Metastability of Discrete-Symmetry Flocks

Abstract

We study the stability of the ordered phase of flocking models with a scalar order parameter. Using both the active Ising model and a hydrodynamic description, we show that droplets of particles moving in the direction opposite to that of the ordered phase nucleate and grow. We characterize analytically this self-similar growth and demonstrate that droplets spread ballistically in all directions. Our results imply that, in the thermodynamic limit, discrete-symmetry flocks -- and, by extension, continuous-symmetry flocks with rotational anisotropy -- are metastable in all dimensions.

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• Phase Coexistence in Nonreciprocal Quorum-Sensing Active Matter
• Emergent complex phases in a discrete flocking model with reciprocal and non-reciprocal interactions
• Fluctuation-Induced First Order Transition to Collective Motion
• A new universality class describes Vicsek's flocking phase in physical dimensions
• Long-range order in two-dimensional systems with fluctuating active stresses
• Motility-Induced Pinning in Flocking System with Discrete Symmetry
• Consequence of anisotropy on flocking: the discretized Vicsek model
• Bubble formation in active binary mixture model
• Reduced density fluctuations via anti-aligning in active matter
• Stability of discrete-symmetry flocks: sandwich state, traveling domains and motility-induced pinning
• Field-controlled interfacial transport and pinning in an active spin system