Apparent superluminal velocities and random walk in the velocity space

We conjecture that the random walk and the corresponding diffusion in the relativistic velocity space is an adequate method for describing the acceleration process in relativistic jets. Considering a simple toy model, the main features of diffusion in the velocity space are demonstrated in both non-relativistic and relativistic regimes.
Comment: 8 pages, 1 figures, to be published in Modern Physics Letters A