Holes and Localization of Gravity
|
The embedding of a thick de Sitter 3-brane into a five-dimensional bulk is studied, assuming a scalar field with potential is present in the bulk. A class of solutions is found in closed form that can represent a thick de Sitter 3-brane interpolating either between two dynamical black holes with a $R \times S_{4}$ topology or between two Rindler-like spacetimes with a $R_{2}\times S_{3}$ topology. The gravitational field is localized in a small region near the center of the 3-brane. The analysis of graviton fluctuations shows that a zero mode exists and separates itself from a set of continuous modes by a mass gap. The existence of such a mass gap is shown to be universal. The scalar perturbations are also studied and shown to be stable.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2002-01-08T21:07:13Z |
2208.08409
|
Schwarzian derivative in higher-order Riccati equations
|
The Sturm-Liouville equation represents the linearized form of the first-order Riccati equation. This provides an evidence for the connection between Schwarzian derivative and this first-order nonlinear differential equation. Similar connection is not obvious for higher-order equations in the Riccati chain because the corresponding linear equations are of order greater than two. With special attention to the second- and third-order Riccati equations we demonstrate that Schwarzian derivative has a natural space in higher Riccati equations. There exist higher-order analogues of the Schwarztan derivative. We demonstrate that equations in the Riccati hierarchy are embedded in these higher-order derivatives.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->math-ph",
"Physics Archive->nlin->nlin.SI"
] | 2022-08-17T17:10:32Z |
hep-lat/0007004
|
Renormalisation and off-shell improvement in lattice perturbation theory
|
We discuss the improvement of flavour non-singlet point and one-link lattice quark operators, which describe the quark currents and the first moment of the DIS structure functions respectively. Suitable bases of improved operators are given, and the corresponding renormalisation factors and improvement coefficients are calculated in one-loop lattice perturbation theory, using the Sheikholeslami-Wohlert (clover) action. To this order we achieve off-shell improvement by eliminating the effect of contact terms. We use massive fermions, and our calculations are done keeping all terms up to first order in the lattice spacing, for arbitrary m^2/p^2, in a general covariant gauge. We also compare clover fermions with fermions satisfying the Ginsparg-Wilson relation, and show how to remove O(a) effects off-shell in this case too, and how this is in many aspects simpler than for clover fermions. Finally, tadpole improvement is also considered.
|
[
"Physics Archive->hep->hep-lat"
] | 2000-07-05T12:29:17Z |
astro-ph/9701181
|
New results on 26Al production in classical novae
|
The production of 26Al by explosions of classical novae has been computed by means of a hydrodynamic code that follows both the accretion and the explosion stages. A special emphasis has been put on the analysis of the influence of the initial abundances of the accreted envelope, as well as on the nuclear reaction rates involved. With the most recent values of chemical composition and reaction rates available, 26Al production is lowered with respect to previous computations. According to our results, the final contribution of novae to the galactic 26Al is at most 0.4 M_sun, which is a small part of the estimated 26Al in the Galaxy derived from COMPTEL observations of the 1809 keV emission.
|
[
"Physics Archive->astro-ph"
] | 1997-01-23T13:36:39Z |
0805.2996
|
Lossy Source Transmission over the Relay Channel
|
Lossy transmission over a relay channel in which the relay has access to correlated side information is considered. First, a joint source-channel decode-and-forward scheme is proposed for general discrete memoryless sources and channels. Then the Gaussian relay channel where the source and the side information are jointly Gaussian is analyzed. For this Gaussian model, several new source-channel cooperation schemes are introduced and analyzed in terms of the squared-error distortion at the destination. A comparison of the proposed upper bounds with the cut-set lower bound is given, and it is seen that joint source-channel cooperation improves the reconstruction quality significantly. Moreover, the performance of the joint code is close to the lower bound on distortion for a wide range of source and channel parameters.
|
[
"Computer Science Archive->cs.IT",
"Mathematics Archive->math.IT"
] | 2008-05-20T02:45:47Z |
2212.07218
|
Key Challenges with Agile Culture -- A Survey among Practitioners
|
Context: Within agile transformations, there are a lot of different challenges coming up. One very important but less considered and treated in research are cultural challenges. Although research shows that cultural clashes and general organizational resistance to change are part of the most significant agile adoption barriers. Objective: Thus, our objective is to tackle this field and come up with important contributions for further research. To this end, we want to identify challenges that arise from the interplay between agility and organizational culture. Method: This is done based on an iterative research approach. On the one hand, we gathered qualitative data among our network of agile practitioners. Then, we derived in sum 15 challenges with agile culture. On the other hand, we gathered quantitative data by means of a questionnaire study with 92 participants. Results: We identified 7 key challenges out of the 15 challenges with agile culture. The results that are presented in a conceptual model show a focus on human aspects that we need to deal with more in future. Conclusion: Based on our results, we started deriving future work aspects to do more detailed research on the topic of cultural challenges while transitioning or using agile methods in software development and beyond.
|
[
"Computer Science Archive->cs.SE"
] | 2022-12-14T13:40:54Z |
1905.10283
|
Enhanced $Z$ boson decays as a new probe of first-order electroweak phase transition at future lepton colliders
|
We study phenomenological consequences of the strong first-order electroweak phase transition in an extension of the standard model with an inert doublet and vector-like leptons motivated by the muon $g-2$ anomaly and dark matter. We find that a condition for the strong first-order electroweak phase transition inevitably induces a large logarithmic enhancement in $Z$ boson decays, which relegates the explanation of the anomalous muon $g-2$ at below 2$\sigma$ level. Our analysis shows that future lepton collider experiments, especially the Giga-$Z$ at the International Linear Collider and Tera-$Z$ at the Circular Electron Positron Collider as well as Future Circular Collider have great capability to explore the nature of the electroweak phase transition, which is complementary to conventional approaches via measurements of the triple Higgs boson coupling and gravitational waves.
|
[
"Physics Archive->hep->hep-ph"
] | 2019-05-24T15:23:15Z |
0902.1742
|
Source position reconstruction and constraints on the galactic magnetic field from ultra-high energy cosmic rays
|
We study the possibility to reconstruct the position of ultra-high energy cosmic ray sources and some properties of the magnetic field along the line of sight towards them in the case that several events from the same source are detected. By considering an illustrative model for the galactic magnetic field, including both a regular and a turbulent component, we estimate the accuracy that can be achieved in the reconstruction. We analyse the effect of the experimental energy and angular resolutions on these results. We show that if about ten events with energies above 30 EeV are detected coming from the same source, it should be possible to reconstruct the source position with an accuracy of 0.5$^{\circ}$ and the integral of the orthogonal component of the magnetic field along the line of sight with an accuracy of 0.6 $\mu$G kpc Z$^{-1}$ (with Z the electric charge of the particles).
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->astro-ph->astro-ph.HE"
] | 2009-02-10T20:43:15Z |
1412.5140
|
Separated Response Functions in Exclusive, Forward $\pi^{\pm}$ Electroproduction on Deuterium
|
Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, $Q^2$, and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in $\pi^-$ and $\pi^+$ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form factor from electroproduction data. Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at central $Q^2$ values of 0.6, 1.0, 1.6 GeV$^2$ at W=1.95 GeV, and $Q^2$=2.45 GeV$^2$ at W=2.22 GeV. There was significant coverage in $\phi$ and $\epsilon$, which allowed separation of $\sigma_{L,T,LT,TT}$. Results: $\sigma_L$ shows a clear signature of the pion pole, with a sharp rise at small -t. In contrast, $\sigma_T$ is much flatter versus t. The longitudinal/transverse ratios evolve with $Q^2$ and t, and at the highest $Q^2$=2.45 GeV$^2$ show a slight enhancement for $\pi^-$ production compared to $\pi^+$. The $\pi^-/\pi^+$ ratio for transverse photons exhibits only a small $Q^2$-dependence, following a nearly universal curve with t, with a steep transition to a value of about 0.25, consistent with s-channel quark knockout. The $\sigma_{TT}/\sigma_T$ ratio also drops rapidly with $Q^2$, qualitatively consistent with s-channel helicity conservation. The $\pi^-/\pi^+$ ratio for longitudinal photons indicates a small isoscalar contamination at W=1.95 GeV, consistent with what was observed in our earlier determination of the pion form factor at these kinematics.
