Active motion assisted by correlated stochastic torques

TL;DR

This paper investigates how correlated stochastic torques influence the motion of active particles, revealing nonmonotonic effects on diffusion and trajectory persistence due to noise correlations.

Contribution

It introduces a model with Ornstein-Uhlenbeck process-driven angular noise, showing how correlations affect particle diffusion and trajectory behavior in active matter.

Findings

Effective diffusion coefficient exhibits a maximum at specific correlation times and noise intensities.

Correlated angular noise can straighten curved trajectories, enhancing diffusion.

Trajectory persistence increases with noise correlation time.

Abstract

The stochastic dynamics of an active particle undergoing a constant speed and additionally driven by an overall fluctuating torque is investigated. The random torque forces are expressed by a stochastic differential equation for the angular dynamics of the particle determining the orientation of motion. In addition to a constant torque, the particle is supplemented by random torques which are modeled as an Ornstein-Uhlenbeck process with given correlation time $\tau_c$. These nonvanishing correlations cause a persistence of the particles' trajectories and a change of the effective spatial diffusion coefficient. We discuss the mean square displacement as a function of the correlation time and the noise intensity and detect a nonmonotonic dependence of the effective diffusion coefficient with respect to both correlation time and noise strength. A maximal diffusion behavior is obtained if the correlated angular noise straightens the curved trajectories, interrupted by small pirouettes, whereby the correlated noise amplifies a straightening of the curved trajectories caused by the constant torque.