Regensburg 2002 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 44: Statistische Physik fernab vom Gleichgewicht II

DY 44.1: Hauptvortrag

Donnerstag, 14. März 2002, 14:30–15:00, H2

Birth and Sudden Death of a Granular Cluster — •Ko van der Weele, Devaraj van der Meer, and Detlef Lohse — Department of Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.

Granular material in N connected compartments is brought into a gaseous state by vertical shaking. For sufficiently strong shaking the gas is equi-partitioned over the compartments, but if the shaking intensity is lowered the uniform distribution gives way (due to the dissipative nature of the particle collisions) to a clustered state. This phase transition is experimentally shown to be of 2nd order for N = 2 and of 1st order for N ≥ 3. 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 (sudden death) and in its further decay shows anomalous diffusion, which goes as t1/3 rather than the standard t1/2. We focus upon the self-similar character of this process.

The observed phenomena are all accounted for within a dynamical flux model.

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