Generic phase diagram of active polar films

TL;DR

This paper presents a theoretical phase diagram for active polar gels, predicting modulated flowing phases and phase separation, which align with experimental observations of biological active systems.

Contribution

It introduces a generalized hydrodynamics framework to analyze the phase behavior of active polar gels, revealing new phases and transitions.

Findings

Prediction of modulated flowing phases

Identification of macroscopic phase separation at high activity

Qualitative agreement with experimental active systems

Abstract

We study theoretically the phase diagram of compressible active polar gels such as the actin network of eukaryotic cells. Using generalized hydrodynamics equations, we perform a linear stability analysis of the uniform states in the case of an infinite bidimensional active gel to obtain the dynamic phase diagram of active polar films. We predict in particular modulated flowing phases, and a macroscopic phase separation at high activity. This qualitatively accounts for experimental observations of various active systems, such as acto-myosin gels, microtubules and kinesins in vitro solutions, or swimming bacterial colonies.