Random very loose packs
Abstract
We measure the number Omega(phi) of mechanically stable states of volume fraction phi of a granular assembly under gravity. The granular entropy S(phi) = log Omega(phi) vanishes both at high density, at phi = phi_rcp, and a low density, at phi = phi_rvlp, where phi_rvlp is a new lower bound we call random very loose pack. phi_rlp is the volume fraction where the entropy is maximal. These findings allow for a clear explanation of compaction experiments, and provide the first first-principle definition of the random loose volume fraction. In the context of the statistical mechanics approach to static granular materials, states with phi < phi_rlp are characterized by a negative temperature.
Cite
@article{arxiv.0805.0220,
title = {Random very loose packs},
author = {Massimo Pica Ciamarra and Antonio Coniglio},
journal= {arXiv preprint arXiv:0805.0220},
year = {2013}
}
Comments
Applet available at http://smcs.na.infn.it/rvlp/rvlp.html Enhanced version resulting from reviewer's comments