Speaker
Description
The CCC+TL cosmological model has been remarkably successful in fitting the Pantheon+ SNe1a data (Brout et al. 2022; Scolnic et al. 2022), the small size of galaxies at cosmic dawn (Lovyagin et al. 2022), the absolute scale of the baryon acoustic oscillations (Carvalho et al 2021), as well as the angular size of the sound horizon (Gupta 2023, 2024, 2025a). Stemming its theoretical conception from Dirac’s large number hypothesis (Dirac 1937), it posits the covarying of the coupling constants (CCC), leaving no room for the dark sector of the standard ΛCDM model, along with the tired light (TL) contribution to the ascertained redshift. In a baryon-only Universe, the CCC+TL is also able to reproduce the observed flat rotation curves of galaxies, extending its validity to astrophysical scales without touching the gravitational laws.
The underlying physics is neatly encoded in the modified FLRW metric. The derived Friedmann equations capture the phenomenology of the Dark Matter and Dark Energy, which essentially emerges through weakening of the forces of nature in an expanding Universe, determined by a dimensionless covarying coupling (G(t)∝f(t)^3, h(t)∝f(t)^2, k(t)∝f(t)^2, c(t)∝f(t)), with f(t) a suitable function, such as f(t)=exp(α(t-t0)), α being a constant. The stretched timeline of the hypothesized scenario (26.7 Gyr) comfortably accommodates the formation timescales of high-z galaxies observed by the James Webb Space Telescope (Naidu et al. 2022). Also, using Cosmic chronometer data (Moresco et al. 2022), we have tested the model's validity, disproving recent claims that wrongly neglected the TL scaling to the differential aging rate.
Future work comprises subsequent tests inferring the Hubble constant through Fast Radio Burst data (Piratova-Moreno et al. 2025) and precision cosmography (Courtois et al. 2025), following the generalised background equations, examining the model predictions at scales of 300 Mpc. Semi-analytical estimates dictate the existence of ample amount of time for structures to form in the CC+TL framework (Gupta 2024b). Numerically, sophisticated simulations are currently being designed, adjusting the N-body integrator, such as RAMSES (Teyssier 2002), and traditional Boltzmann solvers, such as CLASS (Blas, D. et al. 2011). Comparisons with fiducial cosmologies (TNG300, Nelson et al. 2018) and alternative schemes (Samaras et al. 2025) are to be explored.
