A qualitative Langevin-like model for the coexistence of two distinct   granular temperatures
  In the present work, we study qualitatively the physics of granular temperature coexistence, for a mixture of two different species. Our model captures its essential aspects and this allows us to get insights on the physical mechanisms of distinct temperature coexistence, in a way which is not obscured by the complexities of kinetic theories or numerical simulations. Our simple model is consistent with limit situations where we should expect equality for the granular temperatures for the mixture. 
W.A.M. Morgado