|
[
"Physics Archive->nucl->nucl-ex"
] | 2014-12-16T19:54:19Z |
hep-ph/0401218
|
The scalar glueball spectrum
|
We discuss scenarios for scalar glueballs using arguments based on sum rules, spectral decomposition, the $\frac{1}{N_c}$ approximation, the scales of the strong interaction and the topology of the flux tubes. We analyze the phenomenological support of those scenarios and their observational implications. Our investigations hint a rich low lying glueball spectrum.
|
[
"Physics Archive->hep->hep-ph"
] | 2004-01-27T17:30:04Z |
1504.01201
|
Status of the Fermilab (g-2) experiment
|
The upcoming muon (g-2) experiment at Fermilab will measure the anomalous magnetic moment of the muon to a relative precision of 140 ppb, 4 times better than the previous experiment at BNL. The new experiment is motivated by the persistent 3-4 standard deviations difference between the experimental value and the Standard Model prediction, and it will have the statistical sensitivity necessary to either refute the claim or confirm it with a confidence level exceeding a discovery threshold. The experiment is under construction and scheduled to start running in early 2017.
|
[
"Physics Archive->hep->hep-ex",
"Physics Archive->physics->physics.ins-det"
] | 2015-04-06T04:20:03Z |
0804.2183
|
The Dichotomy of the Halo of the Milky Way
|
We summarize evidence that the halo of the Milky Way comprises two different, and broadly overlapping, stellar components. The two structures exhibit different chemical compositions, spatial distributions, and kinematics. These results were obtained through an analysis of more than 20,000 calibration stars from the Sloan Digital Sky Survey (SDSS). The duality of the stellar halo directly impacts galaxy formation models, for the Milky Way and other large spirals.
|
[
"Physics Archive->astro-ph"
] | 2008-04-14T14:12:02Z |
hep-ph/0610177
|
Recent and future experimental evidences for exotic mesons in hard reactions
|
The QCD analysis of the recent experimental data (L3@LEP) of the hard exclusive $\rho\rho$ production in two photon collisions shows that these data can be understood as a signal for the existence of an exotic isotensor resonance with a mass around $1.5 {\rm GeV}$. We also argue that hard exclusive reactions are a powerful tool for an experimental study of exotic hybrid mesons with $J^{PC}=1^{-+}$.
|
[
"Physics Archive->hep->hep-ph"
] | 2006-10-14T14:10:32Z |
2004.00459
|
Spectral self-adaptive absorber/emitter for harvesting energy from the sun and outer space
|
The sun (~6000 K) and outer space (~3 K) are the original heat source and sink for human beings on Earth. The energy applications of absorbing solar irradiation and harvesting the coldness of outer space for energy utilization have attracted considerable interest from researchers. However, combining these two functions in a static device for continuous energy harvesting is unachievable due to the intrinsic infrared spectral conflict. In this study, we developed spectral self-adaptive absorber/emitter (SSA/E) for daytime photothermal and nighttime radiative sky cooling modes depending on the phase transition of the vanadium dioxide coated layer. A 24-hour day-night test showed that the fabricated SSA/E has continuous energy harvesting ability and improved overall energy utilization performance, thus showing remarkable potential in future energy applications.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->physics->physics.optics"
] | 2020-04-01T14:16:29Z |
2210.15324
|
Robust Data2vec: Noise-robust Speech Representation Learning for ASR by Combining Regression and Improved Contrastive Learning
|
Self-supervised pre-training methods based on contrastive learning or regression tasks can utilize more unlabeled data to improve the performance of automatic speech recognition (ASR). However, the robustness impact of combining the two pre-training tasks and constructing different negative samples for contrastive learning still remains unclear. In this paper, we propose a noise-robust data2vec for self-supervised speech representation learning by jointly optimizing the contrastive learning and regression tasks in the pre-training stage. Furthermore, we present two improved methods to facilitate contrastive learning. More specifically, we first propose to construct patch-based non-semantic negative samples to boost the noise robustness of the pre-training model, which is achieved by dividing the features into patches at different sizes (i.e., so-called negative samples). Second, by analyzing the distribution of positive and negative samples, we propose to remove the easily distinguishable negative samples to improve the discriminative capacity for pre-training models. Experimental results on the CHiME-4 dataset show that our method is able to improve the performance of the pre-trained model in noisy scenarios. We find that joint training of the contrastive learning and regression tasks can avoid the model collapse to some extent compared to only training the regression task.
|
[
"Computer Science Archive->cs.SD",
"Electrical Engineering and Systems Science Archive->eess.AS"
] | 2022-10-27T11:04:02Z |
2312.06578
|
Multi-class Support Vector Machine with Maximizing Minimum Margin
|
Support Vector Machine (SVM) stands out as a prominent machine learning technique widely applied in practical pattern recognition tasks. It achieves binary classification by maximizing the "margin", which represents the minimum distance between instances and the decision boundary. Although many efforts have been dedicated to expanding SVM for multi-class case through strategies such as one versus one and one versus the rest, satisfactory solutions remain to be developed. In this paper, we propose a novel method for multi-class SVM that incorporates pairwise class loss considerations and maximizes the minimum margin. Adhering to this concept, we embrace a new formulation that imparts heightened flexibility to multi-class SVM. Furthermore, the correlations between the proposed method and multiple forms of multi-class SVM are analyzed. The proposed regularizer, akin to the concept of "margin", can serve as a seamless enhancement over the softmax in deep learning, providing guidance for network parameter learning. Empirical evaluations demonstrate the effectiveness and superiority of our proposed method over existing multi-classification methods.Code is available at https://github.com/zz-haooo/M3SVM.
|
[
"Computer Science Archive->cs.LG"
] | 2023-12-11T18:09:55Z |
2205.15601
|
Linear independence of certain numbers in the base-$b$ number system
|
Let $(i,j)\in \mathbb{N}\times \mathbb{N}_{\geq2}$ and $S_{i,j}$ be an infinite subset of positive integers including all prime numbers in some arithmetic progression. In this paper, we prove the linear independence over $\mathbb{Q}$ of the numbers \[ 1, \quad \sum_{n\in S_{i,j}}^{}\frac{a_{i,j}(n)}{b^{in^j}},\quad (i,j)\in \mathbb{N}\times \mathbb{N}_{\geq2}, \] where $b\geq2$ is an integer and $a_{i,j}(n)$ are bounded nonzero integer-valued functions on $S_{i,j}$. Moreover, we also establish a necessary and sufficient condition on the subset $\mathcal{A}$ of $\mathbb{N}\times \mathbb{N}_{\geq2}$ for the numbers \[ 1, \quad \sum_{n\in T_{i,j}}^{}\frac{a_{i,j}(n)}{b^{in^j}},\quad (i,j)\in \mathcal{A} \] to be linearly independent over $\mathbb{Q}$ for any given infinite subsets $T_{i,j}$ of positive integers. Our theorems generalize a result of V. Kumar.
|
[
"Mathematics Archive->math.NT"
] | 2022-05-31T08:32:17Z |
cond-mat/0504060
|
Metallic atomic wires on a patterned dihydrogeneted Si(001)
|
Electronic structure calculations for atomic wire of metals like Al, Ga and In are performed for a patterned dihydrogeneted Si(001):1 $\times$ 1 in search of structures with metallic behavior. The dihydrogeneted Si(001) is patterned by depassivating hygrozen atoms only from one row of Si atoms along the [1$\bar{1}$0] direction. Various structures of adsorbed metals and their electronic properties are examined. It is found that Al and Ga atomic wire structures with metallic property are strongly unstable towards the formation of buckled metal dimers leading to semiconducting behavior. Indium atomic wire, however, displays only marginal preference towards the formation of symmetric dimers staying close to the metallic limit. The reasons behind the lack of metallic atomic wires are explored. In addition, a direction is proposed for the realization of metallic wires on the dihydrogeneted Si(001).
