Hubble parameter measurement constraints on the redshift of the deceleration-acceleration transition, dynamical dark energy, and space curvature

TL;DR

This study compiles 38 Hubble parameter measurements to constrain dark energy models, estimate the deceleration-acceleration transition redshift, and assess spatial curvature, finding results consistent with standard cosmology but allowing for alternatives.

Contribution

It provides updated constraints on dark energy parameters and transition redshift using a comprehensive $H(z)$ dataset, including model-independent estimates.

Findings

Measured transition redshift $z_{da} = 0.72 \,\pm\, 0.05$ (model-independent)

$H(z)$ data align with flat $\\Lambda$CDM but do not exclude curved or dynamical dark energy models

Results are sensitive to the assumed Hubble constant value

Abstract

We compile an updated list of 38 measurements of the Hubble parameter $H(z)$ between redshifts $0.07 \leq z \leq 2.36$ and use them to place constraints on model parameters of constant and time-varying dark energy cosmological models, both spatially flat and curved. We use five models to measure the redshift of the cosmological deceleration-acceleration transition, $z_{\rm da}$, from these $H(z)$ data. Within the error bars, the measured $z_{\rm da}$ are insensitive to the model used, depending only on the value assumed for the Hubble constant $H_0$. The weighted mean of our measurements is $z_{\rm da} = 0.72 \pm 0.05\ (0.84 \pm 0.03)$ for $H_0 = 68 \pm 2.8\ (73.24 \pm 1.74)$ km s$^{-1}$ Mpc$^{-1}$ and should provide a reasonably model-independent estimate of this cosmological parameter. The $H(z)$ data are consistent with the standard spatially-flat $\Lambda$CDM cosmological model but do not rule out non-flat models or dynamical dark energy models.