Simulations support protocol independency of the granular temperature

Abstract

A possible approach to the statistical description of granular assemblies starts from Edwards' assumption that all blocked states occupying the same volume are equally probable (S.F. Edwards, R. Oakeshott, Physica A 157, 1080 (1989)). We performed computer simulations using two-dimensional polygonal particles excited periodically according to two different protocols: excitation by pulses of "negative gravity" and excitation by "rotating gravity". The first protocol exhibits a non-monotonous dependency of the mean volume fraction on the pulse strength. The overlapping histogram method is used in order to test whether or not the volume distribution is described by a Boltzmann-like distribution, and to calculate the inverse compactivity as well as the logarithm of the partition sum. We find that the mean volume is a unique function of the measured granular temperature, independently of the protocol and of the branch in $\varphi (g)$ and all determined quantities are in agreement with Edwards' theory.

12 pages, 12 Figures, accepted in Physical Review E