The nonextensive parameter and Tsallis distribution for self-gravitating systems

The properties of the nonextensive parameter q and the Tsallis distribution for self-gravitating systems are studied. A mathematical expression of q is deduced based on the generalized Boltzmann equation, the q-H theorem and the generalized Maxwellian q-velocity distribution in the framework of Tsallis statistics. We obtain a clear understanding of the physics of q different from unity with regard to the temperature gradient and the gravitational potential of the self-gravitating systems. It is suggested that the Tsallis statistics could be statistics suitable for describing the nonequilibrium systems with inhomogeneous temperature and the long-range interactions.