Radiation-like imperfect fluid cosmologies

Radiation-like viscous fluid solutions of the Einstein field equations are presented in which the geometrical part corresponds to the k = 0, R(t) = t exp 1/2 FRW model. It is shown that there are radial solutions, in particular, self-similar solutions, corresponding to the spacetime and which describe radiating imperfect fluids, that are valid everywhere and satisfy all necessary physical requirements. Such solutions are of importance in hydrodynamics, including viscous fluid motion, in astrophysics, and in cosmology.