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2605.01015 2026-05-05 physics.flu-dyn

Leveraging unstructured grids for direct numerical simulations of wall turbulence

利用非结构网格进行壁湍流直接数值模拟

Amirreza Rouhi, Vishal Kumar, Wen Wu, Melissa Kozul, Oriol Lehmkuhl

AI总结 本文提出了一种非结构网格生成框架η-grid,用于壁湍流的直接数值模拟,通过将壁法向和跨度方向的网格尺寸与局部柯尔莫戈洛夫尺度η成比例,实现了更高效的网格生成和计算。

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AI中文摘要

我们提出了一种非结构网格生成框架,用于直接数值模拟(DNSs)的壁湍流,称为η-grid,其基于将壁法向(y)和跨度方向(z)的网格尺寸与局部柯尔莫戈洛夫尺度η成比例。该框架包括一个内层,厚度约为50个粘性单位,其粘性缩放的网格尺寸类似于传统DNS网格;0.3 < Δy+ < 4,Δz+ ~ 5在光滑壁面上,而l+/30 < Δy+, Δz+ < 4在非光滑表面,其中l+是表面最小波长。在内层之上,Δy+~ Δz+ ~ 2η+。我们使用有限体积法(FVM)代码和谱元法(SEM)代码测试η-grid,并进行了湍流通道流和光滑壁面及各种肋条几何形状(如沿流线对齐的微沟槽)的DNS测试,直到摩擦雷诺数δ+0= 1000。我们评估了η-grid与传统笛卡尔网格的精度,以及参考DNS和实验数据。我们发现η-grid与笛卡尔网格在皮肤摩擦系数、平均速度、湍流应力及其频谱图上差异小于1%。在δ+0 ~ 104范围内,η-grid的网格点数(Nη)在光滑壁面上按δ+02.5比例增长,在肋条上按δ+02.0比例增长,而笛卡尔网格和双曲正切y网格(NTanh)的网格点数按δ+03.0比例增长。这导致了巨大的网格节省;当δ+0= 6000时,Nη / NTanh在光滑壁面上约为0.1,在典型降阻三角肋条(尖角60o,粘性缩放间距15)上约为0.03。

英文摘要

We formulate an unstructured grid-generation framework for direct numerical simulations (DNSs) of wall turbulence, termed η-grid, based on setting the wall-normal (y) and spanwise (z) grid sizes proportional to the local Kolmogorov scale η. The framework consists of an inner layer, with a thickness ~50 viscous units, with viscous-scaled grid sizes similar to a conventional DNS grid; 0.3 < Δy+ < 4, Δz+ ~ 5 over a smooth wall, and l+/30 < Δy+, Δz+ < 4 over a non-smooth surface, where l+ is the smallest surface wavelength. Above the inner layer, Δy+~ Δz+ ~ 2η+. We test η-grid with a finite volume method (FVM) code, as well as a spectral element method (SEM) code, and conduct a campaign of DNSs of turbulent channel flow and turbulent boundary layer over smooth wall and various riblet geometries (as streamwise-aligned microgrooves), up to friction Reynolds number δ+0= 1000. We assess the accuracy of the η-grid against the conventional Cartesian grids, as well as the reference DNS and experimental data. We obtain less than 1% difference between the η-grid and the Cartesian grids, in terms of skin-friction coefficient, mean velocity, turbulent stresses, and their spectrograms. Up to δ+0 ~ 104, the number of grid points with the η -grid (Nη) scales proportional to δ+02.5 over smooth wall, and proportional to δ+02.0 over riblets, whereas the number of grid points with a Cartesian grid and hyperbolic tangent y-gird (NTanh) scales proportional to δ+03.0. This leads to an enormous grid saving with the η-grid; by δ+0 = 6000, Nη / NTanh ~ 0.1 over smooth wall, and Nη / NTanh ~ 0.03 over typical drag-reducing triangular riblets with tip angle 60o, and viscous-scaled spacing 15.

2605.01014 2026-05-05 cs.HC

Temporal Out-of-Distribution Detection for Asynchronous Motor Imagery Brain-Computer Interfaces

异步电机意念脑机接口中的时间域异常检测

Chenhao Liu, Siyang Li, Luofei Tan, Dongrui Wu

AI总结 本文提出双阶段EEG检测框架,通过滑动窗口机制和TempDens算法提升异步电机意念脑机接口中异常检测性能,优于传统基线方法。

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AI中文摘要

实时在线脑机接口通常处理连续脑电图(EEG)流,用户通常处于休息状态,仅间歇性进入运动意象任务状态。EEG窗口可能源自定义控制集外的异常运动意象活动。传统闭合集运动意象分类器倾向于将此类输入归类为ID类,导致控制错误。为解决此问题,本文提出双阶段EEG检测框架。滑动窗口机制持续监控EEG信号,第一阶段使用基于EEGNet的休息/任务门控确定当前窗口是否进入控制决策过程。第二阶段仅对任务状态样本执行ID运动意象分类和异常检测。为进一步提高异常拒绝率,我们进一步提出TempDens,结合分类输出能量、深度特征密度和时间一致性得分,从输出、特征和时间动态视角表征分布偏离。实验结果表明,所提方法有效支持连续EEG流中的任务状态检测和异常运动意象识别,优于多种传统异常检测基线方法。本研究将在线运动意象控制重新表述为涉及连续监控、状态鉴别、ID分类和异常拒绝的分层决策问题。

英文摘要

Real online brain--computer interfaces operate on continuous electroencephalography (EEG) streams, where users are usually at rest and enter motor-imagery task states only intermittently. EEG windows may also arise from OOD MI activity outside the predefined control set. Conventional closed-set motor-imagery classifiers tend to assign such inputs to ID classes, which can cause erroneous control. To address this issue, this paper proposes a two-stage EEG detection framework for asynchronous motor-imagery brain--computer interfaces. A sliding-window mechanism continuously monitors EEG signals. The first stage uses an EEGNet-based rest/task gate to determine whether the current window should enter the control-decision process. The second stage performs ID MI classification and out-of-distribution detection only for task-state samples. To improve OOD rejection, we further propose TempDens, which combines classification-output energy, deep-feature density, and temporal-consistency scores to characterize distributional deviation from output, feature, and temporal-dynamic perspectives. Experimental results show that the proposed method effectively supports task-state detection and OOD MI recognition in continuous EEG streams, outperforming multiple conventional OOD baselines. This study reframes online motor-imagery control as a hierarchical decision problem involving continuous monitoring, state discrimination, ID classification, and OOD rejection.

2605.01013 2026-05-05 physics.chem-ph

Modelling Intermediate-Current Transitions in Asymmetric-Valence Binary Electrolytes

不对称价二元电解质中中间电流转变的建模

Georgina C. Ryan, Mohit P. Dalwadi, Ian M. Griffiths

AI总结 本文研究不对称价二元电解质中中间电流转变的机制,通过建立稳态一维Poisson-Nernst-Planck模型,揭示了不同离子价态对电极电容和电池性能的影响,提出了一种新的分析方法。

Comments 31 pages (including supplementary material), 7 figures

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AI中文摘要

不对称价在二元电解质中可以显著影响如反向电渗析电池、电池和超级电容器等系统的性能。为生成这一效应的理论理解,我们考虑了一个稳态一维Poisson-Nernst-Planck模型,该模型考虑了恒定离子流的电解质,重点研究了不同离子价态的一般不对称二元电解质。数值模拟揭示了近平衡和强非平衡稳态区域之间平滑的过渡。这些区域通过一个依赖于价态的过渡点区分,该点在中间电流处出现,经典德拜尺度边界层消失。我们通过渐近分析来表征这一过渡,恢复了Gouy-Chapman和极限电流结果在适当极限下的结果,并确定了当两者都不适用时的正确过渡结果。我们为一般不对称二元电解质提供了电位和离子浓度的隐式解,并且特别地,我们为2z:z、z:2z和z:z电解质提供了渐近复合解的显式解析表达式。我们展示了如何将结果呈现为可预测离子价态和流体流量的中间电流稳态行为的折叠相图。

英文摘要

Asymmetric valences in a binary electrolyte can significantly affect the performance of systems such as reverse electrodialysis cells, batteries, and supercapacitors. To generate a theoretical understanding of this effect, we consider a steady one-dimensional Poisson-Nernst-Planck model of an electrolytic cell with imposed constant ionic fluxes, focusing on varying ion valences in a general asymmetric binary electrolyte. Numerical simulations reveal a smooth transition between the qualitatively distinct near-equilibrium and strongly non-equilibrium steady-state regimes. These regimes are distinguished by a valence-dependent transition point at an intermediate current where the classical Debye-scale boundary layer vanishes. We characterise this transition using asymptotic analysis, recovering the Gouy-Chapman and limiting-current results in the appropriate limits, and determining the correct transition results when neither is appropriate. We provide implicit solutions for the potential and ion concentrations of general asymmetric binary electrolytes and, notably, we provide explicit analytic expressions for the asymptotic composite solutions for 2z:z, z:2z, and z:z electrolytes. We show how the results can be presented in a collapsed phase diagram that can be used to predict qualitative intermediate-current steady-state behaviour in terms of ion valences and fluxes.

