cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
De Branges-Rovnyak realizations of operator-valued Schur functions on the complex right half-plane
Creators: name: Ball, Joseph A.
name: Kurula, Mikael
name: Staffans, Olof J.
name: Zwart, Hans
Publisher: name: arXiv
Year: 2013
Subjects: subject: Optimization and Control (math.OC)
subject: Functional Analysis (math.FA)
subject: FOS: Mathematics
subject: Primary 47A48, 93B15, 47B32, Secondary 93C25, 47A57

description: We give a controllable energy-preserving and an observable co-energy-preserving de Branges-Rovnyak functional model realization of an arbitrary given operator Schur function defined on the complex right-half plane. We work the theory out fully in the right-half plane, without using results for the disk case, in order to expose the technical details of continuous-time systems theory. At the end of the article, we make explicit the connection to the corresponding classical de Branges-Rovnyak realizations for Schur functions on the complex unit disk.
description: 68 pages: General polishing; no essential changes
Evolutionary algorithms support recurrent plasticity in spiking neural network models of neocortical task learning
Creators: name: Qu, Ivyer M.
name: Liu, Huaze
name: Li, Jiayue D.
name: Zhu, Yuqing
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Learning, plasticity and memory

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Soliton-induced nonlocal resonances observed through high-intensity tunable spectrally compressed second-harmonic peaks
Creators: name: Zhou, Binbin
name: Guo, Hairun
name: Bache, Morten
Publisher: name: arXiv
Year: 2013
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Experimental data of femtosecond thick-crystal second-harmonic generation shows that when tuning away from phase matching, a dominating narrow spectral peak appears in the second harmonic that can be tuned over 100's of nm by changing the phase-mismatch parameter. Traditional theory explains this as phase matching between a sideband in the broadband pump to its second-harmonic. However, our experiment is conducted under high input intensities and instead shows excellent quantitative agreement with a nonlocal theory describing cascaded quadratic nonlinearities. This theory explains the detuned peak as a nonlocal resonance that arises due to phase-matching between the pump and a detuned second-harmonic frequency, but where in contrast to the traditional theory the pump is assumed dispersion-free. As a soliton is inherently dispersion-free, the agreement between our experiment and the nonlocal theory indirectly proves that we have observed a soliton-induced nonlocal resonance. The soliton exists in the self-defocusing regime of the cascaded nonlinear interaction and in the normal dispersion regime of the crystal, and needs high input intensities to become excited.
description: submitted, revised version
Plastic Arbor: a modern simulation framework for synaptic plasticity – from single synapses to networks of morphological neurons
Creators: name: Luboeinski, Jannik
name: Schmitt, Sebastian
name: Shafiee Kamalabad, Shirin
name: Hater, Thorsten
name: Bösch, Fabian
name: Tetzlaff, Christian
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Learning, plasticity and memory

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
'Reusers' and 'Unlearners' display distinct effects of forgetting on reversal learning in neural networks
Creators: name: Elpelt, Jonas
name: Eppler, Jens-Bastian
name: Seiler, Johannes P.
name: Rumpel, Simon
name: Kaschube, Matthias
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Learning, plasticity and memory

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Efficiency Maximization for UAV-Enabled Mobile Relaying Systems with Laser Charging
Creators: name: Zhao, Ming-Min
name: Shi, Qingjiang
name: Zhao, Min-Jian
Publisher: name: arXiv
Year: 2019
Subjects: subject: Information Theory (cs.IT)
subject: Signal Processing (eess.SP)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: This work studies the joint problem of power and trajectory optimization in an unmanned aerial vehicle (UAV)-enabled mobile relaying system. In the considered system, in order to provide convenient and sustainable energy supply to the UAV relay, we consider the deployment of a power beacon (PB) which can wirelessly charge the UAV and it is realized by a properly designed laser charging system. To this end, we propose an efficiency (the weighted sum of the energy efficiency during information transmission and wireless power transmission efficiency) maximization problem by optimizing the source/UAV/PB transmit powers along with the UAV's trajectory. This optimization problem is also subject to practical mobility constraints, as well as the information-causality constraint and energy-causality constraint at the UAV. Different from the commonly used alternating optimization (AO) algorithm, two joint design algorithms, namely: the concave-convex procedure (CCCP) and penalty dual decomposition (PDD)-based algorithms, are presented to address the resulting non-convex problem, which features complex objective function with multiple-ratio terms and coupling constraints. These two very different algorithms are both able to achieve a stationary solution of the original efficiency maximization problem. Simulation results validate the effectiveness of the proposed algorithms.
description: 33 pages, 8 figures, accepted for publication in IEEE Transactions on Wireless Communications
Learning Not to Spoof
Creators: name: Byrd, David
Publisher: name: arXiv
Year: 2023
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: Computational Engineering, Finance, and Science (cs.CE)
subject: Multiagent Systems (cs.MA)
subject: Statistical Finance (q-fin.ST)
subject: FOS: Computer and information sciences
subject: FOS: Economics and business

