On the Evolution of the Hubble Constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: A Feasibility Study for GRB-Cosmology in 2030

The difference from 4 to 6 sigma in the Hubble constant (H0) between the values observed with the local (Cepheids and Supernovae Ia, SNe Ia) and the high-z probes (Cosmic Microwave Background obtained by the Planck data) still challenges the astrophysics and cosmology community. Previous analysis has shown that there is an evolution in the Hubble constant that scales as f(z)=H0/(1+z)(eta), where H-0 is H-0(z=0) and eta is the evolutionary parameter. Here, we investigate if this evolution still holds by using the SNe Ia gathered in the Pantheon sample and the Baryon Acoustic Oscillations. We assume H-0=70kms(-1)Mpc(-1) as the local value and divide the Pantheon into three bins ordered in increasing values of redshift. Similar to our previous analysis but varying two cosmological parameters contemporaneously (H-0, omega(0m) in the lambda CDM model and H-0, w(a) in the w(0)w(a)CDM model), for each bin we implement a Markov-Chain Monte Carlo analysis (MCMC) obtaining the value of H-0 assuming Gaussian priors to restrict the parameters spaces to values we expect from our prior knowledge of the current cosmological models and to avoid phantom Dark Energy models with w <-1. Subsequently, the values of H-0 are fitted with the model f(z). Our results show that a decreasing trend with eta & SIM;10(-2) is still visible in this sample. The eta coefficient reaches zero in 2.0 sigma for the lambda CDM model up to 5.8 sigma for w0waCDM model. This trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models, a possible proposition is the modified gravity theories, f(R). This analysis is meant to further cast light on the evolution of H-0 and it does not specifically focus on constraining the other parameters. This work is also a preparatory to understand how the combined probes still show an evolution of the H-0 by redshift and what is the current status of simulations on GRB cosmology to obtain the uncertainties on the omega(0m) comparable with the ones achieved through SNe Ia.

Automated summary

This paper discusses the evolution of the Hubble constant and presents conclusions based on the analysis of supernovae and acoustic oscillation data. The study finds a decreasing trend with eta in the sample, which may be related to astrophysical biases or modified gravity theories. This research is important for understanding the evolution of the Hubble constant.