Electrostatically driven granular media: phase transitions and coarsening.

We report the experimental and theoretical study of electrostatically driven granular material. We show that the charged granular medium undergoes a hysteretic phase transition from the immobile condensed state (granular solid) to a fluidized dilated state (granular gas) with a changing applied electric field. In addition we observe a spontaneous precipitation of dense clusters from the gas phase and subsequent coarsening-coagulation of these clusters. Molecular dynamics simulations show qualitative agreement with experimental results.