Dynamical collective memory in fluidized granular materials
Abstract
Recent experiments with rotational diffusion of a probe in a vibrated granular media revealed a rich scenario, ranging from the dilute gas to the dense liquid with cage effects and an unexpected superdiffusive behavior at large times. Here we setup a simulation that reproduces quantitatively the experimental observations and allows us to investigate the properties of the host granular medium, a task not feasible in the experiment. We discover a persistent collective rotational mode which emerges at high density and low granular temperature: a macroscopic fraction of the medium slowly rotates, randomly switching direction after very long times. Such a rotational mode of the host medium is the origin of probe's superdiffusion. Collective motion is accompanied by a kind of dynamical heterogeneity at intermediate times (in the cage stage) followed by a strong reduction of fluctuations at late times, when superdiffusion sets in.
Cite
@article{arxiv.1907.02389,
title = {Dynamical collective memory in fluidized granular materials},
author = {A. Plati and A. Baldassarri and A. Gnoli and G. Gradenigo and A. Puglisi},
journal= {arXiv preprint arXiv:1907.02389},
year = {2019}
}
Comments
10 pages, 10 figures, merged letter and supplementary information, in press on Physical Review Letters