Phase separation in a mixture of proliferating and motile active matter

TL;DR

This paper investigates how a dense mixture of motile and proliferating particles undergoes phase separation driven by activity and interactions, revealing a new type of phase transition relevant to biological systems.

Contribution

It demonstrates that phase separation occurs in a binary active matter system with proliferation and motility, introducing an effective model with attractive interactions to explain the phenomenon.

Findings

Phase separation occurs at high density and low self-propulsion.

Interactions between motile particles induce condensation.

An effective attractive model reproduces the phase behavior.

Abstract

Proliferation and motility are ubiquitous drivers of activity in biological systems. Here, we study a dense binary mixture of motile and proliferating particles with exclusively repulsive interactions, where homeostasis in the proliferating subpopulation is maintained by pressure-induced removal. Using computer simulations, we show that phase separation emerges naturally in this system at high density and weak enough self-propulsion. We show that condensation is caused by interactions between motile particles induced by the growing phase, and recapitulate this behavior in an effective model of only motile particles with attractive interactions. Our results establish a new type of phase transition and pave a way to reinterpret the physics of dense cellular populations, such as bacterial colonies or tumors, as systems of mixed active matter.