Formation and collision of traveling bands in interacting deformable self-propelled particles.

We study the collective dynamics of interacting deformable self-propelled particles whose migration velocity increases with increasing local density. In two-dimensional numerical simulations of this system, the local density dependence on migration velocity leads to traveling bands similar to those previously reported for Vicsek-type models. We show that a pair of straight bands moving in opposite directions survives a head-on collision. Although traveling bands also appear in systems of constant migration velocity subjected to random noise, they are found to be unstable in a head-on collision.