统计力学
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显示 2025年08月08日, 星期五 新的列表
- [1] arXiv:2508.04983 [中文pdf, pdf, html, 其他]
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标题: 随机循环神经网络中的动能标题: Kinetic energy in random recurrent neural networks评论: 8页,6图主题: 统计力学 (cond-mat.stat-mech) ; 混沌动力学 (nlin.CD) ; 神经与认知 (q-bio.NC)
不稳定固定点与高维神经动力学中的混沌动力学之间的关系仍然不明确。 在本工作中,我们通过将动力学平均场理论与大量数值模拟相结合,研究了随机循环神经网络的动能分布。 我们发现,在耦合方差(突触增益)的关键值处,平均动能从零连续地转移到正值,并且在临界点附近表现出幂律行为。 通过理论进一步计算了稳态活动分布,并与有限尺寸系统的模拟进行了比较。 这项研究为理解动能的景观提供了第一步,这可能反映了非平衡动力学相空间的结构。
The relationship between unstable fixed points and chaotic dynamics in high-dimensional neural dynamics remains elusive. In this work, we investigate the kinetic energy distribution of random recurrent neural networks by combining dynamical mean-field theory with extensive numerical simulations. We find that the average kinetic energy shifts continuously from zero to a positive value at a critical value of coupling variance (synaptic gain), with a power-law behavior close to the critical point. The steady-state activity distribution is further calculated by the theory and compared with simulations on finite-size systems. This study provides a first step toward understanding the landscape of kinetic energy, which may reflect the structure of phase space for the non-equilibrium dynamics.
- [2] arXiv:2508.05031 [中文pdf, pdf, 其他]
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标题: 液体内超球状布朗运动的观察标题: Observation of Super-ballistic Brownian Motion in Liquid评论: 20页,8图主题: 统计力学 (cond-mat.stat-mech)
布朗运动是物理学中的一个基础问题,在热平衡状态下,其均方位移随时间线性变化,这被称为扩散。 在短时间内,均方位移变为弹道式,随t^2变化。 这一效应由爱因斯坦在1907年预测,并最近通过实验观察到。 我们报告说,这个图景仅在平均意义上成立;通过设定特定的初始速度,我们理论上预测并通过实验证实,均方位移变为超弹道式,其幂律标度为t^(5/2)。 这一新结果是由于不可压缩流体的彩色噪声,在设定非零初始速度时导致热力的第一个矩不为零。 这些结果是揭示流体非平衡动力学的第一步。
Brownian motion is a foundational problem in physics and is characterized by a mean squared displacement that scales linearly in time in thermal equilibrium, known as diffusion. At short times, the mean squared displacement becomes ballistic, scaling as t^2. This effect was predicted by Einstein in 1907 and recently observed experimentally. We report that this picture is only true on average; by conditioning specific initial velocities, we predict theoretically and confirm by experiment that the mean squared displacement becomes super-ballistic, with a power scaling law of t^(5/2). This new result is due to the colored noise of incompressible fluids, resulting in a non-zero first moment for the thermal force when conditioned on non-zero initial velocities. These results are a first step towards the unraveling of nonequilibrium dynamics of fluids.
- [3] arXiv:2508.05209 [中文pdf, pdf, html, 其他]
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标题: 非互易极性活性混合物中的熵产生标题: Entropy production in non-reciprocal polar active mixtures主题: 统计力学 (cond-mat.stat-mech) ; 软凝聚态物理 (cond-mat.soft)
活性系统的非平衡特性通常具有双重性,既来自活动本身,也来自组分之间的非互惠耦合。 一个被广泛接受的量化系统偏离平衡程度的指标是信息熵产生率。 在这里,我们提出一个问题,即信息熵产生率在具有非互惠极化耦合的活性混合物中,是否以及如何反映集体行为和转变。 在这样的系统中,非互惠取向耦合可以引发粒子的螺旋运动。 在场论层面,这些时间依赖的螺旋态的转变由所谓的例外点标记。 在这里,我们表明,在粒子层面,当非互惠性足够强时,螺旋态中的熵产生率随着非互惠性的程度增加而增加。 此外,即使在小程度的非互惠性下,通过例外点的转变也会在熵产生率中留下明显的特征,该特征在对应于场论例外点的耦合强度处表现出显著的峰值。 总体而言,熵产生率的增加和峰值反映了粒子层面极化序参数的敏感性。 这种对应关系得到了场论分析的支持,该分析揭示了在长波极限下,熵产生率与极化场的敏感性成比例。
The out-of-equilibrium character of active systems is often twofold, arising from both the activity itself and from non-reciprocal couplings between constituents. A well-established measure to quantify the system's distance from equilibrium is the informatic entropy production rate. Here, we ask the question whether and how the informatic entropy production rate reflects collective behaviors and transitions in an active mixture with non-reciprocal polar couplings. In such systems, non-reciprocal orientational couplings can induce chiral motion of particles. At the field-theoretical level, transitions to these time-dependent chiral states are marked by so-called exceptional points. Here, we show that at a particle level, the entropy production rate within the chiral states increases with the degree of non-reciprocity, provided it is sufficiently strong. Moreover, even at small degrees of non-reciprocity, the transitions via exceptional points leave clear signatures in the entropy production rate, which exhibits pronounced peaks at coupling strengths corresponding to the field-theoretical exceptional points. Overall, the increase and peaks of the entropy production rate mirror the susceptibility of the polarization order parameter at the particle level. This correspondence is supported by a field-theoretical analysis, which reveals that, in the long-wavelength limit, the entropy production rate scales with the susceptibilities of the polarization fields.