2605.01010 2026-05-05 math.AP

Lifespan Lower Estimates for a Strongly Damped Semilinear Wave Equation

强阻尼半线性波动方程的最大存在时间下界估计

Firas Kaabi

AI总结 本文研究强阻尼半线性波动方程在初始数据为(ρϕ,ρh)时,分析缩放参数ρ对最大存在时间下界的影响,证明解至少存在长度与ρ^(- (p-2))相当的时间区间。

Comments 5 pages, no figures

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AI中文摘要

我们考虑初始数据为(ρϕ,ρh)的强阻尼半线性波动方程,其中轮廓固定,仅允许幅值ρ>0变化。本文探讨此缩放如何影响最大存在时间的保证下界。我们证明解至少在长度与ρ^(- (p-2))相当的时间区间内存在。证明基于二次相空间范数的增长:在利用相关Sobolev嵌入估计源项后,问题转化为标量微分不等式。论证中产生的常数与ρ无关,因此初始幅值的依赖性在整个过程中保持明确。

英文摘要

We consider a strongly damped semilinear wave equation with initial data prescribed as $(\varrhoϕ,\varrho h)$, where the profiles are fixed and only the amplitude $\varrho>0$ is allowed to vary. The question addressed here is how this rescaling affects a guaranteed lower bound for the maximal existence time. We show that the solution exists at least on a time interval of length comparable to $\varrho^{-(p-2)}$. The proof is based on the growth of a quadratic phase-space norm: after the source term is estimated by the relevant Sobolev embedding, the problem reduces to a scalar differential inequality. The constants produced in the argument are independent of $\varrho$, so the dependence on the initial amplitude remains explicit throughout.

2605.01009 2026-05-05 math.DS

Stability Theory for Local Iterated Function Systems

局部迭代函数系统的稳定性理论

Elismar R. Oliveira, Paulo Varandas

AI总结 本文研究局部迭代函数系统的稳定性,证明了合同影子与局部吸引子上半连续性之间的关系,并在开放集条件下建立了拓扑稳定性理论,展示了收缩图定向IFS的拓扑稳定性及β变换导出的不稳定局部IFS。

Comments 41 pages; Comments are welcome

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AI中文摘要

我们开发了收缩局部IFS在紧致度量空间上的稳定性理论。不同于经典全局情形,局部系统可能表现出更丰富的符号和几何结构,包括非有限类型的码空间和具有端点的吸引子,导致新的不稳定机制。我们首先证明合同影子暗示局部吸引子的上半连续性和码空间的持久性,从而得到扰动下的组合稳定性准则。在开放集条件 下,我们建立了组合稳定收缩局部系统的强拓扑稳定性,并在紧致流形维度至少为三时证明了逆向蕴含。特别地,我们展示了收缩图定向IFS的拓扑稳定性。我们还构造了由β变换导出的不稳定收缩局部IFS。这些结果表明,在局部设定中,稳定性由收缩与码空间组合刚性之间的相互作用所支配。还给出了对图定向IFS和伪群作用的应用。

英文摘要

We develop a stability theory for contractive local IFSs on compact metric spaces. Unlike the classical global setting, local systems may exhibit a richer symbolic and geometric structure, including code spaces that are not of finite type and attractors with endpoints, leading to new mechanisms of instability. We first prove that concordant shadowing implies upper semicontinuity of the local attractor and persistence of the code space, yielding a criterion for combinatorial stability under perturbations. Under the open set condition, we establish a strong form of topological stability for combinatorially stable contractive local systems, and prove the converse implication on compact manifolds of dimension at least three. In particular, we show that contractive graph-directed IFSs are topologically stable. We also construct contractive local IFSs derived from beta-transformations that are combinatorially unstable. These results show that stability in the local setting is governed by the interplay between contraction and the combinatorial rigidity of the code space. Applications to graph-directed IFSs and pseudogroup actions are also given.

2605.01008 2026-05-05 cs.SE cs.CR quant-ph

Semantics-Based Verification of an Implemented Shor Oracle for ECDLP in Qrisp

基于语义的Qrisp中ECDLP实现的验证

Lei Zhang, Zhiyuan Chen

AI总结 本文提出一种基于语义的验证方法,用于检查Qrisp中ECDLP实现的正确性,通过语义层面的程序验证和复杂度分析,揭示了实现中可能存在的控制问题。

Comments 7 pages, 1 figure, and 1 table; accepted by The 20th International Symposium on Theoretical Aspects of Software Engineering (TASE 2026)

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AI中文摘要

Shor风格的量子算法对于椭圆曲线离散对数问题(ECDLP)的群运算 oracle 的精确语义非常敏感。因此,细微的实现选择可能会破坏预期的数学模型并导致误导性结论。本文介绍了一种面向端到端可编译ECDLP实现的语义优先验证视角,基于Qrisp构建。我们指定了实现的oracle在程序语义层面,推导了其关键组件的细化验证义务,并提供了由此得到的oracle家族的高层复杂度论证。一个小案例研究显示,核心点更新原语在良好输入上与经典参考一致,但受评估工具链控制的执行可能违反预期的控制定律,尽管通过了简单的控制 sanity 检查。这些结果将语义审计定位为可信ECDLP导向量子软件的实用前提。

英文摘要

Shor-style quantum algorithms for the elliptic-curve discrete logarithm problem (ECDLP) are highly sensitive to the exact semantics of their group-operation oracles. Consequently, minor implementation choices can invalidate the intended mathematical model and lead to misleading conclusions. This paper introduces a semantics-first verification perspective for an end-to-end, compilable ECDLP implementation built on Qrisp. We specify the implemented oracle at the level of program semantics, derive refinement-style verification obligations for its key components, and provide a high-level complexity argument for the resulting oracle family. A small case study highlights that (i) the core point-update primitive agrees with a classical reference on well-formed inputs, yet (ii) controlled execution may violate the expected control law under the evaluated toolchain, despite a passing trivial control sanity check. These results position semantic auditing as a practical prerequisite for trustworthy ECDLP-oriented quantum software.

2605.01007 2026-05-05 math.RA math.AT

Nonsymmetric versions of binary quadratic operads

二元二次操作元的非对称版本

F. A. Mashurov, B. K. Sartayev

AI总结 本文研究了结合操作元与二元二次操作元的White Manin积,引入了非对称版本的概念,并给出了判断该积操作元具有此性质的准则,通过实例和反例展示了构造方法,并描述了某些允许非对称版本的操作元的组合性质。

Comments 19 p

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AI中文摘要

在本文中,我们研究了结合操作元$\As$与二元二次操作元$\Var$的White Manin积。我们引入了$\Var$的非对称版本的概念,并提供了一个判断操作元$\As\circ\Var$具有此性质的准则。我们通过多个例子和反例展示了构造过程。最后,对于某些允许非对称版本的操作元,我们描述了它们的组合性质。

英文摘要

In this paper, we study the white Manin product of the associative operad $\As$ with a binary quadratic operad $\Var$. We introduce the notion of a nonsymmetric version of $\Var$ and provide a criterion for determining when the operad $\As\circ\Var$ has this property. We illustrate the construction with several examples and counterexamples. Finally, for some operads admitting nonsymmetric versions, we describe their combinatorial properties.

2605.01005 2026-05-05 astro-ph.EP astro-ph.IM

A Coordinate System for Dynamical Instabilities in Hierarchical Systems in REBOUND

用于研究分层系统动力学不稳定性的一种坐标系统

Tiger Lu, Garett Brown

AI总结 本文提出了一种适用于研究宽双星系统的坐标系统,用于改进TRACE积分器在处理近身接触时的性能,实验表明其在多种场景下表现优于传统方法,且效率更高。

Comments Submitted to AAS Journals, comments welcome

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AI中文摘要

我们实现了适用于研究宽双星系统的坐标系统,该系统适用于TRACE积分器,这是一种广泛使用的开源N体积分包REBOUND中的混合积分器。在传统混合积分器表现不佳的领域,该坐标系统支持系统中任意两体之间的近身接触。我们描述了该坐标的实现,并在REBOUND生态系统中与其他积分器进行了性能基准测试。在行星-行星散射、恒星飞越和ZLK振荡测试中,TRACE在宽双星坐标下的结果在其他混合方法失败时表现定性正确,并在许多情况下返回与高精度IAS15积分器统计相似的结果,速度提升可达9倍。我们还提供了一些使用这些坐标的指导方针。

英文摘要

We implement coordinates suitable for studying wide binary systems in TRACE, a hybrid integrator in the widely used open-source N-body integration package REBOUND. This is a regime in which traditional hybrid integrators perform poorly. The coordinate system supports close encounters between any pair of bodies in the system. We describe the implementation of this coordinate system and benchmark its performance against other integrators in the REBOUND ecosystem. In tests of planet-planet scattering, stellar flybys, and ZLK oscillations. TRACE in wide binary coordinates is qualitatively correct when other hybrid methods fail, and in many cases returns statistically similar results to the high-precision IAS15 integrator with up to 9x speedups. We also provide some guidelines for when use of these coordinates are appropriate.

