Entropy Generation and the Survival of Protogalaxies in an Expanding Universe

Abstract

General formulae are derived for the bulk viscosity, shear viscosity, and heat transport due to radiation , and for the damping rate of sound waves, in an imperfect relativistic fluid. These results are used to evaluate the cosmological entropy production associated with a nonvanishing mean free time of photons, neutrinos, or gravitons, and to calculate the rate of damping of protogalactic fluctuations in the period immediately prior to the recombination of hydrogen.