Hubble Parameter Measurement Constraints on the Redshift of the Deceleration–acceleration Transition, Dynamical Dark Energy, and Space Curvature

Abstract

We compile an updated list of 38 measurements of the Hubble parameter H(z) between redshifts 0.07z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 da , from these H(z) data. Within the error bars, the measured z 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 da =0.72±0.05 (0.84±0.03) for H 0 =68±2.8 (73.24±1.74) km sand should provide a reasonably model-independent estimate of this cosmological parameter. The H(z) data are consistent with the standard spatially flat ΛCDM cosmological model but do not rule out nonflat models or dynamical dark energy models.

Testing Verlinde's emergent gravity in early-type galaxies

“…However, at low redshifts, the shape of H(z) determined from observational probes are almost independent on the exact cosmological model adopted. This is true since various models are fitting the data producing local H(z) values which are consistent with H0 from ΛCDM cosmology within the measurement uncertainties (e.g., Carvalho et al 2008;Zhang et al 2014;Farooq et al 2017). For the redshifts studied in this paper, i.e.…”

Strategies to Ascertain the Sign of the Spatial Curvature

“…The simple fact that, observationally, q 0 is negative [24,[46][47][48], renders j 0 positive in the said model; i.e., cosmic acceleration should be increasing nowadays.…”

“…We use Equation (5) alongside the 28 experimental data H vs. z, in the interval 0.1 ≤ z ≤ 2.36, with their 1σ error bars, compiled by Farook et al [24] and listed in Table 1 (see also Figure 1) for the reader convenience, to draw Figure 2. The latter suggests that, given the experimental uncertainties, the possibility k = −1 also appears compatible with the inequality S A ≥ 0.…”

Accelerated cosmological expansion without tension in the Hubble parameter

“…It defines a singular perturbation of (9) which, after all, is first order in time in ΛCMD. Here, we elaborate on accelerated cosmological expansion by (8) and in ΛCDM, confronted with recent Hubble data H(z) [1,10] over an extended range of redshifts. This development is facilitated by analytic solutions for both in late time cosmology, parameterized by H 0 = H(0) and ω m = Ω M (0) of the Hubble parameter and density of (baryonic and dark) matter at the present redshift z = 0 ( §2).…”

“…While q(0) < 0 appears relatively secure from surveys of the Local Universe, the relationship (1) derives from classical general relativity, i.e., a covariant embedding of Newton's gravitational potential energy U N in geodesic motion in a metric of four-dimensional spacetime based on Einstein's principle of equivalence. 1 Applied to galaxy dynamics, we commonly preserve equivalence of geodesic motion to Newton's picture of force balance between gravitational and inertial forces with inertial mass m equal to gravitating mass m 0 , given by rest-mass energy m 0 c 2 , where c denotes the velocity of light. In particular, the latter is assumed to be scale-free, i.e., m = m 0 is assumed to hold true at arbitrarily small accelerations α conform Newton's second law (a proportional relation between force and acceleration).…”