2605.01004 2026-05-05 astro-ph.HE astro-ph.IM

Neural Posterior Estimation for UHECR source inference from 3D propagation simulations

神经后验估计用于从三维传播模拟中推断极高能宇宙射线源

Nadine Bourriche, Francesca Capel, Nicole Hartmann

AI总结 本文提出基于模拟的推断框架,利用三维CRPropa~3模拟生成校准的后验分布,用于推断UHECR事件的能量、距离、方向和初级成分,实现了高精度的源参数恢复。

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AI中文摘要

极高能宇宙射线源的识别是高能天体物理学中的开放挑战。由于带电粒子在宇宙中传播时会被星系外磁场偏转并失去能量,使源推断变得非常复杂。现有方法要么依赖于简化传播模型,要么使用计算上不可行的蒙特卡洛方法。本文提出了一种基于模拟的推断框架,该框架在三维CRPropa~3传播模拟上进行训练,能够为单个UHECR事件生成校准的后验分布,覆盖能量、距离、方向和初级成分。该模型结合了处理检测到次级粒子数量可变的深度集编码器和归一化流,并在约500万次模拟事件上进行训练,涵盖了广泛的星系外磁场配置。在验证的模拟上,所有源参数均无系统偏差,方向参数约束最佳,源距离最不确定,与底层传播物理一致。初级成分分类在所有质量组中达到≥98.2%的准确率。该框架为当前UHECR数据提供了可扩展且物理可解释的接口,连接详细的传播模拟和贝叶斯源推断。

英文摘要

The identification of ultra-high energy cosmic ray sources is one of the open challenges of high-energy astrophysics. As charged particles travel through the Universe, they are deflected by extragalactic magnetic fields and lose energy through interactions with background radiation, making source inference highly non-trivial. Existing approaches either rely on simplified propagation models or on computationally prohibitive Monte Carlo methods. Here we present a simulation-based inference framework trained on three-dimensional \texttt{CRPropa~3} propagation simulations that produces calibrated posterior distributions over source energy, distance, direction, and primary composition for individual UHECR events. The model combines a Deep Set encoder, handling the variable number of detected secondary particles, with a normalizing flow, and is trained on approximately 5 million simulated events covering a broad range of extragalactic magnetic field configurations. Validated on held-out simulations, all source parameters are recovered without systematic bias, with directional parameters best constrained and source distance most uncertain, consistent with the underlying propagation physics. Primary composition classification achieves $\geq$~98.2\% accuracy across all mass groups. This framework provides a scalable and physically interpretable interface between detailed propagation simulations and Bayesian source inference relevant for current UHECR data.

2605.01002 2026-05-05 astro-ph.HE physics.plasm-ph

Non-uniform particle injection into black hole jets by radiative magnetic reconnection

通过辐射磁重联产生非均匀粒子注入到黑洞喷流中

Rin Oikawa, Kenji Toma, Shigeo S. Kimura

AI总结 研究通过高能光子在黑洞附近非轴对称磁重联中产生电子-正电子对,解释喷流中的等离子体来源及射电辐射机制。

Comments submitted to journal

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AI中文摘要

活动星系核常表现出高度集中的相对论性等离子体喷流,其形成的核心挑战在于喷流燃料的来源。本文研究了由非轴对称磁重联产生的高能光子引发的电子-正电子对产生,通过广义相对论射线追踪计算了喷流中粒子产生率的空间分布,考虑了光子传播和碰撞角度在弯曲时空中的影响。发现该场景能自然提供足够的等离子体解释M87喷流的射电辐射,即使考虑光子各向异性。此外,研究显示旋转黑洞在塑造粒子空间分布中起关键作用,从而影响喷流加速和喷流基部的极高能辐射。

英文摘要

Active galactic nuclei often exhibit highly collimated relativistic plasma outflows launched from the vicinity of their central black holes. One of the key theoretical challenges in understanding black hole jet formation is the origin of the plasma that feeds the jet, which remains poorly understood, particularly in explaining the observed jet emission. In this study, we focus on electron positron pair production generated by high energy photons from non axisymmetric magnetic reconnection near the black hole, as suggested by recent three dimensional general relativistic magnetohydrodynamics simulations. By employing general relativistic ray tracing, we calculate the spatial distribution of the pair production rate in the jet, taking into account photon propagation and collision angles in curved spacetime. We find that our scenario can naturally supply a sufficient amount of plasma to explain the observed radio emission from the M87 jet, even when photon anisotropy is considered. Furthermore, we show that a spinning black hole plays a crucial role in shaping the spartial dsitribution of the pairs, which in turn affects jet acceleration and very high energy emission from the jet base.

2605.01001 2026-05-05 cs.HC

AnimationDiff: A Visual Comparison Tool for Generated 3D Character Animations

AnimationDiff: 用于生成3D角色动画的视觉比较工具

Ludwig Sidenmark, Qian Zhou, George Fitzmaurice, Fraser Anderson

AI总结 AnimationDiff通过结合动画可视化技术与切换叠加/并排比较功能,解决生成3D角色动画的比较难题,提升动画选择效率。

Comments Accepted to ACM DIS 2026

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AI中文摘要

创建3D角色动画传统上需要动画师耗费大量时间和精力。生成方法的进步使创建多个角色动画变体变得容易,但这一能力带来了新的挑战:在时间错位和大量空间数据的情况下比较动画以选择最佳动画。我们提出了AnimationDiff,一种用于生成角色动画的视觉比较工具。AnimationDiff在预期场景和摄像机角度中实现上下文比较,并通过结合已建立的动画可视化技术,嵌入空间信息,实现叠加和并排比较的切换。AnimationDiff还支持过滤以处理信息过载,并通过时间镜头可视化整个动画随时间的变化,以获得概述、对齐和比较。我们在用户研究中评估了AnimationDiff,展示了其在动画比较中的有效性,并为运动比较提供了设计见解。

英文摘要

Creating 3D character animations traditionally requires significant time and effort from the animator. Advancements in generative methods now enable easy creation of multiple character animation variations for use or further editing. However, this capability introduces a new challenge in comparing character animations to select the best animation, which is challenging due to temporal misalignment and the large amount of spatial data. We present AnimationDiff, a visual comparison tool for generated character animations. AnimationDiff enables contextual comparisons in the intended scene and camera angle, and embedding of spatial information by combining established animation visualization techniques and easy switching between overlaid and side-by-side comparisons. AnimationDiff also supports filtering to handle information overload, and Temporal Lenses that visualize entire animations over time for overview, alignment, and comparison. We evaluated AnimationDiff in a user study, showcasing its efficacy in animation comparison and providing design insights for comparing motion.

2605.01000 2026-05-05 astro-ph.GA

Prospects for Observing Galaxy Spectral Energy Distribution from the Radio to the far-Infrared in the Era of Next-Generation Radio Telescopes

在下一代射电望远镜时代观测从射电至远红外的星系光谱能量分布的前景

Ilsang Yoon, Jonathan Letai, Hansung B. Gim, Eric F. Jiménez-Andrade, Intae Jung, Caitlin Casey, Eric J. Murphy, Min S. Yun

AI总结 本文探讨利用下一代射电望远镜观测高红移星系射电-远红外连续谱的能量分布,展示其在宇宙再电离后研究星系形成的能力。

Comments 25 pages, 10 figures, accepted by ApJ

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AI中文摘要

下一代射电望远镜的高灵敏度和角分辨率,结合覆盖三个数量级频率(100 MHz至100 GHz)的频率范围,将能够采样星系的射电和远红外(FIR)光谱能量分布(SED),并推动再电离时代及之后的星系形成研究。我们基于模拟的'能量平衡'全波段SED(从紫外到远红外)扩展至射电,提出在红移高达z≈20时观测星系射电-远红外连续谱的前景。对于现实的紫外恒星形成星系和尘埃恒星形成星系,我们考虑CMB效应和射电-红外相关性,模拟其SED。紫外亮恒星形成星系和尘埃恒星形成星系在当前(ALMA)和下一代(SKA和ngVLA)射电毫米波望远镜覆盖的观测频率上的光度密度演化,表明质量大于10^10 M_sun的星系在任何红移(0 < z < 20)的高频(ν > 90 GHz)下均可被探测。特别是当运行时,ngVLA的高频(约100 GHz)带能够独立于红移探测质量大于10^9 M_sun的星系。SKA的低频观测窗口(小于1 GHz)具有足够的灵敏度,可探测到红移至再电离时期(z=5~7)质量大于10^10 M_sun的尘埃恒星形成星系。我们还表明,如果星系远离本地宇宙(例如,z≈0.1),则异常微波发射(AME)在星系SED中的亮度不显著。

英文摘要

The superb sensitivity and angular resolution of the next-generation radio telescopes with combined frequency coverage of approximately over three orders of magnitude (100 MHz--100 GHz) will sample the radio and far-infrared (FIR) spectral energy distribution (SED) of galaxies and revolutionize the galaxy formation study at the epoch of re-ionization and beyond. We present a prospect of observing the radio--FIR continuum SEDs of galaxies in the redshift of up to $z\approx 20$ based on an ensemble of the simulated `energy balanced' panchromatic SED (from UV to FIR) extended to the radio. For `realistic' populations of UV star-forming galaxies and dusty star-forming galaxies, we simulate their SEDs by accounting for the CMB effect and the radio--IR correlation. The flux density evolution of the UV-bright star-forming galaxies and the dusty star-forming galaxies at the selected observing frequencies covered by the current (ALMA) and next generation (SKA and ngVLA) radio-millimeter telescopes, suggest that massive galaxies (M$_* \gtrsim 10^{10}$M$_{\odot}$) are detectable at any redshift ($0<z<20$) in high frequency ($ν>90$GHz). In particular, when operating, the ngVLA high-frequency ($\approx 100$ GHz) band is capable of detecting galaxies with M$_* \gtrsim 10^{9}$M$_{\odot}$ almost independently from redshift and the SKA low-frequency observing window ($\lesssim1$ GHz) has sufficient sensitivity to detect M$_* \gtrsim 10^{10}$M$_{\odot}$ dusty star-forming galaxies up to the epoch of reionization ($z=5\sim7$). We also show that the brightness of anomalous microwave emission (AME) in the galaxy SED is insignificant if the galaxies are beyond the local Universe (e.g., $z\gtrsim 0.1$).

