Thermodynamically admissible equations for causal dissipative cosmology, galaxy formation, and transport processes in a gravitational collapse

Abstract

We formulate a set of equations for a self-gravitating imperfect fluid that satisfies all the principles of both general relativity and nonequilibrium thermodynamics, where the latter are condensed in the covariant version of the recently proposed general equation for the nonequilibrium reversible-irreversible coupling (GENERIC). In doing so, Einstein's field equation is supplemented by fundamental and clearly structured transport equations for the sources of gravitational fields. The GENERIC framework determines the selection of the appropriate variables and the structure of the field equations compatible with the fundamental laws of thermodynamics. A nonzero cosmological constant cannot be ruled out by thermodynamic consistency criteria. In order to discuss the relationship to previous approaches, the simplified equations for bulk viscous cosmology are presented in some detail.