Motility Induced Phase-separation of Active Particles
Julien Tailleur
Laboratoire Matière et Systèmes complexes, Paris Diderot
Mon, Mar. 05th 2018, 14:00-15:00
Salle Claude Itzykson, Bât. 774, Orme des Merisiers

Passive, thermal particles may undergo phase-separation when attractive forces overcome the entropic cost of creating dense groups of particles. Active, self-propelled particles need no attractive forces to experience the same fate. When their propulsion speeds decreases sufficiently rapidly as the local density of particle increases, whether due to quorum-sensing like interactions or due to repulsive forces, they may undergo a so-called "Motility Induced Phase Separation" (MIPS).

In this talk I will both review this phenomenon and present a recent theory that accounts quantitatively for the phase equilibria observed in MIPS. Starting from a continuum description of scalar active matter, akin to a generalized Cahn-Hilliard equation, I will show how phase-separated profiles emerge from the extremization of an effective free energy. I will illustrate this approach on two well-known models: self-propelled particles interacting either through a density-dependent propulsion speed or via direct pairwise forces and show our theory to account quantitatively for their phase diagrams, providing a unified description of MIPS.

Contact : Marco SCHIRO


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