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2005-04-04T02:36:32Z |
cond-mat/0509115
|
Probing protein-protein interactions by dynamic force correlated spectroscopy (FCS)
|
We develop a formalism for single molecule dynamic force spectroscopy to map the energy landscape of protein-protein complex ($P_1$$P_2$). The joint distribution $P(\tau_1,\tau_2)$ of unbinding lifetimes $\tau_1$ and $\tau_2$ measurable in a compression-tension cycle, which accounts for the internal relaxation dynamics of the proteins under tension, shows that the histogram of $\tau_1$ is not Poissonian. The theory is applied to the forced unbinding of protein $P_1$, modeled as a wormlike chain, from $P_1$$P_2$. We propose a new class of experiments which can resolve the effect of internal protein dynamics on the unbinding lifetimes.
|
[
"Physics Archive->cond-mat->cond-mat.soft"
] | 2005-09-05T17:26:23Z |
1312.4654
|
A Majorization-Minimization Algorithm for Computing the Karcher Mean of Positive Definite Matrices
|
An algorithm for computing the Karcher mean of $n$ positive definite matrices is proposed, based on the majorization-minimization (MM) principle. The proposed MM algorithm is parameter-free, does not need to choose step sizes, and has a theoretical guarantee of asymptotic linear convergence.
|
[
"Mathematics Archive->math.OC"
] | 2013-12-17T06:15:03Z |
1911.09775
|
Interval Reachability Analysis using Second-Order Sensitivity
|
We propose a new approach to compute an interval over-approximation of the finite time reachable set for a large class of nonlinear systems. This approach relies on the notions of sensitivity matrices, which are the partial derivatives representing the variations of the system trajectories in response to variations of the initial states. Using interval arithmetics, we first over-approximate the possible values of the second-order sensitivity at the final time of the reachability problem. Then we exploit these bounds and the evaluation of the first-order sensitivity matrices at a few sampled initial states to obtain an over-approximation of the first-order sensitivity, which is in turn used to over-approximate the reachable set of the initial system. Unlike existing methods relying only on the first-order sensitivity matrix, this new approach provides guaranteed over-approximations of the first-order sensitivity and can also provide such over-approximations with an arbitrary precision by increasing the number of samples.
|
[
"Computer Science Archive->cs.SY",
"Electrical Engineering and Systems Science Archive->eess.SY"
] | 2019-11-21T22:44:32Z |
2310.20411
|
A New Kilohertz Gravitational-Wave Feature from Rapidly Rotating Core-Collapse Supernovae
|
We present self-consistent three-dimensional core-collapse supernova simulations of a rotating $20M_\odot$ progenitor model with various initial angular velocities from $0.0$ to $4.0$ rad s$^{-1}$ using a smoothed particle hydrodynamics code, SPHYNX, and a grid-based hydrodynamics code, FLASH. We identify two strong gravitational-wave features, with peak frequencies of $\sim300$ Hz and $\sim1.3$ kHz in the first $100$ ms postbounce. We demonstrate that these two features are associated with the $m=1$ deformation from the proto-neutron star (PNS) modulation induced by the low-$T/|W|$ instability, regardless of the simulation code. The $300$ Hz feature is present in models with an initial angular velocity between $1.0$ and $4.0$ rad s$^{-1}$, while the $1.3$ kHz feature is present only in a narrower range, from $1.5$ to $3.5$ rad s$^{-1}$. We show that the $1.3$ kHz signal originates from the high-density inner core of the PNS, and the $m=1$ deformation triggers a strong asymmetric distribution of electron anti-neutrinos. In addition to the $300$ Hz and $1.3$ kHz features, we also observe one weaker but noticeable gravitational-wave feature from higher-order modes in the range between $1.5$ and $3.5$ rad s$^{-1}$. Its peak frequency is around $800$ Hz initially and gradually increases to $900-1000$ Hz. Therefore, in addition to the gravitational bounce signal, the detection of the $300$ Hz, $1.3$ kHz, the higher-order mode, and even the related asymmetric emission of neutrinos, could provide additional diagnostics to estimate the initial angular velocity of a collapsing core.
|
[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2023-10-31T12:33:28Z |
2309.05677
|
Optical trapping based on microring resonators with transverse slot structure
|
Over the past few decades, optical manipulation has emerged as a highly successful tool in various fields, such as biology, micro/nanorobotics, and physics. Among the different techniques, the transverse slot optical waveguide has shown remarkable potential in enhancing the field and significantly improving optical trapping capabilities. Additionally, microring resonators have demonstrated the ability to enhance the field at specific resonance wavelengths, enabling the manipulation and capture of particles. In this study, we investigated the impact of the structure on nanoparticle capture by introducing a 50 nm transverse slot in a 5 {\mu}m microring resonator. Through the integration of a transverse slot in the microring resonator, we observed a substantial increase in the maximum bound optical power for a nanosphere with a refractive index of 1.6 and a diameter of 50 nm, reaching 3988.8 pN/W. This value is 2292 times higher than the maximum optical force in a straight waveguide and 2.266 times higher than the maximum optical force in a microring resonator. The proposed structure significantly enhances the optical trapping capabilities for nanoscale particles, thus paving the way for the development of advanced micro/nanomanipulation techniques.
|
[
"Physics Archive->physics->physics.optics"
] | 2023-09-09T09:19:13Z |
2203.13833
|
When removing an independent set is optimal for reducing the chromatic number
|
How large must the chromatic number of a graph be, in terms of the graph's maximum degree, to ensure that the most efficient way to reduce the chromatic number by removing vertices is to remove an independent set? By a reduction to a powerful, known stability form of Brooks' theorem, we answer this question precisely, determining the threshold to within two values (and indeed sometimes a unique value) for graphs of sufficiently large maximum degree.
|
[
"Mathematics Archive->math.CO"
] | 2022-03-25T18:00:27Z |
1904.03880
|
Higher order Dirichlet-to-Neumann maps on graphs and their eigenvalues
|
In this paper, we first introduce higher order Dirichlet-to-Neumann maps on graphs which can be viewed as a discrete analogue of the corresponding Dirichlet-to-Neumann maps on compact Riemannian manifolds with boundary and a higher order generalization of the Dirichlet-to-Neumann map on graphs introduced by Hua-Huang-Wang\cite{HHW} and Hassannezhad-Miclo \cite{HM}. Then, some Raulot-Savo-type estimates on the eigenvalues of the DtN maps introduced are derived.
|
[
"Mathematics Archive->math.DG"
] | 2019-04-08T08:14:49Z |
2312.07021
|
Transferring Modality-Aware Pedestrian Attentive Learning Visible-Infrared Person Re-identification
|
Visible-infrared person re-identification (VI-ReID) aims to search the same pedestrian of interest across visible and infrared modalities. Existing models mainly focus on compensating for modality-specific information to reduce modality variation. However, these methods often lead to a higher computational overhead and may introduce interfering information when generating the corresponding images or features. To address this issue, it is critical to leverage pedestrian-attentive features and learn modality-complete and -consistent representation. In this paper, a novel Transferring Modality-Aware Pedestrian Attentive Learning (TMPA) model is proposed, focusing on the pedestrian regions to efficiently compensate for missing modality-specific features. Specifically, we propose a region-based data augmentation module PedMix to enhance pedestrian region coherence by mixing the corresponding regions from different modalities. A lightweight hybrid compensation module, i.e., the Modality Feature Transfer (MFT), is devised to integrate cross attention and convolution networks to fully explore the discriminative modality-complete features with minimal computational overhead. Extensive experiments conducted on the benchmark SYSU-MM01 and RegDB datasets demonstrated the effectiveness of our proposed TMPA model.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.CV"
] | 2023-12-12T07:15:17Z |
1906.10977
|
The ESO supernovae type Ia progenitor survey (SPY)
|
Close double degenerate binaries are one of the favoured progenitor channels for type Ia supernovae, but it is unclear how many suitable systems there are in the Galaxy. We report results of a large radial velocity survey for double degenerate (DD) binaries using the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY - SPY). Exposures taken at different epochs are checked for radial velocity shifts indicating close binary systems. We observed 689 targets classified as DA (displaying hydrogen-rich atmospheres), of which 46 turned out to possess a cool companion. We measured radial velocities (RV) of the remaining 643 DA white dwarfs. We managed to secure observations at two or more epochs for 625 targets, supplemented by eleven objects meeting our selection criteria from literature. The data reduction and analysis methods applied to the survey data are described in detail. The sample contains 39 double degenerate binaries, only four of which were previously known. 20 are double-lined systems, in which features from both components are visible, the other 19 are single-lined binaries. We provide absolute RVs transformed to the heliocentric system suitable for kinematic studies. Our sample is large enough to sub-divide by mass: 16 out of 44 low mass targets (<= 0.45 Msun) are detected as DDs, while just 23 of the remaining 567 with multiple spectra and mass >0.45 Msun are double. Although the detected fraction amongst the low mass objects (36.4 +/- 7.3%) is significantly higher than for the higher-mass, carbon/oxygen-core dominated part of the sample (3.9 +/- 0.8%), it is lower than the detection efficiency based upon companion star masses >= 0.05 Msun. This suggests either companion stars of mass < 0.05 Msun, or that some of the low mass white dwarfs are single.
