Equilibrium distribution and the equation of state for a weakly relativistic gas with short-range interaction

The systems are considered, for the description of which it is sufficient to take into account the quantities of the order $v^2/c^2$, $v$ being the velocity of particle, $c$ the velocity of light. The equilibrium distribution function and the equation of state are obtained on the basis of the Liouville quasi-relativistic equation for systems of neutral particles with the negligibly small delay of the interaction.