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DY: Dynamik und Statistische Physik

DY 44: Granular Systems

DY 44.2: Talk

Thursday, March 11, 2004, 15:00–15:15, H2

Exploring the phase space of granular material — •Matthias Schröter, Daniel I. Goldman, and Harry L. Swinney — University of Texas at Austin

Edwards and Oakeshott (Physica A 157, 1080 (1989)) proposed a thermodynamic approach to granular media, which is based on the idea that only a finite number of mechanically stable configurations fit a given number of particles in a fixed volume. They introduce a temperature-like state variable named Compactivity. The only experiment designed to measure this quantity was done by Nowak et al. (Phys. Rev. E 57, 1971 (1998), who tapped a column of granular material and measured the the asymptotic density fluctuations. This approach was, however, hampered by long relaxation times and a small range of achievable densities. We will show that the spatially homogeneous driving in a fluidized bed avoids this problem. Our approach allows a test the applicability of the Edwards hypothesis.