- [4] arXiv:2508.05313 [中文pdf, pdf, html, 其他]
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标题: 同时具有重置的随机行走者在网络中的平均首次相遇时间标题: Mean first-encounter times of simultaneous random walkers with resetting on networks评论: 24页,5图期刊参考: J. Phys. A: Math. Theor. 58 325003 (2025)主题: 统计力学 (cond-mat.stat-mech)
我们研究了在网络中具有重置的同步随机行走者的动力学,并推导出马尔可夫随机行走者首次相遇时间的精确解析表达式。 具体而言,我们考虑了网络上两个随机行走者同步动力学的两种情况:当只有一个行走者返回初始节点,以及当两个行走者都返回其初始位置。 在这两种情况下,相遇时间都用正常随机行走的转移矩阵的特征值和特征向量来表示,为重置的影响提供了谱解释。 我们通过在环、Cayley树和使用Erdős-Rényi、Watts-Strogatz和Barabási-Albert算法生成的随机网络上的例子验证了我们的方法,其中重置显著减少了相遇时间。 所提出的框架可以扩展到其他类型的随机行走动力学、传输过程或多行走者场景,在人类移动、流行病传播和复杂系统中的搜索策略方面具有潜在应用。
We investigate the dynamics of simultaneous random walkers with resetting on networks and derive exact analytical expressions for the mean first-encounter times of Markovian random walkers. Specifically, we consider two cases for the simultaneous dynamics of two random walkers on networks: when only one walker resets to the initial node, and when both walkers return to their initial positions. In both cases, the encounter times are expressed in terms of the eigenvalues and eigenvectors of the transition matrix of the normal random walk, providing a spectral interpretation of the impact of resetting. We validate our approach through examples on rings, Cayley trees, and random networks generated using the Erd\H{o}s-R\'enyi, Watts-Strogatz, and Barab\'asi-Albert algorithms, where resetting significantly reduces encounter times. The proposed framework can be extended to other types of random walk dynamics, transport processes, or multiple-walker scenarios, with potential applications in human mobility, epidemic spreading, and search strategies in complex systems.
- [5] arXiv:2508.05327 [中文pdf, pdf, html, 其他]
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标题: 金属中热迁移的热力学模型标题: A Thermodynamic Model for Thermomigration in Metals主题: 统计力学 (cond-mat.stat-mech) ; 材料科学 (cond-mat.mtrl-sci)
我们研究了金属中间隙氢的热迁移机制。 使用统计热力学,我们开发了一个全面的机制模型来捕捉控制效应。 至关重要的是,通过与已发表的实验数据进行验证,我们的结果表明电子风效应起着重要作用,特别是在热迁移方向与热流一致的材料中。 这些发现为影响金属中溶质局域化的因素提供了新的见解。 此外,我们的结果表明,由于忽略了电子效应,原子模型可能不足以进行详细的热迁移研究。
We investigate the mechanisms involved in the thermomigration of interstitial hydrogen in metals. Using statistical thermodynamics, we develop a comprehensive mechanistic model to capture the controlling effects. Crucially, through validation against published experimental data, our results demonstrate that an electron-wind effect plays a significant role, particularly for materials in which the thermomigration direction matches the heat flux. These findings provide new insights into the factors that affect the localisation of solutes in metals. Moreover, our results indicate that atomistic models may be inadequate for detailed thermomigration studies due to the omission of electronic effects.
- [6] arXiv:2508.05528 [中文pdf, pdf, html, 其他]
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标题: 随机成核流体动力学模型中开放边界的应用标题: The use of open boundaries in stochastic hydrodynamic models of nucleation主题: 统计力学 (cond-mat.stat-mech) ; 化学物理 (physics.chem-ph) ; 计算物理 (physics.comp-ph)
随机流体力学是在基础层面上研究一阶相变的重要工具。 结合复杂的自由能模型,例如在经典密度泛函理论中开发的模型,可以对诸如结晶等复杂过程进行建模,并确定诸如自由能势垒、成核路径以及不稳定特征向量和特征值的信息。 后者尤其有趣,因为它们分别在定义自然(无偏)序参数和成核速率中起着关键作用。 正如通常的情况一样,计算现实限制了可以建模的系统大小,这使得难以达到体积有效无限的实验条件。 在本文中,讨论了开放边界条件的使用。 通过使用开放系统,计算结果将更接近实验条件,然而引入开放边界条件引发了一些关于随机模型的问题,例如涨落-耗散关系是否保持,以及自由能表面上的驻点是否仍然是动力学的驻点。
Stochastic hydrodynamics is a central tool in the study of first order phase transitions at a fundamental level. Combined with sophisticated free energy models, e.g. as developed in classical Density Functional Theory, complex processes such as crystallization can be modeled and information such as free energy barriers, nucleation pathways and the unstable eigenvector and eigenvalues determined. The latter are particularly interesting as they play key roles in defining the natural (unbiased) order parameter and the nucleation rate respectively. As is often the case, computational realities restrict the size of system that can be modeled and this makes it difficult to achieve experimental conditions for which the volume is effectively infinite. In this paper, the use of open boundary conditions is discussed. By using an open system, the calculations become much closer to experimental conditions however, the introduction of open boundary conditions raises a number of questions concerning the stochastic model such as whether the fluctuation-dissipation relation is preserved and whether stationary points on the free energy surface remain stationary points of the dynamics.
新提交 (展示 6 之 6 条目 )
- [7] arXiv:2508.04774 (交叉列表自 quant-ph) [中文pdf, pdf, html, 其他]
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标题: 从机器学习中对量子计算机上的通用量子相进行分类标题: Universal quantum phase classification on quantum computers from machine learning评论: 21页,11图,欢迎提出意见主题: 量子物理 (quant-ph) ; 无序系统与神经网络 (cond-mat.dis-nn) ; 统计力学 (cond-mat.stat-mech) ; 强关联电子 (cond-mat.str-el)
物质的量子相分类仍然是凝聚态物理中的一个基本挑战。 我们提出了一种新的框架,将影子断层扫描与现代时间序列机器学习模型相结合,以实现高效且实用的量子相分类。 我们的方法基于通过有限深度局部单元电路的连通性来定义量子相,通过对给定相位的代表性量子态应用哈尔回路演化来生成丰富的训练数据。 这样,训练数据可以从量子模拟器中高效获得。 此外,我们证明先进的时间序列模型可以用于处理训练数据,并实现不依赖于局部序参数的通用量子相分类。 为了验证我们方法的普遍性和多功能性,我们将模型应用于一维量子自旋链,如伊辛模型和轴向最近邻反铁磁伊辛(ANNNI)模型,结果与已知的相变边界表现出良好的一致性。
The classification of quantum phases of matter remains a fundamental challenge in condensed matter physics. We present a novel framework that combines shadow tomography with modern time-series machine learning models to enable efficient and practical quantum phase classification. Our approach leverages the definition of quantum phases based on connectivity through finite-depth local unitary circuits, generating abundant training data by applying Haar random evolution to representative quantum states for a given phase. In this way, the training data can be efficiently obtained from a quantum simulator. Additionally, we demonstrate that advanced time-series models can be used to process the training data and achieve universal quantum phase classification that does not rely on local order parameters. To validate the universality and versatility of our method, we test the model against one-dimensional quantum spin chains such as the Ising model and the axial next-nearest-neighbor Ising (ANNNI) model, showing excellent agreement with known phase boundaries.
