Velocity alignment promotes motility-induced phase separation

TL;DR

This paper investigates how velocity alignment influences phase separation in active particles, revealing that increased alignment promotes clustering and demixing by slowing reorientation dynamics and enhancing correlations.

Contribution

It introduces a combined particle-based and mean-field model to analyze the role of velocity alignment in motility-induced phase separation.

Findings

Velocity alignment enhances clustering in active particles.

Increased alignment leads to larger orientational correlations.

Slower reorientation dynamics promote phase separation.

Abstract

We study the phase behavior of polar Active Brownian Particles moving in two-spatial dimensions and interacting through volume exclusion and velocity alignment. We combine particle-based simulations of the microscopic model with a simple mean-field kinetic model to understand the impact of velocity alignment on the motility-induced phase separation of self-propelled disks. We show that, as the alignment strength is increased, approaching the onset of collective motion from below, orientational correlations grow, rendering the diffusive reorientation dynamics slower. As a consequence, the tendency of particles to aggregate into isotropic clusters is enhanced, favoring the complete de-mixing of the system into a low and high-density phase.