description: As intelligent trading agents based on reinforcement learning (RL) gain prevalence, it becomes more important to ensure that RL agents obey laws, regulations, and human behavioral expectations. There is substantial literature concerning the aversion of obvious catastrophes like crashing a helicopter or bankrupting a trading account, but little around the avoidance of subtle non-normative behavior for which there are examples, but no programmable definition. Such behavior may violate legal or regulatory, rather than physical or monetary, constraints. In this article, I consider a series of experiments in which an intelligent stock trading agent maximizes profit but may also inadvertently learn to spoof the market in which it participates. I first inject a hand-coded spoofing agent to a multi-agent market simulation and learn to recognize spoofing activity sequences. Then I replace the hand-coded spoofing trader with a simple profit-maximizing RL agent and observe that it independently discovers spoofing as the optimal strategy. Finally, I introduce a method to incorporate the recognizer as normative guide, shaping the agent's perceived rewards and altering its selected actions. The agent remains profitable while avoiding spoofing behaviors that would result in even higher profit. After presenting the empirical results, I conclude with some recommendations. The method should generalize to the reduction of any unwanted behavior for which a recognizer can be learned.
Impacts of non-geometric moduli on effective theory of 5D supergravity
Creators: name: Sakamura, Yutaka
name: Yamada, Yusuke
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: 5D supergravity generically has non-geometric moduli other than the radion that belong to 5D vector multiplets. We summarize the impacts of such moduli on 4D effective theory of 5D supergravity on S^1/Z_2. We mainly discuss the structure of the effective Kahler potential including the one-loop quantum corrections. As an illustrative example, we construct a model in which the size of the extra dimension is stabilized at an exponentially large value compared to the Planck length, which is similar to the LARGE volume scenario in string theory.
description: 25 pages, v2: typos corrected, v3: typos corrected
Realistic Saliency Guided Image Enhancement
Creators: name: Miangoleh, S. Mahdi H.
name: Bylinskii, Zoya
name: Kee, Eric
name: Shechtman, Eli
name: Aksoy, Yağız
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Common editing operations performed by professional photographers include the cleanup operations: de-emphasizing distracting elements and enhancing subjects. These edits are challenging, requiring a delicate balance between manipulating the viewer's attention while maintaining photo realism. While recent approaches can boast successful examples of attention attenuation or amplification, most of them also suffer from frequent unrealistic edits. We propose a realism loss for saliency-guided image enhancement to maintain high realism across varying image types, while attenuating distractors and amplifying objects of interest. Evaluations with professional photographers confirm that we achieve the dual objective of realism and effectiveness, and outperform the recent approaches on their own datasets, while requiring a smaller memory footprint and runtime. We thus offer a viable solution for automating image enhancement and photo cleanup operations.
description: For more info visit http://yaksoy.github.io/realisticEditing/
Quantitative evaluation of T-Bar anatomic structure influence upon calcium concentration enhancement
Creators: name: Knodel, Markus M.
name: Dutta Roy, Ranjita
name: Wittum, Gabriel
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Single neurons and biophysics

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Computational modelling of dentate granule cells reveals Pareto optimal trade-off between pattern separation and energy efficiency (economy)
Creators: name: Mittag, Martin
name: Bird, Alexander D.
name: Cuntz, Hermann
name: Jedlicka, Peter
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Single neurons and biophysics

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
String Black Holes as Particle Accelerators to Arbitrarily High Energy
Creators: name: Pradhan, Parthapratim
Publisher: name: arXiv
Year: 2013
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We show that an extremal Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole may act as a particle accelerator with arbitrarily high energy when two uncharged particles falling freely from rest to infinity on the near horizon. We show that the center of mass energy of collision independent of the extreme fine tuning of the angular momentum of the colliding particles. We further show that the center of mass energy of collisions of particles at the ISCO ($r_{ISCO}$) or at the photon orbit ($r_{ph}$) or at the marginally bound circular orbit ($r_{mb}$) i.e. at $r \equiv r_{ISCO}=r_{ph}=r_{mb}=2M$ could be arbitrarily large for the aforementioned spacetimes, which is different from Schwarzschild and Reissner-Nordstrøm spcetimes. For non-extremal GMGHS spacetimes the CM energy is finite and depends upon the asymptotic value of the dilation field ($ϕ_{0}$).
description: Accepted for publication in Astrophysics and Space science
How the presynapse shapes its molecular composition in an energetically optimal manner
Creators: name: Timonidis, Nestor
name: Bergmann, Cornelius
name: Tchumatchenko, Tatjana
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Single neurons and biophysics

