Thiffeault Jean-Luc, Guo Jiajia
Department of Mathematics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Department of Mathematics, University of Michigan, Ann Arbor, Michigan 48109, USA.
Phys Rev E. 2022 Jul;106(1):L012603. doi: 10.1103/PhysRevE.106.L012603.
The active Brownian particle (ABP) model describes a swimmer, synthetic or living, whose direction of swimming is a Brownian motion. The swimming is due to a propulsion force, and the fluctuations are typically thermal in origin. We present a two-dimensional model where the fluctuations arise from nonthermal noise in a propelling force acting at a single point, such as that due to a flagellum. We take the overdamped limit and find several modifications to the traditional ABP model. Since the fluctuating force causes a fluctuating torque, the diffusion tensor describing the process has a coupling between translational and rotational degrees of freedom. An anisotropic particle also exhibits a mass-dependent noise-induced drift, which does not disappear in the overdamped limit. We show that these effects have measurable consequences for the long-time diffusivity of active particles, in particular adding a contribution that is independent of where the force acts.
活性布朗粒子（ABP）模型描述了一个游动者，它可以是合成的或有生命的，其游动方向为布朗运动。游动是由推进力引起的，而涨落通常源于热。我们提出了一个二维模型，其中涨落源于作用于单个点的推进力中的非热噪声，例如由鞭毛产生的力。我们采用过阻尼极限，并发现了对传统ABP模型的若干修正。由于涨落力会导致涨落扭矩，描述该过程的扩散张量在平动和转动自由度之间存在耦合。一个各向异性粒子还表现出与质量相关的噪声诱导漂移，在过阻尼极限下这种漂移不会消失。我们表明，这些效应对于活性粒子的长时间扩散率具有可测量的影响，特别是增加了一个与力作用位置无关的贡献。
