Phys. Rev. E 71, 030301(R) (2005) [4 pages]Stationary state volume fluctuations in a granular medium
A statistical description of static granular material requires ergodic sampling of the phase space spanned by the different configurations of the particles. We periodically fluidize a column of glass beads and find that the sequence of volume fractions ϕ of postfluidized states is history independent and Gaussian distributed about a stationary state. The standard deviation of ϕ exhibits, as a function of ϕ, a minimum corresponding to a maximum in the number of statistically independent regions. Measurements of the fluctuations enable us to determine the compactivity X, a temperaturelike state variable introduced in the statistical theory of Edwards and Oakeshott Physica A 157 1080 (1989). © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevE.71.030301
DOI:
10.1103/PhysRevE.71.030301
PACS:
45.70.−n, 05.40.−a, 64.30.+t, 47.55.Kf
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