On the hyperbolicity and causality of the relativistic Euler system   under the kinetic equation of state
  We show that a pair of conjectures raised in [11] concerning the construction of normal solutions to the relativistic Boltzmann equation are valid. This ensures that the results in [11] hold for any range of positive temperatures and that the relativistic Euler system under the kinetic equation of state is hyperbolic and the speed of sound cannot overcome $c/\sqrt{3}$. 
Juan Calvo
math-ph math.MP