Brane cosmology, Weyl fluid, and density perturbations

TL;DR

This paper introduces a new technique for analyzing relativistic perturbations in generalized brane cosmology, accounting for bulk-brane energy exchange via a Weyl fluid, which may serve as a dark matter candidate.

Contribution

It develops a novel perturbation analysis method that includes a radiative bulk and the Weyl fluid, extending previous multi-fluid cosmological models to brane scenarios.

Findings

Weyl fluid can act as a geometric dark matter candidate.

The technique incorporates bulk-brane energy exchange effects.

Analysis applies to both empty and radiative bulk scenarios.

Abstract

We develop a technique to study relativistic perturbations in the generalised brane cosmological scenario, which is a generalisation of the multi-fluid cosmological perturbations to brane cosmology. The novelty of the technique lies in the inclusion of a radiative bulk which is responsible for bulk-brane energy exchange, and in turn, modifies the standard perturbative analysis to a great extent. The analysis involves a geometric fluid -- called the Weyl fluid -- whose nature and role have been studied extensively both for the empty bulk and the radiative bulk scenario. Subsequently, we find that this Weyl fluid can be a possible geometric candidate for dark matter in this generalised brane cosmological framework.