Stringent constraint on the CCC+TL cosmology with $H(z)$ Measurements

Recently, the Covarying Coupling Constants and Tired Light (CCC+TL) hybrid model was proposed to explain the unexpectedly small angular diameters of high-redshift galaxies observed by the James Webb Space Telescope (JWST) that are challenging to reconcile with the $Λ$CDM model. In this work, we test the CCC+TL model against model-independent Hubble parameter [$H(z)$] measurements obtained from cosmic chronometers. It turns out that the parameter set optimized for the type-Ia supernova (SN Ia) dataset within the CCC+TL model fails to reproduce the $H(z)$ data, but the $Λ$CDM model works well. Statistical comparison using the Bayesian Information Criterion (BIC) strongly favors $Λ$CDM over CCC+TL for the $H(z)$ data, with $Δ\mathrm{BIC} = 60.85$. Additionally, the fit of the CCC+TL model to the $H(z)$ data results in a best-fit value for the speed-of-light variation index parameter $α$ disagreeing with that for the SN Ia data at the $\sim 6σ$ level, demonstrating significant internal tension within the CCC+TL framework.