Maximal entropy distribution functions from generalized R\'enyi entropy
  New class of reference distribution functions for numerical approximation of the solution of the Fokker-Planck equations associated to the charged particle dynamics in tokamak are studied. The reference distribution functions are obtained by maximization of the generalized Renyi entropy under scale-invariant restrictions. Explicit analytic form, with algebraic decay, that is a generalization of the previous distribution with exponential tails was derived. 
Gy\"orgy Steinbrecher, Giorgio Sonnino, Nicolae Pometescu
cond-mat.stat-mech