title: Critical and noncritical jamming of frictional grains.
abstract: We probe the nature of the jamming transition of frictional granular media by studying their vibrational properties as a function of the applied pressure p and friction coefficient mu. The density of vibrational states exhibits a crossover from a plateau at frequencies omega > or similar to omega*(p,mu) to a linear growth for omega < or similar to omega*(p,mu). We show that omega* is proportional to Deltaz, the excess number of contacts per grain relative to the minimally allowed, isostatic value. For zero and infinitely large friction, typical packings at the jamming threshold have Deltaz-->0, and then exhibit critical scaling. We study the nature of the soft modes in these two limits, and find that the ratio of elastic moduli is governed by the distance from isostaticity.
authors.affiliation: Instituut-Lorentz, Universiteit Leiden, Postbus 9506, 2300 RA Leiden, The Netherlands.
authors.forename: Ellák
authors.initials: E
authors.lastname: Somfai
authors.forename: Martin
authors.initials: M
authors.lastname: van Hecke
authors.forename: Wouter G
authors.initials: WG
authors.lastname: Ellenbroek
authors.forename: Kostya
authors.initials: K
authors.lastname: Shundyak
authors.forename: Wim
authors.initials: W
authors.lastname: van Saarloos