An analysis of helium primordial nucleosynthesis with a variable cosmological coupling

TL;DR

This paper investigates how variations in the gravitational coupling during the early Universe's nucleosynthesis affect helium production, using a Brans-Dicke cosmological model to derive constraints from observational data.

Contribution

It introduces a semi-analytical method to compute primordial helium abundance as a function of a variable gravitational coupling within a Brans-Dicke framework.

Findings

Higher G during nucleosynthesis increases helium abundance.

Constraints on G variation are derived from observational helium data.

The model links G variability to primordial element synthesis.

Abstract

The synthesis of helium in the early Universe depends on many input parameters, including the value of the gravitational coupling during the period when the nucleosynthesis takes place. We compute the primordial abundance of helium as function of the gravitational coupling, using a semi-analytical method, in order to track the influence of $G$ in the primordial nucleosynthesis. To be specific, we construct a cosmological model with varying $G$, using the Brans-Dicke theory. The greater the value of $G$ at nucleosynthesis period, the greater the abundance of helium predicted. Using the observational data for the abundance of the primordial helium, constraints for the time variation of $G$ are established.