Scalar-tensor theories of gravity, neutrino physics, and the H0 tension

Abstract

We use Planck 2018 data to constrain the simplest models of scalar-tensor theories characterized by a coupling to the Ricci scalar of the type F(σ)R with F(σ) = N2 pl + ξσ2 . We update our results with previous Planck and BAO data releases obtaining the tightest constraints to date on the coupling parameters, that is ξ < 5.5 × 10−4 for Npl = 0 (induced gravity or equivalently extended Jordan-Brans-Dicke) and (Npl √ 8πG) − 1 < 1.8 × 10−5 for ξ = −1/6 (conformal coupling), both at 95% CL. Because of a modified expansion history after radiation-matter equality compared to the ΛCDM model, all these dynamical models accommodate a higher value for H0 and therefore alleviate the tension between Planck/BAO and distance-ladder measurement from SNe Ia data from 4.4σ at best to 2.7-3.2σ with CMB alone and 3.5-3.6σ including BAO data.