Nonsingular Spherical Models with a Variable Cosmological term

TL;DR

This paper revisits exact non-singular spherically symmetric cosmological models with a time-varying cosmological term, analyzing solutions with perfect fluid and bulk viscosity, consistent with supernova observations.

Contribution

It provides new exact solutions to Einstein's equations with a dynamic cosmological term in non-singular models, extending previous work.

Findings

The cosmological term Λ(t) decreases over time.

Models are consistent with supernova observations.

Multiple solutions for perfect fluid and bulk viscosity are presented.

Abstract

Exact solutions of the Einstein's field equations describing a spherically symmetric cosmological model without a big bang or any other kind of singularity recently obtained by Dadhich and Patel (2000) are revisited. The matter content of the model is a shear-free perfect fluid with isotropic pressure and a radial heat flux. Three different exact solutions are obtained for both perfect fluid and fluid with bulk viscosity. It turns out that the cosmological rerm $\Lambda(t)$ is a decreasing function of time, which is consistent with recent observations of type Ia supernovae.