Temperature Evolution Law of Imperfect Relativistic Fluids
  The first-order general relativistic theory of a generic dissipative (heat-conducting, viscous, particle-creating) fluid is rediscussed from a unified covariant frame-independent point of view. By generalizing some previous works in the literature, we derive a formula for the temperature variation rate, which is valid both in Eckart's (particle) and in the Landau-Lifshitz (energy) frames. Particular attention is paid to the case of gravitational particle creation and its possible cross-effect with the bulk viscosity mechanism. 
R. Silva (UFRN), J. A. S. Lima (UFRN), and M. O. Calv\~ao (UFRJ)