http://arxiv.org/abs/1311.4494
We find the probability density function $\mathcal{P}(v_{\texttt{r}})$ of the relativistic relative velocity for two colliding particles in a non-degenerate relativistic gas. The distribution reduces to Maxwell distribution for the relative velocity in the non-relativistic limit. We find an exact formula for the mean value $\langle v_{\texttt{r}}\rangle$. The mean velocity tends to the Maxwell’s value in the non-relativistic limit and to the velocity of light in the ultra-relativistic limit. At a given temperature $T$, when at least for one of the two particles the ratio of the rest energy over the thermal energy $m c^2/k_B T$ is smaller than 40 the Maxwell distribution is inadequate.
Tue, 19 Nov 13
64/75