Emergent Structures in an Active Polar Fluid : dynamics of shape, scattering and merger

TL;DR

This paper investigates the spontaneous emergence and dynamics of defect structures in active polar fluids, analyzing their shape, interactions, and behaviors such as scattering and merging, with relevance to cellular and colloidal systems.

Contribution

It introduces effective equations of motion for active defect structures, revealing their shape, kinetics, and interaction behaviors in active polar fluids.

Findings

Defect structures can be static or mobile with distinct textures.

Active defects exhibit elastic scattering or merger depending on conditions.

Results are applicable to cell cortex dynamics and active colloidal systems.

Abstract

Spatially localised defect structures emerge spontaneously in a hydrodynamic description of an active polar fluid comprising polar 'actin' filaments and 'myosin' motor proteins that (un)bind to filaments and exert active contractile stresses. These emergent defect structures are characterized by distinct textures and can be either static or mobile - we derive effective equations of motion for these 'extended particles' and analyse their shape, kinetics, interactions and scattering. Depending on the impact parameter and propulsion speed, these active defects undergo elastic scattering or merger. Our results are relevant for the dynamics of actomyosin-dense structures at the cell cortex, reconstituted actomyosin complexes and 2D active colloidal gels.