|
[
"Physics Archive->astro-ph->astro-ph.SR"
] | 2019-06-26T11:10:41Z |
1712.05092
|
Super-resolution Imaging of the Fluorescent Dipole Assembly with Polarized Structured Illumination Microscopy
|
Fluorescence polarization microscopy images both the intensity and orientation of fluorescent dipoles, which plays a vital role in studying the molecular structure and dynamics of bio-complex. However, it is difficult to resolve the dipole assemblies on the subcellular structure and their dynamics in living cells with super-resolution. Here we report polarized structured illumination microscopy (pSIM), which decouples the entangled spatial and angular structured illumination through interpreting the dipoles in spatio-angular hyperspace. We demonstrate its application on a series of biological filamentous systems such as cytoskeleton networks and lambda-DNA, and report the dynamics of short actin sliding through myosin-coated surface. Further, pSIM reveals "side-by-side" organization of the actin ring structure in the membrane-associated periodic skeleton in hippocampal neurons. It also images the dipole dynamics of green fluorescent proteins labeled to the microtubules in live U2OS cells. pSIM can be applied directly to a large variety of commercial or home-built SIM systems.
|
[
"Physics Archive->physics->physics.optics"
] | 2017-12-14T04:42:22Z |
1502.04595
|
The Inverse Spectral Transform for the Dunajski hierarchy and some of its reductions, I: Cauchy problem and longtime behavior of solutions
|
In this paper we apply the formal Inverse Spectral Transform for integrable dispersionless PDEs arising from the commutation condition of pairs of one-parameter families of vector fields, recently developed by S. V. Manakov and one of the authors, to one distinguished class of equations, the so-called Dunajski hierarchy. We concentrate, for concreteness, i) on the system of PDEs characterizing a general anti-self-dual conformal structure in neutral signature, ii) on its first commuting flow, and iii) on some of their basic and novel reductions. We formally solve their Cauchy problem and we use it to construct the longtime behavior of solutions, showing, in particular, that unlike the case of soliton PDEs, different dispersionless PDEs belonging to the same hierarchy of commuting flows evolve in time in very different ways, exhibiting either a smooth dynamics or a gradient catastrophe at finite time.
|
[
"Physics Archive->nlin->nlin.SI"
] | 2015-02-16T16:14:53Z |
astro-ph/9712018
|
Orbital Parameters for the Soft X-ray Transient 4U 1543-47: Evidence for a Black Hole
|
(shortened) Spectroscopic observations of the soft X-ray transient 4U 1543-47 reveal a radial velocity curve with a period of P=1.123 +/- 0.008 days and a semi-amplitude of K_2 = 124 +/- 4 km/sec. The mass function is f(M) = 0.22 +/- 0.02 solar masses. We derive a distance of d = 9.1 +/-1.1 kpc if the secondary is on the main sequence. The V and I light curves exhibit two waves per orbital cycle with amplitudes of about 0.08 mag. We modeled the light curves as ellipsoidal variations in the secondary star and derive extreme inclination limits of 20 <= i <= 40 deg and formal 3 sigma limits of 24 <= i <= 36 deg for a mass ratio Q = M_1/M_2 > 1. However, there are systematic effects in the data that the model does not account for, so the above constraints should be treated with caution. We argue that the secondary star is still on the main sequence and if the secondary star has a mass near the main sequence values for early A-stars (2.3 <= M_2 <= 2.6 solar masses), then the best fits for the 3 sigma inclination range (24 <= i <= 36 deg) and the 3 sigma mass function range (0.16 <= f(M) <= 0.28 solar masses) imply a primary mass in the range 2.7 <= M_1 <= 7.5 solar masses. Thus the mass of the compact object in 4U 1543-47 is likely to be in excess of approximately 3 solar masses and we conclude 4U 1543-47 most likely contains a black hole.
|
[
"Physics Archive->astro-ph"
] | 1997-12-01T22:22:01Z |
2001.10526
|
The Mott transition as a topological phase transition
|
We show that the Mott metal-insulator transition in the standard one-band Hubbard model can be understood as a topological phase transition. Our approach is inspired by the observation that the mid-gap pole in the self-energy of a Mott insulator resembles the zero-energy spectral pole of the localized surface state in a topological insulator. We use NRG-DMFT to solve the infinite-dimensional Hubbard model, and represent the resulting local self-energy in terms of the boundary Green's function of an auxiliary tight-binding chain without interactions. The auxiliary system is of generalized SSH model type; the Mott transition corresponds to a dissociation of domain walls.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2020-01-28T18:57:08Z |
1602.05825
|
Scaling limits of disordered systems and disorder relevance
|
We review recent works where we have shown that disorder relevance is closely related to the existence of non-trivial, random continuum limits
|
[
"Mathematics Archive->math.MP",
"Mathematics Archive->math.PR",
"Physics Archive->math-ph"
] | 2016-02-18T15:01:21Z |
astro-ph/0208326
|
Expected Performance of CryoArray
|
WIMP-nucleon cross sections below 10^(-9) pb may be probed by ton-scale experiments with low thresholds and background rates ~20 events per year. An array of cryogenic detectors ("CryoArray") could perform well enough to reach this goal. Sufficient discrimination and background suppression of photons has already been demonstrated. Reduction of neutron backgrounds may be achieved by siting the experiment deep enough. Removal of the surface-electron backgrounds alone has not yet been demonstrated, but the reductions required even for this troublesome background are quite modest and appear achieveable.
|
[
"Physics Archive->astro-ph"
] | 2002-08-16T23:39:28Z |
2208.08014
|
AUGER: Automatically Generating Review Comments with Pre-training Models
|
Code review is one of the best practices as a powerful safeguard for software quality. In practice, senior or highly skilled reviewers inspect source code and provide constructive comments, considering what authors may ignore, for example, some special cases. The collaborative validation between contributors results in code being highly qualified and less chance of bugs. However, since personal knowledge is limited and varies, the efficiency and effectiveness of code review practice are worthy of further improvement. In fact, it still takes a colossal and time-consuming effort to deliver useful review comments. This paper explores a synergy of multiple practical review comments to enhance code review and proposes AUGER (AUtomatically GEnerating Review comments): a review comments generator with pre-training models. We first collect empirical review data from 11 notable Java projects and construct a dataset of 10,882 code changes. By leveraging Text-to-Text Transfer Transformer (T5) models, the framework synthesizes valuable knowledge in the training stage and effectively outperforms baselines by 37.38% in ROUGE-L. 29% of our automatic review comments are considered useful according to prior studies. The inference generates just in 20 seconds and is also open to training further. Moreover, the performance also gets improved when thoroughly analyzed in case study.
|
[
"Computer Science Archive->cs.SE"
] | 2022-08-17T01:38:01Z |
1710.02825
|
Spectral Singularities, Threshold Gain, and Output Intensity for a Slab Laser with Mirrors
|
We explore the consequences of the emergence of linear and nonlinear spectral singularities in TE modes of a homogeneous slab of active optical material that is placed between two mirrors. We use the results together with two basic postulates regarding the behavior of laser light emission to derive explicit expressions for the laser threshold condition and output intensity for these modes of the slab and discuss their physical implications. In particular, we reveal the details of the dependence of the threshold gain and output intensity on the position and properties of the mirrors and on the real part of the refractive index of the gain material.
