Memory effects, arches and polar defect ordering at the cross-over from wet to dry active nematics

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Hauptverfasser: Nejad, Mehrana Raeisian, Doostmohammadi, Amin, Yeomans, Julia Mary
Format: Preprint
Veröffentlicht: 2020
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author Nejad, Mehrana Raeisian
Doostmohammadi, Amin
Yeomans, Julia Mary
author_facet Nejad, Mehrana Raeisian
Doostmohammadi, Amin
Yeomans, Julia Mary
contents We use analytic arguments and numerical solutions of the continuum, active nematohydrodynamic equations to study how friction alters the behaviour of active nematics. Concentrating on the case where there is nematic ordering in the passive limit, we show that, as the friction is increased, memory effects become more prominent and $+1/2$ topological defects leave increasingly persistent trails in the director field as they pass. The trails are preferential sites for defect formation and they tend to impose polar order on any new $+1/2$ defects. In the absence of noise and for high friction, it becomes very difficult to create defects, but trails formed by any defects present at the beginning of the simulations persist and organise into parallel arch-like patterns in the director field. We show aligned arches of equal width are approximate steady state solutions of the equations of motion which co-exist with the nematic state. We compare our results to other models in the literature, in particular dry systems with no hydrodynamics, where trails, arches and polar defect ordering have also been observed.
format Preprint
id arxiv_https___arxiv_org_abs_2010_04200
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle Memory effects, arches and polar defect ordering at the cross-over from wet to dry active nematics
Nejad, Mehrana Raeisian
Doostmohammadi, Amin
Yeomans, Julia Mary
Soft Condensed Matter
We use analytic arguments and numerical solutions of the continuum, active nematohydrodynamic equations to study how friction alters the behaviour of active nematics. Concentrating on the case where there is nematic ordering in the passive limit, we show that, as the friction is increased, memory effects become more prominent and $+1/2$ topological defects leave increasingly persistent trails in the director field as they pass. The trails are preferential sites for defect formation and they tend to impose polar order on any new $+1/2$ defects. In the absence of noise and for high friction, it becomes very difficult to create defects, but trails formed by any defects present at the beginning of the simulations persist and organise into parallel arch-like patterns in the director field. We show aligned arches of equal width are approximate steady state solutions of the equations of motion which co-exist with the nematic state. We compare our results to other models in the literature, in particular dry systems with no hydrodynamics, where trails, arches and polar defect ordering have also been observed.
title Memory effects, arches and polar defect ordering at the cross-over from wet to dry active nematics
topic Soft Condensed Matter
url https://arxiv.org/abs/2010.04200