Collective motion of self-propelled particles interacting without cohesion

TL;DR

This paper investigates the phase transition and collective behavior of Vicsek-style self-propelled particles in 2D and 3D, revealing a discontinuous transition and complex ordered phases with solitary structures and anomalous fluctuations.

Contribution

It provides a detailed analysis of the nature of the phase transition and characterizes the properties of the ordered phase in self-propelled particle models without cohesion.

Findings

Discontinuous (first-order like) transition to collective motion.

Presence of high-density, high-order solitary structures near transition.

Homogeneous ordered phase with strong density fluctuations and superdiffusion.

Abstract

We present a comprehensive study of Vicsek-style self-propelled particle models in two and three space dimensions. The onset of collective motion in such stochastic models with only local alignment interactions is studied in detail and shown to be discontinuous (first-order like). The properties of the ordered, collectively moving phase are investigated. In a large domain of parameter space including the transition region, well-defined high-density and high-order propagating solitary structures are shown to dominate the dynamics. Far enough from the transition region, on the other hand, these objects are not present. A statistically-homogeneous ordered phase is then observed, which is characterized by anomalously-strong density fluctuations, superdiffusion, and strong intermittency.