An equation of state for active matter

TL;DR

This paper derives an equation of state for active matter by characterizing steady states of active Brownian particles, revealing the significance of many-body interactions even at low densities.

Contribution

It provides a theoretical framework for the steady-state distribution and macroscopic properties of active matter, incorporating many-body effects at low densities.

Findings

Macroscopic quantities can be computed similarly to equilibrium systems.

Derived expressions for pressure and correlation functions.

Numerical simulations confirm theoretical predictions.

Abstract

We characterise the steady states of a suspension of two-dimensional active brownian particles (ABPs). We calculate the steady-state probability distribution to lowest order in Peclet number. We show that macroscopic quantities can be calculated in analogous way to equilibrium systems using this probability distribution. We then derive expressions for the macroscopic pressure and position-orientation correlation functions. We check our results by direct comparison with extensive numerical simulations. A key finding is the importance of many-body effective interactions even at very low densities.