Electrostatically driven granular media: Phase transitions and coarsening

We report the experimental and theoretical study of electrostatically drive n granular material. We show that the charged granular medium undergoes a h ysteretic phase transition from the immobile condensed state (granular soli d) to a fluidized dilated state (granular gas) with a changing applied elec tric field. In addition we observe a spontaneous precipitation of dense clu sters from the gas phase and subsequent coarsening-coagulation of these clu sters. Molecular dynamics simulations show qualitative agreement with exper imental results.