Low Energy Branes, Effective Theory and Cosmology

TL;DR

This paper develops a systematic low-energy approximation method for cosmological brane configurations with a bulk scalar, deriving an effective four-dimensional bi-scalar tensor gravity theory that naturally stabilizes scalar fields.

Contribution

It introduces a linear expansion method for solving five-dimensional brane-bulk systems with arbitrary scalar potentials and matter, leading to a new effective four-dimensional bi-scalar tensor gravity theory.

Findings

The effective theory can stabilize scalar fields without extra mechanisms.

The method applies to arbitrary bulk scalar potentials.

The approach recovers the Randall-Sundrum model as a special case.

Abstract

The low energy regime of cosmological BPS-brane configurations with a bulk scalar field is studied. We construct a systematic method to obtain five-dimensional solutions to the full system of equations governing the geometry and dynamics of the bulk. This is done for an arbitrary bulk scalar field potential and taking into account the presence of matter on the branes. The method, valid in the low energy regime, is a linear expansion of the system about the static vacuum solution. Additionally, we develop a four-dimensional effective theory describing the evolution of the system. At the lowest order in the expansion, the effective theory is a bi-scalar tensor theory of gravity. One of the main features of this theory is that the scalar fields can be stabilized naturally without the introduction of additional mechanisms, allowing satisfactory agreement between the model and current observational constraints. The special case of the Randall-Sundrum model is discussed.