|
[
"Physics Archive->physics->physics.optics",
"Physics Archive->quant-ph"
] | 2017-10-08T11:44:52Z |
2308.07702
|
Better Zero-Shot Reasoning with Role-Play Prompting
|
Modern large language models (LLMs), such as ChatGPT, exhibit a remarkable capacity for role-playing, enabling them to embody not only human characters but also non-human entities like a Linux terminal. This versatility allows them to simulate complex human-like interactions and behaviors within various contexts, as well as to emulate specific objects or systems. While these capabilities have enhanced user engagement and introduced novel modes of interaction, the influence of role-playing on LLMs' reasoning abilities remains underexplored. In this study, we introduce a strategically designed role-play prompting methodology and assess its performance under the zero-shot setting across twelve diverse reasoning benchmarks, encompassing arithmetic, commonsense reasoning, symbolic reasoning, and more. Leveraging models such as ChatGPT and Llama 2, our empirical results illustrate that role-play prompting consistently surpasses the standard zero-shot approach across most datasets. Notably, accuracy on AQuA rises from 53.5% to 63.8%, and on Last Letter from 23.8% to 84.2%. Beyond enhancing contextual understanding, we posit that role-play prompting serves as an implicit Chain-of-Thought (CoT) trigger, thereby improving the quality of reasoning. By comparing our approach with the Zero-Shot-CoT technique, which prompts the model to "think step by step", we further demonstrate that role-play prompting can generate a more effective CoT. This highlights its potential to augment the reasoning capabilities of LLMs.
|
[
"Computer Science Archive->cs.CL"
] | 2023-08-15T11:08:30Z |
hep-th/9904155
|
Puzzles on the Duality between Heterotic and Type IIA Strings
|
We discuss the possibility of the extension of the duality between the webs of heterotic string and the type IIA string to Calabi-Yau 3-folds with another K3 fiber by comparing the dual polyhedron of Calabi-Yau 3-folds given by Candelas, Perevalov and Rajesh.
|
[
"Physics Archive->hep->hep-th"
] | 1999-04-23T03:10:19Z |
math/0702084
|
On Systems of Linear Quaternion Functions
|
A method of reducing general quaternion functions of first degree, i.e., linear quaternion functions, to quaternary canonical form is given. Linear quaternion functions, once reduced to canonical form, can be maintained in this form under functional composition. furthermore, the composition operation is symbolically identical to quaternion multiplication, making manipulation and reduction of systems of linear quaternion functions straight forward.
|
[
"Mathematics Archive->math.RA"
] | 2007-02-04T19:12:53Z |
0706.1436
|
Hybrid inflation followed by modular inflation
|
Inflationary models with a superheavy scale F-term hybrid inflation followed by an intermediate scale modular inflation are considered. The restrictions on the power spectrum P_R of curvature perturbation and the spectral index n_s from the recent data within the power-law cosmological model with cold dark matter and a cosmological constant can be met provided that the number of e-foldings N_HI* suffered by the pivot scale k_*=0.002/Mpc during hybrid inflation is suitably restricted. The additional e-foldings needed for solving the horizon and flatness problems are generated by modular inflation with a string axion as inflaton. For central values of P_R and n_s, the grand unification scale comes out, in the case of standard hybrid inflation, close to its supersymmetric value M_GUT=2.86 x 10^16 GeV, the relevant coupling constant is relatively large (0.005-0.14), and N_HI* is between 10 and 21.7. In the shifted [smooth] hybrid inflation case, the grand unification scale can be identified with M_GUT for N_HI*=21 [N_HI*=18].
|
[
"Physics Archive->astro-ph",
"Physics Archive->hep->hep-ph"
] | 2007-06-11T10:39:18Z |
hep-ph/0009141
|
Matter Enhancement of T Violation in Neutrino Oscillation
|
We study the matter enhancement of T violation in neutrino oscillation with three generations. The magnitude of T violation is proportional to Jarlskog factor J. Recently, the elegant relation, (\Delta_m)_{12}(\Delta_m)_{23}(\Delta_m)_{31}J_{m} = \Delta_{12}\Delta_{23}\Delta_{31}J, was derived, where \Delta_{ij}=\Delta m^2_{ij}/(2E) and subscript m implies the quantities in matter. Using this relation, we reconsider how J_m changes as a function of the matter potential a under the approximation |\Delta m^2_{12}| \ll |\Delta m^2_{13}|. We show that the number of maxima for J_{m} depends on the magnitude of \sin^2 2 \theta_{13} and there are two maxima considering the constraint on \sin^2 2\theta_{13} from the CHOOZ experiment. One maximum of $J_{m} at a = O(\Delta_{12}) is given by J/\sin2\theta_{12}, which leads to the large enhancement of J_m in the case of the SMA MSW solution. The other maximum at a = O(\Delta_{13}) is |\Delta_{12}/\Delta_{13}|J/\sin2\theta_{13}, and the enhancement is possible, if \sin 2 \theta_{13} is small enough. These maximal values are consistent with the results obtained by other methods.
|
[
"Physics Archive->hep->hep-ph"
] | 2000-09-12T13:28:31Z |
1207.5312
|
Memristive properties of single-molecule magnets
|
Single-molecule magnets weakly coupled to two ferromagnetic leads act as memory devices in electronic circuits---their response depends on history, not just on the instantaneous applied voltage. We show that magnetic anisotropy introduces a wide separation of timescales between fast and slow relaxation processes in the system, which leads to a pronounced memory dependence in a wide intermediate time regime. We study the response to a harmonically varying bias voltage from slow to rapid driving within a master-equation approach. The system is not purely memristive but shows a partially capacitive response on short timescales. In the intermediate time regime the molecular spin can be used as the state variable in a two-terminal molecular memory device.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2012-07-23T07:27:48Z |
0803.1159
|
Control of non-Markovian effects in the dynamics of polaritons in semiconductor microcavities
|
We report on time-resolved photoluminescence from semiconductor microcavities showing that an optically controllable mechanism exists to turn on and off memory effects in a polariton system. By increasing the laser pumping pulse intensity we observe revivals of the decaying time-resolved photoluminescence signal, a manifestly non-Markovian behavior of the optically active polaritons. Based on an open quantum system approach we perform a comprehensive analytical and numerical study of the coupling of optically active polaritons to a structured reservoir to confirm the origin of the observed features. Our findings show that negative detunings and strong excitation should occur simultaneously for memory effects to take place.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.other"
] | 2008-03-07T19:36:08Z |
2210.00180
|
Exact evaluations and reciprocity theorems for finite trigonometric sums
|
We evaluate in closed form several classes of finite trigonometric sums. Two general methods are used. The first is new and involves sums of roots of unity. The second uses contour integration and extends a previous method used by two of the authors. Reciprocity theorems for certain trigonometric sums are also established.
|
[
"Mathematics Archive->math.NT"
] | 2022-10-01T03:31:59Z |
cond-mat/9707031
|
Resonant Optical Nonlinearity of Conjugated Polymers
|
When the energy of a pump wave is in resonance with the exciton creation energy, the electric susceptibility of a conjugated polymer in response to the probe wave is altered by the exciton gas. In this paper, we calculate the dependence of this change on the the exciton populations by the equation of motion (EOM) method. The magnitude of optical nonlinearity is also influenced by ambient temperature, by the extent of exciton wave functions, and by the strength of electron-electron interaction. All of these factors can be easily incorporated in the EOM approach systematically. Using the material parameters for polydiacetylene (PDA), the optical Kerr coefficient $n_2$ obtained is about $10^{-8} cm^2/W$, which is close to experimental value, and is four orders of magnitude larger than the value in nonresonant pump experiments.