- [8] arXiv:2508.04864 (交叉列表自 cond-mat.soft) [中文pdf, pdf, html, 其他]
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标题: 非均分散胶体在流体界面处的卡西米尔相互作用标题: Casimir Interaction between Polydisperse Colloids Trapped at a Fluid Interface主题: 软凝聚态物理 (cond-mat.soft) ; 统计力学 (cond-mat.stat-mech)
我们研究了多分散性对被捕获在流体界面处的Janus胶体粒子之间波动诱导相互作用的影响。 使用散射矩阵形式,我们在二维和三维系统中计算了热卡西米尔能量,考虑了胶体的三种不同的波动情景:(a) 固定,(b) 摇摆,以及 (c) 摇摆和倾斜。 我们的结果揭示了对多分散性的显著敏感性,这种敏感性强烈依赖于波动边界条件:虽然固定胶体表现出适度的偏差,但摇摆以及特别是摇摆+倾斜配置由于多分散性导致的能量偏差出现了数量级的放大。 这些效应在大距离下进一步增强。 我们的发现强调了几何形状、胶体波动和波动诱导力之间的相互作用,对胶体自组装和界面工程具有重要意义。
We investigate the effect of polydispersity on fluctuation-induced interactions between Janus colloidal particles trapped at a fluid interface. Using the scattering-matrix formalism, we calculate the thermal Casimir energy in both two- and three-body systems, considering three distinct fluctuation scenarios for the colloids: (a) fixed, (b) bobbing, and (c) bobbing and tilting. Our results reveal a pronounced sensitivity to polydispersity that strongly depends on the fluctuating boundary conditions: while fixed colloids show modest deviations, bobbing and especially bobbing+tilting configurations exhibit orders-of-magnitude amplification in the energy deviation due to polydispersity. These effects are further enhanced at large separations. Our findings highlights the interplay between geometry, colloids fluctuations, and fluctuation-induced forces, with implications for colloidal self-assembly and interface engineering.
- [9] arXiv:2508.05046 (交叉列表自 quant-ph) [中文pdf, pdf, html, 其他]
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标题: 通过随机SWAP测试进行最优量子比特纯化和单位Schur采样标题: Optimal Qubit Purification and Unitary Schur Sampling via Random SWAP Tests评论: 9页 + 17页的附录;5幅图;欢迎提出意见!主题: 量子物理 (quant-ph) ; 无序系统与神经网络 (cond-mat.dis-nn) ; 统计力学 (cond-mat.stat-mech) ; 数学物理 (math-ph) ; 核理论 (nucl-th)
量子比特纯化的目标是将多个噪声副本的未知纯量子态结合起来,以获得一个或多个更接近纯态的副本。 我们证明,仅基于随机SWAP测试的简单协议可以达到与Schur变换相同的保真度,这是最优的。 该协议仅依赖于基本的两量子比特SWAP测试,这些测试将一对量子比特投影到单重态或三重态子空间,以识别和隔离单重态对,然后继续处理剩余的量子比特。 对于一个$n$量子比特的系统,我们表明在大约$T \approx n \ln n$次随机SWAP测试后,会发生一个尖锐的相变:检测到任何新的单重态的概率随着$T$呈指数下降。 同样,每个剩余量子比特的保真度趋近于由Schur变换给出的最优值,误差在$T$上呈指数小。 更广泛地说,该协议在仅进行$2n \ln(n \epsilon^{-1})$次SWAP测试后,可以实现所谓的弱Schur采样和单位Schur采样,误差为$\epsilon$。 也就是说,它提供了一种无损的方法来提取任何关于量子比特排列不变的信息,使其成为量子态层析和计量等任务的强大子程序。
The goal of qubit purification is to combine multiple noisy copies of an unknown pure quantum state to obtain one or more copies that are closer to the pure state. We show that a simple protocol based solely on random SWAP tests achieves the same fidelity as the Schur transform, which is optimal. This protocol relies only on elementary two-qubit SWAP tests, which project a pair of qubits onto the singlet or triplet subspaces, to identify and isolate singlet pairs, and then proceeds with the remaining qubits. For a system of $n$ qubits, we show that after approximately $T \approx n \ln n$ random SWAP tests, a sharp transition occurs: the probability of detecting any new singlet decreases exponentially with $T$. Similarly, the fidelity of each remaining qubit approaches the optimal value given by the Schur transform, up to an error that is exponentially small in $T$. More broadly, this protocol achieves what is known as weak Schur sampling and unitary Schur sampling with error $\epsilon$, after only $2n \ln(n \epsilon^{-1})$ SWAP tests. That is, it provides a lossless method for extracting any information invariant under permutations of qubits, making it a powerful subroutine for tasks such as quantum state tomography and metrology.
- [10] arXiv:2508.05127 (交叉列表自 physics.plasm-ph) [中文pdf, pdf, html, 其他]
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标题: 湍流等离子体中捕食者-被捕食者动力学中的信息传播标题: Information Propagation in Predator-Prey Dynamics of Turbulent Plasma评论: 6页,2图(+补充材料8页,2图)主题: 等离子体物理 (physics.plasm-ph) ; 统计力学 (cond-mat.stat-mech) ; 流体动力学 (physics.flu-dyn)
磁约束聚变等离子体通过漂移波湍流和环向流之间的自调节相互作用表现出类似捕食者-猎物的周期性振荡。 为了阐明这一现象背后的详细机制和因果关系,我们构建了一个包含内在波动的简单随机捕食者-猎客模型,并从信息论的角度分析其统计特性。 我们首先表明,由于内在噪声的放大,该模型表现出称为准周期的持续波动周期性振荡。 这一结果表明,之前在环形等离子体中观察到的周期性振荡可能不是极限环,而是准周期,并且在各种条件下可能广泛观察到这种准周期。 对于该模型,我们进一步证明了环向流的信息被传播到湍流中。 这种信息论分析可能为通过控制环向流来调节湍流提供理论基础。
Magnetically confined fusion plasmas exhibit predator-prey-like cyclic oscillations through the self-regulating interaction between drift-wave turbulence and zonal flow. To elucidate the detailed mechanism and causality underlying this phenomenon, we construct a simple stochastic predator-prey model that incorporates intrinsic fluctuations and analyze its statistical properties from an information-theoretic perspective. We first show that the model exhibits persistent fluctuating cyclic oscillations called quasi-cycles due to amplification of intrinsic noise. This result suggests the possibility that the previously observed periodic oscillations in a toroidal plasma are not limit cycles but quasi-cycles, and that such quasi-cycles may be widely observed under various conditions. For this model, we further prove that information of zonal flow is propagated to turbulence. This information-theoretic analysis may provide a theoretical basis for regulating turbulence by controlling zonal flow.
