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arXiv 2407.08833cond-mat.stat-mech
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边界诱导的经典广义吉布斯集合与角动量

Boundary-induced classical Generalized Gibbs Ensemble with angular momentum

Los Alamos National Laboratory(洛斯阿拉莫斯国家实验室)

Francesco Caravelli, Marc D. Vuffray

AI总结:

研究发现边界形状影响经典硬盘系统热化行为,不同边界收敛于不同集合,角动量作为额外守恒量,且GGE违反时间反演对称性。

摘要:

我们研究了边界形状对受限于经典硬盘系统在低填充分数下的热化行为的影响,因此处于气体态。我们利用分析计算和数值模拟,并利用最大熵原理的洞察,探讨了边界几何如何影响此类系统的热平衡过程。我们的模拟涉及将硬盘限制在不同边界形状内,使用事件驱动和时间驱动模拟,从传统方形边界到圆形边界,显示两者收敛到不同的集合。前者收敛到吉布斯集合,后者收敛到广义吉布斯集合(GGE),角动量作为额外守恒量。我们引入了一个序参量来表征偏离吉布斯集合的偏差,并显示GGE不具有时间反演对称性,它违反了厄尔戈迪性并导致近边界凝聚现象。由于这一点,我们主张在这种情况中麦克斯韦-玻尔兹曼方法应包括角动量。我们最后讨论这些结果如何导致对玻尔-范·莱文定理的特殊违反。

英文摘要:

We investigate the impact of the boundary shape on the thermalization behavior of a confined system of classical hard disks at low packing fraction and thus in the gas regime. We use both analytical calculations and numerical simulations, and leveraging on the insights from the maximum entropy principle, we explore how the geometry of the boundary influences the thermal equilibration process in such systems. Our simulations involve hard disks confined within varying boundary shapes, using both event-driven and time-driven simulations, ranging from conventional square boundaries to circular boundaries, showing that the two converge to different ensembles. The former converges to the Gibbs Ensemble, while the latter converges to the Generalized Gibbs Ensemble (GGE), with angular momentum as the extra conserved quantity. We introduce an order parameter to characterize the deviations from the Gibbs ensemble, and show that the GGE is not time-reversal invariant, it violates ergodicity and leads to a near-boundary condensation phenomenon. Because of this, we argue that Monte Carlo methods should include angular momentum in this situation. We conclude by discussing how these results lead to peculiar violations of the Bohr-van Leeuwen theorem.

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