|
[
"Physics Archive->cond-mat"
] | 1997-07-03T07:56:34Z |
1611.07054
|
An Efficient Training Algorithm for Kernel Survival Support Vector Machines
|
Survival analysis is a fundamental tool in medical research to identify predictors of adverse events and develop systems for clinical decision support. In order to leverage large amounts of patient data, efficient optimisation routines are paramount. We propose an efficient training algorithm for the kernel survival support vector machine (SSVM). We directly optimise the primal objective function and employ truncated Newton optimisation and order statistic trees to significantly lower computational costs compared to previous training algorithms, which require $O(n^4)$ space and $O(p n^6)$ time for datasets with $n$ samples and $p$ features. Our results demonstrate that our proposed optimisation scheme allows analysing data of a much larger scale with no loss in prediction performance. Experiments on synthetic and 5 real-world datasets show that our technique outperforms existing kernel SSVM formulations if the amount of right censoring is high ($\geq85\%$), and performs comparably otherwise.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2016-11-21T21:09:33Z |
2012.03313
|
Preliminary assessment of an integrated SMOS and MODIS application for global agricultural drought monitoring
|
An application of the Soil Moisture Agricultural Drought Index (SMADI) at the global scale is presented. The index integrates surface soil moisture from the SMOS mission with land surface temperature (LST) and Normalized Difference Vegetation Index (NDVI) from MODIS and allows for global drought monitoring at medium spatial scales (0.05 deg).. Biweekly maps of SMADI were obtained from year 2010 to 2015 over all agricultural areas on Earth. The SMADI time-series were compared with state-of-the-art drought indices over the Iberian Peninsula. Results show a good agreement between SMADI and the Crop Moisture Index (CMI) retrieved at five weather stations (with correlation coefficient, R from -0.64 to -0.79) and the Soil Water Deficit Index (SWDI) at the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS) (R=-0.83). Some preliminary tests were also made over the continental United States using the Vegetation Drought Response Index (VegDRI), with very encouraging results regarding the spatial occurrence of droughts during summer seasons. Additionally, SMADI allowed to identify distinctive patterns of regional drought over the Indian Peninsula in spring of 2012. Overall results support the use of SMADI for monitoring agricultural drought events world-wide.
|
[
"Physics Archive->physics->physics.geo-ph"
] | 2020-12-06T16:34:36Z |
2208.07639
|
RAWtoBit: A Fully End-to-end Camera ISP Network
|
Image compression is an essential and last processing unit in the camera image signal processing (ISP) pipeline. While many studies have been made to replace the conventional ISP pipeline with a single end-to-end optimized deep learning model, image compression is barely considered as a part of the model. In this paper, we investigate the designing of a fully end-to-end optimized camera ISP incorporating image compression. To this end, we propose RAWtoBit network (RBN) that can effectively perform both tasks simultaneously. RBN is further improved with a novel knowledge distillation scheme by introducing two teacher networks specialized in each task. Extensive experiments demonstrate that our proposed method significantly outperforms alternative approaches in terms of rate-distortion trade-off.
|
[
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2022-08-16T09:51:57Z |
1806.00976
|
Screened potential of a point charge in a thin film
|
The potential of a point charge in a thin semiconducting film with the thickness below the de Broglie wavelength of the free charge carriers is calculated with and without the screening.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2018-06-04T06:39:59Z |
2305.03855
|
Robust A-Optimal Experimental Design for Bayesian Inverse Problems
|
Optimal design of experiments for Bayesian inverse problems has recently gained wide popularity and attracted much attention, especially in the computational science and Bayesian inversion communities. An optimal design maximizes a predefined utility function that is formulated in terms of the elements of an inverse problem, an example being optimal sensor placement for parameter identification. The state-of-the-art algorithmic approaches following this simple formulation generally overlook misspecification of the elements of the inverse problem, such as the prior or the measurement uncertainties. This work presents an efficient algorithmic approach for designing optimal experimental design schemes for Bayesian inverse problems such that the optimal design is robust to misspecification of elements of the inverse problem. Specifically, we consider a worst-case scenario approach for the uncertain or misspecified parameters, formulate robust objectives, and propose an algorithmic approach for optimizing such objectives. Both relaxation and stochastic solution approaches are discussed with detailed analysis and insight into the interpretation of the problem and the proposed algorithmic approach. Extensive numerical experiments to validate and analyze the proposed approach are carried out for sensor placement in a parameter identification problem.
|
[
"Computer Science Archive->cs.LG",
"Mathematics Archive->math.OC"
] | 2023-05-05T21:43:00Z |
2011.14593
|
Incremental Learning via Rate Reduction
|
Current deep learning architectures suffer from catastrophic forgetting, a failure to retain knowledge of previously learned classes when incrementally trained on new classes. The fundamental roadblock faced by deep learning methods is that deep learning models are optimized as "black boxes," making it difficult to properly adjust the model parameters to preserve knowledge about previously seen data. To overcome the problem of catastrophic forgetting, we propose utilizing an alternative "white box" architecture derived from the principle of rate reduction, where each layer of the network is explicitly computed without back propagation. Under this paradigm, we demonstrate that, given a pre-trained network and new data classes, our approach can provably construct a new network that emulates joint training with all past and new classes. Finally, our experiments show that our proposed learning algorithm observes significantly less decay in classification performance, outperforming state of the art methods on MNIST and CIFAR-10 by a large margin and justifying the use of "white box" algorithms for incremental learning even for sufficiently complex image data.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG"
] | 2020-11-30T07:23:55Z |
2106.16101
|
AdaGDA: Faster Adaptive Gradient Descent Ascent Methods for Minimax Optimization
|
In the paper, we propose a class of faster adaptive Gradient Descent Ascent (GDA) methods for solving the nonconvex-strongly-concave minimax problems by using the unified adaptive matrices, which include almost all existing coordinate-wise and global adaptive learning rates. In particular, we provide an effective convergence analysis framework for our adaptive GDA methods. Specifically, we propose a fast Adaptive Gradient Descent Ascent (AdaGDA) method based on the basic momentum technique, which reaches a lower gradient complexity of $\tilde{O}(\kappa^4\epsilon^{-4})$ for finding an $\epsilon$-stationary point without large batches, which improves the existing results of the adaptive GDA methods by a factor of $O(\sqrt{\kappa})$. Moreover, we propose an accelerated version of AdaGDA (VR-AdaGDA) method based on the momentum-based variance reduced technique, which achieves a lower gradient complexity of $\tilde{O}(\kappa^{4.5}\epsilon^{-3})$ for finding an $\epsilon$-stationary point without large batches, which improves the existing results of the adaptive GDA methods by a factor of $O(\epsilon^{-1})$. Moreover, we prove that our VR-AdaGDA method can reach the best known gradient complexity of $\tilde{O}(\kappa^{3}\epsilon^{-3})$ with the mini-batch size $O(\kappa^3)$. The experiments on policy evaluation and fair classifier learning tasks are conducted to verify the efficiency of our new algorithms.
|
[
"Computer Science Archive->cs.LG",
"Mathematics Archive->math.OC"
] | 2021-06-30T14:47:09Z |
2107.08871
|
Modelling vortex ring growth in the wake of a translating cone
|
Vortex rings have the ability to transport fluid over long distances. They are usually produced by ejecting a volume of fluid through a circular orifice or nozzle. When the volume and velocity of the ejected fluid are known, the vortex' circulation, impulse, and energy can be estimated by the slug flow model. Vortex rings also form in the wake of accelerating axisymmetric bodies. In this configuration, the volume and velocity of the fluid that is injected into the vortex is not known a priori. Here, we present two models to predict the growth of the vortex behind disks or cones. The first model uses conformal mapping and assumes that all vorticity generated ends up in the vortex. The vortex circulation is determined by imposing the Kutta condition at the tip of the disk. The position of the vortex is integrated from an approximation of its velocity, given by Fraenkel. The model predicts well the maximum circulation of the vortex, but does not predict the tail shedding observed experimentally. A second model is based on an axisymmetric version of the discrete vortex method. The shear layer formed at the tip of the cone is discretised by point vortices, which roll-up into a coherent vortex ring. The model accurately captures the temporal evolution of the circulation and the non-dimensional energy. The detrainment of vorticity from the vortex, through the process of tail shedding, is qualitatively captured by the model but remains quantitatively sensitive to the numerical parameters.
|
[
"Physics Archive->physics->physics.flu-dyn"
] | 2021-07-19T13:41:31Z |
1311.1261
|
Hopf algebraic techniques applied to super algebraic groups
|
Reproducing my talk at Algebra Symposium held at Hiroshima University, August 26--29, 2013, I review recent results on super algebraic groups, emphasizing results obtained by myself and my coauthors using Hopf algebraic techniques. The results are all basic, and I intend to make this report into a somewhat informal introduction to the subject.
