Dynamics of Deformable Self-Propelled Particles with Repulsive Interaction

We investigate dynamics of deformable self-propelled particles introducing a soft repulsive interaction which depends on the relative direction of elongation of a pair of particles. Numerical simulations are carried out in two dimensions by changing the noise intensity and the particle density to obtain the phase diagram of the ordered and the disordered phases. The transitions between these two states are investigated in detail both in the low density region and in the high density region. We show by a mean field analysis that deformability is a favorable origin for the transition in the high density region, which occurs as a saddle-node bifurcation.