Information and motility exchange in collectives of active particles

Active systems exploit the interplay of autonomous motility and mechanical interactions to spontaneously organize in complex patterns. In many situations, the collective behavior of active agents is driven by the exchange of information that can change the state of the agents. In a minimal model of information exchange, we have studied numerically run-and-tumble runners with an additional two-state internal variable that specifies their motile or nonmotile state. Motile particles change irreversibly into nonmotile ones upon collision with a nonmotile particle. Once turned non-motile, they can reacquire their motility or ``reawaken’’ at a rate m. When m=0, the system relaxes to an absorbing fractal aggregate of non-motile particles, with fractal dimension controlled by density and tumbling rate [1]. For finite reawakening, we find motile, non-motile and mixed states that can organize in complex spatial patterns. We characterize the kinetics of approach to the steady state and its structure in terms of tumbling and reawakening rates.

[1] M. Paoluzzi, M. Leoni, and M. C. Marchetti, Phys. Rev. E 98, 052603 (2018