2605.00999 2026-05-05 math.OC math.AP

Stackelberg-Nash controllability for a multi-objective Stefan problem

Stackelberg-Nash可控性 for 一个多目标Stefan问题

Thiago C. A de Carvalho, Suerlan Silva, Gilcenio R. de Sousa-Neto, Franciane de B. Vieira

AI总结 本文研究了一维Stefan系统在局部分布式控制下的分层控制问题,结合Stackelberg策略与多个追随者的Nash均衡,形成多目标自由边界问题。通过分析分层控制与移动界面的相互作用,证明原问题可转化为该最优系统null可控性问题,并在合适几何条件下建立局部null可控性结果。

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AI中文摘要

我们研究了一维Stefan系统的分层控制问题,结合Stackelberg策略与多个追随者的Nash均衡,形成多目标自由边界问题。分层控制与移动界面的相互作用导致非线性最优系统,证明原问题可转化为该最优系统的null可控性问题。在合适的控制区域几何条件下,建立局部null可控性结果。证明依赖于线性化系统的可观察性不等式,通过Carleman估计适应于移动边界的存在。这些结果构成了目前已知首次在Stackelberg-Nash框架下处理Stefan系统的处理。

英文摘要

We investigate a hierarchical control problem for a one-dimensional Stefan system with localized distributed controls. The setting combines a Stackelberg strategy with a Nash equilibrium among multiple followers, yielding a multi-objective free-boundary problem. The interaction between the hierarchical control and the moving interface results in a nonlinear optimality system, and we show that the original problem reduces to the null controllability of this optimality system. Under suitable geometric conditions on the control regions, we establish a local null controllability result. The proof relies on an observability inequality for a linearized system, obtained through Carleman estimates adapted to the presence of a moving boundary. These results constitute, to the best of our knowledge, the first treatment of a Stefan system within a Stackelberg-Nash framework.

2605.00997 2026-05-05 math.PR

Asymptotic probability of a fixed edge being on the boundary of the convex hull of a random walk in $\mathbb{Z}^2$

二维随机游走凸包边界中固定边的概率渐进行为

Aleksandr Mysliuk

AI总结 研究二维对称随机游走中固定边在凸包边界多边形中的渐近概率行为,分析步数趋于无穷时的概率渐进行为。

Comments 5 pages

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AI中文摘要

考虑在空间$\mathbb{Z}^2$中的简单对称随机游走。研究当步数趋于无穷时,固定边位于构成凸包边界的多边形中的概率渐进行为。

英文摘要

A simple symmetric random walk in the space $\mathbb{Z}^2$ is considered. The asymptotic behavior as the number of jumps tends to infinity of the probability that a fixed edge of the random walk lies in the polygon that forms the boundary of the convex hull is investigated.

2605.00996 2026-05-05 math.CO cs.DM

Families without $s$-matchings: the other end

没有s-匹配的家庭:另一端

Andrey Kupavskii, Georgy Sokolov

AI总结 研究确定了在n=ms+c时,不含s个不相交集合的最大家族大小,该结果是非均匀的Erdős匹配猜想在极端 clique 情况下的类比。

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AI中文摘要

在本文中,我们确定了最大的家族 $\mathcal F \subset 2^{[n]}$ 不含s个成对不相交的集合,前提是n=ms+c,其中m,c是正整数,且s≥s_0(m, c)。这一结果可以看作是Erdős匹配猜想在极端clique情况下的非均匀类比。

英文摘要

In this paper, we determine the largest family $\mathcal F \subset 2^{[n]}$ without $s$ pairwise disjoint sets, provided $n=ms+c$ for positive integers $m,c$, and $s \geq s_0(m, c)$. This result can be seen as a non-uniform analogue of the results on the Erd\H os Matching Conjecture in the regime when the clique is extremal.

2605.00995 2026-05-05 cs.CC math.CO

On Sampling Lower Bounds for Polynomials

关于多项式采样下界的论文

Mohammad Mahdi Khodabandeh, Igor Shinkar

AI总结 研究低次多项式定义的采样器与伯努利分布的差异,证明对于不同次数的多项式,总变差距离下界具有指数级下降特性。

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AI中文摘要

在本文中,我们继续研究分布复杂性(Viola, Journal of Computing 2012)的研究方向,研究由低次多项式定义的采样器。一个n元组P = (P_1,…, P_n)的函数P_i: F_2^m → F_2定义了{0,1}^n上的分布:从F_2^m中均匀随机抽取X,并输出(P_1(X),…, P_n(X)) ∈ {0,1}^n。我们证明当P由次数为d的多项式定义时,P与伯努利分布Ber(1/3)^⊗n的总变差距离为1-o_n(1),其中o_n(1)是随着n增长而趋于零的函数。对于小的d值,我们证明了以下具体界限。(i)对于d=1,我们有‖P-Ber(1/3)^⊗n‖_{TV} ≥ 1-exp(-Ω(n))。(ii)对于d=2,我们有‖P-Ber(1/3)^⊗n‖_{TV} ≥ 1-exp(-Ω(log(n)/log log(n)))。(iii)对于d=3,我们有‖P-Ber(1/3)^⊗n‖_{TV} ≥ 1-exp(-Ω(√log log(n)))。我们的结果扩展了最近关于采样分布的下界结果,这些结果大多集中在局部采样器、小深度决策树和小深度电路。作为证明的一部分,我们建立了以下结果,可能具有独立兴趣:对于任何次数为d的多项式P:F_2^m → F_2,Pr_X[P(X) = 1]与1/3的距离由某个绝对常数δ=δ_d>0所限制。虽然这个陈述可能看起来显而易见,但我们并不知道有一个简单的证明。证明技术依赖于低次多项式结构结果,即任何有偏的次数为d的多项式可以表示为少量次数为d-1的多项式的函数。

英文摘要

In this work, we continue the line of research on the complexity of distributions (Viola, Journal of Computing 2012), and study samplers defined by low degree polynomials. An $n$-tuple $P = (P_1,\dots, P_n)$ of functions $P_i \colon \mathbb{F}_2^m \to \mathbb{F}_2$ defines a distribution over $\{0,1\}^n$ in the natural way: draw $X$ uniformly at random from $\mathbb{F}_2^m$ and output $(P_1(X),\dots, P_n(X)) \in \{0,1\}^n$. We show that when $P$ is defined by polynomials of degree $d$, the total variation distance of $P$ from the product distribution $\mathrm{Ber}(1/3)^{\otimes n}$ is $1-o_n(1)$, where $o_n(1)$ is a vanishing function of $n$ for any constant degree $d$. For small values of $d$, we show the following concrete bounds. (i) For $d=1$ we have $\|P-\mathrm{Ber}(1/3)^{\otimes n}\|_{TV} \geq 1-\exp(-Ω(n))$. (ii) For $d=2$ we have $\|P-\mathrm{Ber}(1/3)^{\otimes n}\|_{TV} \geq 1-\exp(-Ω(\log(n)/\log\log(n)))$. (iii) For $d=3$ we have $\|P-\mathrm{Ber}(1/3)^{\otimes n}\|_{TV} \geq 1-\exp(-Ω(\sqrt{\log\log(n)}))$. Our results extend the recent lower bound results for sampling distributions, which have mostly focused on local samplers, small depth decision trees, and small depth circuits. As part of our proof, we establish the following result, that may be of independent interest: for any degree-$d$ polynomial $P\colon\mathbb{F}_2^m \to \mathbb{F}_2$ it holds that $\Pr_X[P(X) = 1]$ is bounded away from $1/3$ by some absolute constant $δ= δ_d>0$. Although the statement may seem obvious, we are not aware of an elementary proof of this. The proof techniques rely on the structural results for low degree polynomials, saying that any biased polynomial of degree $d$ can be written as a function of a small number of polynomials of degree $d-1$.

