Cosmological Constraints on $f(T,B)$ Gravity from Observations of Early and Late Universe

TL;DR

This paper develops a combined observational approach to constrain $f(T,B)$ gravity models using early universe nucleosynthesis data and late universe Hubble measurements, refining parameter bounds and testing gravity modifications.

Contribution

It introduces a unified framework that jointly uses early and late universe data to constrain $f(T,B)$ gravity models, improving upon previous methods.

Findings

Joint analysis tightens parameter constraints.

Supports viability of torsion-based gravity modifications.

Provides a robust methodology for future observational tests.

Abstract

This study proposes a unified framework comprising two complementary approaches to constrain three functional forms of $f(T,B)$ gravity, namely the linear, quadratic, and general power law models, by jointly utilizing early and late Universe observations. First, we impose bounds on deviations in the weak interaction freeze-out temperature, informed by the latest measurements of the primordial helium-4 mass fraction. Second, we incorporate direct Hubble parameter data, $H(\mathcal{z})$, obtained from Cosmic Chronometers in the redshift range $0.07\le\mathcal{z}\le2.0$, to trace the expansion history of the Universe. By minimizing a combined chi-square statistic across both datasets, we derive the best-fit values and confidence intervals for each model parameter. The joint analysis significantly refines the parameter constraints compared to methods based solely on Big Bang Nucleosynthesis, thereby offering a more robust test of $f(T,B)$ gravity across cosmic epochs. The results support the viability of torsion-based modifications to General Relativity and provide a consistent methodology for future evaluation using upcoming observational data.