Anomalous velocity distributions in active Brownian suspensions

TL;DR

This paper combines large-scale simulations and analytical theory to study the non-equilibrium velocity distribution of active Brownian particles, revealing universal anomalous behaviors largely independent of system specifics.

Contribution

The authors develop and analytically solve a one-particle model that captures the universal velocity distribution features observed in simulations of active Brownian suspensions.

Findings

Velocity distribution decays as 1/v over multiple decades

Distribution crosses over to Gaussian decay at large velocities

Simulation results agree with the analytical model across damping regimes

Abstract

Large scale simulations and analytical theory have been combined to obtain the non-equilibrium velocity distribution, $f(v)$, of randomly accelerated particles in suspension. The simulations are based on an event-driven algorithm, generalised to include friction. They reveal strongly anomalous but largely universal distributions which are independent of volume fraction and collision processes, which suggests a one-particle model should capture all the essential features. We have formulated this one-particle model and solved it analytically in the limit of strong damping, where we find that $f(v)$ decays as $1/v$ for multiple decades, eventually crossing over to a Gaussian decay for the largest velocities. Many particle simulations and numerical solution of the one-particle model agree for all values of the damping.