# The stability phase diagram of active Brownian particles

## TL;DR

This paper investigates how motility and friction influence phase separation in active Brownian particles, revealing that motility can stabilize the homogeneous phase and that friction controls this process, enabling experimental tuning of phase behavior.

## Contribution

It introduces a quantitative prediction of the spinodal line for active Brownian particles and highlights friction as a key control parameter in motility-induced phase separation.

## Key findings

- Motility promotes the homogeneous phase by resolving collisions.
- Friction controls the transition between phases.
- The phase diagram can be experimentally tuned via friction.

## Abstract

Phase separation in a low-density gas-like phase and a high-density liquid-like one is a common trait of biological and synthetic self-propelling particles' systems. The competition between motility and stochastic forces is assumed to fix the boundary between the homogeneous and the phase-separated phase. Here we demonstrate that motility does also promote the homogeneous phase allowing particles to resolve their collisions. This new understanding allows quantitatively predicting the spinodal-line of hard self-propelling Brownian particles, the prototypical model exhibiting a motility induced phase separation. Furthermore, we demonstrate that frictional forces control the physical process by which motility promotes the homogeneous phase. Hence, friction emerges as an experimentally variable parameter to control the motility induced phase diagram.