Packed swarms on dirt: two-dimensional incompressible flocks with quenched and annealed disorder

Abstract

We show that incompressible polar active fluids can exhibit an ordered, coherently moving phase even in the presence of quenched disorder in two dimensions. Unlike such active fluids with annealed (i.e., time-dependent) disorder only, which behave like equilibrium ferromagnets with long-range interactions, this robustness against quenched disorder is a fundamentally non-equilibrium phenomenon. The ordered state belongs to a new universality class, whose scaling laws we calculate using three different renormalization group schemes, which all give scaling exponents within 0.02 of each other, indicating that our results are quite accurate. Our predictions can be quantitatively tested in readily available artificial active systems, and imply that biological systems such as cell layers can move coherently in vivo, where disorder is inevitable.

arXiv comment6 pages

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Cited by in corpus (6)

• A new universality class describes Vicsek's flocking phase in physical dimensions
• Hydrodynamic theory of two-dimensional incompressible polar active fluids with quenched and annealed disorder
• Novel critical phenomena in compressible polar active fluids: Dynamical and Functional Renormalization Group Studies
• Active Jamming at Criticality
• Dynamics of packed swarms: time-displaced correlators of two dimensional incompressible flocks
• Field-controlled interfacial transport and pinning in an active spin system