The Effect of Anisotropic Extra Dimension in Cosmology

TL;DR

This paper explores a five-dimensional conformal gravity model with an anisotropic extra dimension, constrains its parameters using cosmological data, and discusses implications for dark energy and gravitational constant variations.

Contribution

It introduces a novel anisotropic extra dimension in conformal gravity and constrains its parameters with observational data, linking higher-dimensional theories to cosmological observations.

Findings

Parameter z constrained to be greater than -2.05 (Planck) and -2.09 (WMAP) at 95% confidence.

The model can account for the current dark energy density.

Constraints on the variation of the effective Newtonian constant G_eff are consistent with observations.

Abstract

We consider five dimensional conformal gravity theory which describes an anisotropic extra dimension. Reducing the theory to four dimensions yields Brans-Dicke theory with a potential and a hidden parameter $z$ which implements the anisotropy between the four dimensional spacetime and the extra dimension. We find that a range of value of the parameter $z$ can address the current dark energy density compared to the Planck energy density. Constraining the parameter $z$ and the other cosmological model parameters using the recent observational data consisting of the Hubble parameters, type Ia supernovae, and baryon acoustic oscillations, together with the Planck or WMAP 9-year data of the cosmic microwave background radiation, we find $z>-2.05$ for Planck data and $z>-2.09$ for WMAP 9-year data at 95\% confidence level. We also obtained constraints on the rate of change of the effective Newtonian constant~($G_{\rm eff}$) at present and the variation of $G_{\rm eff}$ since the epoch of recombination to be consistent with observation.