Abstract:
Theoretical treatments of frictional granular matter often assume that it is legitimate to invoke classical
elastic theory to describe its coarse-grained mechanical properties. Here, we show, based on experiments
and numerical simulations, that this is generically not the case since stress autocorrelation functions decay
more slowly than what is expected from elasticity theory. It was theoretically shown that standard elastic
decay demands pressure and torque density fluctuations to be normal, with possibly one of them being
hyperuniform. However, generic compressed frictional assemblies exhibit abnormal pressure fluctuations,
failing to conform with the central limit theorem. The physics of this failure is linked to correlations built in
the material during compression from a dilute configuration prior to jamming. By changing the protocol of
compression, one can observe different pressure fluctuations, and stress autocorrelations decay at large
scales.
