Diversity of phase transitions and phase separations in active fluids

TL;DR

This paper unifies various phase transitions and coexistences in active fluids using hydrodynamic equations, revealing new phases and critical points in active matter systems.

Contribution

It introduces a unified framework for diverse phase behaviors in active fluids and predicts novel phases and critical phenomena.

Findings

Unified description of phase transitions in active fluids

Discovery of a novel co-moving coexistence phase

Identification of a potential new critical point

Abstract

Active matter is not only indispensable to our understanding of diverse biological processes, but also provides a fertile ground for discovering novel physics. Many emergent properties impossible for equilibrium systems have been demonstrated in active systems. These emergent features include motility-induced phase separation, long-ranged ordered (collective motion) phase in two dimensions, and order-disorder phase co-existences (banding and reverse-banding regimes). Here, we unify these diverse phase transitions and phase co-existences into a single formulation based on generic hydrodynamic equations for active fluids. We also reveal a novel co-moving co-existence phase and a putative novel critical point.