Title: Small granular systems and their relevance for descriptions of macroscopic granular packings

Author (Invited): Jerzy Blawzdziewicz, Yale University

Abstract:

In this talk I will present results of our combined numerical, experimental, and theoretical investigations aimed at developing a comprehensive statistical-mechanical description of static and slowly driven granular packings. We focus on small frictionless granular systems, for which the probability distribution of all microstates (i.e., all mechanically-stable packings) can be directly determined by performing a large number of independent experimental or numerical trials. Our investigations reveal many important features of the packing distribution. First, we find that the packing distribution is highly non-uniform, with a small fraction of states dominating the system behavior. This result directly contradicts Edwards' equal-probability assumption. Second, we also find that the evolution of a slowly sheared granular system is strongly non-ergodic. We use our results to propose a new approach in which quasistatic evolution of granular systems is described in terms of uncorrelated transitions between microstates.