Causal non-stationary thermodynamics of non-viscous heat conducting fluids with internal variables

Relativistic non-viscous heat conducting fluids with a vectorial internal variable are modeled according to the dissipation and causality principles. A set of constitutive equations, ensuring the causal nature of the model, is postulated. The second law of thermodynamics is exploited by analyzing a suitable covariant form of the Clausius-Duhem inequality. A modification of the classical theory of heat conduction, allowing a finite speed of propagation of thermal disturbances, is considered.