- [11] arXiv:2508.05406 (交叉列表自 cond-mat.str-el) [中文pdf, pdf, html, 其他]
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标题: 二维量子系统的全局张量网络重正化:从热转变中探测普遍数据的新窗口标题: Global Tensor Network Renormalization for 2D Quantum systems: A new window to probe universal data from thermal transitions主题: 强关联电子 (cond-mat.str-el) ; 统计力学 (cond-mat.stat-mech)
我们提出了一种基于全局优化的新张量网络重正化群(TNR)方案,并引入了一种构建二维量子系统有限温度密度矩阵的新方法。 将这两者结合,形成一种称为热张量网络重正化(TTNR)的新算法,我们在热力学相变点获得了高度精确的共形场论(CFT)数据。 这为数值识别相变提供了一条新的高效途径,为传统的通过临界指数分析提供了替代方案。
We propose a new tensor network renormalization group (TNR) scheme based on global optimization and introduce a new method for constructing the finite-temperature density matrix of two-dimensional quantum systems. Combining these two into a new algorithm called thermal tensor network renormalization (TTNR), we obtain highly accurate conformal field theory (CFT) data at thermal transition points. This provides a new and efficient route for numerically identifying phase transitions, offering an alternative to the conventional analysis via critical exponents.
- [12] arXiv:2508.05588 (交叉列表自 quant-ph) [中文pdf, pdf, html, 其他]
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标题: 投影电荷测量下的纠缠熵淬火动力学:自由费米子情形标题: Quench dynamics of entanglement entropy under projective charge measurements: the free fermion case评论: 32页+附录,5图主题: 量子物理 (quant-ph) ; 统计力学 (cond-mat.stat-mech)
我们考虑投影测量对一维自由费米系统中双部分纠缠熵淬火动力学的影响。 在我们的协议中,我们在一个大的子系统上考虑$U(1)$保守电荷,即粒子数的投影测量,并研究该子系统与其补集之间的纠缠熵。 我们比较来自两类初始状态的动力学,一种是该电荷的本征态,另一种则不是。 此外,我们考虑单个测量以及周期性执行的多个测量的影响。 利用准粒子图像,我们得到了描述纠缠行为的解析表达式,这些表达式具有透明的物理解释。 一般来说,我们发现测量会引入两种不同的纠缠修正,可以分别解释为经典和量子贡献。 经典贡献与测量结果无关,并与电荷分布的方差成对数比例。 相比之下,量子贡献取决于具体的测量结果,在个别实现中可能显著;然而,当对所有可能的结果进行平均时,它变得可以忽略。 我们的表达式在某些相关极限下退化为已知的对称性分辨纠缠和完整计数统计的结果,并通过在尼尔初始态上进行的精确计算得到验证。
We consider the effect of projective measurements on the quench dynamics of the bipartite entanglement entropy in one dimensional free fermionic systems. In our protocol, we consider projective measurements of a $U(1)$ conserved charge, the particle number, on some large subsystem, and study the entanglement entropies between the same subsystem and its complement. We compare the dynamics emanating from two classes of initial states, one which is an eigenstate of the charge and another which is not. Moreover, we consider the effects of a single measurement as well as multiple which are periodically performed. Using the quasiparticle picture, we obtain analytic expressions for the behaviour of the entanglement which admit a transparent physical interpretation. In general, we find that measurements introduce two distinct types of corrections to the entanglement, which can be interpreted separately as classical and quantum contributions. The classical contribution is independent of the measurement outcome and scales logarithmically with variance of the charge distribution. In contrast, the quantum contribution depends on the specific measurement outcome and can be significant for individual realizations; however, it becomes negligible when averaged over all possible outcomes. Our expressions reduce to previously known results for symmetry resolved entanglement and full counting statistics in some relevant limits, and are confirmed by an exact calculation performed on the N\'eel initial state.
- [13] arXiv:2508.05632 (交叉列表自 quant-ph) [中文pdf, pdf, html, 其他]
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标题: 部分投影集合和信息打乱的时空结构标题: Partial projected ensembles and spatiotemporal structure of information scrambling评论: 23页,15图主题: 量子物理 (quant-ph) ; 无序系统与神经网络 (cond-mat.dis-nn) ; 统计力学 (cond-mat.stat-mech)
非平衡量子多体系统中的热化和信息杂乱现象紧密交织:局部子系统动态地趋近于热密度矩阵,而它们的熵则追踪信息的扩散。投影系综——基于互补子系统测量结果的纯态系综——提供了对热化的高阶探测,在较晚时间收敛到普遍的最大熵系综。在本工作中,我们引入部分投影系综(PPE)作为研究信息杂乱的时空结构如何被印刻在投影系综上的框架。PPE是由对子系统补集的空间分离部分进行测量所诱导的子系统混合态系综,通过消除其余部分,自然地捕捉了涉及被丢弃结果或噪声引起的损失的场景。我们表明,PPE的统计涨落忠实跟踪信息扩散的因果光锥,揭示了杂乱动力学如何被编码在系综结构中。此外,我们证明与PPE相关的位字符串概率(PoPs)表现出不同的动力学区域,并提供了一种可实验探测杂乱的手段。PPE涨落和PoPs都对被丢弃区域的大小表现出指数敏感性,反映了在擦除下量子关联的指数退化。我们使用不可积的kicked Ising链验证了这些发现,结合遍历区域的数值计算与自对偶点的精确结果。我们将分析扩展到多体局域(MBL)区域,同时给出了$\ell$-bit模型的分析结果。遍历和MBL区域特有的线性和对数光锥自然地从PPE动力学中出现,确立了它作为探测杂乱和深度热化强大工具的地位。
Thermalisation and information scrambling in out-of-equilibrium quantum many-body systems are deeply intertwined: local subsystems dynamically approach thermal density matrices while their entropies track information spreading. Projected ensembles--ensembles of pure states conditioned on measurement outcomes of complementary subsystems--provide higher-order probes of thermalisation, converging at late times to universal maximum-entropy ensembles. In this work, we introduce the partial projected ensemble (PPE) as a framework to study how the spatiotemporal structure of scrambling is imprinted on projected ensembles. The PPE consists of an ensemble of mixed states induced on a subsystem by measurements on a spatially separated part of its complement, tracing out the remainder, naturally capturing scenarios involving discarded outcomes or noise-induced losses. We show that statistical fluctuations of the PPE faithfully track the causal lightcone of information spreading, revealing how scrambling dynamics are encoded in ensemble structure. In addition, we demonstrate that the probabilities of bit-string probabilities (PoPs) associated with the PPE exhibit distinct dynamical regimes and provide an experimentally accessible probe of scrambling. Both PPE fluctuations and PoPs display exponential sensitivity to the size of the discarded region, reflecting exponential degradation of quantum correlations under erasure. We substantiate these findings using the non-integrable kicked Ising chain, combining numerics in the ergodic regime with exact results at its self-dual point. We extend our analysis to a many-body localised (MBL) regime numerically, along with analytic results for the $\ell$-bit model. The linear and logarithmic lightcones characteristic of ergodic and MBL regimes emerge naturally from PPE dynamics, establishing it as a powerful tool for probing scrambling and deep thermalisation.
