Large-Scale Chaos and Fluctuations in Active Nematics

Sandrine Ngo (1, 2) , Anton Peshkov (3, 2, 1) , Igor S. Aranson (4, 1) , Eric Bertin (5, 6, 1) , Francesco Ginelli (7) , Hugues Chaté (3, 2, 1)

1 MPI-PKS - Max Planck Institute for the Physics of Complex Systems
2 SPEC - UMR3680 - Service de physique de l'état condensé
3 LPTMC - Laboratoire de Physique Théorique de la Matière Condensée
4 Materials Science Division
5 Université de Lyon
6 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
7 Aberdeen University

We show that " dry " active nematics, e.g. collections of shaken elongated granular particles, exhibit large-scale spatiotemporal chaos made of interacting dense, ordered, band-like structures in a parameter region including the linear onset of nematic order. These results are obtained from the study of the relatively simple and well-known (deterministic) hydrodynamic equations describing these systems in a dilute limit, and of a self-propelled particle Vicsek-like model for this class of active matter. In this last case, revisiting the status of the strong fluctuations and long-range correlations now considered as landmarks of orientationally-ordered active phases, we show that the giant number fluctuations observed in the chaotic phase are a trivial consequence of density segregation. However anomalous density fluctuations are present in the homogeneous quasi-ordered nematic phase and characterized by a non-trivial scaling exponent.

Domaines: Physique [physics]

Sandrine Ngo, Anton Peshkov, Igor S. Aranson, Eric Bertin, Francesco Ginelli, et al.. Large-Scale Chaos and Fluctuations in Active Nematics. Physical Review Letters, 2014, 113 (3), pp.38302. ⟨10.1103/PhysRevLett.113.038302⟩. ⟨cea-01384279⟩