Noise-induced vortex reversal of self-propelled particles

TL;DR

This paper investigates how noise can induce vortex reversal in a 2D system of self-propelled particles, revealing a hierarchical reversal process and the effects of noise and particle number on reversal rates.

Contribution

It introduces a detailed analysis of noise-induced vortex reversal in self-propelled particles, identifying the reversal mechanism and rate dependencies on noise and particle number.

Findings

Reversal occurs hierarchically starting from the periphery.

Reversal rate decreases exponentially with inverse noise intensity.

Reversal rate varies nonmonotonically with particle number, with a minimum at intermediate N.

Abstract

We report an interesting phenomenon of noise-induced vortex reversal in a two-dimensional system of self-propelled particles (SPP) with soft-core interactions. With the aid of forward flux sampling, we analyze the configurations along the reversal pathway and thus identify the mechanism of vortex reversal. We find that statistically the reversal exhibits a hierarchical process: those particles at the periphery first change their motion directions, and then more inner layers of particles reverse later on. Furthermore, we calculate the dependence of the average reversal rate on noise intensity $D$ and the number $N$ of SPP. We find that the rate decreases exponentially with the reciprocal of $D$. Interestingly, the rate varies nonmonotonically with $N$ and a minimal rate exists for an intermediate value of $N$.