Phase Equilibria in Motility-Induced Phase Separation
Motility-induced phase separation (MIPS) arises generically in fluids of self-propelled particles when interactions lead to a kinetic slowdown at high densities. We will show how a scalar continuum description of active matter, akin to a generalized Cahn-Hilliard equation, provides a unified description of MIPS. Indeed, it allows to understand the phase equilibria and quantitatively account for the phase diagram and finite size effects of the two models in which MIPS have been most commonly studied: self-propelled particles interacting either through a density-dependent propulsion speed or via direct pairwise forces.