Dynamics of Motility-Induced Clusters: Coarsening beyond Ostwald Ripening

We study the dynamics of clusters of active Brownian disks generated by motility-induced phase separation, by applying an algorithm that we devised to track cluster trajectories. We identify an aggregation mechanism that goes beyond Ostwald ripening but also yields a dynamic exponent characterizing the cluster growth z 1/4 3, in the timescales explored numerically. Clusters of mass M self-propel with enhanced diffusivity D - Pe2/ p . Their fast motion drives aggregation into large fractal structures, which are patchworks of diverse hexatic orders, and coexist with regular, orientationally uniform, smaller ones. To bring out the impact of activity, we perform a comparative study of a passive system that evidences major differences with the active case.

Automated summary

In this paper, we study the dynamics of clusters formed by active Brownian disks generated through motility-induced phase separation. By using a novel algorithm, we identify an aggregation mechanism that goes beyond Ostwald ripening and find a dynamic exponent describing cluster growth. These clusters, driven by self-propelled motion, form large fractal structures containing diverse hexatic orders, as well as smaller, orientationally uniform structures. A comparative study with a passive system highlights the significant differences brought by activity.