Measurements of $H_0$ and reconstruction of the dark energy properties from a model-independent joint analysis

TL;DR

This study uses Gaussian processes to analyze multiple cosmological data sets, accurately measuring the Hubble constant and exploring dark energy properties in a model-independent way, revealing tensions with CMB-based measurements.

Contribution

The paper introduces a joint, model-independent analysis of cosmological data using Gaussian processes to constrain $H_0$ and dark energy properties, providing new insights into their values and behavior.

Findings

$H_0$ measured at 73.78 ± 0.84 km s$^{-1}$Mpc$^{-1}$, consistent with local measurements.

Detected $c^2_s < 0$ at ~2$\sigma$, indicating possible dark energy perturbation anomalies.

Found $X$ potentially negative for $z > 1.5$, suggesting unusual dark energy evolution.

Abstract

Gaussian processes (GP) provide an elegant and model-independent method for extracting cosmological information from the observational data. In this work, we employ GP to perform a joint analysis by using the geometrical cosmological probes such as Supernova Type Ia (SN), Cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the H0LiCOW lenses sample to constrain the Hubble constant $H_0$, and reconstruct some properties of dark energy (DE), viz., the equation of state parameter $w$, the sound speed of DE perturbations $c^2_s$, and the ratio of DE density evolution $X = \rho_{\rm de}/\rho_{\rm de,0}$. From the joint analysis SN+CC+BAO+H0LiCOW, we find that $H_0$ is constrained at 1.1\% precision with $H_0 = 73.78 \pm 0.84$ km s$^{-1}$Mpc$^{-1}$, which is in agreement with SH0ES and H0LiCOW estimates, but in $\sim$6.2$\sigma$ tension with the current CMB measurements of $H_0$. With regard to the DE parameters, we find $c^2_s < 0$ at $\sim$2$\sigma$ at high $z$, and the possibility of $X$ to become negative for $z > 1.5$. We compare our results with the ones obtained in the literature, and discuss the consequences of our main results on the DE theoretical framework.