交叉提交 (展示 7 之 7 条目 )
- [14] arXiv:2410.22586 (替换) [中文pdf, pdf, html, 其他]
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标题: 受扰易轴海森堡自旋链中扩散常数的标度标题: Scaling of diffusion constants in perturbed easy-axis Heisenberg spin chains评论: 12页,12图期刊参考: 物理评论B 112, 054417 (2025)主题: 统计力学 (cond-mat.stat-mech) ; 强关联电子 (cond-mat.str-el) ; 量子物理 (quant-ph)
理解可积自旋-1/2 XXZ链的物理特性已经取得了重大进展,这是由于开发和应用了复杂的分析和数值技术。 特别是,在无限温度下的磁化输运在各向异性参数的不同区域表现出从弹道、超扩散到扩散的行为。 由于可积性是例外而非常规,一个关键问题是可积性破坏扰动下的输运变化。 这个问题包括各向同性点处超扩散的稳定性以及易轴区域中扩散常数的变化。 在我们的工作中,我们通过多种方法研究了扩散常数的变化,并涵盖了封闭系统中的线性响应理论和开放系统中的Lindblad方程,其中我们始终关注周期性边界条件。 在封闭系统中,我们将递归方法的结果与有限系统的计算进行比较,发现扩散常数在整个扰动强度范围内的连续变化的证据。 在与热库弱耦合的开放系统中,我们在非弱扰动范围内发现的扩散常数与封闭系统中的结果定量一致,但在弱扰动极限下存在不一致。 在该极限下使用一个简单模型,我们指出了这种开放系统中扩散常数发散的可能性。
Understanding the physics of the integrable spin-1/2 XXZ chain has witnessed substantial progress, due to the development and application of sophisticated analytical and numerical techniques. In particular, infinite-temperature magnetization transport has turned out to range from ballistic, over superdiffusive, to diffusive behavior in different parameter regimes of the anisotropy. Since integrability is rather the exception than the rule, a crucial question is the change of transport under integrability-breaking perturbations. This question includes the stability of superdiffusion at the isotropic point and the change of diffusion constants in the easy-axis regime. In our work, we study this change of diffusion constants by a variety of methods and cover both, linear response theory in the closed system and the Lindblad equation in the open system, where we throughout focus on periodic boundary conditions. In the closed system, we compare results from the recursion method to calculations for finite systems and find evidence for a continuous change of diffusion constants over the full range of perturbation strengths. In the open system weakly coupled to baths, we find diffusion constants in quantitative agreement with the ones in the closed system in a range of nonweak perturbations, but disagreement in the limit of weak perturbations. Using a simple model in this limit, we point out the possibility of a diverging diffusion constant in such an open system.
- [15] arXiv:2503.06124 (替换) [中文pdf, pdf, html, 其他]
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标题: 两态和三态量子热机与随机重置标题: Two and three-state quantum heat engines with stochastic resetting评论: 15页,6图主题: 统计力学 (cond-mat.stat-mech)
量子热机在过去二十年中经历了广泛的研究。 同时,关于随机重置在各个领域应用的研究正在增加。 我们探讨了随机重置对两能级和三能级量子热机动力学的影响。 提取的功被证明随着重置率的增加而增加。 考虑到由于重置所做的功的有效效率保持不变。 然而,如果忽略由于重置所做的功,那么系统可能会错误地暗示不同的行为,包括错误地推断它根本不是一种热机。 观察到的高效功率超过了没有重置时获得的功率,并且对于三能级发动机来说更高。
Quantum heat engines have undergone extensive studies over the last two decades. Simultaneously, the studies of the applications of stochastic resetting in various fields are on the rise. We explore the effect of stochastic resetting on the dynamics of a two-level and a three-level quantum heat engine. The extracted work is shown to increase with the resetting rate. The effective efficiency that takes into account the work done due to resetting remains constant. However, if the work done due to resetting is ignored, then the system can incorrectly imply a different behaviour, including the false inference that it is not working as an engine at all. The efficient power is observed to increase beyond that obtained in the absence of resetting, and is shown to be higher for a three-level engine.
