COSMOLOGICAL SOLUTIONS OF THE EINSTEIN EQUATIONS WITH A CAUSAL VISCOUS-FLUID

We investigate the behaviour of the solutions to the Einstein equations with a causal viscous fluid source in the case of the spatially flat Robertson-Walker metric. In our model, the bulk viscosity coefficient is related to the energy density as zeta = alpharho(m), and the relaxation time is given by zeta/rho. We find the exact solutions when m = 1/2, and we study analytically the asymptotic stability of the distinct families of solutions for arbitrary m. We find that the qualitative asymptotic behaviour in the far future is not altered by relaxation processes, but they change the behaviour in the past, either excluding deflationary evolutions or making the Universe bounce due to the violation of the energy conditions.