Running Hubble constant from the SNe Ia Pantheon sample?

The mismatch between different independent measurements of the expansion rate of the Universe is known as the Hubble constant ($H_0$) tension, and it is a serious and pressing problem in cosmology. We investigate this tension considering the dataset from the Pantheon sample, a collection of 1048 Type Ia Supernovae (SNe Ia) with a redshift range $0<z<2.26$. We perform a binned analysis in redshift to study if the $H_0$ tension also occurs in SNe Ia data. Hence, we build equally populated subsamples in three and four bins, and we estimate $H_{0}$ in each bin considering the $Λ$CDM and $w_{0}w_{a}$CDM cosmological models. We perform a statistical analysis via a Markov Chain Monte Carlo (MCMC) method for each bin. We observe that $H_0$ evolves with the redshift, using a fit function $H_{0}(z)=\tilde{H}_{0} (1+z)^{-α}$ with two fitting parameters $α$ and $\tilde{H}_{0}$. Our results show a decreasing behavior of $H_0$ with $α\sim 10^{-2}$ and a consistency with no evolution between 1.2 $σ$ and 2.0 $σ$. Considering the $H_0$ tension, we extrapolate $H_{0}(z)$ until the redshift of the last scattering surface, $z=1100$, obtaining values of $H_0$ consistent in 1 $σ$ with the cosmic microwave background (CMB) measurements by Planck. Finally, we discuss possible $f(R)$ modified gravity models to explain a running Hubble constant with the redshift, and we infer the form of the scalar field potential in the dynamically equivalent Jordan frame.

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