Sorbonne Université, CNRS, Laboratoire de Physico-Chimie des Électrolytes et Nanosystèmes Interfaciaux (PHENIX), 4 Place Jussieu, 75005 Paris, France.
Dipartimento di Ingegneria, Università della Campania "Luigi Vanvitelli", 81031 Aversa (CE), Italy.
Phys Rev Lett. 2022 Jan 21;128(3):038001. doi: 10.1103/PhysRevLett.128.038001.
We calculate the diffusion coefficient of an active tracer in a schematic crowded environment, represented as a lattice gas of passive particles with hardcore interactions. Starting from the master equation of the problem, we put forward a closure approximation that goes beyond trivial mean field and provides the diffusion coefficient for an arbitrary density of crowders in the system. We show that our approximation is accurate for a very wide range of parameters, and that it correctly captures numerous nonequilibrium effects, which are the signature of the activity in the system. In addition to the determination of the diffusion coefficient of the tracer, our approach allows us to characterize the perturbation of the environment induced by the displacement of the active tracer. Finally, we consider the asymptotic regimes of low and high densities, in which the expression of the diffusion coefficient of the tracer becomes explicit, and which we argue to be exact.
我们计算了在示意性拥挤环境中，活性示踪剂的扩散系数，该环境表示为具有硬芯相互作用的被动粒子的晶格气体。从问题的主方程出发，我们提出了一种超越简单平均场的封闭近似，为系统中任意拥挤密度提供了扩散系数。我们表明，我们的近似在非常广泛的参数范围内是准确的，并且正确地捕捉到了许多非平衡效应，这些效应是系统活性的特征。除了确定示踪剂的扩散系数外，我们的方法还允许我们描述由活性示踪剂的位移引起的环境的扰动。最后，我们考虑低和高密度的渐近情况，在这些情况下，示踪剂的扩散系数的表达式变得显式，我们认为这些表达式是精确的。
