Constraints on Cosmographic Functions of Cosmic Chronometers Data Using Gaussian Processes

TL;DR

This study uses Gaussian Processes with Hubble parameter data to non-parametrically constrain cosmographic functions, including the snap, providing insights into cosmic expansion without relying on specific models.

Contribution

It introduces a model-independent, Gaussian Process-based approach to reconstruct higher-order cosmographic functions from observational data, enhancing the analysis of cosmic acceleration.

Findings

Estimated transition redshift z_tr ≈ 0.637 with uncertainties

Derived Hubble constant H_0 ≈ 69.45 km/s/Mpc

Results are consistent with ΛCDM model

Abstract

We study observational constraints on the cosmographic functions up to the fourth derivative of the scale factor with respect to cosmic time, i.e., the so-called snap function, using the non-parametric method of Gaussian Processes. As observational data we use the Hubble parameter data. Also we use mock data sets to estimate the future forecast and study the performance of this type of data to constrain cosmographic functions. The combination between a non-parametric method and the Hubble parameter data is investigated as a strategy to reconstruct cosmographic functions. In addition, our results are quite general because they are not restricted to a specific type of functional dependency of the Hubble parameter. We investigate some advantages of using cosmographic functions instead of cosmographic series, since the former are general definitions free of approximations. In general, our results do not deviate significantly from $\Lambda CDM$. We determine a transition redshift $z_{tr}=0.637^{+0.165}_{-0.175}$ and $H_{0}=69.45 \pm 4.34$. Also assuming priors for the Hubble constant we obtain $z_{tr}=0.670^{+0.210}_{-0.120}$ with $H_{0}=67.44$ (Planck) and $z_{tr}=0.710^{+0.159}_{-0.111}$ with $H_{0}=74.03$(SH0ES). Our main results are summarized in table 2.