Long-wavelength instabilities in a system of interacting active particles

TL;DR

This paper develops a continuum model for active particle suspensions to analyze how long-range interactions cause instabilities in ordered phases, revealing different destabilization mechanisms for various particle types.

Contribution

It introduces a microscopic-to-continuum framework to study long-range interaction effects on phase stability in active particle systems.

Findings

Long-range interactions destabilize both isotropic and polar phases.

Different instabilities occur for pullers and pushers due to splay and bend fluctuations.

Quadrupolar particles do not exhibit these long-wavelength instabilities.

Abstract

Based on a microscopic model, we develop a continuum description for a suspension of microscopic self propelled particles. With this continuum description we study the role of long-range interactions in destabilizing macroscopic ordered phases that are developed by short-range interactions. Long-wavelength fluctuations can destabilize both isotropic and also symmetry broken polar phase in a suspension of dipolar particles. The instabilities in a suspension of pullers (pushers) arise from splay (bend) fluctuations. Such instabilities are not seen in a suspension of quadrupolar particles.