Big Bang Nucleosynthesis Constraints on the CCC+TL Cosmology

TL;DR

This paper examines whether Big Bang nucleosynthesis remains compatible with the CCC+TL cosmology, finding that with appropriate rescaling, the predicted light-element abundances are essentially unchanged from standard models.

Contribution

It demonstrates that BBN predictions are preserved under CCC+TL cosmology through specific scaling of interaction and decay rates, extending the model's viability.

Findings

BBN predictions remain consistent with CCC+TL when rates scale with the Hubble rate.

Light-element abundances are nearly identical for standard and CCC+TL scenarios within numerical precision.

Adopting lower baryon density from Pantheon+ data affects lithium and deuterium predictions, but BBN alone cannot distinguish between densities.

Abstract

We investigate whether Big Bang nucleosynthesis (BBN) remains compatible with the Covarying Coupling Constants plus Tired Light (CCC+TL) cosmology. In this framework, only quantities with explicit length dimensionality covary through a universal scaling function $f \left( z \right)$, while dimensionless constants and dimensionless ratios remain invariant. At the redshifts $z$ relevant to BBN, $f \left( z \right )$ approaches a constant plateau $f_{\text{max}} \left( z \right) \simeq 3$, and the tired-light contribution is negligible, so the early-time dynamics reduce to a global rescaling of dimensioned quantities. In particular, the Hubble expansion rate $H$ at fixed temperature $T$ satisfies $H_{\text{CTL}} \left( T \right) = f^{-1}_{\text{max}} H_{\Lambda\text{CDM}}\left( T\right)$, implying a longer cooling time $\Delta t$ between weak freeze-out and the onset of nucleosynthesis by the same factor (CCC+TL labeled as $\textit{CTL}$). We find that BBN predictions are preserved provided the relevant interaction rates $\Gamma$ and decay rates governing the neutron lifetime ${\tau}_n$ share the same plateau scaling as $H$, so that governing combinations such as $\Gamma\text{/}H$ and $\text{exp} \left( -\Delta t \text{/} {\tau}_n \right)$ remain invariant. Implementing these plateau rescalings in the Kawano/NUC123 network (via a single control parameter $\texttt{fctl} \equiv f_{\text{max}}$) yields identical light-element abundances for $\texttt{fctl}= 1$ ($\Lambda$CDM) and $\texttt{fctl} = 3\left( \text{CCC+TL} \right)$ to within $10^{-3} - 10^{-4}$ level, consistent with numerical rounding. We also illustrate that adopting the lower late-time CCC+TL baryon density from the Pantheon+ data fit can reduce the ${}^7\text{Li}$ discrepancy but simultaneously increases D/H, implying that BBN alone does not select between the late-time baryon-density inferences considered here.