The equilibration of a hard-disks system
  The process of equilibration of a colliding hard-disks system is studied in the framework of classical mechanic. The method consists of dividing the nonequilibrium system into the interacting subsystems; the evolution one of these subsystems is analyzed employing generalized Lagrange and Liouville equations. The subsystem-subsystem interaction force is considered as an evolution parameter. The mechanism by which its system equilibrates is described. 
V.M. Somsikov