Flocking in Binary Mixtures of Anti-aligning Self-propelled Particles

Abstract

We consider two species of self-propelled point particles: A-particles and B-particles. The orientations between nearby particles are subject to pair interactions of different strength for A-A-, A-B-(=B-A-) and B-B-interactions, respectively. Even if all interactions involved are repelling, that is, if they locally favor anti-alignment between each pair of particles, we find global polar order of both A-particles and B-particles We find qualitative agreement between agent-based simulations and mean field theory. Beyond mean field, we develop a Boltzmann-scattering theory based on one-sided molecular chaos that yields excellent quantitative agreement with simulations for dilute systems. For large systems, we find, depending on parameters, either micro-phase-separation or static patterns with either patches or stripes that carry different polarization orientations.