标题： 视角：在粗粒度观测系统中的时间不可逆性 显示英文标题

标题： Perspective: Time irreversibility in systems observed at coarse resolution

摘要： 非平衡物理中，时间反演对称性的破坏，即细致平衡的破坏，是核心问题，也是生命的前提条件。然而，在实践中，即从观测中，要明确地定义和量化时间反演对称性（以及其破坏）却相当具有挑战性。对复杂系统的测量具有有限的分辨率，并通常探测的是底层动力学的低维投影，这众所周知会引入记忆效应。在许多微观状态被“合并”到同一可观测“状态”时，或者当引入“反应坐标”以降低数据维度时，微观动力学中时间反演对称性被破坏的特征会变得扭曲或被掩盖。在本文中，我们强调在定义和讨论时间反演对称性以及量化其破坏时，对微观动力学的精确假设、粗粒化和其他简化措施并不是技术细节。这些假设决定了所得出的结论是否符合物理实际或存在矛盾。我们总结了该领域的最新发现，并反思了关键挑战。 显示英文摘要

摘要： A broken time-reversal symmetry, i.e. broken detailed balance, is central to non-equilibrium physics and is a prerequisite for life. However, it turns out to be quite challenging to unambiguously define and quantify time-reversal symmetry (and violations thereof) in practice, that is, from observations. Measurements on complex systems have a finite resolution and generally probe low-dimensional projections of the underlying dynamics, which are well known to introduce memory. In situations where many microscopic states become "lumped" onto the same observable "state" or when introducing "reaction coordinates" to reduce the dimensionality of data, signatures of a broken time-reversal symmetry in the microscopic dynamics become distorted or masked. In this perspective we highlight why in defining and discussing time-reversal symmetry, and quantifying its violations, the precise underlying assumptions on the microscopic dynamics, the coarse graining, and further reductions, are not a technical detail. These assumptions decide whether the conclusions that are drawn are physically sound or inconsistent. We summarize recent findings in the field and reflect upon key challenges.