Cosmological tests of generalized RS brane-worlds with Weyl fluid

TL;DR

This paper tests generalized RS brane-world models with Weyl fluid against supernova and BBN data, finding that all models fit well with small Weyl fluid contributions, and that early radiation is necessary for some models to satisfy BBN constraints.

Contribution

It introduces and tests three generalized RS brane-world models with different Weyl fluid evolution against observational data, highlighting the role of Weyl fluid in cosmology.

Findings

Weyl fluid contributes only a few percent to the total energy density.

All models fit the supernova data reasonably well.

Early radiation is required in some models to satisfy BBN constraints.

Abstract

A class of generalized Randall-Sundrum type II (RS) brane-world models with Weyl fluid are confronted with the Gold supernovae data set and BBN constraints. We consider three models with different evolutionary history of the Weyl fluid, characterized by the parameter $\alpha$. For $\alpha=0$ the Weyl curvature of the bulk appears as dark radiation on the brane, while for $\alpha =2$ and 3 the brane radiates, leaving a Weyl fluid on the brane with energy density decreasing slower than that of (dark) matter. In each case the contribution $\Omega_d$ of the Weyl fluid represents but a few percent of the energy content of the Universe. All models fit reasonably well the Gold2006 data. The best fit model for $\alpha =0$ is for $\Omega_d=0.04$. In order to obey BBN constraints in this model however, the brane had to radiate at earlier times.