title: Towards a relevant set of state variables to describe static granular packings.
abstract: We analyze, experimentally and numerically, the steady states, obtained by tapping, of a two-dimensional granular layer. Contrary to the usual assumption, we show that the reversible (steady state branch) of the density-acceleration curve is nonmonotonous. Accordingly, steady states with the same mean volume can be reached by tapping the system with very different intensities. Simulations of dissipative frictional disks show that equal volume steady states have different values of the force moment tensor. Additionally, we find that steady states of equal stress can be obtained by changing the duration of the taps; however, these states present distinct mean volumes. These results confirm previous speculations that the volume and the force moment tensor are both needed to describe univocally equilibrium states in static granular assemblies.
authors.affiliation: Instituto de Física de Líquidos y Sistemas Biológicos (CONICET La Plata, UNLP), cc. 565, 1900 La Plata, Argentina. luis@iflysib.unlp.edu.ar
authors.forename: Luis A
authors.initials: LA
authors.lastname: Pugnaloni
authors.forename: Iván
authors.initials: I
authors.lastname: Sánchez
authors.forename: Paula A
authors.initials: PA
authors.lastname: Gago
authors.forename: José
authors.initials: J
authors.lastname: Damas
authors.forename: Iker
authors.initials: I
authors.lastname: Zuriguel
authors.forename: Diego
authors.initials: D
authors.lastname: Maza