Classical and ultrarelativistic limits of the Riemann problem for the relativistic Euler fluid with Synge energy

Abstract

Recently, Ruggeri et al. (The Riemann problem of relativistic Euler system with Synge energy, arXiv:2001.04128v1 [math-ph], 2020) studied the Riemann problem of the relativistic Euler system for rarefied monatomic and diatomic gases with a constitutive equation for the energy determined by Synge, which is the only realistic equation compatible with the kinetic theory. The aim of the present work is to consider the classical and ultrarelativistic limits of their results, showing that they are in agreement with those already present in literature.