Mesoscopic theory for fluctuating active nematics

Eric Bertin (1, 2) , Hugues Chaté (3, 4, 1) , Francesco Ginelli , Shradha Mishra (5) , Anton Peshkov (4, 1, 3) , Sriram Ramaswamy (1)

1 MPI-PKS - Max Planck Institute for the Physics of Complex Systems
2 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
3 LPTMC - Laboratoire de Physique Théorique de la Matière Condensée
4 SPEC - UMR3680 - Service de physique de l'état condensé
5 IIT Kharagpur - Indian Institute of Technology Kharagpur

The term active nematics designates systems in which apolar elongated particles spend energy to move randomly along their axis and interact by inelastic collisions in the presence of noise. Starting from a simple Vicsek-style model for active nematics, we derive a mesoscopic theory, complete with effective multiplicative noise terms, using a combination of kinetic theory and Itô calculus approaches. The stochastic partial differential equations thus obtained are shown to recover the key terms argued in EPL 62 (2003) 196 to be at the origin of anomalous number fluctuations and long-range correlations. Their deterministic part is studied analytically, and is shown to give rise to the long-wavelength instability at onset of nematic order (see arXiv:1011.5408). The corresponding nonlinear density-segregated band solution is given in a closed form.

Domaines: Physique [physics]; Mécanique statistique [cond-mat.stat-mech]; Matière Molle [cond-mat.soft]

Eric Bertin, Hugues Chaté, Francesco Ginelli, Shradha Mishra, Anton Peshkov, et al.. Mesoscopic theory for fluctuating active nematics. New Journal of Physics, 2013, 15, pp.85032. ⟨10.1088/1367-2630/15/8/085032⟩. ⟨cea-01478872⟩