We examine an assembly of repulsive disks interacting with a random obstacle array under a periodic drive and find a transition from reversible to irreversible dynamics as a function of drive amplitude or disk density. At low densities and drives, the system rapidly forms a reversible state where the disks return to their exact positions at the end of each cycle. In contrast, at high amplitudes or high densities, the system enters an irreversible state where the disks exhibit normal diffusion. Between these two regimes, there can be an intermediate irreversible state where most of the system is reversible, but localized irreversible regions are present that are prevented from spreading through the system due to a screening effect from the obstacles. We also find states that we term “combinatorial reversible states” in which the disks return to their original positions after multiple driving cycles. In these states, individual disks exchange positions but form the same configurations during the subcycles of the larger reversible cycle.

中文翻译：

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随机障碍物阵列中周期性驱动圆盘的可逆、不可逆和混合机制

我们检查了在周期性驱动下与随机障碍物阵列相互作用的排斥圆盘的集合，并发现了从可逆到不可逆动力学的转变，作为驱动振幅或圆盘密度的函数。在低密度和驱动器下，系统快速形成可逆状态，其中磁盘在每个周期结束时返回到其精确位置。相反，在高振幅或高密度下，系统进入不可逆状态，其中圆盘表现出正常扩散。在这两种状态之间，可能存在中间不可逆状态，其中系统的大部分是可逆的，但存在局部不可逆区域，由于障碍物的屏蔽效应，这些区域无法在系统中扩散。我们还发现了我们称之为“组合可逆状态”的状态，其中磁盘在多个驱动周期后返回到其原始位置。在这些状态下，各个磁盘交换位置，但在较大可逆循环的子循环期间形成相同的配置。