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Discovering and Certifying Lower Bounds for the Online Bin Stretching Problem
Creators: name: Böhm, Martin
name: Simon, Bertrand
Publisher: name: arXiv
Year: 2020
Subjects: subject: Data Structures and Algorithms (cs.DS)
subject: FOS: Computer and information sciences

description: There are several problems in the theory of online computation where tight lower bounds on the competitive ratio are unknown and expected to be difficult to describe in a short form. A good example is the Online Bin Stretching problem, in which the task is to pack the incoming items online into bins while minimizing the load of the largest bin. Additionally, the optimal load of the entire instance is known in advance. The contribution of this paper is twofold. We use the Coq proof assistant to formalize the Online Bin Stretching problem and provide a program certifying lower bounds of this problem. Because of the size of the certificates, previously claimed lower bounds were never formally proven. To the best of our knowledge, this is the first use of a formal verification toolkit to certify a lower bound for an online problem. We also provide the first non-trivial lower bounds for Online Bin Stretching with 6, 7 and 8 bins, and increase the best known lower bound for 3 bins. We describe in detail the algorithmic improvements which were necessary for the discovery of the new lower bounds, which are several orders of magnitude more complex.
An elementary illustrated introduction to simplicial sets
Creators: name: Friedman, Greg
Publisher: name: arXiv
Year: 2008
Subjects: subject: Algebraic Topology (math.AT)
subject: Category Theory (math.CT)
subject: Geometric Topology (math.GT)
subject: FOS: Mathematics
subject: 18G30, 55U10

description: This is an expository introduction to simplicial sets and simplicial homotopy theory with particular focus on relating the combinatorial aspects of the theory to their geometric/topological origins. It is intended to be accessible to students familiar with just the fundamentals of algebraic topology.
description: Several minor errata corrected since published version. A list of changes is provided at the end of the document
Stochastic Mechanistic Interaction
Creators: name: Berzuini, Carlo
name: Dawid, A. Philip
Publisher: name: arXiv
Year: 2013
Subjects: subject: Methodology (stat.ME)
subject: FOS: Computer and information sciences

description: We propose a fully probabilistic formulation of the notion of mechanistic interaction (interaction in some fundamental mechanistic sense) between the effects of putative (possibly continuous) causal factors A and B on a binary outcome variable Y indicating 'survival' vs 'failure'. We define mechanistic interaction in terms of departure from a generalized 'noisy OR' model, under which the multiplicative causal effect of A (resp., B) on the probability of failure cannot be enhanced by manipulating B (resp., A). We present conditions under which mechanistic interaction in the above sense can be assessed via simple tests on excess risk or superadditivity, in a possibly retrospective regime of observation. These conditions are defined in terms of generalized conditional independence relationships (generalised because they may involve non-stochastic 'regime indicators') that can often be checked on a graphical representation of the problem. Inference about mechanistic interaction between direct, or path-specific, causal effects can be accommodated in the proposed framework. The method is illustrated with the aid of a study in experimental psychology.
description: 28 pages, 4 figures
Chernoff approximations of Feller semigroups in Riemannian manifolds
Creators: name: Mazzucchi, Sonia
name: Moretti, Valter
name: Remizov, Ivan
name: Smolyanov, Oleg
Publisher: name: arXiv
Year: 2020
Subjects: subject: Functional Analysis (math.FA)
subject: Mathematical Physics (math-ph)
subject: Analysis of PDEs (math.AP)
subject: Probability (math.PR)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: primary 47D06 secondary 58J65, 58A05, 35K15, 35C99, 41A99

description: Chernoff approximations of Feller semigroups and the associated diffusion processes in Riemannian manifolds are studied. The manifolds are assumed to be of bounded geometry, thus including all compact manifolds and also a wide range of non-compact manifolds. Sufficient conditions are established for a class of second order elliptic operators to generate a Feller semigroup on a (generally non-compact) manifold of bounded geometry. A construction of Chernoff approximations is presented for these Feller semigroups in terms of shift operators. This provides approximations of solutions to initial value problems for parabolic equations with variable coefficients on the manifold. It also yields weak convergence of a sequence of random walks on the manifolds to the diffusion processes associated with the elliptic generator. For parallelizable manifolds this result is applied in particular to the representation of Brownian motion on the manifolds as limits of the corresponding random walks.
description: 36 pages, no figures. Title and abstract changed. Minor corrections, some proposition generalised
Solutions of Liouville equations with non-trivial profile in dimensions 2 and 4
Creators: name: Albesiano, Roberto
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35A01

description: We prove the existence of a family of non-trivial solutions of the Liouville equation in dimensions two and four with infinite volume. These solutions are perturbations of a finite-volume solution of the same equation in one dimension less. In particular, they are periodic in one variable and decay linearly to $-\infty$ in the other variables. In dimension two, we also prove that the periods are arbitrarily close to $πk, k \in \mathbb{N}$ (from the positive side). The main tool we employ is bifurcation theory in weighted Hölder spaces.
description: 40 pages
Resolution except for minimal singularities II. The case of four variables
Creators: name: Bierstone, Edward
name: Lairez, Pierre
name: Milman, Pierre D.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Algebraic Geometry (math.AG)
subject: Complex Variables (math.CV)
subject: FOS: Mathematics
subject: Primary 14B05, 14E15, 32S45, Secondary 14J17, 32S05, 32S10, 58K50

