Supernovae, CMB, and Gravitational Leakage into Extra Dimensions
Cédric Deffayet, Susana J. Landau, Julien Raux, Matias Zaldarriaga, Pierre Astier
TL;DR
This paper investigates a late-time acceleration mechanism based on gravitational leakage into an extra dimension within the DGP brane-world framework. It derives the background expansion from a modified Friedmann equation $H^2 + k/a^2 = \left( \sqrt{\frac{\rho}{3 M_{\rm Pl}^2} + \frac{1}{4 r_c^2}} + \frac{1}{2 r_c} \right)^2$ and an effective $w^{eff}_X(z)$, showing acceleration without a cosmological constant and a standard FRW limit when $H^{-1} \ll r_c$. It confronts the model with type Ia SN from SCP and CMB data, performing a four-parameter fit $(\Omega_M,\Omega_{r_c},{\cal M},\alpha)$ for the SN distance, and finds current observations compatible with the model. The paper also provides the perturbation evolution equations, highlighting that future measurements of structure growth could severely constrain or distinguish this scenario from $\Lambda$CDM.
Abstract
We discuss observational constraints coming from CMB and type Ia supernovae, for the model of accelerated universe produced by gravitational leakage into extra dimensions. Our fits indicate that the model is currently in agreement with the data. We also give the equations governing the evolution of cosmological perturbations. Future observations will be able to severely constrain the model.