Cosmic expansion with matter creation and bulk viscosity
Víctor H. Cárdenas, Miguel Cruz, Samuel Lepe
Abstract
We explore the cosmological implications at effective level of matter creation effects in a dissipative fluid for a Friedmann-Lemaitre-Robertson-Walker geometry; we also perform a statistical analysis for this kind of model. By considering an inhomogeneous ansatz for the particle production rate, which we obtain for a created matter of dark matter type, we can have a quintessence scenario or a future singularity known as a little rip; this is in dependence of the value of a constant parameter, $\ensuremath{\eta}$, which characterizes the matter production effects. The dimensionless age of this kind of universe is computed, showing that this number is greater than the standard cosmology value; this is typical of universes with the presence of dark energy. The inclusion of baryonic matter is studied. We implement the construction of the particle production rate for a dissipative fluid by considering two approaches for the expression of the bulk viscous pressure: we find that, in the Eckart model, we have a big rip singularity leading to a catastrophic matter production, and in the truncated version of the Israel-Stewart model this rate remains bounded, which leads to a quintessence scenario. For a nonadiabatic dissipative fluid, we obtain a positive temperature, and the cosmic expansion obeys the second law of thermodynamics.