- [16] arXiv:2507.17750 (替换) [中文pdf, pdf, html, 其他]
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标题: 周期TASEP中电流波动的尺度性质标题: Scaling Properties of Current Fluctuations in Periodic TASEP评论: 36页,6图主题: 统计力学 (cond-mat.stat-mech) ; 数学物理 (math-ph)
我们研究环形结构上完全不对称简单排斥过程(TASEP)中的电流涨落,该环形结构有$N$个位点和$p$个粒子。通过引入一个变形参数$\gamma$,我们分析了控制时间积分电流统计的倾斜算子。利用坐标Bethe假设,我们推导出标度累积生成函数(SCGF)的隐式表达式,即最大的特征值,以及谱间隙,两者都以Bethe根表示。通过使用Cassini卵形的几何结构来描述它们的渐近行为。在固定粒子密度的热力学极限下,我们识别出一种动力学相变,用于区分涨落区域。对于$\gamma>0$,SCGF表现出与系统大小成比例的 ballistic 增长,$\lambda_1 \sim N$。 相反,对于$\gamma<0$,SCGF 收敛到$-1$当$N\to\infty$。 这种转变反映在谱间隙中,它控制系统的松弛时间尺度。 对于$\gamma>0$,间隙以多项式速度关闭,$\Delta \sim N^{-1}$,与增强电流的快速松弛一致。 对于 $\gamma<0$,间隙指数消失,$\Delta \sim \exp(-cN)$,表明具有减弱电流的亚稳态。 我们的非微扰结果为驱动粒子系统中的大偏差和松弛动力学提供了见解。
We study current fluctuations in the Totally Asymmetric Simple Exclusion Process (TASEP) on a ring with $N$ sites and $p$ particles. By introducing a deformation parameter $\gamma$, we analyze the tilted operator that governs the statistics of the time-integrated current. Employing the coordinate Bethe ansatz, we derive implicit expressions for the scaled cumulant generating function (SCGF), i.e. the largest eigenvalue, and the spectral gap, both in terms of Bethe roots. Their asymptotic behaviour is characterized by using the geometric structure of Cassini oval. In the thermodynamic limit at fixed particle density, we identify a dynamical phase transition separating fluctuation regimes. For $\gamma>0$, the SCGF exhibits ballistic growth with system size, $\lambda_1 \sim N$. In contrast, for $\gamma<0$, the SCGF converges to $-1$ as $N\to\infty$. This transition is reflected in the spectral gap, which controls the system's relaxation timescale. For $\gamma>0$, the gap closes at polynomial speed, $\Delta \sim N^{-1}$, consistent with rapid relaxation with enhanced current. For $\gamma<0$, the gap vanishes exponentially, $\Delta \sim \exp(-cN)$, signaling metastability with diminished current. Our non-perturbative results provide insights into large deviations and the relaxation dynamics in driven particle systems.
- [17] arXiv:2507.17827 (替换) [中文pdf, pdf, html, 其他]
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标题: 无平均的流体力学——硬杆研究标题: Hydrodynamics without Averaging -- a Hard Rods Study评论: 43页,4图主题: 统计力学 (cond-mat.stat-mech)
在可积硬杆模型的例子中,我们研究了在单一粗粒化样本上的(广义)流体动力学近似的质量。这与传统的平均适当局部平衡态的方法相反。虽然在数学上更为模糊,新方法的一个主要优势是它使我们能够区分内在扩散与“对流引起的扩散”效应。对于硬杆,我们发现内在扩散不存在,这与最近的发现一致并加以澄清。有趣的是,结果也适用于非局部热态,证明在此模型中,流体动力学并不需要局部平衡的假设。
On the example of the integrable hard rods model we study the quality of the (generalized) hydrodynamic approximation on a single coarse-grained sample. This is opposed to the traditional approach which averages over an appropriate local equilibrium state. While mathematically more ambiguous, a major advantage of the new approach is that it allows us to disentangle intrinsic diffusion from `diffusion from convection' effects. For the hard rods we find intrinsic diffusion is absent, which agrees with and clarifies recent findings. Interestingly, the results also apply to not locally thermal states, demonstrating that hydrodynamics (in this model) does not require the assumption of local equilibrium.
- [18] arXiv:2507.20106 (替换) [中文pdf, pdf, 其他]
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标题: 二维或更高维超立方格子上 Hubbard 模型中非平凡局部守恒量的缺失标题: Absence of nontrivial local conserved quantities in the Hubbard model on the two or higher dimensional hypercubic lattice评论: 24页,8张图。版本2中的小修正主题: 统计力学 (cond-mat.stat-mech) ; 数学物理 (math-ph) ; 量子物理 (quant-ph)
通过扩展Shiraishi在2019年开发的策略,我们证明了在$d$维超立方晶格上具有$d\ge2$的标准Hubbard模型不承认任何非平凡的局部守恒量。 该定理强烈表明该模型是不可积的。 据我们所知,这是Shiraishi关于无守恒量证明的首次扩展到费米子模型。 尽管我们的证明遵循Shiraishi的原始策略,但与Shiraishi和Tasaki对$S=\tfrac12$二维或更高维量子自旋系统的相应定理的证明相比,它本质上更加微妙;我们的证明需要三个步骤,而Shiraishi和Tasaki的证明仅需两个步骤。 为了完成我们的证明,还需要部分确定一维Hubbard模型的守恒量。
By extending the strategy developed by Shiraishi in 2019, we prove that the standard Hubbard model on the $d$-dimensional hypercubic lattice with $d\ge2$ does not admit any nontrivial local conserved quantities. The theorem strongly suggests that the model is non-integrable. To our knowledge, this is the first extension of Shiraishi's proof of the absence of conserved quantities to a fermionic model. Although our proof follows the original strategy of Shiraishi, it is essentially more subtle compared with the proof by Shiraishi and Tasaki of the corresponding theorem for $S=\tfrac12$ quantum spin systems in two or higher dimensions; our proof requires three steps, while that of Shiraishi and Tasaki requires only two steps. It is also necessary to partially determine the conserved quantities of the one-dimensional Hubbard model to accomplish our proof.
