Initial-state dependence of phase behaviors in a dense active system

There are rich emergent phase behaviors in non-equilibrium active systems. Flocking and clustering are two representative dynamic phases. The relationship between both the phases is still unclear. Herein, we numerically investigate the evolution of flocking and clustering in a system consisting of self-propelled particles with active reorientation. We consider the interplay between flocking and clustering phases with different initial configurations, and observe a domain in steady state order parameter phase diagrams sensitive to the choice of initial configurations. Specifically, by tuning the initial degree of polar ordering, either a more ordered flocking or a disordered clustering state can be observed in the steady state. These results enlighten us to manipulate emergent behaviors and collective motions of an active system, and are qualitatively different from the emergence of a new bi-stable regime observed in aligned active particles due to an explicit attraction [New J. Phys. 14 073033 (2012)].