|
[
"Mathematics Archive->math.AG",
"Mathematics Archive->math.RT"
] | 2013-11-06T01:20:18Z |
2104.03824
|
On The Gap Between Software Maintenance Theory and Practitioners' Approaches
|
The way practitioners perform maintenance tasks in practice is little known by researchers. In turn, practitioners are not always up to date with the proposals provided by the research community. This work investigates the gap between software maintenance techniques proposed by the research community and the software maintenance practice. We carried out a survey with 112 practitioners from 92 companies and 12 countries. We concentrate on analyzing if and how practitioners understand and apply the following subjects: bad smells, refactoring, software metrics, and change impact analysis. This study shows that there is a large gap between research approaches and industry practice in those subjects, especially in change impact analysis and software metrics.
|
[
"Computer Science Archive->cs.SE"
] | 2021-04-08T15:08:10Z |
2207.01804
|
Can large inhomogeneities generate target patterns?
|
We study the existence of target patterns in oscillatory media with weak local coupling and in the presence of an impurity, or defect. We model these systems using a viscous eikonal equation posed on the plane, and represent the defect as a perturbation. In contrast to previous results we consider large defects, which we describe using a function with slow algebraic decay, i.e., $g \sim {\mathcal O}(1/|x|^m)$ for $m \in (1,2]$. We prove that these defects are able to generate target patterns and that, just as in the case of strongly localized impurities, their frequency is small beyond all orders of the small parameter describing their strength. Our analysis consists of finding two approximations to target pattern solutions, one which is valid at intermediate scales and a second one which is valid in the far field. This is done using weighted Sobolev spaces, which allow us to recover Fredholm properties of the relevant linear operators, as well as the implicit function theorem, which is then used to prove existence. By matching the intermediate and far field approximations we then determine the frequency of the pattern that is selected by the system.
|
[
"Mathematics Archive->math.AP"
] | 2022-07-05T04:16:35Z |
1210.3452
|
Dynamics of neutrino-driven winds: inclusion of accurate weak interaction rates in strong magnetic fields
|
Solving Newtonian steady-state wind equations with accurate weak interaction rates and magnetic fields (MFs) of young neutron stars considered, we study the dynamics and nucleosynthesis of neutrino-driven winds (NDWs) from proto neutron stars (PNSs). For a typical 1.4 M$_{\odot}$ PNS model, we find the nucleosynthesis products are closely related to the luminosity of neutrinos and anti-neutrinos. The lower the luminosity is, the larger effect to the NDWs caused by weak interactions and MFs is. At a high anti-neutrino luminosity of typically $8\times 10^{51}$ erg s$^{-1}$, neutrinos and anti-neutrinos dominate the processes in a NDW and the MFs hardly change the wind's properties. While at a low anti-neutrino luminosity of $10^{51}$ erg s$^{-1}$ at the late stage of a NDW, the mass of product and nucleosynthesis are changed significantly in the strong MFs, they are less important than those in the early stage when the anti-neutrino luminosity is high. Therefore for the most models considered for the NDWs from PNSs, based on our calculations the influences of MFs and the net weak interactions on the nucleosynthesis is not significant.
|
[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2012-10-12T08:34:47Z |
1905.08522
|
Approximations of Mckean-Vlasov SDEs with Irregular Coefficients
|
The goal of this paper is to approximate several kinds of {\it Mckean-Vlasov SDEs} with {\it irregular coefficients} via weakly interacting particle systems. More precisely, propagation of chaos and convergence rate of Euler-Maruyama scheme associated with the consequent weakly interacting particle systems are investigated for Mckean-Vlasov SDEs, where (i) the diffusion terms are H\"older continuous by taking advantage of Yamada-Watanabe's approximation approach and (ii) the drifts are H\"older continuous by freezing distributions followed by invoking Zvonkin's transformation trick.
|
[
"Mathematics Archive->math.PR"
] | 2019-05-21T09:50:19Z |
astro-ph/0405308
|
Discovery of kilogauss magnetic fields in three DA white dwarfs
|
We have detected longitudinal magnetic fields between 2 and 4 kG in three (WD 0446$-$790, WD 1105$-$048, WD 2359$-$434) out of a sample of 12 normal DA white dwarfs by using optical spectropolarimetry done with the VLT Antu 8 m telescope equipped with FORS1. With the exception of 40 Eri B (4 kG) these are the first positive detections of magnetic fields in white dwarfs below 30 kG. Although suspected, it was not clear whether a significant fraction of white dwarfs contain magnetic fields at this level. These fields may be explained as fossil relics from magnetic fields in the main-sequence progenitors considerably enhanced by magnetic flux conservation during the shrinkage of the core. A detection rate of 25 % (3/12) may indicate now for the first time that a substantial fraction of white dwarfs have a weak magnetic field. This result, if confirmed by future observations, would form a cornerstone for our understanding on the evolution of stellar magnetic fields. Keywords: stars: white dwarfs - stars: magnetic fields - stars: individual: WD0446-790, WD1105-048, WD2359-434
|
[
"Physics Archive->astro-ph"
] | 2004-05-17T08:26:56Z |
2007.13088
|
Unveiling shape resonances in H + HF collisions at cold energies
|
Resonances are associated with the trapping of an intermolecular complex, and are characterized by a series of quantum numbers such as the total angular momentum and the parity, representative of a specific partial wave. Here we show how at cold temperatures the rotational quenching of HF(j=1,2) with H is strongly influenced by the presence of manifolds of resonances arising from the combination of a single value of the orbital angular momentum with different total angular momentum values. These resonances give rise up to a two-fold increase in the thermal rate coefficient at the low temperatures characteristic of the interstellar medium. Our results show that by selecting the relative geometry of the reactants by alignment of the HF rotational angular momentum, it is possible to decompose the resonance peak, disentangling the contribution of different total angular momenta to the resonance.
|
[
"Physics Archive->physics->physics.atom-ph",
"Physics Archive->quant-ph"
] | 2020-07-26T09:51:18Z |
0709.3406
|
Equal Superposition Transformations and Quantum Random Walks
|
The largest ensemble of qubits which satisfy the general transformation of equal superposition is obtained by different methods, namely, linearity, no-superluminal signalling and non-increase of entanglement under LOCC. We also consider the associated quantum random walk and show that all unitary balanced coins give the same asymmetric spatial probability distribution. It is further illustrated that unbalanced coins, upon appropriate superposition, lead to new unbiased walks which have no classical analogues.
|
[
"Physics Archive->quant-ph"
] | 2007-09-21T11:34:58Z |
cond-mat/9908396
|
New mechanism of X-ray radiation from a relativistic charged particle in a dielectric random medium
|
We have considered X-ray radiation of a relativistic charged particle moving in a system consisting of microspheres distributed randomly in a dielectric material. A new mechanism based on the diffusional scattering of pseudophotons is suggested. The result leads to a stronger dependence of radiation intensity on the particle energy, than that predicted by the traditional transition radiation theory,and explains a recent experiment on such a system of randomly distributed superconducting granules.
|
[
"Physics Archive->cond-mat->cond-mat.dis-nn"
] | 1999-08-27T10:40:34Z |
2011.01900
|
Warped Language Models for Noise Robust Language Understanding
|
Masked Language Models (MLM) are self-supervised neural networks trained to fill in the blanks in a given sentence with masked tokens. Despite the tremendous success of MLMs for various text based tasks, they are not robust for spoken language understanding, especially for spontaneous conversational speech recognition noise. In this work we introduce Warped Language Models (WLM) in which input sentences at training time go through the same modifications as in MLM, plus two additional modifications, namely inserting and dropping random tokens. These two modifications extend and contract the sentence in addition to the modifications in MLMs, hence the word "warped" in the name. The insertion and drop modification of the input text during training of WLM resemble the types of noise due to Automatic Speech Recognition (ASR) errors, and as a result WLMs are likely to be more robust to ASR noise. Through computational results we show that natural language understanding systems built on top of WLMs perform better compared to those built based on MLMs, especially in the presence of ASR errors.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.CL"
] | 2020-11-03T18:26:28Z |
1503.05328
|
Time-Reversal-Symmetric Single-Photon Wave Packets for Free-Space Quantum Communication
|
Readout and retrieval processes are proposed for efficient, high-fidelity quantum state transfer between a matter qubit, encoded in the level structure of a single atom or ion, and a photonic qubit, encoded in a time-reversal-symmetric single-photon wave packet. They are based on controlling spontaneous photon emission and absorption of a matter qubit on demand in free space by stimulated Raman adiabatic passage. As these processes do not involve mode selection by high-finesse cavities or photon transport through optical fibers, they offer interesting perspectives as basic building blocks for free-space quantum-communication protocols.
