Viscous Bianchi type I universes in brane cosmology

Abstract

We consider the dynamics of a viscous cosmological fluid in the generalized Randall-Sundrum model for an anisotropic, Bianchi type I brane. To describe the dissipative effects we use the Israel-Hiscock-Stewart full causal thermodynamic theory. By assuming that the matter on the brane obeys a barotropic linear equation of state, and that the bulk viscous pressure has a power-law dependence on the energy density, the general solution of the field equations can be obtained in an exact parametric form. The solutions obtained describe generally a non-inflationary braneworld. In the large time limit the brane universe isotropizes, ending in an isotropic and homogeneous state. The evolution of the temperature and the comoving entropy of the universe is also considered, and it is shown that due to viscous dissipative processes a large amount of entropy is created in the early stages of evolution of the braneworld.