Cosmic expansion with matter creation and bulk viscosity

TL;DR

This paper investigates how matter creation and bulk viscosity influence cosmic expansion, analyzing different models and their implications for universe evolution, including singularities and thermodynamic consistency.

Contribution

It introduces a novel analysis of matter creation effects in dissipative fluids within FLRW cosmology, comparing Eckart and Israel-Stewart models and their impact on cosmic fate.

Findings

Eckart model predicts a big rip singularity due to catastrophic matter production.

Israel-Stewart model yields a bounded matter production rate, avoiding singularities.

The universe's age is increased compared to standard cosmology, consistent with dark energy presence.

Abstract

We explore the cosmological implications at effective level of matter creation effects in a dissipative fluid for a FLRW geometry; we also perform a statistical analysis for this kind of model. By considering an inhomogeneous Ansatz for the particle production rate we obtain that for created matter of dark matter type we can have a quintessence scenario or a future singularity known as little rip; in dependence of the value of a constant parameter, $\eta$, 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 presence of dark energy. The inclusion of baryonic matter is studied. By implementing 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 Eckart model we have a big rip singularity leading to a catastrophic matter production and in the truncated version of the Israel-Stewart model such rate remains bounded leading to a quintessence scenario. For a non adiabatic dissipative fluid, we obtain a positive temperature and the cosmic expansion obeys the second law of thermodynamics.