Defect configuration of an active nematic around a circular obstacle

TL;DR

This paper investigates the behavior of topological defects in active nematic liquid crystals around a circular obstacle, combining numerical simulations and theoretical analysis to understand defect configurations influenced by activity and flow fields.

Contribution

It introduces a combined numerical and analytical approach to study defect configurations in active nematics near obstacles, extending passive nematic theories to active systems.

Findings

Numerical simulations show deviations from passive defect configurations due to activity.

Theoretical calculations qualitatively match simulation results.

Study provides insights applicable to biological systems with obstacles.

Abstract

To enhance the understanding of the behavior of active nematic, it is important to understand the behavior of topological defects. In this paper, we study the configuration of topological defects of a two-dimensional active nematic around a circular obstacle. In the case of a passive nematic liquid crystal, the equilibrium configuration of defects can be easily identified by the method of image charges. In the case of an active nematic, however, one must take account of the flow field generated by active constituents, and the problem of identifying the defect configuration becomes complicated. We first perform numerical simulations and investigate how the stationary defect configuration deviates from the passive case. Furthermore, we carry out a theoretical calculation based on an analytical expression relating the defect velocity with the force exerted on the defect. Our theoretical calculation qualitatively reproduces the simulation results. Our study may be applied to describing the behaviour of e.g. cell populations in the presence of obstacles, and has the potential to benefit related fields, e.g., developmental biology.