HIGHER-DERIVATIVE THEORY WITH VISCOSITY

Cosmological solutions in a higher derivative theory have been obtaine d with an imperfect fluid. We consider both power law and exponential models of the early universe. We discuss cosmological models in the Ec kart, truncated and full causal theories. In the full-causal theory, w e distinguish between two cases, one with the temperature obeying a po wer law behavior and the other relaxing this assumption. The exponenti al solution permits a realistic scenario when the behavior of the temp erature is not of the power-law type.