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

Abstract

There are rich emergent phase behaviors in non-equilibrium active systems. Flocking and clustering are two representative dynamic phases. The relationship between these two phases is still unclear. In the paper, we numerically investigate the evolution of flocking and clustering in a system consisting of selfpropelled 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 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 [Großmann R, Schimansky-Geier L and Romanczuk P 2012 New J. Phys. 14 073033].

Flocking and clustering in mixtures of self-propelled particles with or without active reorientation

“…We measure the local density for each disk by calculating the Voronoi cell [28]. By numerical simulation, we find that when local density is larger than a certain threshold [26], the disk is located in a certain dense cluster. Then ρ is defined by the fraction of particles located in the dense cluster [29].…”

“…However, none of these models explicitly includecollision avoidance which is a movement strategy commonly adopted by animals [23][24][25]. In our previous work [26,27], we presented a model of self-propelled disks with active reorientation in analogy to collision avoidance in animal herds. We found the coupling of self-propulsion and active reorientation leads to rich phases including clustering and collective flocking without explicit alignment interaction.…”