Analytical approach to chiral active systems: suppressed phase separation of interacting Brownian circle swimmers

TL;DR

This paper develops a predictive field theory for chiral active systems, specifically Brownian circle swimmers, showing that their angular propulsion suppresses phase separation, with results validated by simulations.

Contribution

The authors derive a novel field theory linking circle swimmers to noncircling particles, predicting suppression of phase separation due to angular propulsion, supported by simulations.

Findings

Angular propulsion suppresses motility-induced phase separation.

Analytical expressions for spinodal and critical point depend on angular propulsion.

Good agreement between theoretical predictions and Brownian dynamics simulations.

Abstract

We consider chirality in active systems by exemplarily studying the phase behavior of planar systems of interacting Brownian circle swimmers with a spherical shape. Continuing previous work presented in [G.-J. Liao, S. H. L. Klapp, Soft Matter, 2018, 14, 7873-7882], we derive a predictive field theory that is able to describe the collective dynamics of circle swimmers. The theory yields a mapping between circle swimmers and noncircling active Brownian particles and predicts that the angular propulsion of the particles leads to a suppression of their motility-induced phase separation, being in line with previous simulation results. In addition, the theory provides analytical expressions for the spinodal corresponding to the onset of motility-induced phase separation and the associated critical point as well as for their dependence on the angular propulsion of the circle swimmers. We confirm our findings by Brownian dynamics simulations and an analysis of the collective dynamics using a weighted graph-theoretical network. The agreement between results from theory and simulation is found to be good.