Stability at Random Close Packing

TL;DR

This paper derives a new structural constraint for packings of hard particles, linking contact force distribution and pair distribution function, which may explain observed rearrangement avalanches in such packings.

Contribution

It introduces a novel bound between force and positional distributions in particle packings, connecting microscopic structure to macroscopic rearrangement phenomena.

Findings

Derived a bound: γ ≥ 1/(2+θ) relating force and pair distribution exponents.

Suggests the bound is saturated in real packings, explaining avalanche behavior.

Links structural constraints in packings to glassy material theories.

Abstract

The requirement that packings of hard particles, arguably the simplest structural glass, cannot be compressed by rearranging their network of contacts is shown to yield a new constraint on their microscopic structure. This constraint takes the form a bound between the distribution of contact forces P(f) and the pair distribution function g(r): if P(f) \sim f^{\theta} and g(r) \sim (r-{\sigma})^(-{\gamma}), where {\sigma} is the particle diameter, one finds that {\gamma} \geq 1/(2+{\theta}). This bound plays a role similar to those found in some glassy materials with long-range interactions, such as the Coulomb gap in Anderson insulators or the distribution of local fields in mean-field spin glasses. There is ground to believe that this bound is saturated, offering an explanation for the presence of avalanches of rearrangements with power-law statistics observed in packings.