description: In this sequel to Resolution except for minimal singularities I, we find the smallest class of singularities in four variables with which we necessarily end up if we resolve singularities except for normal crossings. The main new feature is a characterization of singularities in four variables which occur as limits of triple normal crossings singularities, and which cannot be eliminated by a birational morphism that avoids blowing up normal crossings singularities.
description: 23 pages. Section 3 revised. Results unchanged
Stratified incomplete local simplex tests for curvature of nonparametric multiple regression
Creators: name: Song, Yanglei
name: Chen, Xiaohui
name: Kato, Kengo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: Principled nonparametric tests for regression curvature in $\mathbb{R}^{d}$ are often statistically and computationally challenging. This paper introduces the stratified incomplete local simplex (SILS) tests for joint concavity of nonparametric multiple regression. The SILS tests with suitable bootstrap calibration are shown to achieve simultaneous guarantees on dimension-free computational complexity, polynomial decay of the uniform error-in-size, and power consistency for general (global and local) alternatives. To establish these results, a general theory for incomplete $U$-processes with stratified random sparse weights is developed. Novel technical ingredients include maximal inequalities for the supremum of multiple incomplete $U$-processes.
description: Accepted to Bernoulli
Presynaptic Activity-dependent calcium dynamics in cytosol & ER, and a brief proposal for a morphodynamic model of growth cone motility
Creators: name: Flores-Pretell, Nicole
name: Dutta Roy, Ranjita
name: Gonzalez-Esparza, Daniel
name: Logashenko, Dmitry
name: Breit, Markus
name: Knodel, Markus M.
name: Wittum, Gabriel
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Single neurons and biophysics

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Creative telescoping for rational functions using the Griffiths-Dwork method
Creators: name: Bostan, Alin
name: Lairez, Pierre
name: Salvy, Bruno
Publisher: name: arXiv
Year: 2013
Subjects: subject: Symbolic Computation (cs.SC)
subject: FOS: Computer and information sciences

