Scalar-tensor theories of gravity, neutrino physics, and the $H_0$ tension. (arXiv:2004.14349v2 [astro-ph.CO] UPDATED)

<a href="http://arxiv.org/find/astro-ph/1/au:+Ballardini_M/0/1/0/all/0/1">Mario Ballardini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Braglia_M/0/1/0/all/0/1">Matteo Braglia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Finelli_F/0/1/0/all/0/1">Fabio Finelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paoletti_D/0/1/0/all/0/1">Daniela Paoletti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Starobinsky_A/0/1/0/all/0/1">Alexei A. Starobinsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Umilta_C/0/1/0/all/0/1">Caterina Umiltà</a>

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(sigma)

R$ with $F(sigma) = N_{pl}^2 + xi sigma^2$. We update our results with

previous $Planck$ and BAO data releases obtaining the tightest constraints to

date on the coupling parameters, that is $xi < 5.5 times 10^{-4}$ for

$N_{pl}=0$ (induced gravity or equivalently extended Jordan-Brans-Dicke) and

$(N_{pl} sqrt{8 pi G})-1 < 1.8 times 10^{-5}$ for $xi = -1/6$ (conformal

coupling), both at 95% CL. Because of a modified expansion history after

radiation-matter equality compared to the $Lambda$CDM model, all these

dynamical models accommodate a higher value for $H_0$ and therefore alleviate

the tension between $Planck$/BAO and distance-ladder measurement from SNe Ia

data from $4.4sigma$ at best to $2.3sigma$. We show that all these results

are robust to changes in the neutrino physics. In comparison to the

$Lambda$CDM model, partial degeneracies between neutrino physics and the

coupling to the Ricci scalar allow for smaller values $N_{rm eff} sim 2.8$,

$1sigma$ lower compared to the standard $N_{rm eff} = 3.046$, and relax the

upper limit on the neutrino mass up to 40%.

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(sigma)

R$ with $F(sigma) = N_{pl}^2 + xi sigma^2$. We update our results with

previous $Planck$ and BAO data releases obtaining the tightest constraints to

date on the coupling parameters, that is $xi < 5.5 times 10^{-4}$ for

$N_{pl}=0$ (induced gravity or equivalently extended Jordan-Brans-Dicke) and

$(N_{pl} sqrt{8 pi G})-1 < 1.8 times 10^{-5}$ for $xi = -1/6$ (conformal

coupling), both at 95% CL. Because of a modified expansion history after

radiation-matter equality compared to the $Lambda$CDM model, all these

dynamical models accommodate a higher value for $H_0$ and therefore alleviate

the tension between $Planck$/BAO and distance-ladder measurement from SNe Ia

data from $4.4sigma$ at best to $2.3sigma$. We show that all these results

are robust to changes in the neutrino physics. In comparison to the

$Lambda$CDM model, partial degeneracies between neutrino physics and the

coupling to the Ricci scalar allow for smaller values $N_{rm eff} sim 2.8$,

$1sigma$ lower compared to the standard $N_{rm eff} = 3.046$, and relax the

upper limit on the neutrino mass up to 40%.

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