Athermal Phase Separation of Self-Propelled Particles with no Alignment

TL;DR

This paper investigates how self-propelled particles without alignment interactions undergo phase separation and clustering, demonstrating that such behaviors are generic in non-equilibrium active matter systems.

Contribution

It provides a combined numerical and analytical study of phase separation in self-propelled particles lacking alignment, highlighting the universality of clustering in active systems.

Findings

Isotropic fluid phase separates below close packing

Large number fluctuations observed in the system

Clustering behavior is a generic property of active matter

Abstract

We study numerically and analytically a model of self-propelled polar disks on a substrate in two dimensions. The particles interact via isotropic repulsive forces and are subject to rotational noise, but there is no aligning interaction. As a result, the system does not exhibit an ordered state. The isotropic fluid phase separates well below close packing and exhibits the large number fluctuations and clustering found ubiquitously in active systems. Our work shows that this behavior is a generic property of systems that are driven out of equilibrium locally, as for instance by self propulsion.