Submitted to Proc. Nat. Acad. Sci. · March 5, 2026
Chaos-generating periodic orbits of topological defects in confined active nematics
Brandon Klein, Alejandro J. Soto Franco, Md Mainul Hasan Sabbir, Matthew J. Deutsch, Ross Kliegman, Robin L. B. Selinger, Kevin A. Mitchell, Daniel A. Beller
First Page
click to open PDF
Abstract
Active nematics in two dimensions stir themselves efficiently through internally generated chaotic flows, largely driven by motile +1/2 disclinations. We investigate how this tendency toward chaotic fluid stirring can, counterintuitively, produce certain ordered, periodic flows in confinement, characterised by stable periodic orbits of +1/2 disclinations. We computationally study two-dimensional active nematics in systems with boundary conditions requiring a prescribed number n of excess +1/2 disclinations, using Beris–Edwards nematohydrodynamics simulations alongside an agent-based simulation approach. We find that when confinement is sufficiently strong to prevent defect pair-nucleation, but not strong enough to arrest all flow, then n = 3 defects generically follow a “golden braid” orbit as observed recently in experiments, and we predict a “silver braid” orbit of n = 4 defects. For these results and for greater numbers of defects, we show that the periodic or chaotic nature of the dynamics is determined by a balance between the number of defects and the number of vortices in the flow field, suggesting a new design criterion for ordered flows in active nematics.