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Screw symmetry, chiral hydrodynamics, and odd instability in active cholesterics
Gareth P Alexander1, S J Kole2,3, Ananyo Maitra4,5
1University of Warwick, Department of Physics, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.
Physical Review. E
|December 23, 2025
Summary
Active cholesterics exhibit chirality in structure and stress, leading to novel curl forces and active instabilities. This study clarifies their hydrodynamics and reveals a new instability mechanism driven by screw symmetry.
Area of Science:
- Soft Matter Physics
- Chiral Materials Science
- Fluid Dynamics
Background:
- Active cholesterics possess chirality in both structure and active stresses.
- Chirality in active materials leads to complex hydrodynamic behaviors, including curl forces.
- Understanding these behaviors is crucial for developing novel active materials.
Purpose of the Study:
- To derive and clarify the hydrodynamics of active cholesterics with continuous screw symmetry.
- To investigate the role of chiral activity and screw symmetry in active instabilities.
- To identify new active instabilities distinct from existing models.
Main Methods:
- Derivation of hydrodynamic equations from active Ericksen-Leslie equations using a geometric approach.
- Analysis of the nonlinear structure of active hydrodynamics.
- Linearization of pseudolayer hydrodynamics to study active instabilities.
Main Results:
- Clarified the hydrodynamics of continuous screw symmetry in active cholesterics.
- Identified generalized odd elastic forces originating from equilibrium free energy.
- Discovered a new active instability driven by antagonistic chiral activity and screw symmetry, with a distinct threshold and wave vector.
Conclusions:
- Screw symmetry in active cholesterics generates unique hydrodynamic contributions and active instabilities.
- The findings provide insights into the behavior of chiral active matter and potential applications.
- This work advances the understanding of active fluid dynamics and phase transitions in chiral systems.
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