Local disalignment can promote coherent collective motion through rapid information transfer

Abstract: When particles move at a constant speed and have the tendency to align their directions of motion, ordered large scale movement can emerge despite significant levels of noise. Many variants of this model of self-propelled particles have been studied to explain the coherent motion of groups of birds, fish or microbes. Here, we generalize the exactly aligning collision rule of the classical model of self-propelled particles to the case where particles after the collision tend to move in slightly different directions away from each other, as characterized by a collision angle $\alpha$. We map out the resulting phase diagram and find that, in sufficiently dense systems, small disalignment can lead to higher global alignment of particle movement directions. We show that in this dense regime, global alignment is accompanied by a grid-like spatial structure which allows information to rapidly percolate accross the system by a "domino" effect. Our results elucidate the relevance of disalignment for the emergence of collective motion in models with exclusively repulsive interaction terms.