description: Creative telescoping algorithms compute linear differential equations satisfied by multiple integrals with parameters. We describe a precise and elementary algorithmic version of the Griffiths-Dwork method for the creative telescoping of rational functions. This leads to bounds on the order and degree of the coefficients of the differential equation, and to the first complexity result which is simply exponential in the number of variables. One of the important features of the algorithm is that it does not need to compute certificates. The approach is vindicated by a prototype implementation.
Bilinear R Parity Violation at the ILC - Neutrino Physics at Colliders
Creators: name: List, Jenny
name: Vormwald, Benedikt
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: Supersymmetry (SUSY) with bilinearly broken R parity (bRPV) offers an attractive possibility to explain the origin of neutrino masses and mixings. In such scenarios, the study of neutralino decays at colliders gives access to neutrino sector parameters. The ILC offers a very clean environment to study the neutralino properties as well as its subsequent decays, which typically involve a $W$ or $Z$ boson and a lepton. This study is based on ILC beam parameters according to the Technical Design Report for a center of mass energy of $500\,\mathrm{GeV}$. A full detector simulation of the International Large Detector (ILD) was performed for all Standard Model backgrounds and for $\widetildeχ_1^0$-pair production within a simplified model. The bRPV parameters are fixed according to current neutrino data. In this scenario, the $\widetildeχ_1^0$ mass can be reconstructed with an uncertainty of $δm = (40(\text{stat.}) + 50(\text{syst.}))\,\mathrm{MeV}$ for an integrated luminosity of $500\,\mathrm{fb}^{-1}$ from direct $\widetildeχ_1^0$-pair production, thus, to a large extent independently of the rest of the SUSY spectrum. The achievable precision on the atmospheric neutrino mixing angle $\sin^2 θ_{23}$ from measuring the neutralino branching fractions $\mathrm{BR}(\widetildeχ_1^0 \rightarrow W μ)$ and $\mathrm{BR}(\widetildeχ_1^0 \rightarrow W τ)$ at the ILC is better than current uncertainties from neutrino experiments. Thus, the ILC could have the opportunity to unveil the mechanism of neutrino mass generation.
description: 21 pages, 10 figures, accepted for publication in EPJC
Games on graphs: A minor modification of payoff scheme makes a big difference
Creators: name: Zhang, Qiang
name: Qi, Tianxiao
name: Li, Keqiang
name: Di, Zengru
name: Wu, Jinshan
Publisher: name: arXiv
Year: 2013
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Computer Science and Game Theory (cs.GT)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Various social dilemma games that follow different strategy updating rules have been studied on many networks.The reported results span the entire spectrum, from significantly boosting,to marginally affecting,to seriously decreasing the level of cooperation.Experimental results that are qualitatively different from theoretical prediction have also been reported.It is widely believed that the results are largely determined by three elements,including payoff matrices of the underlying 2*2 games,the way that the strategic states of the players are updated and the structure of the networks.Here we discuss the impact of a seemly non-essential mechanism -- what we refer to as a "payoff scheme". Specifically, in each round after the states of all of the players are determined,the payoff scheme is how each player's payoff is calculated.In addition to the two conventions in which either the accumulated or the averaged payoff is calculated from playing with all of the neighboring players,we here study the effects of calculating the payoff from pairing up with one random player from among the neighboring players. Based on probability theory, in a situation of uncorrelated events, the average payoff that involves all of the neighbors should,in principal,be equivalent to the payoff from pairing up with one neighbor.However,our simulation of games on graphs shows that, in many cases,the two payoff schemes lead to qualitatively different levels of cooperation.This finding appears to provide a possible explanation for a wide spectrum of observed behaviors in the literature.We have also observed that results from the randomly-pairing-one mechanism are more robust than the involving-all-neighbours mechanism because,in the former case, neither the other three main elements nor the initial states of the players have a large impact on the final level of cooperation compared with in the latter case.
description: 23 pages,171 figures
Structured randomness: Jamming of soft discs and pins
Creators: name: Wentworth-Nice, Prairie
name: Ridout, Sean A.
name: Jenike, Brian
name: Liloia, Ari
name: Graves, Amy L.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Simulations are used to find the zero temperature jamming threshold, $ϕ_j$, for soft, bidisperse disks in the presence of small fixed particles, or "pins", arranged in a lattice. The presence of pins leads, as one expects, to a decrease in $ϕ_j$. Structural properties of the system near the jamming threshold are calculated as a function of the pin density. While the correlation length exponent remains $ν= 1/2$ at low pin densities, the system is mechanically stable with more bonds, yet fewer contacts than the Maxwell criterion implies in the absence of pins. In addition, as pin density increases, novel bond orientational order and long-range spatial order appear, which are correlated with the square symmetry of the pin lattice.
description: 9 pages, 11 figures, 1 table; This is v2 of an article, revised thanks to peer review
Proto-Strange Quark Star Structure
Creators: name: Bordbar, Gholam Hossein
name: Sadeghi, Fatemeh
name: Kayanikhoo, Fatemeh
name: Poostforush, Ahmad
Publisher: name: arXiv
Year: 2020
Subjects: subject: Nuclear Theory (nucl-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: In this paper, we investigate the newborn strange quark stars with constant entropy. We also use the MIT bag model to calculate the thermodynamic properties in two cases; the density-dependent bag constant and the fixed bag constant (B = 90 MeV). We show that the equation of state becomes stiffer by using the density dependent bag constant and by increasing the entropy. Furthermore, we show that the adiabatic index of the system reaches to 4/3 at high densities. Later, we calculate the structure of a strange quark star using the equation of state and the general relativistic equations of hydrostatic equilibrium, the Tolman-Oppenheimer-Volkoff (TOV) equations. We show that the gravitational mass of the star decreases by increasing the entropy and the maximum gravitational mass is larger when we use the density-dependent bag constant at fixed central energy density. It is shown that the mass-radius relation for this system obeys M R^ 3 for different cases of the calculations. Finally, we show that for a given stellar mass considering the fixed bag constant, the maximum gravitational red shift of a strange quark star occurs at larger values of entropy.
description: 7 pages, 10 figures, Ind J. Phys. (2020) accepted for publication
Convergence analysis of direct minimization and self-consistent iterations
Creators: name: Cancès, Eric
name: Kemlin, Gaspard
name: Levitt, Antoine
Publisher: name: arXiv
Year: 2020
Subjects: subject: Numerical Analysis (math.NA)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: This article is concerned with the numerical solution of subspace optimization problems, consisting of minimizing a smooth functional over the set of orthogonal projectors of fixed rank. Such problems are encountered in particular in electronic structure calculation (Hartree-Fock and Kohn-Sham Density Functional Theory -DFT- models). We compare from a numerical analysis perspective two simple representatives, the damped self-consistent field (SCF) iterations and the gradient descent algorithm, of the two classes of methods competing in the field: SCF and direct minimization methods. We derive asymptotic rates of convergence for these algorithms and analyze their dependence on the spectral gap and other properties of the problem. Our theoretical results are complemented by numerical simulations on a variety of examples, from toy models with tunable parameters to realistic Kohn-Sham computations. We also provide an example of chaotic behavior of the simple SCF iterations for a nonquadratic functional.
On $k$-point configuration sets with nonempty interior
Creators: name: Greenleaf, Allan
name: Iosevich, Alex
name: Taylor, Krystal
Publisher: name: arXiv
Year: 2020
Subjects: subject: Classical Analysis and ODEs (math.CA)
subject: Combinatorics (math.CO)
subject: FOS: Mathematics
subject: 58J40, 05B10

