Relativistic gas: Moment equations and maximum wave velocity

Abstract

For a rarefied relativistic gas we consider the N-moment equations associated with the relativistic Boltzmann–Chernikov equation and we require the compatibility with the entropy principle thus obtaining a closed symmetric hyperbolic system. This interesting form permits one to deduce a lower and an upper bound for the maximum velocity of a wave propagating in a monoatomic or a degenerate gas of fermions or bosons and to prove that when this number N increases this velocity tends to the speed of light.