Collective motion of Active Brownian Particles with polar alignment

TL;DR

This study explores how velocity-alignment influences collective motion in active particles, revealing complex pattern formations and phase behaviors beyond traditional models, with implications for understanding flocking phenomena.

Contribution

It introduces an extended Active Brownian Particles model incorporating velocity-alignment, analyzing its impact on flocking and pattern formation in two-dimensional active particle systems.

Findings

Flocking onset is mainly controlled by velocity-alignment strength.

Rich pattern formations include polar clusters and large-scale traveling structures.

A phase diagram summarizes diverse collective behaviors.

Abstract

We present a comprehensive computational study of the collective behavior emerging from the competition between self-propulsion, excluded volume interactions and velocity-alignment in a two-dimensionnal model of active particles. We consider an extension of the Active Brownian Particles model where the self-propulsion direction of the particles aligns with the one of their neighbors. We analyze the onset of collective motion (flocking) in a low-density regime (10% surface area) and show that it is mainly controlled by the strength of velocity-alignment interactions: the competition between self-propulsion and crowding effects plays a minor role in the emergence of flocking. However, above the flocking threshold, the system presents a richer pattern formation scenario than analogous models without alignment interactions (Active Brownian Particles) or excluded volume effects (Vicsek-like models). Depending on the parameter regime, the structure of the system is characterized by either a broad distribution of finite-sized polar clusters or the presence of an amorphous, highly fluctuating, large-scale traveling structure which can take a lane-like or band-like form (and usually a hybrid structure which is halfway in between both). We establish a phase diagram that summarizes collective behavior of polar Active Brownian Particles and propose a generic mechanism to describe the complexity of the large-scale structures observed in systems of repulsive self-propelled particles.