Corrected constraints on big bang nucleosynthesis in a modified gravity model of $f(R) \propto R^n$

TL;DR

This study examines big bang nucleosynthesis within a modified gravity framework where the gravitational action scales as R^n, constraining the model's parameter n using observed light element abundances.

Contribution

It provides the first detailed analysis of primordial element abundances in an R^n gravity model and constrains the parameter n using observational data.

Findings

The parameter n is tightly constrained around 1, with (n-1)=(-0.86±1.19)×10^{-4} at 95% confidence.

The model's predictions for element abundances are consistent with observational data within the constrained parameter range.

The study narrows down viable modifications to gravity during the early universe based on nucleosynthesis constraints.

Abstract

Big bang nucleosynthesis in a modified gravity model of $f(R)\propto R^n$ is investigated. The only free parameter of the model is a power-law index $n$. We find cosmological solutions in a parameter region of $1< n \leq (4+\sqrt{6})/5$. We calculate abundances of $^4$He, D, $^3$He, $^7$Li, and $^6$Li during big bang nucleosynthesis. We compare the results with the latest observational data. It is then found that the power-law index is constrained to be $(n-1)=(-0.86\pm 1.19)\times 10^{-4}$ (95 % C.L.) mainly from observations of deuterium abundance as well as $^4$He abundance.