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 σ₈ and the current matter mass-energy density Ω_m from cluster number counts and weak lensing tomography, are considered in our numerical calculations. The strongest bound we find is |f_{R 0}|<3.7 ×10^-6 at 95% C.L. Forthcoming cluster surveys covering 10 000 deg² in the sky, with galaxy surface densities of O (10 ) arcmin^-2 could improve the precision in the σ₈-Ω_m relationship, tightening the above constraint.