Is Thick Brane Model Consistent with the Recent Observations?

TL;DR

This paper tests the thick brane cosmological model against recent observational data, finding it suggests an open universe which conflicts with WMAP's flat universe results.

Contribution

It provides the first comprehensive observational constraints on the thick brane model using multiple recent cosmological datasets.

Findings

Supports an open universe with specific density parameters

Shows inconsistency of the model with WMAP's flat universe results

Constrains model parameters using supernova, CMB, and BAO data

Abstract

There exist many observational evidences implying the expansion of our universe is undergoing a late-time acceleration, the mechanism of this acceleration is yet unknown. In the so-called thick brane model this phenomena is attributed to the thickness of the brane along the extra dimension. In this study we mainly rely to the consistency of this model with most recent observational data related to the background evolution. The new Supernova Type Ia (SNIa) Gold sample and Supernova Legacy Survey (SNLS) data, the position of the acoustic peak at the last scattering surface from the WMAP observations and the baryon acoustic oscillation peak found in the Sloan Digital Sky Survey (SDSS) are used to constrain the free parameter of the thick codimension 1 brane model. To infer its consistency with age of our universe, we compare the age of old cosmological objects with what computed using the best fit values for the model parameters. When the universe is matter dominated, $w=0$, at 68% level of confidence, the combination of Gold sample SNIa, CMB shift parameter and SDSS databases provides $\Omega_m=0.31_{-0.02}^{+0.02}$, $\Omega_{\cal{C}}=0.05_{-0.01}^{+0.01}$, $w_r=-1.40_{-0.20}^{+0.20}$, hence a spatially open universe with $\Omega_k=0.21_{-0.08}^{+0.08}$. The same combination with SNLS supernova observation gives $\Omega_m=0.28_{-0.02}^{+0.03}$, $\Omega_{\cal{C}}=0.037_{-0.004}^{+0.003}$, $w_r=-2.05_{-0.15}^{+0.15}$ consequently provides a spatially open universe $\Omega_k=0.11_{-0.07}^{+0.10}$. These results obviously seem to be in contradiction with the most recent WMAP results indicating a flat universe.