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2605.20042 2026-05-20 physics.optics

Quantum analysis of multi-frequency laser with photonic time crystal

多频激光的量子分析:基于光子时间晶体

Igor Protsenko, Alexander Uskov

AI总结 本文研究了整合光子时间晶体的多频激光的生成机制,通过理论分析探讨了多频激光的振荡条件、输出功率和光谱特性。

Comments 27 pages, 5 figures

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AI中文摘要

本研究考虑了整合光子时间晶体(PTC)的激光器的操作,其目的是生成一个具有多个广泛分离的光学频率特征的场。该激光器同时受到提案和理论研究的探讨。该激光器包含一个活性介质和一个PTC,位于由两个重叠配置的光子晶体构成的小型谐振腔中。PTC由外部场调制。激光场光谱中的尖峰由PTC调制频率分离。已经开发出具有PTC的激光的量子模型,并分析了具有多频尖峰的激光模式。研究重点在于研究激光振荡条件、输出功率和激光场光谱。讨论了在现实条件下实现具有PTC的多频激光的实验实现。

英文摘要

The present study considers the operation of a laser that incorporates a photonic time crystal (PTC), the purpose of which is to generate a field characterised by multiple widely separated optical frequencies. This laser is the subject of both a proposal and theoretical investigation. The laser comprises an active medium and a PTC within a small cavity constructed from two photonic crystals that are positioned in an overlapping configuration. PTC is modulated by an external field. The spikes in the laser field spectrum are separated by the PTC modulation frequency. The development of a quantum model of the laser with PTC has been achieved, and the analysis of a lasing mode with multi-frequency spikes has been made. The investigation focused on the study of lasing conditions, output power, and the lasing field spectra. The experimental realization of the multi-frequency laser with PTC under realistic conditions is discussed.

2605.20041 2026-05-20 math.PR

Fourier Representations of Spectral Densities in Long-Memory Processes

谱密度的傅里叶表示在长记忆过程中的研究

Valentin Vidril

AI总结 本文研究了长记忆过程的谱密度傅里叶级数特性,指出即使在没有绝对可和性的情况下,傅里叶级数可能无界发散,同时探讨了在自协方差或谱密度呈现正则变化时傅里叶级数的收敛性。

Comments 36 pages, 2 figures

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AI中文摘要

本文旨在进一步澄清在二次意义上表现出长记忆的进程中的某些细微方面。我们构造了一个长记忆随机序列,其绝对自协方差序列发散,其谱密度的傅里叶级数几乎处处无界发散。这表明,对于一般的长记忆过程,如果只知道其自协方差不绝对可和,则应谨慎处理其谱密度的傅里叶级数。另一方面,已知如果假设自协方差或谱密度呈现正则变化,并结合相关缓慢变化函数的适当条件,则谱密度的傅里叶级数处处收敛,除了可能在0处。我们构造的过程可以轻松模拟,并比较其经验自协方差与理论自协方差。

英文摘要

In this article, we aim to further clarify certain subtle aspects of processes that exhibit long memory in the second-order sense. We construct a long-memory stochastic sequence, in the sense that the series of absolute autocovariances diverges, whose spectral density has an almost everywhere unboundedly divergent Fourier series. This suggests that the Fourier series of the spectral density of a generic long-range dependent process, one for which nothing is known except that its autocovariances are not absolutely summable, should be handled with great care. On the other hand, it is known that if one assumes regularly varying behavior for the autocovariances or the spectral density, along with suitable conditions on the associated slowly varying function, then the Fourier series of the spectral density converges everywhere, except possibly at 0. The process we construct can easily be simulated, and we compare its empirical and theoretical autocovariances.

2605.20038 2026-05-20 eess.SY cs.SY

A New Simple-to-Configure Self-Perturbing Multivariable Extremum-Seeking Controller

一种新的易于配置的自扰动多变量极值寻求控制器

Timothy I. Salsbury, Min Gyung Yu

AI总结 本文提出了一种新的随机继电器基于极值寻求控制器,用于多输入单输出系统,通过简化配置过程提高实际应用的可行性,展示了静态和动态系统的优化性能。

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Journal ref
Salsbury, Timothy I., and Min Gyung Yu. "A New Simple-to-Configure Self-Perturbing Multivariable Extremum-Seeking Controller." IFAC-PapersOnLine 58.28 (2024): 756-761
AI中文摘要

本文提出了一种新的随机继电器基于极值寻求控制器(ESC)用于多输入单输出(MISO)系统。该工作的目标是开发一种比其他方法更易于配置的算法,从而更容易地应用于现实问题。首先为静态映射开发了解决方案,然后将其适应于一般动态系统的类别。静态情况下的可配置参数数量为每个输入通道一个,而动态版本只需额外一个参数。通过使用随机继电器增益来解决梯度识别问题,并为静态情况提供了简单的稳定性证明。仿真测试展示了该策略在优化静态和动态系统方面的性能。

英文摘要

This paper presents a new stochastic relay-based extremum-seeking controller (ESC) for multi-input-single-output (MISO) systems. The goal of this work was to create an algorithm that is much simpler to configure than alternative approaches making deployment to real-world problems easier. A solution is developed first for a static map and then adapted for a general class of dynamic systems. The number of configurable parameters is one per input channel for the static case and only one additional parameter is needed for the dynamic version. The problem of gradient identification is solved via the use of stochastic relay gains and a simple stability proof for the static case is presented. Simulation tests demonstrate the performance of the strategy for optimizing both static and dynamic systems.

2605.20034 2026-05-20 hep-lat hep-ph nucl-th

Charmonium properties at high temperatures from lattice QCD

强子性质在高温下的格点QCD研究

Rasmus Normann Larsen, Peter Petreczky, Jorge Luis Dasilva Golan, Johannes H. Weber

AI总结 利用格点QCD研究高温下介子性质,通过计算扩展介子算符的相关函数,发现所有低于开底夸克阈值的charmonium态在该温度范围内存在,但随温度升高热宽度显著增加,且热宽度大小遵循charmonium大小的层次结构。

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AI中文摘要

我们利用格点QCD研究非零温度下153 MeV < T < 305 MeV范围内的charmonium性质。我们使用HISQ作用于动态夸克,Wilson clover作用于价层魅夸克,并计算扩展介子算符的相关函数。我们的格点QCD结果证实在此温度范围内所有低于开魅阈值的charmonium态均存在。然而,charmonium态获得显著的热宽度,其随温度升高而增加。热宽度的大小遵循charmonium大小的层次结构,即较小的基态charmonium具有比较大的激发态更小的热宽度。

英文摘要

We study charmonium properties at non-zero temperature in the temperature range 153 MeV $<T<$ 305 MeV using lattice QCD. We use HISQ action for dynamical quarks and Wilson clover action for valence charm quarks and calculate the correlation function of extended meson operators. Our lattice QCD results are consistent with the existence of all charmonium states below the open charm threshold in this temperature region. However, charmonium states acquire sizable thermal width, which increases with increasing temperature. The size of the thermal width follows the hierarchy of charmonium sizes, i.e. the smaller ground state charmonium has a smaller thermal width than the larger excited charmonia.

2605.20031 2026-05-20 math-ph cond-mat.mtrl-sci math.MP

Concurrent enforcement of polyconvexity and true-stress-true-strain monotonicity in incompressible isotropic hyperelasticity: application to neural network constitutive models

在不可压缩各向同性超弹性中同时满足多凸性和真实应力-真实应变单调性:应用于神经网络本构模型

Maximilian P. Wollner, Dominik K. Klein, Herbert Baaser, Gerhard A. Holzapfel, Patrizio Neff

AI总结 本文研究了在不可压缩各向同性超弹性中同时满足多凸性和真实应力-真实应变单调性的条件,并探讨了其在神经网络本构模型中的应用,展示了不同参数化方法在材料行为描述中的不同逼近能力。

Comments 25 pages, 4 figures

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AI中文摘要

为实现本构建模目的而设计的物理增强型神经网络(PANNs)近年来在多种材料行为方面受到了广泛关注。本文在最近关于本构不等式研究的进展背景下,重新审视了各向同性不可压缩超弹性类别的经典框架。我们证明了多凸性对于一大类不可压缩应变能函数意味着真实应力-真实应变单调性。由此得到的弹性定律同时满足物理合理的Legendre-Hadamard(或椭圆性)条件以及应力随应变增加而增加的观念。这些结果随后指导了四个不同的PANNs的架构,这些架构随后被校准到三个不同的实验数据集上。我们展示了不同的PANN参数化方法——在先验条件下满足相同的本构约束——在描述材料行为方面的逼近能力各不相同。此外,即使不同的参数化方法在校准范围内表现相当,它们在外推时也显示出显著差异。这一观察促使对PANNs预测能力的深入讨论,这也对通过神经网络建模更复杂材料行为具有启示作用。

英文摘要

The design of physics-augmented neural networks (PANNs) for the purposes of constitutive modeling has received considerable attention as of late for a variety of material behaviors. Here, we revisit the classical framework of isotropic incompressible hyperelasticity in light of recent advances in the study of constitutive inequalities. We show that polyconvexity implies true-stress-true-strain monotonicity for a large class of incompressible strain-energy functions. The resulting elastic law obeys the physically reasonable Legendre-Hadamard (or ellipticity) condition as well as the notion of increasing stress with increasing strain. These results then inform the architecture of four distinct PANNs which are subsequently calibrated to three different sets of experimental data each. We show that different PANN parametrizations - satisfying the same constitutive constraints a priori - have varying approximation power for the description of material behavior. Moreover, even when distinct parametrizations perform comparatively well within the calibration regime, they show pronounced differences in extrapolation. This observation motivates a critical discussion about the predictive power of PANNs which also has implications for the modeling of more complex material behavior by virtue of neural networks.

