Tiziano Schiavone
University of Pisa, Italy

Abstract
The Hubble constant (H0) tension is a serious big deal in cosmology: the inconsistency between independent measurements of H0 related to probes in the late (Cepheids and Supernovae Ia, SNe Ia) and early Universe (cosmic microwave background, CMB) ranges from 4σ to 6σ. We investigate the H0 tension considering data from the Pantheon sample, a collection of 1048 SNe Ia, and the baryon acoustic oscillations (BAOs). We perform a redshift binned analysis to check the H0 values inside each bin via a MCMC method in the ΛCDM and w0waCDM cosmological models. After obtaining the values of H0 in each bin, we observe unexpectedly a slowly decreasing trend of H0(z) with the redshift, independently of the sample, the two cosmological models or the number of bins. Interestingly, the extrapolated values of H0(z) at the redshift of the last scattering surface, z=1100, are compatible in 1σ with the CMB measurements. If it is not due to statistical fluctuations, H0(z) could be caused by an evolution of a hidden astrophysical parameter, or alternatively it may be a signal of new physics. In this regard, we propose an f(R) modified gravity scenario in the dynamically equivalent Jordan frame, discussing the form of a scalar field potential able to explain a running H0(z).
[This talk is based on arXiv:2103.02117 and arXiv:2201.09848]

2022 November 23, 14:30

IA/U.Lisboa
Faculdade de Ciências da Universidade de Lisboa (C8.2.12)
Campo Grande, 1749-016 Lisboa