Intermittency and clustering in a system of self-driven particles

Intermittent behavior is shown to appear in a system of self-driven interacting particles. In the ordered phase, most particles move in the same approximate direction, but the system displays a series of intermittent bursts during which the order is temporarily lost. This intermittency is characterized and its statistical properties are found analytically for a reduced system containing only two particles. For large systems, the particles aggregate into clusters that play an essential role in the intermittent dynamics. The study of the cluster statistics shows that both the cluster sizes and the transition probability between them follow power-law distributions. The exchange of particles between clusters is shown to satisfy detailed balance.