Generalized thermodynamics of Motility-Induced Phase Separation: Phase equilibria, Laplace pressure, and change of ensembles

TL;DR

This paper develops a generalized thermodynamic framework for motility-induced phase separation in active matter, incorporating surface tension and forces to analyze phase equilibria and ensemble changes.

Contribution

It introduces a nonequilibrium thermodynamic formalism that extends classical concepts to active systems with MIPS, including generalized surface tension and forces.

Findings

Identification of a generalized surface tension controlling finite-size effects.

Development of generalized forces enabling new thermodynamic ensembles.

Application of the framework to active particles with different interaction types.

Abstract

Motility-induced phase separation (MIPS) leads to cohesive active matter in the absence of cohesive forces. We present, extend and illustrate a recent generalized thermodynamic formalism which accounts for its binodal curve. Using this formalism, we identify both a generalized surface tension, that controls finite-size corrections to coexisting densities, and generalized forces, that can be used to construct new thermodynamic ensembles. Our framework is based on a nonequilibrium generalization of the Cahn-Hilliard equation and we discuss its application to active particles interacting either via quorum-sensing interactions or directly through pairwise forces.