2605.00993 2026-05-05 astro-ph.GA

The complex history of NGC 1427A revealed by its star clusters and star formation history

NGC 1427A的复杂历史通过其星团和恒星形成历史揭示

Katja Fahrion, Michael Hilker, Avinash Chaturvedi, Juan P. Carvajal, Thomas H. Puzia

AI总结 通过分析NGC 1427A的星团和恒星形成历史,研究其在星系团中的环境影响,发现多个恒星形成事件,包括年轻和中年星团,推断其经历了Ram-pressure stripping和潮汐相互作用或小规模星系合并。

Comments Accepted for publication in A&A, 11 pages

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AI中文摘要

在星系团密集环境中形成低质量星系为研究环境效应如何塑造恒星形成历史提供了机会。我们结合MUSE积分场光谱观测和可用多波段成像,分析NGC 1427A的恒星形成历史。通过拟合222个恒星团候选者的光谱能量分布,利用星团作为过去恒星形成事件的存活示踪体,发现多个恒星形成事件。特别是发现年轻星团(约10 Myr)和中年星团(约100-300 Myr),并解释这些群体在Fornax星系团中NGC 1427A轨道演化的背景下,推断该星系经历了Ram-pressure stripping、潮汐相互作用或小规模星系合并。

英文摘要

Star-forming low-mass galaxies in the dense environments of galaxy clusters provide opportunities to study how environmental effects such as ram-pressure stripping, tidal interactions, or galaxy mergers shape a galaxy's star formation history. We combined integral-field spectroscopic observations with the Multi Unit Spectroscopic Explorer (MUSE) and available multi-band imaging of the star-forming galaxy NGC 1427A, located near the centre of the Fornax galaxy cluster, at a distance of 20 Mpc. Our aim was to trace the evolutionary history of NGC 1427A using the star formation history reconstructed from the integrated spectra and employing star clusters as surviving tracers of past star formation episodes. We fitted the spectral energy distribution of 222 star cluster candidates using archival $u,g,r$, and $i$ photometry to derive the ages and masses. For 58 clusters, we additionally incorporated their MUSE spectra in the fits and found an encouraging agreement between the photometric and spectroscopic results. The comparison of the age distribution of star clusters with star formation histories from a full spectrum fitting of the MUSE data found a reasonable agreement, with evidence for multiple episodes of star formation throughout the history of NGC 1427A. In particular, we found a population of young clusters ($\sim$ 10 Myr) that is located along the star formation edge and within the northern object, and a population of intermediate-age clusters ($\sim$ 100 - 300 Myr) with corresponding peaks in the star formation history of NGC 1427A. We interpret these populations in the context of the orbital evolution of NGC 1427A in the Fornax cluster and conclude that this galaxy has experienced not only ram-pressure stripping, but also tidal interactions or even a minor galaxy merger. The northern object is likely a regular component of the galaxy.

2605.00992 2026-05-05 astro-ph.IM physics.ed-ph physics.soc-ph

Recommendations for the Astronomy Graduate Admissions Process

天文学研究生招生流程的建议

Emily M. Levesque, Courtney D. Dressing, Rachel Ivie, Grace Krahm, Meredith A. MacGregor, Daniel R. Piacitelli, Tom Rice

AI总结 本文提出改进天文学研究生招生流程的建议,包括统一申请格式、沟通机制和时间线,以提高透明度和公平性。

Comments 5 pages; to be published in the Bulletin of the AAS

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AI中文摘要

作为AAS研究生招生工作组(WGGA),我们分享了改进和标准化天文学研究生招生关键要素的简要建议。大多数天文学研究生项目在招生流程上有大量重叠,但现有要求的小差异和沟通透明度的不足使学生和项目都面临更大挑战。为改善此情况,基于AAS研究生招生任务小组(GATF)报告的工作,我们建议对申请内容、沟通和时间线进行几项简单直接的更改。这些包括由两封500字推荐信、一封1500字申请文书、申请人简历和非官方成绩单组成的申请格式,以及包含有效透明沟通和鼓励申请者于4月1日进行“初步筛选日期”的招生时间线。

英文摘要

As the AAS Working Group on Graduate Admissions (WGGA) we are sharing brief recommendations for improving and standardizing key elements of the graduate admissions process in astronomy. Most astronomy graduate programs have large areas of overlap in their admissions processes; however, the existing small variations in requirements and mismatches in communication and transparency make admissions more challenging for students and programs alike. To improve this situation, and building on the work presented in the AAS Graduate Admissions Task Force (GATF) report we recommend a few simple and straightforward changes for application content, communication, and timelines. These include an application format that consists of 1) two 500-word recommendation letters, 2) one 1500-word application essay, 3) an applicant CV, and 4) unofficial transcripts; and an admissions timeline that includes effective and transparent communication from programs and encouraging an April 1st "down-select date" for applicants.

2605.00991 2026-05-05 astro-ph.CO hep-ph

Implications of \textit{SARAS3} data for Coulomb-like interacting dark matter

SARAS3数据对类似库仑相互作用暗物质的影响

Shikhar Mittal, Prakhar Bansal, Harry Bevins, Saurabh Singh

AI总结 研究SARAS3数据对库仑型相互作用暗物质的约束,通过联合贝叶斯拟合发现信号参数弱约束,但数据排除了深吸收特征,限制了暗物质信号幅度。

Comments 30 pages, 11 figures. Comments are welcome

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AI中文摘要

宇宙黎明时期的21厘米信号是探测暗物质与物质相互作用的潜在敏感探针。本文研究了SARAS3在55.5-84.4 MHz频段未检测到的含义,针对库仑型相互作用暗物质(IDM)进行分析。与以往主要关注物质冷却的约束分析不同,本文通过自洽模型考虑了气体过冷和结构形成抑制,延迟恒星形成起始时间,从而抑制早期Lyα、X射线和电离背景。通过联合贝叶斯拟合全球21厘米信号模型和灵活的前景模型,发现信号参数在排除前景后仍弱约束。无结果具有信息量:数据排除了观测频段内的深吸收特征,最强限制在z=23.6(ν≈57.7 MHz),其中T21≥-277.6 mK(3σ)。比较IDM和标准冷暗物质情景,发现无统计显著偏好IDM(贝叶斯因子B≈1.7)。虽然未约束物质-暗物质相互作用强度,但SARAS3未检测到结果对这一类模型中全球21厘米信号幅度设定了有意义的上限。

英文摘要

The 21-cm signal from cosmic dawn is a potentially sensitive probe of interactions between dark matter (DM) and baryons. We investigate the implications of the SARAS3 non-detection in the 55.5-84.4 MHz band for Coulomb-like interacting DM (IDM). In contrast to earlier constraint analyses that focused primarily on baryon cooling, we model the interaction self-consistently by including both excess cooling of the gas and the suppression of structure formation, which delays the onset of star formation and hence suppresses the Ly$α$, X-ray, and ionizing backgrounds at early times. We perform a joint Bayesian fit of a global 21-cm signal model and a flexible foreground model to the SARAS3 antenna temperature, and find that the signal parameters remain weakly constrained after marginalizing over the foregrounds. The null result is nonetheless informative: the data disfavour deep absorption features within the observed band, with the strongest bound at $z = 23.6$ ($ν\approx 57.7$ MHz), where $T_{21} \gtrsim -277.6$ mK at $3σ$. Comparing the IDM and standard cold dark matter scenarios, we find no statistically significant preference for IDM (Bayes factor $B \approx 1.7$). While we do not constrain the strength of baryon-DM interactions, the SARAS3 non-detection places a meaningful upper bound on the amplitude of the global 21-cm signal in this class of models.

2605.00990 2026-05-05 astro-ph.GA

NEFERTITI: Linking early galaxy formation to the assembly of the Milky Way

NEFERTITI:将早期星系形成与银河系的组装联系起来

Ioanna Koutsouridou, Stefania Salvadori, Ása Skúladóttir, Viola Gelli, Elka Rusta, Lapo Querci, David S. Aguado, Alice Mori

AI总结 该研究利用NEFERTITI模型和30个高分辨率模拟,探讨早期星系形成与银河系组装的关系,揭示了恒星形成过程及金属丰度对银河系结构的影响。

Comments 20 pages, 17 figures, 2 tables. Submitted to ApJ

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AI中文摘要

我们使用NEFERTITI星系形成模型的新实现,结合约30个高分辨率Caterpillar暗物质模拟,将早期星系形成与银河系(MW)的组装联系起来,直至红移z=0。本地约束的模型解析了宿主第一代恒星的minihaloes,并自洽地追踪不均匀的电离和化学富集。Ia型星形成始于z≈27,峰值在z≈10-15,并持续到z≈5,产生质量为M*≈10-5×10^5 M☉的Ia型系统。当前Ia型星的后代覆盖[Fe/H]<-9到[Fe/H]≈-1,最金属贫乏的星通常由1-4个低能超新星前体富集。双极不稳定超新星的后代更多形成于大质量haloes(M_vir>10^8 M☉),通常外部富集,反映了强烈反馈和延迟恢复。这些早期系统是现今银河系金属贫乏成分的构建块:尽管90%的总恒星质量在原地形成,但吸积成分在[Fe/H]<-1时占主导地位,并解释了几乎所有[Fe/H]<-3的恒星。吸积人口主要由少数(约5个)大质量(M*>10^8 M☉)被摧毁的矮星构成,但低质量系统在低金属度时变得越来越重要,超致密矮星系的类比贡献了约25%在[Fe/H]<-3时。我们的模型同时再现了金属贫乏MW恒星和JWST“Hebe”星系在z≈11时的性质,支持其作为纯Ia型系统的身份。最终,NEFERTITI是解释即将来临的本地和高z观测以联系近场和远场宇宙学的关键工具。

