Gravitation in the Microcanonical Ensemble: Appropriate Scaling Leading   to Extensivity and Thermalization
  We introduce a simple model of hard spheres with gravitational interactions, for which we study a suitable scaling limit. Usual extensive properties are maintained notwithstanding the long range of gravitational interaction. We show that a local thermalization spontaneously emerges within a microcanonical description of the stationary state. In the considered scaling limit, the resulting density profile can be determined in a hydrostatic approach. 
Maxime Champion, Angel Alastuey, Thierry Dauxois, Stefano Ruffo
cond-mat.stat-mech