Looking for an extra dimension with tomographic cosmic shear
Yong-Seon Song
TL;DR
The paper addresses distinguishing DGP brane-world gravity from dark energy models that yield similar expansion histories. It introduces a tomographic cosmic-shear framework that separates geometry and growth via direct measurements of the angular-diameter-distance proxies $\bar{r}_i$ and the growth-factor parameters $F_i$. In DGP, the growth of structure is suppressed by weakened gravity, modifying the Poisson equation with a factor $(1-\frac{1}{2r_cH})^{-1}$, leading to a different growth history than DE even at fixed $H(z)$. A Fisher-matrix analysis combining future CMB priors and weak-lensing surveys shows that $\bar{r}_i$ and $F_i$ can be measured with multi-percent precision, enabling discrimination between DGP and DE; ground-based G2$\pi$ can separate them at ~95% CL when fitting both, while space-based S3000 provides a meaningful but smaller separation. Joint measurements of geometry and growth thus constrain the crossover scale $r_c$ and offer a practical test of extra dimensions with upcoming surveys.
Abstract
The cosmic acceleration was discovered in one of the brane-based models. We are interested in discriminating this model from the dark energy by tomographic cosmic shear. Growth factors are different in the two models when one adjusts parameters to get nearly identical H(z). The two models could be distinguished with independent determinations of both geometrical factors and the growth factor. We introduce new parameterizations to separate the influence of geometry and the influence of growth on cosmic shear maps. We find that future observations will be able to distinguish between both models.