title: Following fluctuating signs: Anomalous active superdiffusion of swimmers in anisotropic media.
abstract: Active (i.e., self-propelled or swimming) particles moving through an isotropic fluid exhibit conventional diffusive behavior. We report anomalous diffusion of an active particle moving in an anisotropic nematic background. While the translational motion parallel to the nematic director shows ballistic behavior, the long-time transverse motion is superdiffusive, with an anomalous scaling proportional to tlnt of the mean-square displacement with time t. This behavior is predicted by an analytical theory that we present here and is corroborated by numerical simulation of active particle diffusion in a simple lattice model for a nematic liquid crystal. It is universal for any collection of self-propelled elements (e.g., bacteria or active rods) moving in a nematic background, provided only that the swimmers are sufficiently dilute that their interactions with each other can be neglected and that they do not perform hairpin turns.
authors.affiliation: Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: John
authors.initials: J
authors.lastname: Toner
authors.affiliation: Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.
authors.forename: Hartmut
authors.initials: H
authors.lastname: Löwen
authors.affiliation: Laboratoire de Physique des Solides, UMR 8502, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.
authors.forename: Henricus H
authors.initials: HH
authors.lastname: Wensink