Scaling of cluster growth for coagulating active particles

TL;DR

This paper investigates the unique growth dynamics of clusters formed by active particles, revealing how propulsion mechanisms influence growth rates and can lead to rapid, even explosive, cluster expansion.

Contribution

It provides a theoretical and simulation-based analysis of how active particle propulsion affects cluster growth, highlighting novel scaling behaviors and conditions for explosive growth.

Findings

Cluster velocity scaling depends on propulsion and alignment.

Persistence length increases with cluster size.

Explosive growth can occur under certain conditions.

Abstract

Cluster growth in a coagulating system of active particles (such as microswimmers in a solvent) is studied by theory and simulation. In contrast to passive systems, the net velocity of a cluster can have various scalings dependent on the propulsion mechanism and alignment of individual particles. Additionally, the persistence length of the cluster trajectory typically increases with size. As a consequence, a growing cluster collects neighbouring particles in a very efficient way and thus amplifies its growth further. This results in unusual large growth exponents for the scaling of the cluster size with time and, for certain conditions, even leads to "explosive" cluster growth where the cluster becomes macroscopic in a finite amount of time.