Spherically symmetric cosmological spacetimes with dust and radiation - numerical implementation

TL;DR

This paper introduces a numerical method for simulating spherically symmetric cosmological spacetimes with dust and radiation, enabling the study of non-linear effects during early universe epochs and dark energy models.

Contribution

The paper develops a new numerical implementation for Einstein's equations with dust and radiation in spherical symmetry, including non-comoving fluids and inhomogeneities.

Findings

Code accurately models spacetime evolution and observable quantities.

Late-time behavior is sensitive to initial radiation inhomogeneity.

Models can explore effects during decoupling and big-bang nucleosynthesis.

Abstract

We present new numerical cosmological solutions of the Einstein Field Equations. The spacetime is spherically symmetric with a source of dust and radiation approximated as a perfect fluid. The dust and radiation are necessarily non-comoving due to the inhomogeneity of the spacetime. Such a model can be used to investigate non-linear general relativistic effects present during decoupling or big-bang nucleosynthesis, as well as for investigating void models of dark energy with isocurvature degrees of freedom. We describe the full evolution of the spacetime as well as the redshift and luminosity distance for a central observer. After demonstrating accuracy of the code, we consider a few example models, and demonstrate the sensitivity of the late time model to the degree of inhomogeneity of the initial radiation contrast.