description: We give conditions for $k$-point configuration sets of thin sets to have nonempty interior, applicable to a wide variety of configurations. This is a continuation of our earlier work \cite{GIT19} on 2-point configurations, extending a theorem of Mattila and Sjölin \cite{MS99} for distance sets in Euclidean spaces. We show that for a general class of $k$-point configurations, the configuration set of a $k$-tuple of sets, $E_1,\,\dots,\, E_k$, has nonempty interior provided that the sum of their Hausdorff dimensions satisfies a lower bound, dictated by optimizing $L^2$-Sobolev estimates of associated generalized Radon transforms over all nontrivial partitions of the $k$ points into two subsets. We illustrate the general theorems with numerous specific examples. Applications to 3-point configurations include areas of triangles in $\mathbb R^2$ or the radii of their circumscribing circles; volumes of pinned parallelepipeds in $\mathbb R^3$; and ratios of pinned distances in $\mathbb R^2$ and $\mathbb R^3$. Results for 4-point configurations include cross-ratios on $\mathbb R$, triangle area pairs determined by quadrilaterals in $\mathbb R^2$, and dot products of differences in $\mathbb R^d$.
description: 31 pages, no figures, minor revision for publication
Hierarchical Block Structures and High-resolution Model Selection in Large Networks
Creators: name: Peixoto, Tiago P.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Social and Information Networks (cs.SI)
subject: Physics and Society (physics.soc-ph)
subject: Machine Learning (stat.ML)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Discovering and characterizing the large-scale topological features in empirical networks are crucial steps in understanding how complex systems function. However, most existing methods used to obtain the modular structure of networks suffer from serious problems, such as being oblivious to the statistical evidence supporting the discovered patterns, which results in the inability to separate actual structure from noise. In addition to this, one also observes a resolution limit on the size of communities, where smaller but well-defined clusters are not detectable when the network becomes large. This phenomenon occurs not only for the very popular approach of modularity optimization, which lacks built-in statistical validation, but also for more principled methods based on statistical inference and model selection, which do incorporate statistical validation in a formally correct way. Here we construct a nested generative model that, through a complete description of the entire network hierarchy at multiple scales, is capable of avoiding this limitation, and enables the detection of modular structure at levels far beyond those possible with current approaches. Even with this increased resolution, the method is based on the principle of parsimony, and is capable of separating signal from noise, and thus will not lead to the identification of spurious modules even on sparse networks. Furthermore, it fully generalizes other approaches in that it is not restricted to purely assortative mixing patterns, directed or undirected graphs, and ad hoc hierarchical structures such as binary trees. Despite its general character, the approach is tractable, and can be combined with advanced techniques of community detection to yield an efficient algorithm that scales well for very large networks.
description: 18 pages, 9 figures + Supplemental Material
Interplay of itinerant magnetism and reentrant spin-glass behavior in Fe$_{x}$Cr$_{1-x}$
Creators: name: Benka, Georg
name: Bauer, Andreas
name: Schmakat, Philipp
name: Säubert, Steffen
name: Seifert, Marc
name: Jorba, Pau
name: Pfleiderer, Christian
Publisher: name: arXiv
Year: 2020
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: When suppressing the itinerant antiferromagnetism in chromium by doping with the isostructual itinerant ferromagnet iron, a dome of spin-glass behavior emerges around a putative quantum critical point at an iron concentration $x \approx 0.15$. Here, we report a comprehensive investigation of polycrystalline samples of Fe$_{x}$Cr$_{1-x}$ in the range $0.05 \leq x \leq 0.30$ using x-ray powder diffraction, magnetization, ac susceptibility, and neutron depolarization measurements, complemented by specific heat and electrical resistivity data for $x = 0.15$. Besides antiferromagnetic ($x < 0.15$) and ferromagnetic regimes ($0.15 \leq x$), we identify a dome of reentrant spin-glass behavior at low temperatures for $0.10 \leq x \leq 0.25$ that is preceded by a precursor phenomenon. Neutron depolarization indicates an increase of the size of ferromagnetic clusters with increasing $x$ and the Mydosh parameter $ϕ$, inferred from the ac susceptibility, implies a crossover from cluster-glass to superparamagnetic behavior. Taken together, these findings consistently identify Fe$_{x}$Cr$_{1-x}$ as an itinerant-electron system that permits to study the evolution of spin-glass behavior of gradually varying character in unchanged crystalline environment.
Keldysh approach to the renormalization group analysis of the disordered electron liquid
Creators: name: Schwiete, G.
name: Finkel'stein, A. M.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We present a Keldysh nonlinear sigma-model approach to the renormalization group analysis of the disordered electron liquid. We include both the Coulomb interaction and Fermi-liquid type interactions in the singlet and triplet channels into the formalism. Based on this model, we reproduce the coupled renormalization group equations for the diffusion coefficient, the frequency, and interaction constants previously derived with the replica model in the imaginary time technique. With the help of source fields coupling to the particle-number and spin densities, we study the density-density and spin density-spin density correlation functions in the diffusive regime. This allows us to obtain results for the electric conductivity and the spin susceptibility and thereby to re-derive the main results of the one-loop renormalization group analysis of the disordered electron liquid in the Keldysh formalism.
description: 29 pages, 15 figures
Hexagonal warping on optical conductivity of surface states in Topological Insulator Bi_{2}Te_{3}
Creators: name: Li, Zhou
name: Carbotte, J. P.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: ARPES studies of the protected surface states in the Topological Insulator $% Bi_{2}Te_{3}$ have revealed the existence of an important hexagonal warping term in its electronic band structure. This term distorts the shape of the Dirac cone from a circle at low energies to a snowflake shape at higher energies. We show that this implies important modifications of the interband optical transitions which no longer provide a constant universal background as seen in graphene. Rather the conductivity shows a quasilinear increase with a slightly concave upward bending as energy is increased. Its slope increases with increasing magnitude of the hexagonal distortion as does the magnitude of the jump at the interband onset. The energy dependence of the density of states is also modified and deviates downward from linear with increasing energy.
description: 6 pages, 4 figures, accepted to Phys. Rev. B
Neuronal degeneracy: an information-energy trade-off?
Creators: name: Sommer, Philip
name: Bird, Alexander D.
name: Jedlicka, Peter
name: Triesch, Jochen
Publisher: name: G-Node
Year: 2024
Subjects: Computational Neuroscience
Single neurons and biophysics

