2023MNRAS.524.3385G

Deep space observations of the JWST have revealed that the structure and masses of very early Universe galaxies at high redshifts ($z\sim15$), existing at $\sim$0.3 Gyr after the Big Bang, may be as evolved as the galaxies in existence for $\sim10$ Gyr. The JWST findings are thus in strong tension with the ${\rm{\Lambda}}$CDM cosmological model. While tired light (TL) models have been shown to comply with the JWST angular galaxy size data, they cannot satisfactorily explain isotropy of the cosmic microwave background (CMB) observations or fit the supernovae distance modulus versus redshift data well. We have developed hybrid models that include the tired light concept in the expanding universe. The hybrid ${\rm{\Lambda}}$CDM model fits the supernovae type 1a data well but not the JWST observations. We present a model with covarying coupling constants (CCC), starting from the modified FLRW metric and resulting Einstein and Friedmann equations, and a CCC + TL hybrid model. They fit the Pantheon + data admirably, and the CCC + TL model is compliant with the JWST observations. It stretches the age of the Universe to 26.7 Gyr with 5.8 Gyr at $z = 10$ and 3.5 Gyr at $z = 20$, giving enough time to form massive galaxies. It thus resolves the 'impossible early galaxy' problem without requiring the existence of primordial black hole seeds or modified power spectrum, rapid formation of massive population III stars, and super Eddington accretion rates. One could infer the CCC model as an extension of the ${\rm{\Lambda}}$CDM model with a dynamic cosmological constant.