An Introduction to Motility-Induced Phase Separation

TL;DR

This paper reviews the fundamental mechanisms and recent theoretical and computational advances in understanding motility-induced phase separation, a key phenomenon in active matter systems without alignment interactions.

Contribution

It provides a comprehensive overview of the main theoretical and computational efforts over the last decade in studying MIPS in microscopic active particle models.

Findings

Understanding of the feedback loop causing phase separation

Characterization of structural properties of MIPS

Insights into dynamical behaviors of active particles

Abstract

Motility-induced phase separation, MIPS, is arguably the most well-studied collective phenomenon occurring in active matter without alignment interactions (scalar active matter). Its basic origin is simple: since self-propelled particles accumulate where they move slowly, having a propulsion speed that decreases steeply enough with density, due to collisions or chemical interactions, leads to a feedback loop that induces the formation of a dense phase. In these notes, I will discuss some of the main theoretical and computational efforts that have been made over the last decade in understanding the basic structural and dynamical properties of MIPS phase coexistence in microscopic active particle models.