Department of Biological Physics, Etvos University, Budapest; Department of Computer Science, Budapest University of Economics; Budapest,
Abstract: We study a model of flocking in order to describe the transitions during the collective motion of organisms (e.g., birds) in three dimensions. In this model the particles representing the organisms are self-propelled, i.e., they move with the same absolute velocity. In addition, the particles locally interact by choosing at each time step the average direction of motion of their neighbours and the eects of fluctuations are taken into account as well. We present the first results for large-scale flocking in the presence of noise in three dimensions. We show that depending on the control parameters both disordered and long-range ordered phases can be observed. The corresponding phase diagram has a number of features which are qualitatively dierent from those typical for the analogous equilibrium models.
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