On the current status of Modified Gravity

Abstract

We revisit the cosmological viability of the Hu $\&$ Sawicki modified gravity scenario. The impact of such a modification on the different cosmological observables, including gravitational waves, is carefully described. The most recent cosmological data, as well as constraints on the relationship between the clustering parameter ${\sigma }_8$ and the current matter mass-energy density ${\Omega }_m$ from cluster number counts and weak lensing tomography, are considered in our numerical calculations. The strongest bound we find is $|f_{R0}|<3.7\times 10^{-6}$ at $95\%$~CL. Forthcoming cluster surveys covering 10,000 deg${}^2$ in the sky, with galaxy surface densities of $\mathcal{O}(10)$~arcmin${}^{-2}$ could improve the precision in the ${\sigma }_8$-${\Omega }_m$ relationship, tightening the above constraint.

Comments: 11 pages, 6 figures and 2 Tables. Final published version in the PRD journal