description: Bernstein Conference 2024 abstract. https://bernstein-conference.de
Computing periods of rational integrals
Creators: name: Lairez, Pierre
Publisher: name: arXiv
Year: 2014
Subjects: subject: Symbolic Computation (cs.SC)
subject: Algebraic Geometry (math.AG)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics
subject: Primary 68W30, secondary 14K20, 14F40, 33F10

description: A period of a rational integral is the result of integrating, with respect to one or several variables, a rational function over a closed path. This work focuses particularly on periods depending on a parameter: in this case the period under consideration satisfies a linear differential equation, the Picard-Fuchs equation. I give a reduction algorithm that extends the Griffiths-Dwork reduction and apply it to the computation of Picard-Fuchs equations. The resulting algorithm is elementary and has been successfully applied to problems that were previously out of reach.
description: To appear in Math. comp. Supplementary material at http://pierre.lairez.fr/supp/periods/
A deterministic algorithm to compute approximate roots of polynomial systems in polynomial average time
Creators: name: Lairez, Pierre
Publisher: name: arXiv
Year: 2015
Subjects: subject: Numerical Analysis (math.NA)
subject: Computational Complexity (cs.CC)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: 68Q25, 65H10, 65H20, 65Y20

description: We describe a deterministic algorithm that computes an approximate root of n complex polynomial equations in n unknowns in average polynomial time with respect to the size of the input, in the Blum-Shub-Smale model with square root. It rests upon a derandomization of an algorithm of Beltrán and Pardo and gives a deterministic affirmative answer to Smale's 17th problem. The main idea is to make use of the randomness contained in the input itself.
Outage-Constrained Robust Beamforming for Intelligent Reflecting Surface Aided Wireless Communication
Creators: name: Zhao, Ming-Min
name: Liu, An
name: Zhang, Rui
Publisher: name: arXiv
Year: 2020
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: In intelligent reflecting surface (IRS) aided wireless communication systems, channel state information (CSI) is crucial to achieve its promising passive beamforming gains. However, CSI errors are inevitable in practice and generally correlated over the IRS reflecting elements due to the limited training with discrete phase shifts, which degrade the data transmission rate and reliability. In this paper, we focus on investigating the effect of CSI errors to the outage performance in an IRS-aided multiuser downlink communication system. Specifically, we aim to jointly optimize the active transmit precoding vectors at the access point (AP) and passive discrete phase shifts at the IRS to minimize the AP's transmit power, subject to the constraints on the maximum CSI-error induced outage probability for the users. First, we consider the single-user case and derive the user's outage probability in terms of the mean signal power (MSP) and variance of the received signal at the user. Since there is a trade-off in tuning these two parameters to minimize the outage probability, we propose to maximize their weighted sum with the optimal weight found by one-dimensional search. Then, for the general multiuser case, since the users' outage probabilities are difficult to obtain in closed-form due to the inter-user interference, we propose a novel constrained stochastic successive convex approximation (CSSCA) algorithm, which replaces the non-convex outage probability constraints with properly designed convex surrogate approximations. Simulation results verify the effectiveness of the proposed robust beamfoming algorithms and show their significant performance improvement over various benchmark schemes.
description: 15 pages, 14 figures, accepted for publication in IEEE Transactions on Signal Processing
Computing the Chow variety of quadratic space curves
Creators: name: Bürgisser, Peter
name: Kohn, Kathlén
name: Lairez, Pierre
name: Sturmfels, Bernd
Publisher: name: arXiv
Year: 2015
Subjects: subject: Algebraic Geometry (math.AG)
subject: Symbolic Computation (cs.SC)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: 14C05, 14-04

