Susceptibility of Polar Flocks to Spatial Anisotropy

Alexandre Solon, Hugues Chaté, John Toner, and Julien Tailleur
Phys. Rev. Lett. 128, 208004 – Published 20 May 2022
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Abstract

We study the effect of spatial anisotropy on polar flocks by investigating active q-state clock models in two dimensions. In contrast to the equilibrium case, we find that any amount of anisotropy is asymptotically relevant, drastically altering the phenomenology from that of the rotationally invariant case. All of the well-known physics of the Vicsek model, from giant density fluctuations to microphase separation, is replaced by that of the active Ising model, with short-range correlations and complete phase separation. These changes appear beyond a length scale that diverges in the q limit, so that the Vicsek-model phenomenology is observed in finite systems for weak enough anisotropy, i.e., sufficiently high q. We provide a scaling argument which explains why anisotropy has such different effects in the passive and active cases.

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  • Received 4 January 2022
  • Accepted 18 April 2022

DOI:https://doi.org/10.1103/PhysRevLett.128.208004

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & ThermodynamicsCondensed Matter, Materials & Applied PhysicsPolymers & Soft Matter

Authors & Affiliations

Alexandre Solon1, Hugues Chaté2,3,1, John Toner4, and Julien Tailleur5

  • 1Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, 75005 Paris, France
  • 2Service de Physique de l’Etat Condensé, CEA, CNRS Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette, France
  • 3Computational Science Research Center, Beijing 100094, China
  • 4Department of Physics and Institute for Fundamental Science, University of Oregon, Eugene, Oregon 97403, USA
  • 5Université de Paris, Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, 75205 Paris, France

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Issue

Vol. 128, Iss. 20 — 20 May 2022

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