2605.20029 2026-05-20 cond-mat.str-el

Vortex order in magnetic frustrated GeNi$_2$O$_4$ and GeCo$_2$O$_4$ spinels

磁性 frustrated GeNi₂O₄ 和 GeCo₂O₄ 硫化物中的涡旋序

K. Beauvois, J. Robert, M. Songvilay, J. Ollivier, B. Fåk, E. Ressouche, N. Qureshi, R. Ballou, S. Petit, S. Lenne, P. Manuel, S. DeBrion, P. Strobel, V. Simonet

AI总结 通过研究基于奇异磁性对象如 Bloch 点或涡旋的新 spin textures,发现 GeNi₂O₄ 和 GeCo₂O₄ 硫化物中可以通过磁性各向异性和复杂相互作用的相互作用稳定 2-k 磁结构,从而形成短周期 spin vortex 晶体。

Comments Main text: 12 pages, 8 figures, 1 table Supp Mat: 7 pages, 6 figures, 4 tables

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AI中文摘要

在寻找基于奇异磁性对象如 Bloch 点或涡旋的新 spin textures 的过程中,spinels 作为一种有趣的平台出现,由于磁性各向异性和复杂相互作用在 pyrochlore 晶格上的相互作用远超最近邻。基于对 GeB₂O₄ 家族成员(B=Co 和 Ni)交换相互作用相图的探索,我们通过同时建模非弹性中子散射测量和单晶中子衍射数据,表明这些化合物中可能稳定 2-k 磁结构。这导致了短周期 spin vortex 晶体的形成,该结构由 3-k Bloch 点结构的磁性各向异性所诱导。我们的研究解释了这些多 k spin textures 在 frustrated antiferromagnets 中的形成以及其各向异性依赖的演变。

英文摘要

In the search for new spin textures based on singular magnetic objects like Bloch-points or vortices, spinel compounds emerge as an interesting playground due to the interplay between magnetic anisotropy and complex interactions that extend well beyond first neighbors on a pyrochlore lattice. Based on an exploration of the exchange interaction phase diagrams of members of the Ge$B_2$O$_4$ family with $B$=Co and Ni, we show, using simultaneous modeling of inelastic neutron scattering measurements and single-crystal neutron diffraction data, that a 2-$k$ magnetic structure may be stabilized in these compounds. This leads to a short period spin vortex crystal, a variant induced by the magnetic anisotropy of the 3-$k$ Bloch-point structure predicted for isotropic spins. Our study rationalizes the formation of these multi-$k$ spin textures in frustrated antiferromagnets, as well as their anisotropy-dependent evolution.

2605.20027 2026-05-20 astro-ph.CO astro-ph.GA

ComPACT: Mass-Redshift Properties of the galaxy cluster catalogue

ComPACT:银河团目录的质量-红移特性

S. Voskresenskaia, N. Lyskova, I. Zaznobin, A. Meshcheryakov

AI总结 该研究通过卷积神经网络分析公开的ACT+Planck地图,构建了ComPACT银河团目录,并探讨了其质量-红移特性及完整性,发现约60%的候选者被确认为银河团,且在高红移和高质量区域扩展了SZ选择的Planck-like银河团人口。

Comments 14 pages, 11 figures, Submitted to A&A

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AI中文摘要

机器学习方法越来越多地应用于天文学调查,为检测和研究银河团提供了强大的工具。我们研究了ComPACT银河团目录的质量-红移特性及完整性,该目录是通过卷积神经网络应用于公开的结合ACT+Planck地图构建的。ComPACT目录包含2,962个通过SZ选择的银河团候选者。我们通过文献信息和基于DESI Legacy Imaging Surveys数据的光度技术估计红移以确认银河团。银河团质量是从ACT+Planck和Planck Compton-y地图通过SZ缩放关系得出的。通过在真实微波地图中注入模拟的银河团来评估完整性。我们确认大约60%的ComPACT候选者为银河团。红移范围从0.007 < z < 1.7,包括大约116个新的测量。质量被确定为56%的样本,覆盖范围为(0.25 - 13.1) × 10¹⁴ ~M_⊙,包括158个新的质量确定。我们识别出五个之前未报告的高质量银河团(M_{500c} > 6 × 10¹⁴ ~M_⊙)在z > 0.7处,将已知此类系统的数量增加了约10%。ComPACT目录扩展了SZ选择的Planck-like银河团人口,尤其是在高红移和高质量区域,展示了深度学习方法在微波数据中检测银河团的有效性。

英文摘要

Machine-learning methods are increasingly applied to astronomical surveys, providing powerful tools for detecting and studying galaxy clusters. We investigate the mass-redshift properties and completeness of the ComPACT galaxy cluster catalogue, constructed using a convolutional neural network applied to publicly available combined ACT+Planck maps. The ComPACT catalogue contains 2,962 SZ-selected galaxy cluster candidates. We confirm clusters by estimating redshifts using literature information and photometric techniques based on DESI Legacy Imaging Surveys data. Cluster masses are derived from ACT+Planck and Planck Compton-y maps via SZ scaling relations. The completeness is assessed using simulated cluster injections into real microwave maps. We confirm approximately $\sim$60 % of the ComPACT candidates as galaxy clusters. The redshifts span the range $0.007 < z < 1.7$, including approximately 116 new measurements. Masses are obtained for 56 % of the sample, covering the range $(0.25 - 13.1) \times 10^{14} ~M_\odot$ and including 158 new mass determinations. We identify five previously unreported massive clusters ($M_{500c} > 6 \times 10^{14}~M_\odot$) at $z > 0.7$, increasing the known population of such systems by approximately 10 %. The ComPACT catalogue expands the SZ-selected Planck-like cluster population, especially at high redshift and high mass, demonstrating the effectiveness of deep-learning approaches for cluster detection in microwave data.

2605.20026 2026-05-20 math.PR

Quasihelix properties of selected Volterra Gaussian processes

选定Volterra高斯过程的准螺旋性质

Yuliya Mishura, Kostiantyn Ralchenko

AI总结 本文研究了几种具有温控、幂加权和对数核的高斯Volterra过程的局部准螺旋和广义准螺旋性质,包括温控分数布朗运动和广义分数布朗运动型过程,探讨了参数值对性质的影响。

Comments 13 pages

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AI中文摘要

我们研究了几种具有温控、幂加权和对数核的高斯Volterra过程的局部准螺旋和广义准螺旋性质,包括温控分数布朗运动和广义分数布朗运动型过程。这些性质在所涉及的参数值上具有显著差异,我们详细考虑了所有可能的情况。

英文摘要

We study local quasihelix and generalized quasihelix properties of several Gaussian Volterra processes with tempered, power-weighted, and logarithmic kernels, including tempered fractional Brownian motions and generalized fractional Brownian motion-type processes. These properties depend significantly on the values of the parameters involved, and we consider all possible cases in detail.

