Birth and sudden death of a granular cluster

Granular material is vibro-fluidized in N connected compartments. For sufficiently strong shaking the particles are statistically uniformly distributed over the compartments, but if the shaking intensity is lowered this uniform distribution gives way to a clustered state. The clustering transition is experimentally shown to be of 2nd order for N = 2 compartments and of 1st order for . In particular, the latter is hysteretic, involves long-lived transient states, and exhibits a striking lack of time reversibility. In the strong shaking regime, a cluster breaks down very abruptly and in its further decay shows anomalous diffusion, with the length scale going as t1/3 rather than the standard t1/2. We focus upon the self-similar nature of this process. The observed phenomena are all accounted for within a flux model.