Onset of Collective and Cohesive Motion

TLDR

Previous studies suggested a nontrivial critical point for collective motion of self‑propelled particles. The authors investigate the onset of collective motion, with and without cohesion, in groups of noisy self‑propelled particles interacting locally. They analyze the system using a minimal Vicsek‑type model of locally interacting particles in two dimensions. They find that the phase transition is always discontinuous and that cohesion is lost near onset due to density, velocity, and shape fluctuations. Phys.

Abstract

We study the onset of collective motion, with and without cohesion, of groups of noisy self-propelled particles interacting locally. We find that this phase transition, in two space dimensions, is always discontinuous, including for the minimal model of Vicsek et al. [Phys. Rev. Lett. 75, 1226 (1995)]] for which a nontrivial critical point was previously advocated. We also show that cohesion is always lost near onset, as a result of the interplay of density, velocity, and shape fluctuations.