2605.20024 2026-05-20 cs.HC cs.CY

Journeys of Parents with LGBTQ+ Children: How Trauma and Healing Reshape Identity and (Mis)Informating Practices

LGBTQ+儿童父母的旅程:创伤与疗愈如何重塑身份和(误)信息实践

Soonho Kwon, Dong Whi Yoo, Koustuv Saha, Shaowen Bardzell, Younah Kang

AI总结 研究探讨了韩国LGBTQ+个体父母在得知孩子性取向后,如何应对恐惧、孤立和迷失带来的情感破裂,通过接触与性取向相关的(误)信息来缓解情绪压力,并逐渐倾听与性取向相关的现实。通过这一过程,研究强调父母如何重构支持性身份,从而改变其信息实践,使其在评估相关(误)信息时更加批判性,并发展策略以保护自己免受有害叙述的影响,同时积极挑战 misinformation 以支持经历相似经历的人。

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AI中文摘要

本研究探讨了韩国LGBTQ+个体父母在得知孩子性取向后,如何应对恐惧、孤立和迷失带来的情感破裂,通过接触与性取向相关的(误)信息来缓解情绪压力,并逐渐倾听与性取向相关的现实。通过这一过程,我们强调父母如何重构支持性身份,从而改变其信息实践,使其在评估相关(误)信息时更加批判性,并发展策略以保护自己免受有害叙述的影响,同时积极挑战 misinformation 以支持经历相似经历的人。本工作对CSCW的贡献包括:(1)突出LGBTQ+个体父母,这一被忽视但关键的 Stakeholder 组;(2)展示创伤-疗愈过程后身份重构如何改变信息实践;(3)论证解决 misinformation 需要超越个体事实性判断,考虑其关系、文化和情感维度。此外,我们邀请CSCW学者重新考虑抽象化与人性化信息之间的平衡,探索未来为LGBTQ+儿童父母设计的可能性,并反思研究者作为集体研究社区中参与者的作用。

英文摘要

This study examines how parents of LGBTQ+ individuals in South Korea navigate the emotional rupture fueled by fear, isolation, and disorientation after learning their children's queer identity, encounter queer-related (mis)information as a way of coping with this emotional toll, and come to listen to queer realities relationally. Through this process, we highlight how parents reconstruct their identities as supportive parents, which reshapes their informating practices, making them more critical in assessing queer-related (mis)information, developing strategies to protect themselves from harmful narratives, and actively challenging misinformation to support others navigating similar experiences. This work contributes to CSCW by (1) foregrounding parents of LGBTQ+ individuals, an underrepresented yet critical stakeholder group in Queer HCI; (2) demonstrating how identity reconfiguration following a trauma-healing process could transform information practices; and (3) arguing that addressing misinformation requires attention beyond individual fact-based discerning to account for its relational, cultural, and emotional dimensions. Further, we invite CSCW scholars to reconsider the balance between abstracting and humanizing information, explore future design possibilities for parents of LGBTQ+ children, and reflect on the role of researchers as participants in collective research communities fueled by care.

2605.20020 2026-05-20 cond-mat.str-el

Tunable magnetotransport through kinetically hindered first-order phase transitions in an antiferromagnetic metal

通过抗铁磁金属中受动能抑制的一阶相变实现可调磁输运

Jaime M. Moya, Scott B. Lee, Sudipta Chatterjee, Nitish Mathur, Grigorii Skorupskii, Connor J. Pollak, Leslie M. Schoop

AI总结 研究通过抗铁磁金属CeCoGe₃中受动能抑制的一阶相变实现可控的多级电阻状态,展示了其在神经形态计算中的应用潜力。

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AI中文摘要

可控的多级电阻状态对记忆技术如神经形态计算具有吸引力,但具有此类行为的稳健材料平台仍然有限。本文表明,非中心对称的抗铁磁金属CeCoGe₃通过受动能抑制的一阶磁相变提供了一种途径。在施加磁场下通过受动能抑制的一阶相变冷却会产生一种磁玻璃态,其中高温和低温磁相共存。通过控制样品冷却时的磁场,可以调节这些相的相对比例,而电导率直接敏感于该比例。因此,证明了CeCoGe₃支持稳定的多级电阻态。这些结果将受动能抑制的一阶相变识别为实现可控多级磁电阻态的有前途的途径。

英文摘要

Controllable multilevel resistance states are of interest for memory technologies like neuromorphic computing, but robust materials platforms toward such behavior remain limited. Here, we show that the non-centrosymmetric antiferromagnetic metal CeCoGe$_3$ suggests one such route through a kinetically hindered first-order magnetic transition. Cooling through the kinetically hindered first-order transition in an applied magnetic field produces a magnetic glass state in which high- and low-temperature magnetic phases coexist. The relative fraction of these phases can be controlled by the applied field in which the sample is cooled, and the electrical resistance is directly sensitive to that fraction. As a result, it is demonstrated that CeCoGe$_3$ supports stable multilevel resistive states. These results identify kinetically hindered first-order phase transitions as a promising route towards controllable multilevel magnetoresistive states.

2605.20019 2026-05-20 quant-ph math-ph math.MP

Induced transitions in non-Hermitian spin-boson models with time-dependent boundaries

非厄密itian自旋-玻色模型中诱导的跃迁与时间依赖边界

Andreas Fring, Marta Reboiro

AI总结 本文研究了一个具有复耦合的非厄密itian扩展的Schütte-Da~Providência自旋-玻色哈密顿量,并通过时间依赖的Dyson映射将其转换为具有实即时能谱的厄密itian哈密顿量。 squeezing贡献产生一个缩放项,使厄密itian伙伴可以被解释为具有移动边界的系统的固定域表示。虽然固定边界厄密itian模型保持Q=N-S_0并禁止相差两个玻色子量子的跃迁,但边界运动则打开这些通道。对于具有常数背景参数的闭合边界协议,一阶积分跃迁振幅消失,反映了常数squeezing的幺正性质。而非厄密itian参数在边界运动中变化时,会产生非平凡的跃迁控制,通过改变着装基底,允许边界诱导跃迁被相干干涉抑制或增强。

Comments 16 pages, 1 figure

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AI中文摘要

我们研究了一个具有复耦合的时间依赖非厄密itian扩展的Schütte-Da~Providência自旋-玻色哈密顿量。一个包含压缩变换的时间依赖Dyson映射将模型,在一个可接受的有界范围内,映射到一个具有实即时能谱的厄密itian哈密顿量。压缩贡献产生一个缩放项,使厄密itian伙伴可以被解释为具有移动边界的系统的固定域表示。虽然固定边界厄密itian模型保持Q=N-S_0并禁止相差两个玻色子量子的跃迁,但边界运动则打开这些通道。对于具有常数背景参数的闭合边界协议,一阶积分跃迁振幅消失,反映了常数squeezing的幺正性质。而非厄密itian参数在边界运动中变化时,会产生非平凡的跃迁控制,通过改变着装基底,允许边界诱导跃迁被相干干涉抑制或增强。

英文摘要

We study a time-dependent non-Hermitian extension of the Schütte-Da~Providência spin-boson Hamiltonian with complex couplings. A time-dependent Dyson map containing a squeezing transformation maps the model, in an admissible bounded regime, to a Hermitian Hamiltonian with real instantaneous energy spectrum. The squeezing contribution generates a dilatation term allowing the Hermitian partner to be interpreted as a fixed-domain representation of a system with moving boundaries. While the fixed-boundary Hermitian model conserves $Q=N-S_0$ and forbids transitions between sectors differing by two bosonic quanta, the boundary motion opens such channels. For closed boundary protocols with constant background parameters the first-order integrated transition amplitude vanishes, reflecting the unitary nature of constant squeezing. Nontrivial transition control arises when the non-Hermitian parameter varies during the boundary motion, changing the dressed basis and allowing boundary-induced transitions to be suppressed or enhanced by coherent interference.

2605.20018 2026-05-20 math.CA

The Law of the iterated logaritm for smooth functions

关于光滑函数的迭代对数定律

José G. Llorente, Artur Nicolau

AI总结 本文证明了上半空间中光滑函数的迭代对数定律版本,展示梯度和拉普拉斯算子梯度的大小条件如何导致自改进增长性质,应用于非调和情形。

Comments 18 pages

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AI中文摘要

证明了上半空间中光滑函数的迭代对数定律的一个版本。作为结果,我们展示某些关于梯度和拉普拉斯算子梯度的大小条件导致自改进增长性质。这些结果应用于和谐性不存在的情况。

英文摘要

A version of the Law of the Iterated Logarithm for smooth functions in the upper-half space is proved. As a consequence, we show that certain size conditions on the gradient and the gradient of the laplacian of a smooth function, lead to self-improvement growth properties. The results are applied in situations where harmonicity is not present.