- [19] arXiv:2410.06039 (替换) [中文pdf, pdf, html, 其他]
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标题: 量子增强热化标题: Quantum Enhancement of Thermalization期刊参考: 物理评论快报 135 (2025), 060404主题: 量子气体 (cond-mat.quant-gas) ; 统计力学 (cond-mat.stat-mech) ; 混沌动力学 (nlin.CD)
多体系统在具有大量自由度时的平衡性质通常预期由统计力学来描述。 这种预期与热化现象密切相关,表现为时间依赖可观测量中的能量均分,这在量子和经典系统中都会发生,但表现可能非常不同。 通过研究超冷玻色气体中单个晶格位点的种群动力学,我们表明,在量子系统中向平衡状态的弛豫过程可以比其经典对应物快几个数量级。 经典混沌量揭示了这是由于量子系统中的波包能够通过类似隧穿的机制逃离低效的经典输运区域。 由于所呈现的现象发生在广泛的参数范围内,并且在弱无序系统中仍然存在,我们预计它会在各种多体系统中出现,并且可以在最先进的量子模拟平台中直接进行实验验证。
Equilibrium properties of many-body systems with a large number of degrees of freedom are generally expected to be described by statistical mechanics. Such expectations are closely tied to the observation of thermalization, as manifested through equipartition in time-dependent observables, which takes place both in quantum and classical systems but may look very different in comparison. By studying the dynamics of individual lattice site populations in ultracold bosonic gases, we show that the process of relaxation toward equilibrium in a quantum system can be orders of magnitude faster than in its classical counterpart. Classical chaos quantifiers reveal that this is due to a wave packet in a quantum system being able to escape regions of inefficient classical transport by a mechanism akin to tunneling. Since the presented phenomenon takes place in a broad parameter range and persists in weakly disordered systems, we expect that it occurs in a variety of many-body systems and is amenable to direct experimental verification in state-of-the-art quantum simulation platforms.
- [20] arXiv:2410.24143 (替换) [中文pdf, pdf, html, 其他]
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标题: 量子群作为全局对称性 II. 库仑气体构造标题: Quantum Groups as Global Symmetries II. Coulomb Gas Construction评论: v1:55页,23图;v2:更正了打字错误;v3:改进了OPE系数的计算;v4:更正了打字错误,少量修改主题: 高能物理 - 理论 (hep-th) ; 统计力学 (cond-mat.stat-mech) ; 数学物理 (math-ph)
我们研究一种共形场论,它出现在具有$U_q(sl_2)$全局对称性的自旋链的无限体积极限中。 该理论中的大多数算符都是缺陷末端算符,这使得$U_q(sl_2)$对称性变换可以以一致的方式作用于它们。 我们使用库仑气体技术来构造关联函数并计算模型的所有OPE系数,同时证明由量子群对称性施加的性质确实被关联函数满足。 特别是,我们处理理论中存在的非手征算符。 自由玻色子实现阐明了附加到算符上的缺陷的起源。 我们还评论了量子群在广义最小模型中的作用。
We study a conformal field theory that arises in the infinite-volume limit of a spin chain with $U_q(sl_2)$ global symmetry. Most operators in the theory are defect-ending operators which allows $U_q(sl_2)$ symmetry transformations to act on them in a consistent way. We use Coulomb gas techniques to construct correlation functions and compute all OPE coefficients of the model, as well as to prove that the properties imposed by the quantum group symmetry are indeed satisfied by the correlation functions. In particular, we treat the non-chiral operators present in the theory. Free boson realization elucidates the origin of the defects attached to the operators. We also comment on the role of quantum group in generalized minimal models.
- [21] arXiv:2411.09761 (替换) [中文pdf, pdf, html, 其他]
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标题: 各向异性反铁磁体的有效场理论:禁带戈德斯通子、伪戈德斯通子和相变标题: An EFT for anisotropic anti-ferromagnets: gapped Goldstones, pseudo-Goldstones, and phase transitions评论: 讨论已添加,拼写错误已修复主题: 强关联电子 (cond-mat.str-el) ; 统计力学 (cond-mat.stat-mech) ; 高能物理 - 理论 (hep-th)
我们构建并讨论了在外部磁场存在下各向异性反铁磁体的低能有效场论。 这种有效理论简单但丰富,具有多种现象,如禁带戈德斯通玻色子、伪戈德斯通玻色子和“自旋翻转”相变,所有这些都在该理论的有效范围内。 我们还详细讨论了在磁场存在下自由理论的量子化过程,由于存在单时间导数项,这一过程变得不平凡。 这类材料为量子场论中的奇异现象提供了一个宝贵的测试领域。 此外,我们明确地将有效理论与特定反铁磁体(即氧化镍)的短距离理论进行了匹配。 后者尤其相关,鉴于最近提出利用这种材料来寻找轻暗物质的建议。 作为我们研究的副产品,我们还重新评估了离散对称性在磁性材料中的作用,并以完全符合正确低能有效场论理念的方式呈现。
We build and discuss a low energy effective field theory for anisotropic anti-ferromagnets in presence of an external magnetic field. Such an effective theory is simple yet rich, and features a number of phenomena such as the appearance of gapped Goldstones, pseudo-Goldstones and a "spin flop" phase transition, all within the regime of validity of the theory. We also discuss in detail, the quantization procedure of the free theory in the presence of a magnetic field, which is made non-trivial by the presence of a single-time derivative term. This class of materials make a precious test field for exotic phenomena in quantum field theory. Moreover, we explicitly perform the matching of the effective theory to the short distance theory of a specific anti-ferromagnet, namely, nickel oxide. The latter is particularly relevant in light of recent proposals of employing this material towards the hunt for light dark matter. As a byproduct of our study, we also re-evaluate the role played by discrete symmetries in magnetic materials, presenting it in a way that is completely consistent with the proper low energy EFT ideology.
