Dynamics of ensemble of active brownian particles controlled by noise

Dynamics of an ensemble of small number of active Brownian particles is studied by means of numerical simulations. The particles are influenced by independent sources of noise, passive and active, and interact with each other through a global velocity field. We suppose that active noise affects to direction of the particle velocity only. Behaviour of the large ensemble and behaviour of the small one are compared. Mean velocity of particles of the large ensemble was analytically estimated earler. We show that a noise-induced "order–disorder" transition accompaniated by a bistability phenomena is observed in a small ensemble. A borderline of a coupling coefficient moves up while reducing the number of particles. Influence of passive noise leads to conversion of bistability to bimodality. There are two most probable values of a particle velocity in the last case. Borders of regions of bistability and bimodality are defined by the stochastic bifurcations of different kinds.