2605.20017 2026-05-20 cond-mat.mtrl-sci cond-mat.mes-hall

Geometry-Dependent Crack Interaction and Toughening in Graphene

依赖几何的裂纹相互作用与石墨烯中的增韧

Suyeong Jin, Jung-Wuk Hong, Alexandre F. Fonseca

AI总结 研究通过计算模拟探讨了石墨烯中平行裂纹的裂纹宽度和裂纹间距耦合效应,发现增大裂纹宽度会增强机械性能对裂纹间距的敏感性,从而显著提高峰值应力、断裂应变和韧性,提出了裂纹几何设计图以识别裂纹凝聚、独立传播和增强韧性区域。

Comments 25 pages, 9 figures, 1 table, 2 appendices

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AI中文摘要

相邻裂纹之间的相互作用已被证明对石墨烯的断裂行为有显著影响。尽管先前研究主要关注裂纹间距,但裂纹宽度的作用仍不明确。此处通过计算模拟研究了裂纹宽度和裂纹间距(W_gap)对含有平行裂纹的石墨烯的拉伸响应的耦合效应。结果表明,增加裂纹宽度会增强机械性能对裂纹间距的敏感性,在足够大的W_gap下导致峰值应力、断裂应变和韧性显著增强。对于窄裂纹,裂纹凝聚主导并导致脆性断裂。相反,较宽的裂纹促进延迟的连接体破裂、增加的能量吸收和类似延展性断裂行为。归一化的韧性及断裂应变超过等效单裂纹系统的两倍以上。提出了一种裂纹几何设计图以识别裂纹凝聚、独立传播和增强韧性区域。

英文摘要

The interaction between neighboring cracks has been shown to strongly influence the fracture behavior of graphene. While previous studies focused primarily on crack spacing, the role of crack width remains poorly understood. Here, computational simulations are performed to investigate the coupled effects of crack width and inter-crack spacing $(W_\text{gap})$ on the tensile response of graphene containing parallel cracks. The results show that increasing crack width amplifies the sensitivity of mechanical properties to crack spacing, leading to significant enhancement of peak stress, fracture strain, and toughness at sufficiently large $W_\text{gap}$. For narrow cracks, crack coalescence dominates and causes brittle failure. In contrast, wider cracks promote delayed ligament rupture, increased energy absorption and ductile-like fracture behavior. The normalized toughness and fracture strain exceed those of equivalent single-crack systems by more than twofold. A crack-geometry design map is proposed to identify regimes of crack coalescence, independent propagation, and enhanced toughness.

2605.20015 2026-05-20 hep-ex

Search for soft unclustered energy patterns containing muons in the final state in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

在13 TeV的pp碰撞中,使用ATLAS探测器寻找包含μ子的软非簇状能量模式

ATLAS Collaboration

AI总结 该研究通过分析ATLAS探测器收集的140 fb$^{-1}$数据,寻找包含μ子的软非簇状能量模式(SUEPs)的迹象,基于隐藏峡谷场景中的标量媒介体通过胶子融合产生,结果未观察到显著超额,设定了媒介体产生截面与衰变到SUEP分支比的排除限。

Comments 45 pages in total, author list starting page 28, 12 figures, 3 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2018-56/

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AI中文摘要

软非簇状能量模式(SUEPs)指的是高多重性、各向同性的低动量粒子分布,可能出现在强耦合隐藏扇区理论中。本文使用在2015-2018年间由ATLAS探测器在大型强子对撞机上收集的140 fb$^{-1}$质子-质子碰撞数据,研究了在最终状态包含μ子的SUEPs。分析针对隐藏峡谷场景中通过胶子融合产生标量媒介体的SUEP特征。未观察到显著超额于标准模型预期的现象。对于媒介体质量m_S分别为750 GeV、400 GeV和125 GeV,设定了媒介体产生截面与衰变到SUEP分支比的排除限,分别为0.05 fb、0.4 fb和70 fb;最后一个值,当将媒介体识别为标准模型希格斯玻色子时,对应于约0.2%的分支比上限。

英文摘要

Soft unclustered energy patterns (SUEPs) refer to high-multiplicity, isotropic distributions of low-momentum particles that could arise in strongly-coupled hidden sector theories. A search for SUEPs whose decay products contain muons in the final state is presented using 140 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}$ = 13 TeV collected by the ATLAS detector at the Large Hadron Collider during 2015-2018. The analysis targets SUEP signatures via gluon-gluon fusion production of a scalar mediator in Hidden Valley scenarios. No significant excess over the Standard Model expectation is observed. Exclusion limits are set on the product of the mediator production cross section and the branching fraction for its decay into a SUEP, down to 0.05 fb for a mediator mass of $m_S$ = 750 GeV, 0.4 fb for $m_S$ = 400 GeV, and 70 fb for $m_S$ = 125 GeV; the last value, when identifying the mediator with the Standard Model Higgs boson, translates to an upper limit on the branching fraction of around 0.2%.

2605.20013 2026-05-20 hep-th gr-qc

Approaching the surface of an Exotic Compact Object

接近奇异紧致物体的表面

Shokoufe Faraji, Samir D. Mathur

AI总结 本文研究了量子引力中奇异紧致物体(ECO)表面附近的真空爱因斯坦方程,发现其度规呈现混沌行为,类似于宇宙学中大爆炸附近的'宇宙弹球'现象,且部分潜在墙壁转变为'悬崖',导致某些紧致方向坍缩至零大小,从而在弦论中自然延续到 fuzzball 内部几何。

Comments 12 pages, 1 figure, Essay awarded 4th prize in the Gravity Research Foundation 2026 Awards for Essays on Gravitation

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AI中文摘要

许多量子引力方法要求将传统黑洞几何体替换为奇异紧致物体(ECO),其表面具有较大的但非无限的红移。我们论证在接近 ECO 表面时,真空爱因斯坦方程暗示一个具有混沌性质的度规,随着接近表面,其振荡幅度不断增大。这种行为类似于宇宙学中大爆炸附近发现的'宇宙弹球'现象。对于 ECO,部分潜在墙壁的符号发生变化,转变为'悬崖',导致某些紧致方向坍缩至零大小。在弦论中,这种压缩自然地延续到 fuzzball 内部几何,其中紧致方向坍缩形成单极子。

英文摘要

Many approaches to quantum gravity require replacing the traditional black hole geometry with an Exotic Compact Object (ECO), which has a large but not infinite redshift at its surface. We argue that near the ECO surface, the vacuum Einstein equations imply a metric that is chaotic, with increasingly large oscillations as we approach the surface. This behavior is analogous to the `cosmic billiards' found in the BKL analysis of cosmology near the big bang. For the ECO, some of the potential walls of this billiards change sign to become `cliffs', resulting in a runaway behavior where some compact directions squeeze to zero size. In string theory such squeezing yields a natural continuation to the interior geometry of fuzzballs, where compact directions collapse to create monopoles.

2605.20012 2026-05-20 econ.EM

Testing Heteroskedasticity Under Measurement Error

在测量误差下检验异方差性

Xiaojun Song, Jichao Yuan

AI总结 本文提出了一种新的方法,用于检测受测量误差污染的回归模型中的异方差性。该方法基于整合条件矩(ICM)方法,构造了基于去卷积残差标记经验过程的检验统计量,并在普通光滑和超光滑情况下建立了其渐近性质,假设测量误差分布已知。针对未知测量误差分布的问题,本文利用基于重复测量的测量误差特征函数估计器。此外,根据测量误差分布是否已知,提出了两种计算上具有吸引力的乘法-bootstrap方法,成功解决了参数估计效应的问题。最后,通过模拟结果和玉米产量及家庭预算份额的实证研究,证实了所提检验的优良性质。

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AI中文摘要

在本文中,我们提出了一种新的方法来检测受测量误差污染的回归模型中的异方差性。具体来说,受整合条件矩(ICM)方法的启发,我们构造了基于去卷积残差标记经验过程的检验统计量,并在普通光滑和超光滑情况下建立了其渐近性质,假设测量误差分布已知。针对未知测量误差分布的问题,本文利用基于重复测量的测量误差特征函数估计器。此外,根据测量误差分布是否已知,为从案例依赖的极限零分布中获得临界值,我们提出了两种计算上具有吸引力的乘法-bootstrap方法,其中成功解决了参数估计效应的问题。最后,模拟结果和关于玉米产量和家庭预算份额的实证研究证实了所提检验的优良性质。

英文摘要

In this paper, we propose a novel approach to detect heteroskedasticity in regression models with regressors contaminated by measurement error. Specifically, inspired by the integrated conditional moment (ICM) approach, we construct test statistics based on a deconvolved residual-marked empirical process and establish their asymptotic properties in both ordinary smooth and supersmooth cases, assuming the measurement error distribution is known. The issue of an unknown measurement error distribution is addressed by employing estimators of the measurement error characteristic function based on repeated measurements. Furthermore, depending on whether the measurement error distribution is known or not, to obtain critical values from the case-dependent limiting null distributions, we propose two computationally attractive multiplier bootstrap methods where the "parameter estimation effect" is successfully addressed. Finally, simulation results and empirical studies about corn yields and household budget shares confirm the favorable properties of the proposed tests.

