Late time cosmic acceleration from vacuum Brans-Dicke theory in 5D

TL;DR

This paper demonstrates that in 5D scalar-vacuum Brans-Dicke theory, the observed late-time cosmic acceleration naturally arises for certain parameter ranges, but is incompatible with large values of the Brans-Dicke parameter ,  within this framework.

Contribution

It shows the equivalence of 5D vacuum Brans-Dicke equations to 4D with a potential and matter, and analyzes conditions for cosmic acceleration related to the parameter .

Findings

Accelerated expansion occurs for  between -1.5 and -1.

Large  values are incompatible with acceleration in this model.

The model links 5D vacuum solutions to 4D cosmological behavior.

Abstract

We show that the scalar-vacuum Brans-Dicke equations in 5D are equivalent to Brans-Dicke theory in 4D with a self interacting potential and an effective matter field. The cosmological implication, in the context of FRW models, is that the observed accelerated expansion of the universe comes naturally from the condition that the scalar field is not a ghost, i.e., $\omega > - 3/2$. We find an effective matter-dominated 4D universe which shows accelerated expansion if $- 3/2 < \omega < - 1$. We study the question of whether accelerated expansion can be made compatible with large values of $\omega$, within the framework of a 5D scalar-vacuum Brans-Dicke theory with variable, instead of constant, parameter $\omega$. In this framework, and based on a general class of solutions of the field equations, we demonstrate that accelerated expansion is incompatible with large values of $\omega$.