The Simple Non-degenerate Relativistic Gas: Statistical Properties and   Brownian Motion
  This paper shows a novel calculation of the mean square displacement of a classical Brownian particle in a relativistic thermal bath. The result is compared with the expressions obtained by other authors. Also, the thermodynamic properties of a non-degenerate simple relativistic gas are reviewed in terms of a treatment performed in velocity space. 
A. Sandoval-Villalbazo, A. Aragones-Munoz, A. L. Garcia-Perciante