5-dimensional Brans-Dicke Theory and Cosmic Acceleration

TL;DR

This paper explores a 5-dimensional scalar-tensor theory extending Brans-Dicke theory, demonstrating that two scalar fields can naturally explain the universe's current accelerated expansion within a cosmological model.

Contribution

It introduces a 5D generalization of Brans-Dicke theory with a reduction to 4D, showing how scalar fields can account for cosmic acceleration.

Findings

Two scalar fields can explain cosmic acceleration.

The model aligns with observational constraints.

The theory provides a natural extension of Brans-Dicke cosmology.

Abstract

We consider a 5-dimensional scalar-tensor theory which is a direct generalization of the original 4-dimensional Brans-Dicke theory to 5-dimensions. By assuming that there is a hypersurface-orthogonal spacelike Killing vector field in the underlying 5-dimensional spacetime, the theory is reduced to a 4-dimensional theory where the 4-metric is coupled with two scalar fields. The cosmological implication of this reduced theory is then studied in the Robertson-Walker model. It turns out that the two scalar fields may account naturally for the present accelerated expansion of our universe. The observational restriction of the reduced cosmological model is also analyzed.