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Updated: Sep 17, 2025
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Forming, Confining, and Observing Microtubule-Based Active Nematics
Published on: January 13, 2023
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Nonlinear Spontaneous Flow Instability in Active Nematics
Ido Lavi1,2, Ricard Alert3,4,5, Jean-François Joanny6,7
1Universitat de Barcelona, Departament de Física de la Matèria Condensada, Martí i Franquès 1, 08028 Barcelona, Spain and UBICS (University of Barcelona Institute of Complex Systems), Martí i Franquès 1, 08028 Barcelona, Spain.
Physical Review Letters
|June 27, 2025
Summary
Even stable active nematics can transition to spontaneous flows via nonlinear instability. This discontinuous transition, where resting and flowing states coexist, is predicted for various systems, including contractile rods.
Area of Science:
- Soft Matter Physics
- Nonlinear Dynamics
- Active Matter
Background:
- Active nematics typically exhibit spontaneous flows due to linear instability from a uniform state.
- Understanding transitions in active matter is crucial for predicting complex behaviors like turbulence.
Purpose of the Study:
- To investigate nonlinear instabilities in active nematics that can lead to spontaneous flows.
- To explore the coexistence of quiescent and flowing states in active nematic systems.
- To characterize the shift from continuous to discontinuous transitions with varying parameters.
Main Methods:
- Weakly nonlinear analysis to study bifurcations.
- Numerical simulations to trace the bifurcation diagram of striped patterns.
- Analysis of flow-alignment parameter effects on system stability.
Main Results:
- A linearly stable uniform state can undergo a nonlinear instability, causing a discontinuous transition to spontaneous flow.
- The pitchfork bifurcation changes from supercritical (continuous) to subcritical (discontinuous) with altered flow-alignment parameters.
- Coexistence of quiescent and flowing states is possible in these systems.
Conclusions:
- Discontinuous spontaneous flow transitions are predicted for a broad range of active nematic parameters.
- These findings are relevant to active nematic turbulence and applicable to systems like contractile rods.
- The predictions offer testable hypotheses for experimental studies using cell layers or cytoskeletal suspensions.
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