Observational Constraints on Braneworld Geometry

TL;DR

This paper investigates the cosmological evolution and observational constraints of 5D braneworld models with a bulk scalar field, showing that the geometry is strongly warped and branes are far apart, with implications for late-time cosmology.

Contribution

It provides a general analysis of braneworld cosmology with a bulk scalar, including observational constraints, and reveals the tendency of negative tension branes to evolve towards null warp-factor states.

Findings

Negative tension branes tend to evolve towards null warp-factor states.

The braneworld geometry must be strongly warped with branes far apart.

Observational tests constrain the branes' interaction and separation.

Abstract

The low energy regime of 5D braneworld models with a bulk scalar field is studied. The setup is rather general and includes the Randall-Sundrum and dilatonic braneworlds models as particular cases. We discuss the cosmological evolution of the system and conclude that, in a two brane system, the negative tension brane is generally expected to evolve towards a null warp-factor state. This implies, for late time cosmology, that both branes end up interacting weakly. We also analyze the observational constraints imposed by solar-system and binary-pulsar tests on the braneworld configuration. This is done by considering the small deviations produced by the branes on the 4D gravitational interaction between bodies in the same brane. Using these constraints we show that the geometry around the braneworld is strongly warped, and that both branes must be far apart.