Is there a concordance value for $H_0$?

TL;DR

This study compares cosmological model predictions with observational data to estimate the current expansion rate of the Universe, finding that different models yield similar $H_0$ values consistent with some measurements but not others.

Contribution

It provides a comprehensive joint analysis of multiple datasets to constrain cosmological parameters and compares different models' fits, including spatially flat and inhomogeneous models.

Findings

$H_0$ estimates are consistent with CMB measurements.

Models are statistically indistinguishable except for LTB.

$H_0$ differs from Cepheids-based measurements by 2.5$\sigma$.

Abstract

We test the theoretical predictions of several cosmological models against different observables to compare the indirect estimates of the current expansion rate of the Universe determined from model fitting with the direct measurements based on Cepheids data published recently. We perform a statistical analysis of type Ia supernova (SN Ia), Hubble parameter, and baryon acoustic oscillation data. A joint analysis of these datasets allows us to better constrain cosmological parameters, but also to break the degeneracy that appears in the distance modulus definition between $H_0$ and the absolute B-band magnitude of SN Ia, $M_0$. From the theoretical side, we considered spatially flat and curvature-free $\Lambda$CDM, $w$CDM, and inhomogeneous Lema\^{i}tre-Tolman-Bondi (LTB) models. To analyse SN Ia we took into account the distributions of SN Ia intrinsic parameters. For the $\Lambda$CDM model we find that $\Omega_m=0.35\pm0.02$, $H_0=(67.8\pm1.0)\,$km$\,$s$^{-1}/$Mpc, while the corrected SN absolute magnitude has a normal distribution ${\cal N}(19.13,0.11)$. The $w$CDM model provides the same value for $\Omega_m$, while $H_0=(66.5\pm1.8)\,$km$\,$s$^{-1}/$Mpc and $w=-0.93\pm0.07$. When an inhomogeneous LTB model is considered, the combined fit provides $H_0=(64.2\pm1.9)\,$km$\,$s$^{-1}/$Mpc. Both the Akaike information criterion and the Bayes factor analysis cannot clearly distinguish between $\Lambda$CDM and $w$CDM cosmologies, while they clearly disfavour the LTB model. For the $\Lambda$CDM, our joint analysis of the SN Ia, the Hubble parameter, and the baryon acoustic oscillation datasets provides $H_0$ values that are consistent with CMB-only Planck measurements, but they differ by $2.5\sigma$ from the value based on Cepheids data.