2605.20011 2026-05-20 cond-mat.mtrl-sci

Mesoscale Domain Evolution Mechanism during Alternating Current (AC) Poling of Relaxor Ferroelectrics

介观尺度域演变机制:在交流电极化中的弛豫铁电材料

Yuan-Jie Sun, Bo Wang, Long-Qing Chen

AI总结 研究探讨了在交流电极化过程中,弛豫铁电材料中介观尺度域壁演变的机制,发现域壁间距比决定了域壁的不可逆消除,揭示了长程弹性相互作用导致的不对称性破缺。

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AI中文摘要

铁电域变体在能量等效的情况下,预期在极化反转下保持不变。然而,最近对弛豫铁电晶体的实验表明,在交流电极化过程中,倾斜域壁会发生不可逆的消除,而其介观尺度机制仍不清楚。本文通过相场模拟研究了在近二维层状几何结构中,含有71°和109°域壁的菱形Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$--PbTiO$_3$单晶在交流电极化过程中的域壁运动。模拟结果表明,在极化反转过程中,域壁行为取决于71°和109°域壁之间的间距比。紧密排列的71°域壁经历不可逆的消除,而更广泛分离的域壁得以保留,而109°域壁保持完整。确定了一个域壁消除的阈值比,并发现其依赖于机械边界条件。通过跟踪域壁轨迹,我们归因于相邻71°域壁由于长程弹性相互作用导致的非同步运动。这种集体运动打破了能量等效域变体之间的对称性,导致极化反转过程中的不可逆域壁消除。这些发现为极化反转过程中集体域壁演变提供了机理见解,并表明由接近驱动的对称性破缺可能为具有高域壁密度的铁电材料中的域工程提供介观尺度机制。

英文摘要

Ferroelectric domain variants that are energetically equivalent are expected to remain preserved during polarization reversal under a symmetry-preserving electric field. However, recent experiments on relaxor-ferroelectric crystals have revealed irreversible elimination of inclined domain walls during AC poling, while the underlying mesoscale mechanism remains unclear. Here, we investigate the domain-wall motion during AC poling of rhombohedral Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$--PbTiO$_3$ single crystals containing both 71$^\circ$ and 109$^\circ$ domain walls within a quasi-two-dimensional laminated geometry using phase-field simulations. The simulations reveal that the domain-wall behavior during polarization reversal depends on the spacing ratio between the 71$^\circ$ and 109$^\circ$ domain walls. Closely spaced 71$^\circ$ domain walls undergo irreversible elimination, whereas more widely separated walls are preserved, while the 109$^\circ$ domain walls remain intact. A threshold ratio for domain-wall elimination is identified and found to depend on the mechanical boundary conditions. By tracking the domain-wall trajectories during the switching process, we attribute this behavior to unsynchronized motion of neighboring 71$^\circ$ domain walls arising from long-range elastic interactions when the walls become strongly coupled. This collective motion breaks the symmetry between energetically equivalent domain variants and leads to irreversible domain-wall elimination during polarization reversal. These findings provide mechanistic insight into collective domain-wall evolution during polarization reversal and suggest that proximity-driven symmetry breaking may provide a mesoscale mechanism for domain engineering in ferroelectric materials with high domain-wall densities.

2605.20010 2026-05-20 math.AG

Enriques' characterization of Abelian surfaces in positive characteristic

Enriques对正特征下阿贝尔面的特征化

Jefferson Baudin, Gebhard Martin

AI总结 本文在正特征p≥7的代数闭域中扩展Enriques的特征化结果,证明了每个具有h^1(X,O_X)=2和p_1(X)=p_2(X)=1的光滑射影表面X都与阿贝尔面birational等价,并在p≤5时给出更精确的替代结果。

Comments 12 pages, comments welcome

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AI中文摘要

在代数闭域中特征p≥7的情况下,我们扩展Enriques的特征化结果,证明每个具有h^1(X, O_X)=2且p_1(X)=p_2(X)=1的光滑射影表面X都与阿贝尔面birational等价。该特征化在p≤5时失效,我们给出了更精确的替代结果。

英文摘要

Extending Enriques' characterization to algebraically closed fields of characteristic $p \geq 7$, we show that every smooth projective surface $X$ with $h^1(X, \mathcal{O}_X) = 2$ and $p_1(X) = p_2(X) = 1$ is birational to an Abelian surface. This characterization fails if $p \leq 5$, and we give a sharp alternative.

2605.20007 2026-05-20 stat.ME

Identifying Interventional Joint Distributions via Extended Bridge Functions

通过扩展桥梁函数识别干预性联合分布

Constantin Schott

AI总结 本文提出扩展桥梁函数,用于识别联合干预分布,解决了传统方法无法保留所有相关代理变量的问题,并将其应用于近端识别算法,基于核操作构建了通用框架。

Comments 38 pages, 4 figures

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AI中文摘要

现有接近因果推断中的识别结果通常专注于使用标准结果或治疗桥梁函数的边际干预分布。这些方法通常无法识别包含所有用于定义相应桥梁函数的代理变量的联合干预分布。然而,在许多应用中,这些联合干预分布是自然的目标。我们引入了扩展桥梁函数,并推导出识别联合干预分布的新结果,这些结果可能保留所有相关代理变量。然后,我们将这些结果应用于近端识别算法,其中干预内核自然地作为中间对象出现,从而基于核操作获得一个通用框架。

英文摘要

Existing identification results in proximal causal inference often focus on marginal interventional distributions using standard outcome or treatment bridge functions. These methods do not generally identify joint interventional distributions that contain all proxy variables that were used to define the corresponding bridge functions. In many applications, however, these joint interventional distributions are a natural target of interest. We introduce extended bridge functions and derive new identification results for joint interventional distributions that may retain all relevant proxy variables. We then apply these results to proximal identification algorithms, where interventional kernels naturally arise as intermediate objects, yielding a generalized framework based on kernel operations.

2605.20003 2026-05-20 stat.ME stat.AP

Estimating treatment duration effects via clone-censor-weight: a breast cancer case study

通过克隆-删失加权估计治疗持续时间效应:乳腺癌案例研究

Charlotte Voinot, Noémie Simon-Tillaux, Emma Torrini, Stefan Michiels, Bernard Sebastien, Clément Berenfeld, Julie Josse

AI总结 本文研究了在观察性生存数据中估计治疗持续时间效应的问题,提出克隆-删失加权框架以模拟治疗持续时间策略的目标试验,通过仿真研究比较了多种估计方法,并在乳腺癌队列中应用该框架,揭示了克隆-删失方法的实用性和局限性。

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AI中文摘要

在本文中,我们研究了在观察性生存数据中估计治疗持续时间效应的问题,其中治疗和协变量历史随时间演变,较长的观察持续时间只能在事件未发生且随访持续的个体中获得,导致朴素分析中存在永恒时间偏差。克隆-删失加权(CCW)框架提供了一种实用的方法来模拟治疗持续时间策略的目标试验,但若干方法学方面仍不够清楚。我们专注于静态治疗持续时间策略,在两种复杂性递增的设置中进行研究:仅基线混淆,以及具有时间变化协变量的混淆。我们正式化了CCW背后的假设,特别强调治疗可接受性、放松的干预规则以及人工删失与自然删失的区别。然后通过仿真研究比较了克隆和删失后的几种估计方法,包括逆概率删失加权(IPCW)、G公式和双重稳健估计器,评估其稳健性、变异性以及对删失模型误设定的敏感性。最后,我们将该框架应用于乳腺癌队列,以模拟比较2年与5年辅助他莫昔芬在早期乳腺癌中的目标试验。由于事件数量少且2年策略支持有限,估计与显著不确定性相关。这些发现突显了CCW的实用相关性和局限性,并强调了在复杂纵向观察研究中敏感性分析的重要性。

英文摘要

In this work, we study the estimation of treatment duration effects in observational survival data, where treatment and covariate histories evolve over time and longer observed durations are only attainable among individuals who remain event-free and under follow-up, leading to immortal time bias under naive analyses. The cloning-censoring-weighting (CCW) framework provides a practical approach to emulate target trials of treatment duration strategies, but several methodological aspects remain insufficiently understood. We focus on static treatment duration strategies under two settings of increasing complexity: baseline confounding only, and confounding with time-varying covariates. We formalize the assumptions underlying CCW, with particular emphasis on treatment admissibility, relaxed intervention rules, and the distinction between artificial and natural censoring. We then compare several estimation approaches after cloning and censoring, including inverse probability of censoring weighting (IPCW), the G-formula, and doubly robust estimators, through simulation studies assessing robustness, variability, and sensitivity to censoring model misspecification. Finally, we apply the framework to a Breast Cancer cohort to emulate a target trial comparing 2 versus 5 years of adjuvant tamoxifen in early stage breast cancer. Due to the small number of events and limited support for the 2-year strategy, estimates are associated with substantial uncertainty. These findings highlight both the practical relevance and the limitations of CCW, and underscore the importance of sensitivity analyses in complex longitudinal observational settings.

