Cosmological expansion on a dilatonic brane-world

TL;DR

This paper develops a covariant formalism to analyze how bulk scalar fields influence brane-world cosmology, revealing scenarios with initial accelerated expansion that avoid singularities.

Contribution

It introduces a covariant approach to derive 4D Einstein equations in brane-world models with scalar fields, exploring their cosmological implications.

Findings

Demonstrates the impact of bulk scalar fields on brane gravity.

Identifies a novel universe expansion scenario avoiding initial singularity.

Analyzes effects of non-minimal scalar coupling on cosmology.

Abstract

In this paper we study brane-world scenarios with a bulk scalar field, using a covariant formalism to obtain a 4D Einstein equation via projection onto the brane. We discuss, in detail, the effects of the bulk on the brane and how the scalar field contribute to the gravitational effects. We also discuss choice of conformal frame and show that the frame selected by the induced metric provides a natural choice. We demonstrate our formalism by applying it to cosmological scenarios of Randall-Sundrum and Horava-Witten type models. Finally we consider the cosmology of models where the scalar field couples non-minimally to the matter on the brane. This gives rise to a novel scenario where the universe expands from a finite scale factor with an initial period of accelerated expansion, thus avoiding the singularity and flatness problem of the standard big bang model.