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 ΛCDM 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 ΛCDM model works well. Statistical comparison using the Δχ2 strongly favors ΛCDM over CCC+TL for the H(z) data, with Δχ2 = 61.52. Crucially, the CCC+TL framework exhibits a severe internal tension, where the SN Ia-optimized speed-of-light variation index α is rejected by the H(z) dataset with a likelihood ratio of R ≈ 1.7 × 10⁻¹⁴. Our result suggests that the tension posed by JWST observations of compact high-z galaxies may originate from the intrinsic properties and evolution of galaxies in the early universe.