Title: Rigidity of Marginal Solids

Author (Invited): Bulbul Chakraborty, Brandeis University

Abstract:

Dry granular materials are non-cohesive with the grains interacting via purely repulsive contact forces. The emergence of mechanical rigidity in these systems is a collective process, which unlike other types of solids, is controlled completely by boundary forces, especially in the limit of infinitely rigid grains or where the deformation of individual grains can be ignored. In this limit, I will argue that two dimensional granular solids exhibit topological order that imparts rigidity to the system. The theoretical analysis is based on very general arguments that take into account the zero temperature nature of granular solids. I will show that topological order inhibits local spatial fluctuations making these marginal solids robust. I will show comparisons of the theoretical predictions to properties of an experimentally generated ensemble of jammed states created by shear. Based on these, I will propose that the topological order concept can help us understand many puzzling features of granular solids.