2605.20002 2026-05-20 math.CO

Locally Semi-Equitable Colourings of BIBDs

BIBD的局部半公平着色

Andrea C. Burgess, William Kellough, David A. Pike

AI总结 本文研究了BIBD的ℓ-着色问题,其中每个块中缺少一种颜色,其余ℓ-1种颜色恰好出现k/(ℓ-1)次,并建立了存在此类着色的若干必要条件,同时利用这些着色的BIBD为Hadamard矩阵、 affine平面和双素数幂的存在性提供了新的必要条件。

Comments 30 pages, 5 figures

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AI中文摘要

我们研究了$(v,k,λ)$-BIBD(平衡不完全块设计)的ℓ-着色,其中每个块中缺少一种颜色,其余ℓ-1种颜色恰好出现$ rac{k}{\ell-1}$次。我们建立了此类着色存在的若干必要条件。我们还利用这些着色的BIBD为Hadamard矩阵、affine平面和双素数幂的存在性提供了新的必要条件。

英文摘要

We study $\ell$-colourings of $(v,k,λ)$-BIBDs (balanced incomplete block designs) where, within each block, one colour is absent and each of the $\ell-1$ other colours appears exactly $\frac{k}{\ell-1}$ times. We establish several necessary conditions for such colourings to exist. We also use these coloured BIBDs to provide new necessary conditions for the existence of Hadamard matrices, affine planes, and twin prime powers.

2605.20001 2026-05-20 math-ph hep-th math.MP

Numerical approach to the modular operator for fermionic systems

费米子系统的模算子的数值方法

Henning Bostelmann, Daniela Cadamuro, Christoph Minz

AI总结 本文提出了一种数值方法,用于近似一维质量Majorana场局部子代数的Tomita-Takesaki模算子,通过时间零数据的空间离散化在单粒子水平上进行计算,并比较了不同边界条件下的结果与质量为零时的解析表达式,发现模算子对质量有非平凡依赖性。

Comments 25 pages, 16 figures

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AI中文摘要

我们数值近似了一维质量Majorana场局部子代数的Tomita-Takesaki模算子。我们的方法在单粒子水平上工作,通过时间零数据的空间离散化进行计算。我们考虑的局部子空间与一个双锥和两个双锥的不相交并集相关。为了避免边界效应,我们主要选择时空为圆柱体;考虑了不同的边界条件(反周期性和周期性)。我们将数值结果与已知的解析表达式在无质量情况下进行比较。结果表明,模算子对质量有非平凡依赖性。在两个双锥的情况下,模生成器不仅有''局部''贡献(支持在配置空间对角线上),还有''双局部''项(连接两个双锥区域);我们发现后者在高质量情况下不如预期显著。

英文摘要

We numerically approximate the Tomita-Takesaki modular operator for local subalgebras of the 1+1-dimensional massive Majorana field. Our method works at the one-particle level with a discretisation of time-0 data in position space. The local subspaces we consider are associated with one double cone and with the disjoint union of two double cones. In order to avoid boundary effects, we primarily choose the overall spacetime to be a cylinder; different choices of boundary conditions (antiperiodic and periodic) are considered. We compare our numerical results to known analytic expressions in the massless case. It turns out that the modular operator has a non-trivial dependence on the mass. In the case of two double cones, the modular generator does not only have ''local'' contributions (supported on the diagonal in configuration space) but also ''bilocal'' terms (connecting the two double cone regions); we find the latter to be less prominent at higher masses, in line with expectations.

2605.20000 2026-05-20 math.DG

Newman--Penrose formalism in $3$-dimensional trans-Sasakian manifolds

在3维转萨斯金 manifold 中的Newman-Penrose形式化

Prachi, Marie-Amélie Lawn, Mukut Mani Tripathi

AI总结 本文利用Newman-Penrose形式化研究3维转萨斯金manifolds,通过标量旋系数(加速度、剪切、扩张、扭力)编码结构向量场的几何,并推导了转萨斯金manifolds的曲率和拉普拉斯恒等式,以及其主要子类的公式,如里奇张量、标量曲率、爱因斯坦条件、粗糙拉普拉斯、特征向量场的散度和和谐性,同时给出了多个示例。

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AI中文摘要

我们利用Newman-Penrose形式化研究3维转萨斯金manifolds。在这一框架中,结构向量场的几何由标量旋系数编码:加速度、剪切、扩张和扭力。一个关键观察是,在维度3的情况下,转萨斯金条件等价于特征向量场定义了一个无剪切的测地线族,或者等价于通过测地线的共形分解。因此,Newman-Penrose方程为Baird和Wood在调和映射理论中研究的共形分解提供了直接的标量形式。在此框架内,我们推导了转萨斯金manifolds的曲率和拉普拉斯恒等式及其主要子类的公式,包括里奇张量、标量曲率、爱因斯坦条件、粗糙拉普拉斯、特征向量场的散度和和谐性,以及若干示例。作为应用,我们考虑与固定齐性度量类型E(κ,τ)兼容的转萨斯金结构。我们证明了一个刚性结果:在非空间形式情况下,Newman-Penrose方程迫使特征向量场为垂直的。因此,对于τ≠0且κ≠4τ²,每一个兼容的转萨斯金结构都是标准的垂直α-萨斯金结构;而对于τ=0且κ≠0,它则是垂直且共形辛的。特别地,这些非空间形式的齐性度量不具有任何真正的兼容转萨斯金结构。

英文摘要

We study $3$-dimensional trans-Sasakian manifolds using the Newman--Penrose formalism. In this framework, the geometry of the structure vector field is encoded by scalar spin coefficients: acceleration, shear, expansion, and twist. A central observation is that, in dimension $3$, the trans-Sasakian condition is equivalent to the characteristic vector field defining a shear-free geodesic congruence, or equivalently a conformal foliation by geodesics. Thus, the Newman--Penrose equations provide a direct scalar formulation of the conformal foliations studied by Baird and Wood in the theory of harmonic morphisms. Within this framework, we derive curvature and Laplacian identities for trans-Sasakian manifolds and their main subclasses, including formulae for the Ricci tensor, scalar curvature, Einstein condition, rough Laplacian, divergence and harmonicity of the characteristic vector field, together with several illustrative examples. As an application, we consider trans-Sasakian structures compatible with fixed homogeneous metrics of type ${\Bbb E}(κ,τ)$. We prove a rigidity result: in the non-space-form cases, the Newman--Penrose equations force the characteristic vector field to be vertical. Hence, for $τ\neq0$ and $κ\neq4τ^2$, every compatible trans-Sasakian structure is the canonical vertical $α$-Sasakian structure, while for $τ=0$ and $κ\neq0$, it is vertical and cosymplectic. In particular, these non-space-form homogeneous metrics admit no proper compatible trans-Sasakian structures.

2605.19998 2026-05-20 cond-mat.mes-hall

Ellipticity effects on diffusive magnon spin and heat transport in easy-plane ferromagnets

椭圆性对易平面铁磁体中扩散磁旋和热输运的影响

Nicolas Vidal-Silva, Alejandro O. Leon

AI总结 本文研究了易平面铁磁体中椭圆磁旋的扩散输运,通过推导磁旋色散关系和磁旋从Landau-Lifshitz-Gilbert方程出发,结合玻尔兹曼输运方程和扰动分析,得到了磁旋和热导率,揭示了椭圆性对磁旋输运系数的影响,并预测了磁旋热输运的增强效应。

Comments Published in Journal of Magnetism and Magnetic Materials

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AI中文摘要

当磁性材料包含磁旋激发,即磁旋时,局部磁化可以在圆形或椭圆形轨道上旋转,后者在存在垂直于平衡磁化方向的磁各向异性时自然出现。本文研究了易平面铁磁体中椭圆磁旋的扩散输运。我们的分析从推导磁旋色散关系和磁旋出发,基于具有垂直磁各向异性的Landau-Lifshitz-Gilbert方程。然后,利用弛豫时间近似下的玻尔兹曼输运方程和扰动分析,得到了磁旋和磁旋热导率,量化了绝缘体中的磁旋输运。我们的计算表明,在三维和二维系统中,椭圆性对磁旋输运系数的影响导致增强或减少,这取决于考虑的是具有易轴或难轴垂直于平面轴的磁体。另一方面,我们的结果预测了对于易轴和难轴磁性系统,磁旋热输运均被增强。本研究支持了之前关于磁旋椭圆性的研究,并向澄清其对磁旋输运性质的影响迈出了一步。

英文摘要

When a magnetic material hosts spin-wave excitations, or magnons, the local magnetization can rotate in circular or elliptical orbits, the latter arising naturally in the presence of magnetic anisotropies transverse to the equilibrium magnetization. This article investigates the diffusive transport of elliptical magnons in easy-plane ferromagnets. Our analysis starts with the derivation of the magnon dispersion relation and magnon spin from the Landau-Lifshitz-Gilbert equation with a perpendicular magnetic anisotropy. Then, using the Boltzmann transport equation in the relaxation time approximation and perturbation analysis, the magnon-spin and magnon thermal conductivities are obtained, quantifying the magnon transport in the insulator. Our calculations demonstrate that, in both three- and two-dimensional systems, the effects of ellipticity on magnon transport coefficients result in an enhancement or a decrease, depending on whether magnets with a easy or hard perpendicular-to-plane axis are considered, respectively. On the other hand, our results predict an enhancement of the magnon heat transport for both easy- and hard-axis magnetic systems. Our study supports previous works on magnon ellipticity and makes a step towards clarifying its effect on magnon transport properties.

