Spontaneous Micro Flocking of Active Inertial Particles without Alignment Interaction

TL;DR

This paper demonstrates through simulations that active inertial particles with purely repulsive interactions can spontaneously form micro-flocks during motility induced phase separation, even without alignment interactions.

Contribution

It introduces the discovery of micro-flocking behavior in inertial active particles without alignment, expanding understanding of collective motion mechanisms.

Findings

Confirmation of MIPS in inertial active particles

Identification of micro-flocking transition

Quantitative characterization using velocity order parameter

Abstract

Observing spontaneous velocity ordering or flocking during motility induced phase separation (MIPS) in a system of spherical active Brownian particles without alignment interaction is challenging. We take up this problem by performing simulations of spherical active inertial particles with purely repulsive potential in presence of thermal noise and absence of any explicit alignment interaction. Our results not only show the presence of MIPS, but also reveal a micro-flocking transition. We characterize this transition in terms of a velocity order parameter as well as a characteristic length scale derived from the spatial correlation of the velocities.