Recent experiments exhibit a rate-dependence for granular shear such that the stress grows linearly in the logarithm of the shear rate, \dot{\gamma}. Assuming a generalized activated process mechanism, we show that these observations are consistent with a recent proposal for a stress-based statistical ensemble. By contrast, predictions for rate-dependence using conventional energy-based statistical mechanics to describe activated processes, predicts a rate dependence that of (\ln (\dot{\gamma}))^{1/2}.
@article{arxiv.0810.4891,
title = {Why Do Granular Materials Stiffen with Shear Rate? A Test of Novel Stress-Based Statistics},
author = {Robert P. Behringer and Dapeng Bi and Bulbul Chakraborty and Silke Henkes and Robert R. Hartley},
journal= {arXiv preprint arXiv:0810.4891},
year = {2009}
}