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DY: Fachverband Dynamik und Statistische Physik

DY 43: Active Matter IV (joint session DY/BP/CPP)

DY 43.1: Invited Talk

Thursday, March 21, 2024, 09:30–10:00, BH-N 334

Flocking by turning away — •Ricard Alert — Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

Flocking, as paradigmatically exemplified by birds, is the coherent collective motion of active agents. As originally conceived, flocking emerges through alignment interactions between the agents. Here, I will show a new mechanism of flocking based on interactions that reorient agents away from each other. Combining simulations, kinetic theory, and experiments, we demonstrate this mechanism of flocking in self-propelled Janus colloids with stronger repulsion on the front than on the rear. We show that, unlike for alignment interactions, the emergence of polar order from turn-away interactions requires particle repulsion. The polar flocking state is stable because particles achieve a compromise between turning away from left and right neighbors. These findings could help to reconcile the observations that cells can flock despite turning away from each other via contact inhibition of locomotion. Overall, our work shows that flocking is a very robust behavior that arises even when the orientational interactions seem to prevent it.

Keywords: active matter; flocking; active colloids; collective motion