Relativistic Lévy processes

Abstract: In this contribution, we investigate how to correctly describe sums of independent and identically distributed random velocities in the theory of special relativity. We derive a one-dimensional probability distribution of velocities stable under relativistic velocity addition. In a given system, this allows identifying distinct physical regimes in terms of the distribution's concavity at the origin and the probability of measuring relativistic velocities. These features provide a protocol to assess the relevance of stochastic relativistic effects in actual experiments. As examples, we find agreement with previous results about heavy-ion diffusion and show that our findings are consistent with the distribution of momentum deviations observed in measurements of antiproton cooling.