Testing the R_h = ct Universe Jointly with the Redshift-dependent Expansion rate and Angular-diameter and Luminosity Distances

We use three different data sets, specifically H(z) measurements from cosmic chronometers, the HII-galaxy Hubble diagram, and reconstructed quasar-core angular-size measurements, to perform a joint analysis of three flat cosmological models: the R_h = ct Universe, ΛCDM, and wCDM. For R_h = ct, the 1σ best-fit value of the Hubble constant H₀ is 62.336±1.464 km s⁻¹ Mpc⁻¹, which matches previous measurements (∼ 63 km s⁻¹ Mpc⁻¹) based on best fits to individual data sets. For ΛCDM, our inferred value of the Hubble constant, H₀ = 67.013 ± 2.578 km s⁻¹ Mpc⁻¹, is more consistent with the Planck optimization than the locally measured value using Cepheid variables, and the matter density Ω_m = 0.347 ±0.049 similarly coincides with its Planck value to within 1σ. For wCDM, the optimized parameters are H₀ = 64.718 ± 3.088 km s⁻¹ Mpc⁻¹, Ω_m = 0.247 ± 0.108 and w = −0.693 ± 0.276, also consistent with Planck. A direct comparison of these three models using the Bayesian Information Criterion shows that the R_h = ct universe is favored by the joint analysis with a likelihood of ∼ 97% versus . 3% for the other two cosmologies.