  The behavior of a bidisperse inelastic gas vertically shaken in a
compartmentalized container is investigated using two different approaches: the
first is a mean-field dynamical model, which treats the number of particles in
the two compartments and the associated kinetic temperatures in a
self-consistent fashion; the second is an event-driven numerical simulation.
Both approaches reveal a non-stationary regime, which has no counterpart in the
case of monodisperse granular gases. Specifically, when the mass difference
between the two species exceeds a certain threshold the populations display a
bistable behavior, with particles of each species switching back and forth
between compartments. The reason for such an unexpected behavior is attributed
to the interplay of kinetic energy non-equipartition due to inelasticity with
the energy redistribution induced by collisions. The mean-field model and
numerical simulation are found to agree qualitatively.
