Micro-flock patterns and macro-clusters in chiral active Brownian disks

TL;DR

This paper investigates how chiral active Brownian disks form micro-flock patterns and macro-clusters, demonstrating that these patterns persist despite excluded volume interactions, with micro-flock size scaling linearly with particle radius.

Contribution

It shows that micro-flock and macro-cluster patterns survive in chiral active matter with excluded volume interactions, maintaining characteristic size scaling laws.

Findings

Micro-flock patterns and macro-clusters persist with excluded volume interactions.

Cluster size fluctuations are significantly enhanced.

Micro-flock size scales linearly with single-swimmer radius.

Abstract

Chiral active particles (or self-propelled circle swimmers) feature a rich collective behavior, comprising rotating macro-clusters and micro-flock patterns which consist of phase-synchronized rotating clusters with a characteristic self-limited size. These patterns emerge from the competition of alignment interactions and rotations suggesting that they might occur generically in many chiral active matter systems. However, although excluded volume interactions occur naturally among typical circle swimmers, it is not yet clear if macro-clusters and micro-flock patterns survive their presence. The present work shows that both types of pattern do survive but feature strongly enhance fluctuations regarding the size and shape of the individual clusters. Despite these fluctuations, we find that the average micro-flock size still follows the same characteristic scaling law as in the absence of excluded volume interactions, i.e. micro-flock sizes scale linearly with the single-swimmer radius.