Casimir stresses in active nematic films

• Published in: New Journal of Physics
• Main Authors: Abhik Basu, Jean-Francois Joanny, Frank Jülicher, Jacques Prost
• Format: Article
• Language: English
• Published: IOP Publishing 2019-01-01
• Subjects: hydrodynamics; Casimir stress; active fluids
• Online Access: https://doi.org/10.1088/1367-2630/ab5628

We calculate the Casimir stresses in a thin layer of active fluid with nematic order. By using a stochastic hydrodynamic approach for an active fluid layer of finite thickness L , we generalize the Casimir stress for nematic liquid crystals in thermal equilibrium to active systems. We show that the active Casimir stress differs significantly from its equilibrium counterpart. For contractile activity, the active Casimir stress, although attractive like its equilibrium counterpart, diverges logarithmically as L approaches a threshold of the spontaneous flow instability from below. In contrast, for small extensile activity, it is repulsive, has no divergence at any L and has a scaling with L different from its equilibrium counterpart.