English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We investigate whether the $4.4\sigma$ tension on $H_0$ between SH$_{0}$ES2019 and Planck 2018 can be alleviated by a variation of Newton's constant$G_N$ between the early and the late Universe. This changes the Hubble ratebefore recombination, similarly to adding $\Delta N_{\rm eff}$ extrarelativistic degrees of freedom. We implement a varying $G_N$ in ascalar-tensor theory of gravity, with a non-minimal coupling $(M^2+\beta\phi^2)R$. If the scalar $\phi$ starts in the radiation era at an initial value$\phi_I \sim 0.5~M_p$ and with $\beta<0$, a dynamical transition occursnaturally around the epoch of matter-radiation equality and the field evolvestowards zero at late times. As a consequence, the $H_0$ tension betweenSH$_{0}$ES (2019) and Planck 2018+BAO slightly decreases, as in $\Delta N_{\rmeff}$ models, to the 3.8$\sigma$ level. We then perform a fit to a combinedPlanck, BAO and supernovae (SH$_0$ES and Pantheon) dataset. When includinglocal constraints on Post-Newtonian (PN) parameters, we find$H_0=69.08_{-0.71}^{+0.6}~\text{km/s/Mpc}$ and a marginal improvement of$\Delta\chi^2\simeq-3.2$ compared to $\Lambda$CDM, at the cost of 2 extraparameters. In order to take into account scenarios where local constraintscould be evaded, we also perform a fit without PN constraints and find$H_0=69.65_{-0.78}^{+0.8}~\text{km/s/Mpc}$ and a more significant improvement$\Delta\chi^2=-5.4$ with 2 extra parameters. For comparison, we find that the$\Delta N_{\rm eff}$ model gives $H_0=70.08_{-0.95}^{+0.91}~\text{km/s/Mpc}$and $\Delta\chi^2=-3.4$ at the cost of one extra parameter, which disfavors the$\Lambda$CDM limit just above 2$\sigma$, since $\Delta N_{\rmeff}=0.34_{-0.16}^{+0.15}$. Overall, our varying $G_N$ model performs similarlyto the $\Delta N_{\rm eff}$ model in respect to the $H_0$ tension, if aphysical mechanism to remove PN constraints can be implemented.

The $H_0$ tension: $\Delta G_N$ vs. $\Delta N_{\rm eff}$