英文摘要

We use a new implementation of the NEFERTITI galaxy formation model, coupled to $\sim 30$ high-resolution Caterpillar dark-matter simulations of Milky Way (MW) analogues, to connect early galaxy formation with the MW's assembly down to $z=0$. Our locally-constrained model resolves minihaloes hosting the first PopIII stars and self-consistently tracks inhomogeneous ionization and chemical enrichment. PopIII star formation begins at $z\simeq27$, peaks at $z\simeq10-15$, and persists down to $z\lesssim5$, producing PopIII systems with $M_*\sim10-5\times10^5\:{\rm M_\odot}$. The present-day descendants of PopIII stars span ${\rm [Fe/H]<-9}$ to ${\rm [Fe/H]\approx-1}$, with the most metal-poor stars typically enriched by a few (1-4) low-energy supernova progenitors. Pair-instability supernova descendants more commonly form in massive haloes ($M_{\rm vir}>10^8\:{\rm M_\odot}$), often externally enriched, reflecting the strong feedback and delayed recovery following energetic explosions. These early systems serve as building blocks for the present-day Galaxy's metal-poor component: although 90$\%$ of the total stellar mass formed in situ, the accreted component dominates at $[{\rm Fe/H}]<-1$ and accounts for nearly all stars with $[{\rm Fe/H}]<-3$. This accreted population is largely built by a few ($\sim5$) massive ($M_*>10^8\:{\rm M_\odot}$) destroyed dwarfs, but lower-mass systems become increasingly important at low metallicities, with ultra-faint and classical dSph analogues contributing $\sim25\%$ at $[{\rm Fe/H}]<-3$. Our model simultaneously reproduces the properties of metal-poor MW stars and the JWST "Hebe" galaxy at $z\sim11$, supporting its identification as a pure PopIII system. Ultimately, NEFERTITI is a key tool to interpret upcoming local and high-$z$ observations linking the near- and far-field cosmology.

2605.00989 2026-05-05 hep-ph hep-ex

$CP$ violation in neutral kaon mixing in $D^0\rightarrow K_SK_S$

中性K介子混合引起的CP破坏在 $D^0\rightarrow K_S K_S$ 中

Yuval Grossman, Guglielmo Papiri, Stefan Schacht

AI总结 研究中性K介子混合引起的CP破坏在 $D^0\rightarrow K_S K_S$ 中,发现其贡献来自二级弱相互作用,估计在 $10^{-6}$ 级,远低于实验灵敏度和预期的 charm 分量贡献。

Comments 14 pages, 1 figure

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AI中文摘要

我们研究了由中性K介子混合引起的CP破坏在 $a_{CP}(D^0 \rightarrow K_S K_S)$ 中。我们表明,中性K介子混合的贡献仅与 $D$ 衰变中的二级弱相互作用相关。我们估计这种效应在 $10^{-6}$ 级,因此相对于当前实验灵敏度和预期的charm分量贡献来说可以忽略不计。

英文摘要

We study CP violation induced by neutral kaon mixing in $a_{CP}(D^0 \rightarrow K_S K_S)$. We show that the contribution from neutral kaon mixing arises only in connection with second-order weak interactions in $D$ decays. We estimate this effect to be at the $10^{-6}$ level, and thus negligible compared to current experimental sensitivity and to the expected contribution from CP violation in the charm sector.

2605.00987 2026-05-05 hep-th

A gravity interpretation for the complex Euclidean saddles of the ABJM index

关于ABJM指数的复杂欧几里得鞍点的引力解释

Minwoo Suh

AI总结 本文通过引力视角解释ABJM指数中的复杂欧几里得鞍点,揭示M5膜不稳定性与化学势偏移的关系。

Comments 26 pages

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AI中文摘要

超共形指数是一种计数1/16 BPS态的广义配分函数,其关于减少化学势的Legendre变换对应于反de Sitter时空中的电荷旋转黑洞的Bekenstein-Hawking熵。然而,$\mathcal{N}=4$超Yang-Mills理论的超共形指数似乎允许化学势的偏移,而偏移项的贡献呈指数发散。通过展示缠绕D3膜的不稳定性,解决了这一谜团。类比地,我们研究了ABJM指数和M5膜不稳定性准则。

英文摘要

The superconformal index is a grand-canonical partition function that counts the 1/16-BPS states in the theory, and its Legendre transform with respect to reduced chemical potentials accounts for the Bekenstein-Hawking entropy of electrically charged rotating black holes in anti-de Sitter spacetime. However, the superconformal index of $\mathcal{N}=4$ super Yang-Mills theory appears to allow shifts in chemical potentials, and the contributions of the shifted terms diverge exponentially. This puzzle was resolved by showing the instability of wrapped D3-branes corresponding to the shifts in the gravitational on-shell action. Analogously, we study the ABJM index and the M5-brane instability criterion.

2605.00986 2026-05-05 gr-qc astro-ph.HE astro-ph.SR

Series solutions to the TOV equations

TOV方程的级数解

Paulo Luz

AI总结 本文提出TOV方程的通用级数解,通过方程状态及其热力学变量导数计算系数,建立解析解的性质及其与方程状态正则性的关系,并利用Padé近似法推导解析解,用于近似恒星半径和质量,同时扩展到分段方程状态。

Comments 34 pages, 3 figures

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AI中文摘要

我们提出了Tolman-Oppenheimer-Volkoff方程的通用级数解,开发了计算幂级数系数的算法,该算法基于方程状态及其热力学变量的导数。利用这些结果,我们建立了解析解的一般性质及其与方程状态正则性的关系。通过Padé近似理论,我们推导了解析函数的级数表示,其收敛域可能包括孤立极点。这些解析解随后用于获得闭式表达式以近似恒星对象的半径和质量。我们应用该理论到特定模型,即具有仿射方程状态的流体和多聚体流体,并将结果与数值积分的结果进行比较。最后,我们将该理论扩展到分段方程状态,推导出可以在过渡超曲面处匹配的级数解。

英文摘要

We present general series solutions to the Tolman-Oppenheimer-Volkoff equations for compact stellar objects. We develop an algorithm to compute the coefficients of the power series in terms of the equation of state and its derivatives with respect to the thermodynamic variables. Using these results, we establish general properties of analytic solutions and their relation to the regularity of the equation of state. Applying the theory of Padé approximants, we derive series representations for meromorphic functions whose domains of convergence may include isolated poles. These analytic solutions are then used to obtain closed-form expressions to approximate the radius and mass of stellar objects. We apply the formalism to specific models, namely fluids with affine equations of state and polytropic fluids, and compare the results with those obtained from numerical integration. Lastly, we extend the formalism to piecewise equations of state, deriving series solutions that can be matched across transition hypersurfaces.

2605.00985 2026-05-05 astro-ph.HE astro-ph.GA astro-ph.SR

On the isotropy of viscosity in accretion discs

关于吸积盘粘性各向同性的研究

Chris Nixon, Jim Pringle

AI总结 本文通过X射线双星的长期观测,检验Ogilvie模型对吸积盘演化描述的准确性,发现粘性可能存在轻微非各向同性特征。

Comments 5 pages, accepted for publication in MNRAS

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AI中文摘要

吸积盘是许多天体系统中的核心部分,通过将引力势能转化为辐射能量。许多系统中存在盘形变的证据,从原行星盘的空间分辨观测到超大质量黑洞周围盘的光变曲线和谱线特征。 warped盘的动力学主要由内部粘性物理性质控制。虽然通常粘性源于流体磁性,但磁化盘的模拟无法匹配平面盘的角动量输运速率,因此无法确定驱动吸积和盘形变的扭矩比例。Ogilvie的解析工作是最全面的warped盘演化模型,但其假设需要检验。特别是,它假设盘粘性为纳维-斯托克斯,因此是小尺度且各向同性的。本文尝试通过X射线双星的长期观测来检验该模型,这些系统有良好的粘性成分估计,通过有无盘偏移和进动证据的系统,可以约束使盘扁平化的粘性成分。我们得出结论,观测约束表明Ogilvie模型对盘演化有充分描述,但存在粘性可能略微非各向同性的迹象。

英文摘要

Accretion discs are fundamental to many astrophysical systems, providing the conversion of gravitational potential energy into radiation that we can observe. In many systems there is evidence that discs are warped; from spatially-resolved observations of protoplanetary discs, to the features of lightcurves and line profiles from discs around supermassive black holes in galaxy centres. The dynamics of warped discs is largely controlled by the physical nature of the internal disc viscosity. While typically disc viscosity is hydromagnetic in origin, simulations of magnetized discs cannot match observed rates of angular momentum transport in planar discs and thus cannot be used to determine the ratio of the torques responsible for driving accretion to those responsible for evolving the disc warp. The analytic work of Ogilvie is the most comprehensive model for warped disc evolution, but makes assumptions that need to be tested. In particular, it assumes that the disc viscosity is Navier-Stokes, and therefore small-scale and isotropic. Here we attempt to test this model using the long periods of X-ray binaries that are due to precession of the disc. These systems have well-constrained estimates of the component of viscosity responsible for driving accretion, and by looking at systems with and without evidence for disc misalignment and precession we can constrain the component of viscosity responsible for flattening the disc. We conclude that the observational constraints suggest that the Ogilvie model provides an adequate description of the disc evolution, but that there are indications that the internal disc viscosity might be marginally non-isotropic.

