title: Large-scale chaos and fluctuations in active nematics.
abstract: We show that dry active nematics, e.g., collections of shaken elongated granular particles, exhibit large-scale spatiotemporal chaos made of interacting dense, ordered, bandlike structures in a parameter region including the linear onset of nematic order. These results are obtained from the study of both the well-known (deterministic) hydrodynamic equations describing these systems and of the self-propelled particle model they were derived from. We prove, in particular, that the chaos stems from the generic instability of the band solution of the hydrodynamic equations. Revisiting the status of the strong fluctuations and long-range correlations in the particle model, we show that the giant number fluctuations observed in the chaotic phase are a trivial consequence of density segregation. However anomalous, curvature-driven number fluctuations are present in the homogeneous quasiordered nematic phase and characterized by a nontrivial scaling exponent.
authors.affiliation: Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and SUPA, Physics Department, IPAM and Institute for Complex Systems and Mathematical Biology, King's College, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Ngo
authors.affiliation: Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, 75252 Paris, France.
authors.forename: Anton
authors.initials: A
authors.lastname: Peshkov
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
authors.forename: Igor S
authors.initials: IS
authors.lastname: Aranson
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and Laboratoire Interdisciplinaire de Physique, Université Joseph Fourier Grenoble, CNRS UMR 5588, BP 87, 38402 Saint-Martin d'Hères, France and Université de Lyon, Laboratoire de Physique, ENS Lyon, CNRS, 46 allée d'Italie, 69007 Lyon, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Bertin
authors.affiliation: SUPA, Physics Department, IPAM and Institute for Complex Systems and Mathematical Biology, King's College, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ginelli
authors.affiliation: Service de Physique de l'Etat Condensé, CNRS URA 2464, CEA-Saclay, 91191 Gif-sur-Yvette, France and Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany and LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, 75252 Paris, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Chaté