2605.19997 2026-05-20 eess.SP

CAT-MoEformer: Context-Aware Temporal MoE Transformer for Beam Prediction

CAT-MoEformer:基于上下文的时序MoE变换器用于波束预测

Changkai Zhou, Cunhua Pan, Hong Ren, Jiangzhou Wang

AI总结 本文提出CAT-MoEformer,一种结合场景条件混合专家(MoE)前馈网络的上下文感知变换器,用于从压缩的上行链路探测观测中主动预测毫米波波束。该方法通过三阶不对称卷积网络和 squeeze-and-excitation 重校准块提取频束相关特征,采用预训练的GPT-2模型建模波束序列的时间演变,并用场景条件MoE-FFN模块替代上层变换器的前馈网络,通过轻量级门控网络将场景标签和归一化用户设备速度映射到专家混合权重,从而在物理传播描述符上进行路由决策,避免了基于潜在隐藏状态的负载不平衡问题。

Comments 13 pages, 5 figures

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AI中文摘要

本文提出CAT-MoEformer,一种基于上下文的时序MoE变换器,用于主动预测毫米波波束。该方法通过三阶不对称卷积网络和squeeze-and-excitation重校准块提取频束相关特征,采用预训练的GPT-2模型建模波束序列的时间演变,并用场景条件MoE-FFN模块替代上层变换器的前馈网络。通过轻量级门控网络将场景标签和归一化用户设备速度映射到专家混合权重,从而在物理传播描述符上进行路由决策,避免了基于潜在隐藏状态的负载不平衡问题。为此,引入了三阶段训练策略:第一阶段通过硬专家分配建立场景特定的专业化,第二阶段通过隔离门控网络训练使软路由分布与硬划分对齐,第三阶段通过top-1硬推断进一步微调模型,在确定性单专家激活下最大化场景特定精度。在3GPP TR 38.901城市宏通道模拟中,64,000个用户样本的仿真结果表明,CAT-MoEformer实现了94.88%的Top-1波束预测准确率和80.62%的波束切换瞬间准确率,分别比CNN+GPT-2基线高出2.33%和9.55%,推理延迟为0.52 ms。

英文摘要

This paper proposes CAT-MoEformer, a context-aware transformer with scene-conditioned mixture-of-experts (MoE) feed-forward networks, for proactive mmWave beam prediction from compressed uplink pilot observations. The spatial encoder comprises a three-layer asymmetric convolutional network followed by a squeeze-and-excitation recalibration block, which extracts frequency-beam correlation features from pilot tensors without explicit channel reconstruction. A truncated pretrained GPT-2 backbone models the temporal evolution of beam sequences, with the feed-forward networks in the upper three transformer layers replaced by scene-conditioned MoE-FFN modules. A lightweight gating network maps the scenario label and normalized user equipment speed to expert mixing weights, conditioning the routing decision on physical propagation descriptors rather than on latent hidden states. This design yields interpretable expert assignments and eliminates the load imbalance associated with token-level routing. To prevent expert collapse under soft routing, a three-stage training strategy is introduced: hard expert assignment in the first stage establishes scene-specific specialization, isolated gating network training in the second stage aligns the soft routing distribution with the hard partition, and top-1 hard inference in the third stage fine-tunes the model under deterministic single-expert activation to maximize scene-specific precision. Simulation results on 3GPP TR 38.901 Urban Macro channel simulations with $64{,}000$ user samples demonstrate that CAT-MoEformer achieves a Top-1 beam prediction accuracy of $94.88\%$ and a beam switching instant accuracy of $80.62\%$, representing gains of $2.33\%$ and $9.55\%$ respectively over a CNN+GPT-2 baseline, with an inference latency of $0.52$~ms.

2605.19996 2026-05-20 physics.optics

Reconfigurable generation of high-power structured light via nonlinear beam shaping

基于非线性光束成形的高功率结构光可重构生成

KyeoReh Lee, Baichuan Huang, Peyman Ahmadi, Mert Ercan, Stefan Rothe, Chun-Wei Chen, Hui Cao

AI总结 本文提出了一种基于非线性光束成形的高功率结构光生成方法,通过低功率种子光的全场控制,实现了从高功率多模光纤激光放大器中生成多种结构光束,如高斯光束、贝塞尔光束、矢量光束和轨道角动量光束,并展示了该方法在高功率下的实时可编程性和可扩展性。

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AI中文摘要

高功率结构光在材料加工、高速光学通信以及可编程电子束、等离子体和核态等领域具有广泛应用。按需生成结构光和对光束剖面的自适应控制对于许多实际应用至关重要,但在高功率下实现起来具有挑战性。本文展示了一种通过全场控制低功率种子光,从高功率多模光纤激光放大器中实现结构光的可重构生成。一种基于复杂非线性输入-输出关系局部线性近似的高效非线性光束成形方案被开发并现场实现。通过超过500瓦的功率,多种结构光束如高斯光束、贝塞尔光束、矢量光束和轨道角动量光束直接从光纤放大器中生成。该方案实现了结构光的实时可编程性,并可轻松扩展到更高的功率水平。这项工作为控制高维非线性系统提供了一个通用框架,无需准确的知识或可 tractable 模型。

英文摘要

High-power structured light has a wide range of applications, from material processing and high-capacity optical communications to programmable electron beams, plasmas, and nuclear states. On-demand generation of structured light and adaptive control of beam profiles are essential for many practical applications, but are difficult to achieve at high power. Here, we demonstrate reconfigurable generation of structured light from a high-power multimode-fiber laser amplifier through full-field control of a low-power seed. An efficient nonlinear beam shaping scheme based on a local linear approximation of the complex nonlinear input--output relation is developed and realized in situ. Diverse structured beams such as Gaussian, Bessel, vector and orbital angular momentum beams are directly generated from the fiber amplifier at powers exceeding 500 W. Our scheme enables real-time programmability of structured light and is readily scalable to even higher power levels. This work provides a general framework for controlling high-dimensional nonlinear systems without accurate knowledge or tractable model.

2605.19994 2026-05-20 physics.flu-dyn

Performance Evaluation of RANS-Based Turbulence Models in Predicting Turbulent Non-Premixed Swirling Combustion within a Realistic Can Combustor

基于真实喷嘴燃烧室的RANS湍流模型性能评估:预测非预混旋流燃烧

Aishvarya Kumar, Ram Prakash Bharti

AI总结 本文通过计算流体动力学分析,评估了不同湍流模型对燃烧室中流动、热场和组分场的影响,发现SST $k-ω$模型在预测轴向速度、横向速度、湍动能和剪切应力以及温度和组分浓度方面表现更优,且能更准确地预测燃烧室中的回流区和旋涡核心。

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AI中文摘要

本研究对真实喷嘴燃烧室中的燃烧流动进行了全面的计算流体动力学分析,评估了不同湍流模型对流动、热场和组分场的影响。非预混燃烧建模采用假设(beta)PDF方法结合San Diego反应机制的稳态层流火焰let模型,湍流采用RANS方法建模。分析了湍流模型(标准$k-ε$、可实现$k-ε$、SST $k-ω$、LPS-RSM)对速度场(平均轴向速度、平均横向速度、湍动能和剪切应力)的影响,以及对温度和组分($\ce{C3H8}$,$\ce{CO2}$,$\ce{CO}$)浓度的影响。分析显示,尽管SST $k-ω$模型的各向同性湍流粘性公式存在明显缺陷,但其预测了平均轴向速度、平均横向速度、湍动能和剪切应力更为准确。此外,它比其他模型更准确地预测了燃烧室中的流动特征,如中心回流区(CRZ)和中心旋涡核心(CVC)。此外,该模型预测了主区温度更高,这得到了$\ce{C3H8}$预测较低和湍动能升高支持,两者均表明强混合和高效的热量释放。此外,SST $k-ω$模型预测了最紧凑的化学计量比混合分数气泡,涵盖了CRZ和剪切层,表明大部分燃烧发生在主区。相应的进步变量也表明主区和剪切层中具有高值,证实了反应接近完成,这由出口处$\ce{C3H8}$和$\ce{CO}$的预测极低支持。

英文摘要

This study has presented a comprehensive computational fluid dynamics (CFD) analysis of combustion flow in a realistic can combustor, evaluating the influence of various turbulence models on flow, thermal, and species fields. The non-premixed combustion modeling is performed using a presumed (beta) PDF approach in conjunction with a steady laminar flamelet model employing the San Diego reaction mechanism, and the turbulence is modeled using the RANS approach. The influence of turbulence models (standard $k-ε$, realizable $k-ε$, SST $k-ω$, LPS-RSM) on the velocity field, such as the mean axial velocity, mean transverse velocity, turbulent kinetic energy (TKE) and shear stress, is analyzed, besides their influence on temperature and species (\ce{C3H8}, \ce{CO2}, and \ce{CO}) concentration. Analysis showed that despite the shortcomings of the isotropic turbulent viscosity formulation of the SST $k-ω$ model being evident, it predicted the mean axial velocity, mean transverse velocity, turbulent kinetic energy and shear stress more accurately. Additionally, it predicted the flow features expected in a can combustor, such as the central recirculation zone (CRZ) and central vortex core (CVC), more accurately than other models. Besides, the model predicted a higher temperature in the primary zone, which is supported by a lower prediction of \ce{C3H8}, and elevated TKE, both of which support strong mixing and efficient heat release. Furthermore, the SST $k-ω$ model predicted the most compact stoichiometric mixture fraction bubble, encompassing CRZ and shear layers, indicating that the majority of the combustion occurs in the primary zone. The corresponding progress variables also indicated high values in the primary zone and shear layers, confirming near completion of the reaction, supported by negligible prediction of \ce{C3H8} and \ce{CO} at the outlet.