|
[
"Physics Archive->quant-ph"
] | 2015-03-18T10:18:06Z |
1610.05623
|
Topology of the Electroweak Vacua
|
In the Standard Model, the electroweak symmetry is broken by a complex, $SU(2)$-doublet Higgs field and the vacuum manifold $SU(2)\times U(1)/U(1)$ has the topology of a 3-sphere. We remark that there exist theoretical alternatives that are locally isomorphic, but in which the vacuum manifold is homeomorphic to an arbitrary non-trivial principal $U(1)$-bundle over a 2-sphere. These alternatives have non-trivial fundamental group and thus feature topologically-stable electroweak strings. An alternative based on the manifold $\mathbb{R}P^3$ (with fundamental group $\mathbb{Z}/2$) allows custodial protection of gauge boson masses and their couplings to fermions, but, in common with all alternatives to $S^3$, has a problem with fermion masses.
|
[
"Physics Archive->hep->hep-ph",
"Physics Archive->hep->hep-th"
] | 2016-10-18T14:11:47Z |
1707.07019
|
Unified Halo-Independent Formalism From Convex Hulls for Direct Dark Matter Searches
|
Using the Fenchel-Eggleston theorem for convex hulls (an extension of the Caratheodory theorem), we prove that any likelihood can be maximized by either a dark matter 1- speed distribution $F(v)$ in Earth's frame or 2- Galactic velocity distribution $f^{\rm gal}(\vec{u})$, consisting of a sum of delta functions. The former case applies only to time-averaged rate measurements and the maximum number of delta functions is $({\mathcal N}-1)$, where ${\mathcal N}$ is the total number of data entries. The second case applies to any harmonic expansion coefficient of the time-dependent rate and the maximum number of terms is ${\mathcal N}$. Using time-averaged rates, the aforementioned form of $F(v)$ results in a piecewise constant unmodulated halo function $\tilde\eta^0_{BF}(v_{\rm min})$ (which is an integral of the speed distribution) with at most $({\mathcal N}-1)$ downward steps. The authors had previously proven this result for likelihoods comprised of at least one extended likelihood, and found the best-fit halo function to be unique. This uniqueness, however, cannot be guaranteed in the more general analysis applied to arbitrary likelihoods. Thus we introduce a method for determining whether there exists a unique best-fit halo function, and provide a procedure for constructing either a pointwise confidence band, if the best-fit halo function is unique, or a degeneracy band, if it is not. Using measurements of modulation amplitudes, the aforementioned form of $f^{\rm gal}(\vec{u})$, which is a sum of Galactic streams, yields a periodic time-dependent halo function $\tilde\eta_{BF}(v_{\rm min}, t)$ which at any fixed time is a piecewise constant function of $v_{\rm min}$ with at most ${\mathcal N}$ downward steps. In this case, we explain how to construct pointwise confidence and degeneracy bands from the time-averaged halo function. Finally, we show that requiring an isotropic ...
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->hep->hep-ph"
] | 2017-07-21T18:40:47Z |
1411.1330
|
Anomalous CDW ground state in Cu$_2$Se: a wave-like fluctuation of $\it{dc}$ I-V curve near 50 K
|
A charge density wave (CDW) ground state is observed in polycrystalline Cu$_2$Se below 125 K, which corresponds to an energy gap of 40.9 meV and an electron-phonon coupling constant of 0.6. Due to the polycrystalline structure, the Peierls transition process has been expanded to a wide temperature range from 90 to 160 K. The Hall carrier concentration shows a continuous decrease from 2.1$\times$10$^{20}$ to 1.6$\times$10$^{20}$ cm$^{-3}$ in the temperature range from 160 K to 80 K, while almost unchanged above 160 K and below 90 K. After entering the CDW ground state, a wave-like fluctuation was observed in the I-V curve near 50 K, which exhibits as a periodic negative differential resistivity in an applied electric field due to the current. We also investigated the doping effect of Zn, Ni, and Te on the CDW ground state. Both Zn and Ni doped Cu$_2$Se show a CDW character with increased energy gap and electron-phonon coupling constant, but no notable Peierls transition was observed in Te doped Cu$_2$Se. Similar wave-like I-V curve was also seen in Cu$_{1.98}$Zn$_{0.02}$Se near 40 K. The regular fluctuation in $\it{dc}$ I-V curve was not magnetic field sensitive, but temperature and sample size sensitive.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2014-11-05T17:18:07Z |
1802.07437
|
Binary Constrained Deep Hashing Network for Image Retrieval without Manual Annotation
|
Learning compact binary codes for image retrieval task using deep neural networks has attracted increasing attention recently. However, training deep hashing networks for the task is challenging due to the binary constraints on the hash codes, the similarity preserving property, and the requirement for a vast amount of labelled images. To the best of our knowledge, none of the existing methods has tackled all of these challenges completely in a unified framework. In this work, we propose a novel end-to-end deep learning approach for the task, in which the network is trained to produce binary codes directly from image pixels without the need of manual annotation. In particular, to deal with the non-smoothness of binary constraints, we propose a novel pairwise constrained loss function, which simultaneously encodes the distances between pairs of hash codes, and the binary quantization error. In order to train the network with the proposed loss function, we propose an efficient parameter learning algorithm. In addition, to provide similar / dissimilar training images to train the network, we exploit 3D models reconstructed from unlabelled images for automatic generation of enormous training image pairs. The extensive experiments on image retrieval benchmark datasets demonstrate the improvements of the proposed method over the state-of-the-art compact representation methods on the image retrieval problem.
|
[
"Computer Science Archive->cs.CV"
] | 2018-02-21T06:20:59Z |
0706.3294
|
Moriond 07 proceedings:"Extension of the frequency-range of interferometers for the "magnetic" components of gravitational waves?"
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Recently some papers in the literature have shown the presence and importance of the so-called {}"magnetic" components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In this paper the response functions for the magnetic components are re-analysed in the full frequency dependence answering to the question of the title.
|
[
"Physics Archive->gr-qc"
] | 2007-06-22T09:28:04Z |
2108.10437
|
Longitudinal Distance: Towards Accountable Instance Attribution
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Previous research in interpretable machine learning (IML) and explainable artificial intelligence (XAI) can be broadly categorized as either focusing on seeking interpretability in the agent's model (i.e., IML) or focusing on the context of the user in addition to the model (i.e., XAI). The former can be categorized as feature or instance attribution. Example- or sample-based methods such as those using or inspired by case-based reasoning (CBR) rely on various approaches to select instances that are not necessarily attributing instances responsible for an agent's decision. Furthermore, existing approaches have focused on interpretability and explainability but fall short when it comes to accountability. Inspired in case-based reasoning principles, this paper introduces a pseudo-metric we call Longitudinal distance and its use to attribute instances to a neural network agent's decision that can be potentially used to build accountable CBR agents.
|
[
"Computer Science Archive->cs.AI"
] | 2021-08-23T22:50:23Z |
cond-mat/9906131
|
The anomalous metallic ferromagnetic state of Sr doped manganites
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We deduce a model relevant for the anomalous metallic state of Sr doped manganites at low temperatures within the ferromagnetic phase. It provides a natural explanation to several anomalous features observed experimentally, such as the vanishing Drude contribution in optical conductivity, the pseudo-gap in the density of states, an the unusual dispersion observed in photoemission.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 1999-06-09T12:30:38Z |
0912.3206
|
Driving sandpiles to criticality and beyond
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A popular theory of self-organized criticality relates driven dissipative systems to systems with conservation. This theory predicts that the stationary density of the abelian sandpile model equals the threshold density of the fixed-energy sandpile. We refute this prediction for a wide variety of underlying graphs, including the square grid. Driven dissipative sandpiles continue to evolve even after reaching criticality. This result casts doubt on the validity of using fixed-energy sandpiles to explore the critical behavior of the abelian sandpile model at stationarity.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2009-12-16T20:55:29Z |
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