title: Shocks near jamming.
abstract: Nonlinear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed and demonstrate that the elementary excitations are strongly nonlinear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.
authors.affiliation: Instituut-Lorentz, Universiteit Leiden, P.O. Box 9056, 2300 RA Leiden, The Netherlands. gomez@lorentz.leidenuniv.nl
authors.forename: Leopoldo R
authors.initials: LR
authors.lastname: Gómez
authors.forename: Ari M
authors.initials: AM
authors.lastname: Turner
authors.forename: Martin
authors.initials: M
authors.lastname: van Hecke
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Vitelli