2605.00984 2026-05-05 astro-ph.GA

Merge and Strip II: Imprint of galaxy formation physics and viscosity on baryon-dominated dwarf galaxies

合并与剥离II:星系形成物理和粘性对气态主导矮星系的影响

Anna Ivleva, Klaus Dolag, Rhea-Silvia Remus, Duncan A. Forbes, Tirso Marin-Gilabert

AI总结 本文通过模拟星系合并过程,探讨粘性和恒星反馈对矮星系形成的影响,发现恒星反馈适度时,长寿命潮汐矮星系可形成,并支持Virgo星团中蓝候选星可能是剥离的TDGs。

Comments 16 pages, 7 figures, 2 tables; submitted to A&A

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AI中文摘要

受星团内异常矮星系(如蓝候选星、暗星系和超稀释星系)的发现启发,我们进行了星系合并的水动力学模拟。我们改变了粘性和恒星反馈方案,真实模拟可能的水动力学拖拽和流体不稳定性条件,以及通过恒星反馈驱动加热和气体流失导致的内部不稳定性。我们发现,如果恒星反馈适度,长寿命潮汐矮星系(TDGs)可以在所有适用于星团的粘性值下形成。我们的结果扩展了云破碎模拟研究,探讨了星团内介质中的混合问题。最小的云团气体质量约为$M_\text{gas} \sim 10^7 \text{ M}_\odot$,并达到相对较低的最终漂移速度$\sim 100 \text{ km/s}$。作用于这一类云团的最低可能雷诺数约为$Re \sim 1$,对于完全Spitzer粘性。几乎所有TDGs都显示出升高的恒星形成率$0.01-0.1 \text{ M}_\odot / \text{yr}$,这一速率在数十亿年中保持稳定。基于其匹配特性,我们支持Virgo星团中观测到的蓝候选星很可能是剥离的TDGs。类似的特征也出现在与暗星系和气态主导UDGs的比较中,表明这些对象中的子样本也是长寿命TDGs。本工作提供了有力证据,表明剥离从星系合并是形成星团中稳定冷气体云和无暗物质星系的可行途径。

英文摘要

Motivated by the discovery of peculiar dwarf galaxies inside galaxy clusters such as blue candidates (BCs), dark galaxies and ultra-diffuse galaxies (UDGs), we present hydrodynamic simulations of galaxy mergers in cluster environments. We vary the viscosity and stellar feedback prescriptions, realistically modelling possible conditions for hydrodynamic drag and fluid instabilities, as well as internal destabilization through stellar feedback-driven heating and gas loss. We find that long-lived tidal dwarf galaxies (TDGs) can form throughout all viscosity values applicable to galaxy clusters if stellar feedback is moderate. Our results expand on studies of cloud crushing simulations, investigating the entrainment problem in intracluster medium ambience. The smallest clouds have gas masses on the order of $M_\text{gas} \sim 10^7 \text{ M}_\odot$ and reach relatively low final drift velocities of $\sim 100 \text{ km/s}$. The lowest possible Reynolds number acting on this class of clouds is $Re \sim 1$ for full Spitzer viscosity. Almost all TDGs display elevated star formation rates of $0.01-0.1 \text{ M}_\odot / \text{yr}$, which are stable across several Gyr. Based on their matching properties, we support that BCs observed in the Virgo cluster are likely stripped TDGs. Similar features are also found in comparison with dark galaxies and baryon-dominated UDGs, implying that a subsample of these objects are also long-lived TDGs. This work provides robust evidence that stripping from galaxy mergers is a viable channel for the formation of stable cold gas clouds and dark matter-deficient galaxies observed in galaxy clusters.

2605.00983 2026-05-05 quant-ph

Multimode Strong-Coupling Processes in Circuit QED Lattices

电路量子电动力学晶格中的多模强耦合过程

Won Chan Lee, Ali Fahimniya, Kellen O'Brien, Yu-Xin Wang, Alexandra Behne, Maya Amouzegar, Alexey V. Gorshkov, Alicia J. Kollár

AI总结 研究多模强耦合在电路量子电动力学晶格中的新现象,包括电路拉格朗日分析和强波混叠共振实验,揭示了新特征如带隙、抬高退化、展宽平面带和频率依赖的跃迁。

Comments 20 pages, 8 figures

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AI中文摘要

电路量子电动力学系统为探索多模腔QED的强耦合 regime 提供了理想平台。本文报道了多模强耦合中的两种新现象:一种电路拉格朗日分析,捕捉到强光子-光子耦合的超越紧束缚效应,以及在量子比特响应中观测到的强波混叠共振。我们的电路分析揭示了新特征,如新兴的带隙、抬高的退化、展宽的平面带和频率依赖的跃迁。在多模光子环境中,强量子比特-光子耦合进一步导致涉及多个正常模式的多光子过程。我们演示了一种强四波混叠过程,涉及量子比特的激发和多个模式之间的同时频率转换。值得注意的是,这种波混叠过程由光子晶格中的局域平面带模式主导,这些模式对transmon量子比特具有最强的耦合。

英文摘要

Circuit QED systems provide an ideal platform for exploring the strong-coupling regime of multimode cavity QED. Here we present two new phenomena from multimode strong coupling: a circuit Lagrangian analysis which captures beyond tight-binding effects of strong photon-photon coupling and experimental observation of strong wave-mixing resonances in the qubit response. Our circuit analysis reveals qualitatively new features such as emergent band gaps, lifted degeneracies, broadened flat bands, and frequency-dependent hopping. Within the multimode photon environment, strong qubit-photon coupling in turn gives rise to multiphoton processes involving multiple normal modes. We demonstrate a strong four-wave-mixing process involving excitation of a qubit and simultaneous frequency conversion between modes. Notably, this wave-mixing process is dominated by localized flat-band modes of the photonic lattice, which exhibit the strongest coupling to the transmon qubit.

2605.00982 2026-05-05 astro-ph.GA

Stellar mass and morphology segregation in pairs and multiplets in the cosmic web

星系质量与形态在宇宙网中的分隔

G. Torres-Ríos, S. Verley, I. Pérez, M. Argudo-Fernández, B. Bidaran, S. Duarte Puertas, Y. K. González-Koda

AI总结 研究宇宙大尺度结构中星系位置对其质量与形态的影响,发现局部环境对星系质量分布和形态比例有显著影响,且在空洞中仍存在伴星,支持宿主暗物质晕性质与大尺度环境相关。

Comments 15 pages, 12 figures. Accepted for publication in A&A

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AI中文摘要

本文研究了银河系在宇宙大尺度结构(LSS)中的位置是否影响其恒星质量(M*)和形态。我们试图区分局部和大尺度环境对分布的影响。我们对红移范围0.02 < z ≤ 0.04且log M* / M_⊙ ≥ 9.5的25309个星系按主要LSS(空洞、星团、非星团非空洞,称为NCNV)和局部环境(单体和多重体;有伴星和无伴星的星系)进行分类。我们展示了这些环境中的恒星质量与形态分布,并对星系对子样本进行了分析。即使在空洞中,约22%的星系仍有伴星。恒星质量分布显示,无论局部环境如何,空洞中的星系质量更小。空洞中的卫星相对于中心星系的质量比在NCNV对中更小。在形态方面,LSS越密集,早期型星系比例越高,即使在单体中也是如此。在空洞和NCNV中,晚期型多重体倾向于为晚期螺旋星系。在星系对中,中心星系倾向于更早型,而卫星则更晚型。经过精心挑选以避免形态不完整,样本显示早期型星系和多重体的比例略高于先前研究。我们得出结论,局部环境单独不足以解释本地宇宙中星系质量分布和形态。观测到的质量分布支持一种情景,即星系组装依赖于宿主暗物质晕,而这些晕的性质与大尺度环境相关。这可以解释空洞中低质量星系比在更密集环境中更少的现象,并为多重体的共同进化起源提供基础。

英文摘要

In this work, we investigate whether the location of galaxies within the large-scale structures (LSS) of the Universe affects their stellar mass ($M_\star$) and morphology. To this end, we attempt to disentangle the effects of local and large-scale environments in their distributions. We classify 25309 galaxies in the redshift range ${0.02 < z \leq 0.04}$ with $\log M_\star/\rm{M}_\odot \geq 9.5$ in terms of the main LSS (voids, clusters, and not clusters nor voids, referred to as NCNV) and local environment (singlets and multiplets; galaxies with and without companions). We present the stellar mass and morphology distributions in these environments, and for a subsample of galaxy pairs. Even in voids, we find that $\sim22\%$ of galaxies have companions. Stellar mass distributions show that galaxies are less massive in voids, regardless of their local environment. Satellites in voids are, too, less massive relative to their centrals than in NCNV pairs. In terms of morphology, the denser the LSS, the greater is the proportion of early-type galaxies, even among singlets. In voids and NCNV, late-type multiplets tend to be later-type spirals than singlets. In pairs, centrals tend to be more early-type than satellites. The sample, curated to avoid morphology incompleteness, yields slightly higher fractions of early-type galaxies and multiplets than previous studies. We conclude that the local environment alone is insufficient to explain the distribution of stellar mass and the morphology of galaxies in the local Universe. The observed mass distributions support a scenario in which galaxy assembly depends critically on the host halos, and the properties of these halos are related to their large-scale environment. This would explain the finding of lower-mass galaxies in voids than in denser environments, and provide a basis for considering a common evolutionary origin for multiplets.

