标题： 运动约束在模型活性物质时间反演对称性破缺中的作用 显示英文标题

标题： Role of kinematic constraints in the time reversal symmetry breaking of a model active matter

摘要： 活性物质系统本质上是非平衡的，并通过利用其内部能源来执行机械功。 时间反演对称性破坏（BTRS）是这种耗散非平衡动力学的特征。 我们引入了一种稳健、实验可访问、非侵入性和定量的BTRS度量方法，该方法基于碰撞事件中的Kullback-Leibler散度，在我们新型的人工活性物质中进行了演示，该物质由电池供电的球形滚动机器人组成，其在不同运动模式下的能量特性可以高精度测量。 我们的无量纲度量表征了来自与环境相互作用的运动学约束如何影响耗散和内部能量特性。 我们提出这种BTRS的度量方法作为远离平衡的实证估计。 从能量角度出发，我们展示了非平凡的涨落对称性，这揭示了活性能量可能普遍的热力学特性。 作为我们实验性活性系统中BTRS的多体结果，我们演示了由活性引起的聚集现象，这在平衡情况下没有对应物。 显示英文摘要

摘要： Active-matter systems are inherently out-of-equilibrium and perform mechanical work by utilizing their internal energy sources. Breakdown of time-reversal symmetry (BTRS) is a hallmark of such dissipative non-equilibrium dynamics. We introduce a robust, experimentally accessible, noninvasive, quantitative measure of BTRS in terms of the Kullback-Leibler divergence in collision events, demonstrated in our novel artificial active matter, comprised of battery-powered spherical rolling robots whose energetics in different modes of motion can be measured with high precision. Our dimensionless measure characterizes how dissipation and internal energetics are influenced by kinematic constraints from interactions with the environment. We propose this measure of BTRS as an empirical estimate of the distance from equilibrium. An energetic insight into this departure of active matter from equilibrium comes from our demonstration of a non-trivial fluctuation symmetry, which reveals a potentially universal thermodynamic characteristic of active energetics. As a many-body consequence of BTRS in our experimental active system, we demonstrate the emergence of activity-induced herding, which has no equilibrium analogue.