Nonlinear spontaneous flow instability in active nematics
Abstract
Active nematics exhibit spontaneous flows through a well-known linear instability of the uniformly-aligned quiescent state. Here we show that even a linearly stable uniform state can experience a nonlinear instability, resulting in a discontinuous transition to spontaneous flows. In this case, quiescent and flowing states may coexist. Through a weakly nonlinear analysis and a numerical study, we trace the bifurcation diagram of striped patterns and show that the underlying pitchfork bifurcation switches from supercritical (continuous) to subcritical (discontinuous) by varying the flow-alignment parameter. We predict that the discontinuous spontaneous flow transition occurs for a wide range of parameters, including systems of contractile flow-aligning rods. Our predictions are relevant to active nematic turbulence and can potentially be tested in experiments on either cell layers or active cytoskeletal suspensions.
Cite
@article{arxiv.2403.16841,
title = {Nonlinear spontaneous flow instability in active nematics},
author = {Ido Lavi and Ricard Alert and Jean-François Joanny and Jaume Casademunt},
journal= {arXiv preprint arXiv:2403.16841},
year = {2026}
}