description: Quadrics in the Grassmannian of lines in 3-space form a 19-dimensional projective space. We study the subvariety of coisotropic hypersurfaces. Following Gel'fand, Kapranov and Zelevinsky, it decomposes into Chow forms of plane conics, Chow forms of pairs of lines, and Hurwitz forms of quadric surfaces. We compute the ideals of these loci.
Dynamic Tilting of Ferroelectric Domain Walls via Optically Induced Electronic Screening
Creators: name: Ahn, Youngjun
name: Everhardt, Arnoud S.
name: Lee, Hyeon Jun
name: Park, Joonkyu
name: Pateras, Anastasios
name: Damerio, Silvia
name: Zhou, Tao
name: DiChiara, Anthony D.
name: Wen, Haidan
name: Noheda, Beatriz
name: Evans, Paul G.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Optical excitation perturbs the balance of phenomena selecting the tilt orientation of domain walls within ferroelectric thin films. The high carrier density induced in a low-strain BaTiO3 thin film by an above-bandgap ultrafast optical pulse changes the tilt angle that 90° a/c domain walls form with respect to the substrate-film interface. The dynamics of the changes are apparent in time-resolved synchrotron x-ray scattering studies of the domain diffuse scattering. Tilting occurs at 298 K, a temperature at which the a/b and a/c domain phases coexist but is absent at 343 K in the better ordered single-phase a/c regime. Phase coexistence at 298 K leads to increased domain-wall charge density, and thus a larger screening effect than in the single-phase regime. The screening mechanism points to new directions for the manipulation of nanoscale ferroelectricity.
kruX: Matrix-based non-parametric eQTL discovery
Creators: name: Qi, Jianlong
name: Asl, Hassan Foroughi
name: Bjorkegren, Johan
name: Michoel, Tom
Publisher: name: arXiv
Year: 2013
Subjects: subject: Genomics (q-bio.GN)
subject: FOS: Biological sciences

description: The Kruskal-Wallis test is a popular non-parametric statistical test for identifying expression quantitative trait loci (eQTLs) from genome-wide data due to its robustness against variations in the underlying genetic model and expression trait distribution, but testing billions of marker-trait combinations one-by-one can become computationally prohibitive. We developed kruX, an algorithm implemented in Matlab, Python and R that uses matrix multiplications to simultaneously calculate the Kruskal-Wallis test statistic for several millions of marker-trait combinations at once. KruX is more than ten thousand times faster than computing associations one-by-one on a typical human dataset. We used kruX and a dataset of more than 500k SNPs and 20k expression traits measured in 102 human blood samples to compare eQTLs detected by the Kruskal-Wallis test to eQTLs detected by the parametric ANOVA and linear model methods. We found that the Kruskal-Wallis test is more robust against data outliers and heterogeneous genotype group sizes and detects a higher proportion of non-linear associations, but is more conservative for calling additive linear associations. In summary, kruX enables the use of robust non-parametric methods for massive eQTL mapping without the need for a high-performance computing infrastructure.
description: minor revision; 6 pages, 5 figures; software available at http://krux.googlecode.com
Multiple binomial sums
Creators: name: Bostan, Alin
name: Lairez, Pierre
name: Salvy, Bruno
Publisher: name: arXiv
Year: 2015
Subjects: subject: Symbolic Computation (cs.SC)
subject: Combinatorics (math.CO)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics
subject: 05A10, 33F10, 68W30

description: Multiple binomial sums form a large class of multi-indexed sequences, closed under partial summation, which contains most of the sequences obtained by multiple summation of products of binomial coefficients and also all the sequences with algebraic generating function. We study the representation of the generating functions of binomial sums by integrals of rational functions. The outcome is twofold. Firstly, we show that a univariate sequence is a multiple binomial sum if and only if its generating function is the diagonal of a rational function. Secondly, we propose algorithms that decide the equality of multiple binomial sums and that compute recurrence relations for them. In conjunction with geometric simplifications of the integral representations, this approach behaves well in practice. The process avoids the computation of certificates and the problem of the appearance of spurious singularities that afflicts discrete creative telescoping, both in theory and in practice.
The surprising Crab pulsar and its nebula: A review
Creators: name: Buehler, Rolf
name: Blandford, Roger
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The Crab nebula and its pulsar (referred to together as "Crab") have historically played a central role in astrophysics. True to their legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae.
description: Review for Reports on Progress in Physics, 31 pages, 11 figures. For a video abstract see the journal web page of the article or http://bcove.me/391e37dv