2605.19993 2026-05-20 physics.comp-ph

Diversity-Aware Batch-Mode Active Learning for Efficient Sampling in Data-Driven Constitutive Modeling

面向多样性的批量模式主动学习用于数据驱动本构建模中的高效采样

Ronak Shoghi, Lukas Morand, Dirk Helm, Alexander Hartmaier

AI总结 本文提出了一种面向多样性的批量模式主动学习方法,通过在数据驱动本构建模中高效生成信息丰富的数据集,减少机器学习模型的重新训练次数。

Comments 23 pages, 7 figures

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AI中文摘要

材料的本构行为通过应力、应变和可能的其他内部变量之间的关系进行建模。这导致了机器学习模型相对高维的特征空间,使得高效生成信息丰富的数据集至关重要,因为暴力方法会受到维度灾难的影响。本文介绍了一种面向多样性的批量模式查询-委员会主动学习策略,以在最低成本下生成信息含量最大的数据集。与现有方法不同,该新方法在每次迭代中选择多个信息丰富且非冗余的查询,从而同时生成信息丰富的数据集并减少机器学习重新训练的次数。该方法的核心组件是一个基于余弦相似度的度量标准,通过促进批次内的多样性来补充基于委员会方差的不确定性标准。查询选择由委员会方差和促进多样性的标准引导。该方法在数据驱动本构建模中的高效应力空间采样中进行了基准测试。在此设置中,一个支持向量分类器的委员会近似所谓的屈服面,这是一个将六维应力空间划分为弹性域和塑性域的流形。我们证明该方法能够稳健地处理不同的批次大小,保持高批次内多样性,并快速减少委员会不确定性。所得到的机器学习屈服面在预测精度上与顺序主动学习相当,但需要显著更少的重新训练次数。这使得所提出的策略成为数据驱动本构建模中应力空间采样以及通过每次迭代的同时数据收集减少求解时间的有效方法。

英文摘要

The constitutive behavior of materials is modeled through relationships between stress, strain, and possibly additional internal variables. This results in relatively high-dimensional feature spaces for machine learning models rendering the efficient generation of informative datasets essential as brute force methods suffer from the curse of dimensionality. This work introduces a diversity-aware batch-mode query-by-committee active-learning strategy to generate datasets of maximum information content at minimum cost. In contrast to existing methods, this novel method selects multiple informative, non-redundant queries per iteration, enabling concurrent generation of informative datasets and reducing the number of machine-learning retraining cycles. A central component of this method is a cosine-similarity-based metric that complements the uncertainty criterion based on committee variance by promoting within-batch diversity. The query selection is guided by committee variance and a diversity-promoting criterion. The approach is benchmarked for efficient stress-space sampling in data-driven constitutive modeling. In this setting, a committee of support vector classifiers approximates the so-called yield surface, which is a manifold dividing the six-dimensional stress space into an elastic and plastic domain. We demonstrate that the method handles different batch sizes robustly, maintains high within batch diversity, and rapidly reduces committee uncertainty. The resulting machine learning yield surfaces achieve predictive accuracy comparable to sequential active learning, while requiring substantially fewer retraining cycles. This makes the proposed approach an efficient strategy for stress space sampling in data driven constitutive modeling and for reducing time to solution via concurrent data collection in each iteration.

2605.19992 2026-05-20 eess.SY cs.SY math.OC

Robust synchronization for multi-agent systems governed by PDEs with observable and unobservable disturbances

由PDEs支配的多智能体系统中观测与不可观测扰动的鲁棒同步

Yongchun Bi, Jun Zheng, Guchuan Zhu, Jiye Zhang

AI总结 本文研究了由抛物型偏微分方程支配的多智能体系统在存在可观测和不可观测扰动下的鲁棒同步问题,设计了仅使用边界输出测量的扰动观测器以估计可观测的Dirichlet边界扰动并确保在不可观测扰动存在时观测器误差系统的鲁棒性,然后利用参考信号和局部输出信息构建分布式同步控制器,使所有智能体跟踪参考轨迹,特别在无不可观测扰动时实现指数跟踪,同时在控制器实施过程中保留鲁棒性。进一步分析了不可观测的Dirichlet-Robin边界扰动对同步性能的影响,并通过证明同步误差系统的解的有界性来证明这一点。此外,为表征所有扰动的影响,建立了闭环系统的输入到状态稳定性(ISS)。对于涉及的系统,广义Lyapunov方法和递归技术被广泛应用于稳定性分析,而提升技术和半群理论被用于证明系统的适定性。仿真结果验证了所提出的控制方案,展示了有效的扰动估计和抑制、鲁棒同步以及在各种场景下的ISS性质。

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AI中文摘要

本文研究了由抛物型偏微分方程支配的多智能体系统在存在可观测和不可观测扰动下的鲁棒同步问题。利用仅有的边界输出测量,设计了一个扰动观测器以估计可观测的Dirichlet边界扰动,同时确保在不可观测扰动存在于域内时观测器误差系统的鲁棒性。仅利用参考信号和局部输出信息,构建了分布式同步控制器,使所有智能体能够跟踪参考轨迹。特别地,在没有不可观测扰动的情况下实现了指数跟踪,而在控制器实施过程中出现额外不可观测扰动时仍保持鲁棒性。进一步分析了不可观测的Dirichlet-Robin边界扰动对同步性能的影响,通过证明同步误差系统的解的有界性来证明这一点。此外,为表征所有扰动的影响,建立了闭环系统的输入到状态稳定性(ISS)。对于涉及的系统,广义Lyapunov方法和递归技术被广泛应用于稳定性分析,而提升技术和半群理论被用于证明系统的适定性。仿真结果验证了所提出的控制方案,展示了有效的扰动估计和抑制、鲁棒同步以及在各种场景下的ISS性质。

英文摘要

This paper investigates robust synchronization for multi-agent systems (MASs) governed by parabolic partial differential equations in the presence of both observable and unobservable disturbances. Using only boundary output measurements, a disturbance observer is designed to estimate observable Dirichlet boundary disturbances while ensuring robustness of the observer error system with unobservable disturbances occurring in the domain. Using only the reference signal and local output information, distributed synchronization controllers are then constructed to enable all agents to track the reference trajectory. In particular, exponential tracking is achieved in the absence of unobservable disturbances, while robustness is preserved when additional unobservable disturbances occur during controller implementation. We further analyze the impact of unobservable Dirichlet-Robin boundary disturbances on synchronization performance by proving the boundedness of solutions to the synchronization error system. Moreover, to characterize the influence of all disturbances, input-to-state stability (ISS) is established for the closed-loop system. For the involved systems, the generalized Lyapunov method and the recursion technique are extensively employed in the stability analysis, and the lifting technique and semigroup theory are used to prove the well-posedness. Simulation results validate the proposed control scheme, demonstrating effective disturbance estimation and rejection, robust synchronization, and the ISS properties under various scenarios.

2605.19991 2026-05-20 cs.IT math.IT math.PR

On the exact decoding error probability exponent of the random coding on BSC

关于在BSC上随机编码的解码错误概率指数的精确性

Marat V. Burnashev

AI总结 本文研究了在二元对称信道上随机编码的解码错误概率指数,通过新的随机变量和的分布结果推导出精确的指数表达式。

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AI中文摘要

对于在二元对称信道上的信息传输,考虑了指数数量的消息传输。推导了精确的解码错误概率指数。证明基于对某一随机变量和的分布的新结果。

英文摘要

For the information transmission over a binary symmetric channel the random coding is used. The transmission of exponential number of messages is considered. The exact decoding error probability exponent is derived. The proof is based on the new results on the distribution of a certain sum of random variables.