Long-wavelength instabilities in a system of interacting active particles

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.

Instabilities in a growing system of active particles: scalar and vectorial systems

“…37 Bend and splay elastic energy can stabilize both modes of perturbations and this is shown in the second term in t r . 37,41 The interesting physics is in the real part of the frequency that is denoted by o r = v(q, n 0 )q. When the hydrodynamic instabilities are stabilized by nematic elastic energy or other stabilization mechanisms, 42 stable traveling waves can propagate in the system with the corresponding group velocity given by v. Propagation of such active waves is directly related to the parameter b, the growthmediated torque.…”

Controlling stability and transport of magnetic microswimmers by an external field

“…1. Notably, pushers and pullers exhibit distinct instability patterns that result from the divergence of bend and splay fluctuations [50][51][52], respectively. The 3D visualisation of the density field in fig.…”