Equivalence of equilibrium states in tapped granular beds

LUIS A. PUGNALONI; IVÁN SÁNCHEZ; PAULA A. GAGO; MARTÍN MIZRAHI; NICOLÁS E. BUENO; DIEGO MAZA; IKER ZURIGUEL; MANUEL CARLEVARO; FERNANDO VERICAT

Viña del Mar (Chile)

Workshop; Southern Workshop on Granular Materials 2009; 2009

In 1989, Edwards and Oakeshott proposed that the mean volume of a granular sample at equilibrium is the only macroscopic variable (apart from the number of grains) needed to characterize the state. The equilibrium state is a collection of static microstates (or inherent states) obtained by repeated excitations of fixed duration and intensity. A number of studies have claimed this is indeed the case in different situations where an equilibrium state of given mean volume has been reached through different types of excitations (e.g. different duration and intensity). We argue that such ”different excitations” are most probably equivalent in the sense that the same effective perturbation is induced on the sample. Then, we show that a particular tapping protocol can lead to equilibrium states of equal mean volume under excitations that are truly different. We explore the equivalence of these equal volume states obtained in experiments and in five different well known models of granular compaction. (Oral Communication)