- [22] arXiv:2503.18068 (替换) [中文pdf, pdf, html, 其他]
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标题: 伪巨数涨落和微泳体悬浮液中的向列序标题: Pseudo-giant number fluctuations and nematic order in microswimmer suspensionsIsmail El Korde, Dóra Bárdfalvy, Jason M. Lewis, Alexander Morozov, Cesare Nardini, Joakim Stenhammar评论: 已被《物理评论快报》接受发表主题: 软凝聚态物理 (cond-mat.soft) ; 统计力学 (cond-mat.stat-mech) ; 生物物理 (physics.bio-ph)
巨数波动(GNFs),其中局部粒子数$\langle N \rangle$的标准偏差$\Delta N$比$\sqrt{\langle N \rangle}$增长得更快,是具有取向序的干活性物质系统的一个标志性特性,例如振动板上的颗粒集合。这与动量守恒的(“湿”)活性物质系统形成对比,例如游泳细菌的悬浮液,在这些系统中没有关于GNFs的理论预测,尽管已经报告了许多关于这种增强波动的实验观察。在本信中,我们数值确认了在经历集体运动转变的三维推动者微游动器悬浮液中超级高斯数波动的出现。这些波动在转变之上急剧出现,但仅当细菌的持续长度$\ell_p = v_s / \lambda$足够大时才出现,其中$v_s$是细菌的游泳速度,$\lambda$是翻转率。 关键的是,这些“伪GNFs”与真正的GNFs不同,因为它们仅出现在集体运动状态下向列畴典型尺寸$\xi$以下的长度尺度上,而该尺寸又与单个游动体的持久长度$\ell_p$成正比。因此,我们的结果表明,在生物活性物质系统中观察到的密度涨落增强实际上是在介观长度尺度之外会衰减的瞬时效应,并引发了在流体流动存在的情况下,“真正”的具有普遍性质的GNFs能存在到何种程度的问题。
Giant number fluctuations (GNFs), whereby the standard deviation $\Delta N$ in the local number of particles $\langle N \rangle$ grows faster than $\sqrt{\langle N \rangle}$, are a hallmark property of dry active matter systems with orientational order, such as a collection of granular particles on a vibrated plate. This contrasts with momentum-conserving ("wet") active matter systems, such as suspensions of swimming bacteria, where no theoretical prediction of GNFs exist, although numerous experimental observations of such enhanced fluctuations have been reported. In this Letter, we numerically confirm the emergence of super-Gaussian number fluctuations in a 3-dimensional suspension of pusher microswimmers undergoing a transition to collective motion. These fluctuations emerge sharply above the transition, but only for sufficiently large values of the bacterial persistence length $\ell_p = v_s / \lambda$, where $v_s$ is the bacterial swimming speed and $\lambda$ the tumbling rate. Crucially, these "pseudo-GNFs" differ from true GNFs, as they only occur on length scales shorter than the typical size $\xi$ of nematic patches in the collective motion state, which is in turn proportional to the single-swimmer persistence length $\ell_p$. Our results thus suggest that observations of enhanced density fluctuations in biological active matter systems actually represent transient effects that decay away beyond mesoscopic length scales, and raises the question to what extent "true" GNFs with universal properties can exist in the presence of fluid flows.
- [23] arXiv:2504.02937 (替换) [中文pdf, pdf, html, 其他]
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标题: 耗散动力学中的渐近异常稳态标题: Asymptotic Exceptional Steady States in Dissipative Dynamics评论: 7+5页,3+5图主题: 量子物理 (quant-ph) ; 量子气体 (cond-mat.quant-gas) ; 统计力学 (cond-mat.stat-mech) ; 强关联电子 (cond-mat.str-el)
谱退化在耗散动力学的Liouvillian生成元中通常作为例外点出现,此时相应的非厄米算符变得不可对角化。 稳态,即Liouvillians的零模,被视为这一规则的一个基本例外,因为一个不可能定理排除了那里的不可对角化退化。 在这里,我们证明耗散态制备中的发散时间尺度问题在很大程度上等同于在热力学极限下向禁止的例外稳态场景的渐近接近。 通过对从量子主方程中编码的NP完全可满足性问题到对称保护拓扑相的耗散制备的案例研究,我们揭示了当前问题的计算复杂性与趋向例外稳态的有限尺寸标度之间的密切关系,展示了指数和多项式标度的实例。 将Lindblad主方程中量子跳跃的权重$W$作为参数进行形式处理,我们表明在物理值$W=1$处的例外稳态可以被理解为标志动力不稳定性开始的临界点。
Spectral degeneracies in Liouvillian generators of dissipative dynamics generically occur as exceptional points, where the corresponding non-Hermitian operator becomes non-diagonalizable. Steady states, i.e. zero-modes of Liouvillians, are considered a fundamental exception to this rule since a no-go theorem excludes non-diagonalizable degeneracies there. Here, we demonstrate that the crucial issue of diverging timescales in dissipative state preparation is largely tantamount to an asymptotic approach towards the forbidden scenario of an exceptional steady state in the thermodynamic limit. With case studies ranging from NP-complete satisfiability problems encoded in a quantum master equation to the dissipative preparation of a symmetry protected topological phase, we reveal the close relation between the computational complexity of the problem at hand, and the finite size scaling towards the exceptional steady state, exemplifying both exponential and polynomial scaling. Formally treating the weight $W$ of quantum jumps in the Lindblad master equation as a parameter, we show that exceptional steady states at the physical value $W=1$ may be understood as a critical point hallmarking the onset of dynamical instability.
- [24] arXiv:2507.22461 (替换) [中文pdf, pdf, html, 其他]
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标题: 在里德伯原子量子模拟器中实现海森堡型量子自旋模型的建议标题: Proposal for realizing Heisenberg-type quantum-spin models in Rydberg atom quantum simulators评论: 主:10名法师,4个图示,补充材料:17页,13个图示,10张表格主题: 量子气体 (cond-mat.quant-gas) ; 统计力学 (cond-mat.stat-mech) ; 强关联电子 (cond-mat.str-el) ; 原子物理 (physics.atom-ph) ; 量子物理 (quant-ph)
我们研究两个里德伯原子$|nS_{1/2}, m_J\rangle$和$|(n+1)S_{1/2}, m_J\rangle$之间相互作用的磁场依赖性。在这一设置中,有效自旋-1/2哈密顿量的形式为{\it XXZ}模型。我们表明{\it XXZ}模型的各向异性参数可以通过施加磁场进行调节,并且特别地,在福斯特共振点附近该参数会发生剧烈变化。基于这一结果,我们提出在不依赖弗洛凯工程的情况下,实现自旋-1/2和自旋-1海森堡型量子自旋模型的实验方案。我们的结果为未来里德伯原子量子模拟器的实验提供了指导,并为海森堡模型中出现的量子多体现象提供了见解。
We investigate the magnetic-field dependence of the interaction between two Rydberg atoms, $|nS_{1/2}, m_J\rangle$ and $|(n+1)S_{1/2}, m_J\rangle$. In this setting, the effective spin-1/2 Hamiltonian takes the form of an {\it XXZ} model. We show that the anisotropy parameter of the {\it XXZ} model can be tuned by applying a magnetic field, and in particular, that it changes drastically near the F\"orster resonance points. Based on this result, we propose experimental realizations of spin-1/2 and spin-1 Heisenberg-type quantum spin models in Rydberg atom quantum simulators, without relying on Floquet engineering. Our results provide guidance for future experiments of Rydberg atom quantum simulators and offer insight into quantum many-body phenomena emerging in the Heisenberg model.