Onset of collective and cohesive motion

Guillaume Grégoire (1) , Hugues Chaté (2)

1 MSC - Matière et Systèmes Complexes
2 SPEC - UMR3680 - Service de physique de l'état condensé

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. {\bf 75},1226 (1995)] for which a non-trivial 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.

Mots clés: Cohesive properties; Collective motion; Out-of-equilibrium system phase transitions

Domaines: Autre [cond-mat.other]; Mécanique statistique [cond-mat.stat-mech]

Guillaume Grégoire, Hugues Chaté. Onset of collective and cohesive motion. Physical Review Letters, 2004, 92 (2), pp.025702. ⟨10.1103/PhysRevLett.92.025702⟩. ⟨hal-00001019⟩