1.d Relativistic Thermodynamics

Relativistic Thermodynamics attempts to describe physical processes taking into account their macroscopic variables as well as energy dissipation. In the relativistic representation of such macroscopic physical systems one has two types of variables: universal (Tmn), describing energy density and momentum, and specific, that define the components of the system. The dynamics of specific variables and of diverse flows (besides energy and momentum flows) is governed by the phenomenological equations of Causal Relativistic Thermodynamics. The present research program has two main branches. The first aims at the derivation of the relativistic equations of a simple fluid, submitted to dissipative processes, and is based upon Landau?s formulation - which is still scarcely known in the literature. The process of expansion (or contraction) of homogeneous and isotropic cosmological models (Friedman-Robertson-Walker model) as a far-from-equilibrium process was studied next. In particular, the efficiency of dissipation as a mechanism useful to avoid the occurrence of the typical singularity of Friedmann-Robertson-Walker metrics was examined. Subsequently, it is intended to enlarge the existing formalism in order to include many-component fluids and fluids endowed with internal structure (spin). In this last case, consequences of the coupling of spin to the gravitational field were already obtained, as well as some applications to Cosmology and conformally flat metrics.

The second branch of research, derived from the first one, envisages a systematic study of relativistic systems (with ponderable matter) interacting with the electromagnetic field. The modifications induced in the theory when the magnetic field is coupled directly to the space-time curvature will be studied next. Finally, as a consequence of this research program, macroscopic systems interacting with gravity will be investigated, so as to understand the nature of the influence of the gravitational filed upon the thermodynamical properties of such systems. This study also includes the analysis and calculation of fluctuations and stability problems of cosmological models.