Metastability of Constant-Density Flocks

Abstract

We study numerically the Toner-Tu field theory where the density field is maintained constant, a limit case of "Malthusian" flocks for which the asymptotic scaling of correlation functions in the ordered phase is known exactly. While we confirm these scaling laws, we also show that such constant-density flocks are metastable to the nucleation of a specific defect configuration, and are replaced by a globally disordered phase consisting of asters surrounded by shock lines that constantly evolves and remodels itself. We demonstrate that the main source of disorder lies along shock lines, rendering this active foam fundamentally different from the corresponding equilibrium system. We thus show that in the context of active matter also, a result obtained at all orders of perturbation theory can be superseded by non-perturbative effects, calling for a different approach.

arXiv comment6 pages, 4 figures

References in corpus (25)

• Novel type of phase transition in a system of self-driven particles
• Flocks, herds, and schools: A quantitative theory of flocking
• Generic theory of active polar gels: a paradigm for cytoskeletal dynamics
• Pattern formation of microtubules and motors: inelastic interaction of polar rods
• A Reanalysis of the Hydrodynamic Theory of Fluid, Polar-Ordered Flocks
• Macroscopic equations for pattern formation in mixtures of microtubules and motors
• On the Perturbation Expansion of the KPZ-Equation
• Self-organized Pattern Formation in Motor-Microtubule Mixtures
• Birth, Death and Flight: A Theory of Malthusian Flocks
• Quantitative Assessment of the Toner and Tu Theory of Polar Flocks
• Critical Phenomenon of the Order-Disorder Transition in Incompressible Flocks
• Swarming in the Dirt: Ordered Flocks with Quenched Disorder
• Breakdown of Ergodicity and Self-Averaging in Polar Flocks with Quenched Disorder
• Extensile to contractile transition in active microtubule-actin composites generates layered asters with programmable lifetimes
• Susceptibility of Polar Flocks to Spatial Anisotropy
• Emergent Structures in an Active Polar Fluid : dynamics of shape, scattering and merger
• Hydrodynamic Theory of Flocking in the Presence of Quenched Disorder
• Small Obstacle in a Large Polar Flock
• Topology-driven ordering of flocking matter
• Incompressible polar active fluids in the moving phase
• Moving, reproducing, and dying beyond Flatland: Malthusian flocks in dimensions $d>2$
• Coarsening in the two-dimensional incompressible Toner-Tu equation: Signatures of turbulence
• A novel nonequilibrium state of matter: a $d=4-\epsilon$ expansion study of Malthusian flocks
• Active polar flock with birth and death
• Phase ordering, topological defects, and turbulence in the 3D incompressible Toner-Tu equation

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