Randall-Sundrum brane cosmology: modification of late-time cosmic dynamics by exotic matter

TL;DR

This paper demonstrates that Randall-Sundrum brane effects can significantly influence large-scale cosmic dynamics, especially with exotic matter, altering the expected future attractors in cosmological models.

Contribution

It shows that RS brane effects impact late-time cosmology through matter dynamics, extending their significance beyond short distances to large scales, especially with exotic matter fields.

Findings

RS effects can turn future attractors into saddle points.

Exotic matter fields like phantom and tachyon fields exhibit similar RS effects.

The impact is specific to models modifying the matter side of Friedmann equations.

Abstract

In this paper we show, through the study of concrete examples, that, depending on the cosmic dynamics of the energy density of matter degrees of freedom living in the brane, Randall-Sundrum (RS) brane effects can be important not only at short distances (UV regime), but also at large cosmological scales (IR regime). Our first example relies on the study, by means of the dynamical systems tools, of a toy model based in a non-linear electrodynamics (NLED) Lagrangian. Then we show that other, less elaborated models, such as the inclusion of a scalar phantom field, and of a tachyon phantom field -- trapped in the brane -- produce similar results. The form of the RS correction seems to convert what would have been future attractors in general relativity into saddle points. The above "mixing of scales" effect is distinctive only of theories that modify the right-hand-side (matter part) of the Friedmann equation, so that, for instance, DGP-brane models do not show this feature.