COLLECTIVE MOTION IN A SYSTEM OF MOTILE ELEMENTS

Clusters of biological organisms often show diverse collective motions . Considering the physical properties of active elements with mutual i nteractions, we propose a mathematical model of collective motion. Sev eral kinds of cluster motion seen in nature, including collective rota tion, chaos, and wandering, occur in computer simulations of our deter ministic model. By introducing a set of dimensionless parameters, we c ategorize the collective motions and obtain their phase diagram. We an alyze the collective motions with a disorder parameter and Lyapunov sp ectra to characterize their transitions.