2605.00981 2026-05-05 quant-ph

The minimal example of quantum network Bell nonlocality

量子网络贝尔非局域性的最小示例

Erwan Don, Jessica Bavaresco, Patryk Lipka-Bartosik, Nicolas Gisin, Nicolas Brunner, Alejandro Pozas-Kerstjens

AI总结 研究发现三角网络中无需输入选择即可产生贝尔非局域关联,通过构建量子模型验证了非局域性的最小网络配置。

Comments 8 pages, 4 figures, RevTeX 4.2. The computational appendix is available at https://www.github.com/Shamaii/minimal-network-nonlocality

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AI中文摘要

近年来,贝尔非局域性研究已扩展到量子网络,其中多个独立源将物理系统分配给远距离参与者进行局部测量。在此背景下,一个核心问题是如何确定产生贝尔非局域关联的最小网络配置。本文通过识别目标分布家族并证明其非局域性,构建了能精确再现目标分布的量子模型。该方法基于高阶量子操作的正式主义,考虑观测变量数量及其基数,构成了支持量子网络非局域性的最小场景。此外,通过分析显式量子模型,获得了生成量子网络非局域分布的新见解。

英文摘要

In recent years, the study of Bell nonlocality has been generalized to quantum networks, where multiple independent sources distribute physical systems to distant parties who perform local measurements. In this context, a central open question is to identify the minimal network configuration in which quantum resources produce Bell nonlocal correlations. Here we address this question and show that quantum nonlocality is possible in the triangle network where the parties have no input choices and produce only binary-valued outcomes. To do so, we start by identifying a family of target distributions and proving their nonlocality. Next, we construct an explicit quantum model that reproduces the target distributions to machine precision. For this, we develop an efficient method for parameterizing quantum distributions in networks, inspired by the formalism of higher-order quantum operations. When considering the number of observed variables and their cardinality, this constitutes the smallest scenario possible that supports quantum nonlocality in networks. Moreover, by analyzing the explicit quantum model, we obtain new insights into how nonlocal distributions can be generated in quantum networks.

2605.00980 2026-05-05 astro-ph.CO astro-ph.IM

Coverage is not enough: Frequentist tests of simulation-based inference for primordial non-Gaussianity

覆盖率不足:基于模拟的频繁检验用于原始非高斯性

Toka Alokda, Cristiano Porciani, Alexander Eggemeier

AI总结 研究探讨了基于模拟的推断(SBI)在原始非高斯性参数化中的可靠性问题,比较了基于对比神经比率估计(CNRE)的SBI与基于似然的推断(LBI)在不同统计量上的表现,发现SBI在后验尾部存在偏差,需改进验证策略。

Comments 15 pages, 9 figures, 2 tables. Submitted to Astronomy & Astrophysics. Comments are welcome

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AI中文摘要

(摘要) 基于模拟的推断(SBI)已成为从复杂非线性数据中提取宇宙学信息的强大框架,尤其在无法获得解析似然的情况下。其可靠性通常通过基于覆盖率的诊断在先验预测分布下评估,仅在平均意义上探测校准,而不约束固定参数值下的后验行为,这在实际推断中相关。我们研究了这些限制在原始非高斯性中的情况,参数化为$f_\mathrm{NL}$,使用暗物质晕场的模拟。我们比较了基于对比神经比率估计(CNRE)的SBI与基于功率谱、双谱和小波散射变换(WST)系数的似然推断(LBI)在1000次重复中的表现。SBI和LBI在后验均值和偏斜度上一致,而方差在平均上一致但重复间一致性较弱。偏度差异更大,表明后验尾部存在差异。这些影响在功率谱中已存在,而功率谱和双谱结合时最为显著,SBI后验往往过于自信,可能比单独统计量产生更弱的约束,尽管通过覆盖率测试。WST系数进一步收紧$f_\mathrm{NL}$的约束,即使限制在大尺度上。我们的结果强调了高阶统计量的潜力以及需要验证策略以探测后验形状的必要性,而不仅仅是标准覆盖率诊断。

英文摘要

(Abridged) Simulation-based inference (SBI) has emerged as a powerful framework for extracting cosmological information from complex, non-linear data where analytical likelihoods are unavailable. Its reliability is commonly assessed using coverage-based diagnostics under the prior predictive distribution, which probe calibration only in an averaged sense and do not constrain posterior behavior at fixed parameter value, the regime relevant for practical inference. We investigate these limitations in the context of primordial non-Gaussianity, parameterized by $f_\mathrm{NL}$, using simulations of the dark matter halo field. We compare SBI based on contrastive neural ratio estimation (CNRE) with likelihood-based inference (LBI) using the power spectrum, bispectrum, and wavelet scattering transform (WST) coefficients across 1000 realizations. SBI and LBI agree well on posterior means and skewness, while the variance agrees on average but shows weaker realization-by-realization consistency. Larger differences arise in the kurtosis, indicating discrepancies in the posterior tails. These effects are already present for the power spectrum - where the Gaussian likelihood assumed in LBI is best justified - and are most pronounced for the combined power spectrum and bispectrum, where SBI posteriors are often underconfident and can yield weaker constraints than either statistic individually, despite passing coverage tests. WST coefficients further tighten constraints on $f_\mathrm{NL}$, even when restricted to large scales. Our results highlight both the potential of higher-order statistics and the need for validation strategies that probe the posterior shape beyond standard coverage diagnostics.

2605.00979 2026-05-05 quant-ph cond-mat.str-el hep-th

Universality of Quantum Gates in Particle and Symmetry Constrained Subspaces

量子门在粒子和对称约束子空间中的普遍性

Andreas Stergiou, Nicolas PD Sawaya

AI总结 本文通过李代数技术证明了在约束子空间中,硬件高效门可实现状态制备的通用性,通过Pauli Z dressing机制将多平面旋转分解为单平面生成元,从而保证了通用性。

Comments 32 pages, 8 figures. Code used in this work is available at https://github.com/andstergiou/fuzzy-ising-vqe

详情
AI中文摘要

在近期量子计算机上模拟物理系统往往需要在受约束的子空间中准备状态,例如具有固定粒子数或自旋的状态。我们利用李代数技术证明了硬件高效门在这些子空间中进行状态制备的通用性。关键机制是Pauli Z dressing:重叠门的交换子产生在共享量子比特上的Pauli Z算符,作为旁观者投影器,将多平面旋转分解为单平面生成元,这些生成元跨越完整的so(w)代数,其中w是受约束子空间的维度,从而保证了真实状态制备的通用性。添加独立的复相位扩展到su(w),使任意复状态制备成为可能。我们提供了一个计算高效的标准雅可比准则,用于验证电路能否从几乎任何参数配置探索目标流形上的任何方向。我们的发现适用于许多问题领域,包括费米 Hubbard 模型、玻色 Hubbard 模型和分子电子结构。我们应用我们的框架到两个物理设置:我们证明了二进制编码的多级粒子 ansatz 在守恒粒子数子空间中的完备性,并为三维伊辛共形场论(CFT)的模糊球正则化构造了对称保持电路。对于后者,我们变分地准备基态和激发态以提取CFT标度维度。

英文摘要

Simulating physical systems on near-term quantum computers often requires preparing states within constrained subspaces, like those with fixed particle number or spin. We use Lie algebraic techniques to prove that hardware-efficient gates are universal for state preparation in these subspaces. The key mechanism is Pauli $Z$ dressing: commutators of overlapping gates produce Pauli $Z$ operators on shared qubits, acting as spectator projectors that decompose multi-plane rotations into single-plane generators spanning the full $\mathfrak{so}(w)$ algebra, where $w$ is the dimension of the constrained subspace, thereby guaranteeing universality for real state preparation. Adding independent complex phases extends this to $\mathfrak{su}(w)$, enabling arbitrary complex state preparation. We provide a computationally efficient Jacobian criterion for verifying that a circuit can explore any direction on the target manifold from almost any parameter configuration. Our findings are applicable to many problem areas, including Fermi-Hubbard models, Bose-Hubbard models, and molecular electronic structure. We apply our framework to two physical settings: we prove the completeness of the binary encoded multi-level particles ansatz on the conserved-particle-number subspace, and we construct symmetry-preserving circuits for the fuzzy sphere regularisation of the 3D Ising conformal field theory (CFT). For the latter, we variationally prepare the ground and excited states to extract CFT scaling dimensions.