Defect loops in three-dimensional active nematics as active multipoles

Houston, A. J.H. and Alexander, G. P. (2022) Defect loops in three-dimensional active nematics as active multipoles. Physical Review E, 105(6), L062601. (doi: 10.1103/PhysRevE.105.L062601) (PMID:35854622)

Abstract

We develop a description of defect loops in three-dimensional active nematics based on a multipole expansion of the far-field director and show how this leads to a self-dynamics dependent on the loop's geometric type. The dipole term leads to active stresses that generate a global self-propulsion for splay and bend loops. The quadrupole moment is nonzero only for nonplanar loops and generates a net “active torque,” such that defect loops are both self-motile and self-orienting. Our analysis identifies right- and left-handed twist loops as the only force- and torque-free geometries, suggesting a mechanism for generating an excess of twist loops. Finally, we determine the Stokesian flows created by defect loops and describe qualitatively their hydrodynamics.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Houston, Dr Alexander
• Authors: Houston, A. J.H., and Alexander, G. P.
• College/School: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
• Journal Name: Physical Review E
• Publisher: American Physical Society
• ISSN: 2470-0045
• ISSN (Online): 2470-0053