Relativistic fluid models are of considerable interest in several areas of astrophysics, plasma physics, and nuclear physics. Here we will mention briefly some of these areas and emphasize the problems which form the physical motivations for the theories expounded in this book.

Theories of gravitational collapse and models of supernova explosions (Van Riper, 1979; Chevalier, 1981; Shapiro and Teukolsky, 1983) are based on a relativistic fluid model for the star. In most models a key feature is the occurrence of an outward propagating relativistic shock. The precise conditions under which the shock forms at some point with exactly the necessary strength to expel the bulk of the star but still leave behind a remnant remain to be studied in detail and are the subject of current investigation. The effects of deviations from spherical symmetry due to an initial angular momentum and magnetic field must also be assessed. This requires the use of relativistic magneto-fluid dynamical models (Yodzsis, 1971; Maeda and Oohara 1982; Sloan and Smarr, 1986). The problem of the shock stability when traversing regions where the equation of state softens could be of interest for supernova models.

In the theories of galaxy formation, relativistic fluid models have been used in order to describe the evolution of perturbations of the baryon and radiation components of the cosmic medium (Peebles, 1980). Other components consisting of collisionless particles (such as massive neutrinos or photinos) are usually treated within a kinetic framework (Peebles, 1980).