Definition of temperature in dense granular media

In this paper we report the measurement of a pseudotemperature for compacting granular media on the basis of the fluctuation-dissipation relations in the aging dynamics of a model system. From the violation of the fluctuation-dissipation theorem emerges an effective temperature (a dynamical temperature T-dyn) whose value depends, on the particle density. We compare the results for T-dyn at several densities with the values of Edwards' compactivity at the corresponding densities [S. F. Edwards; in Granular Matter: An Interdisciplinary Approach, edited by A. Mehta (Springen-Verlag, New York, 1994) and references therein]. It turns out that the dynamical temperature and Edwards' compactivity coincide on a large range of densities, opening in this way the door to experimental checks as well as theoretical constructions.