Cosmological constraints on f ( T, B ) gravity from observations of early and late universe

Abstract We present a unified framework that combines early- and late-Universe observations to constrain three functional realizations of f T , B gravity: the linear, quadratic, and general power-law models. First, constraints on deviations from the standard weak interaction freeze-out temperature are derived using the most recent measurements of the primordial helium-4 mass fraction. Second, we perform a joint analysis incorporating five priors: Type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, Big Bang Nucleosynthesis, and Cosmic Microwave Background in order to place bounds on the model parameters. The joint likelihood analysis significantly tightens the constraints compared to individual datasets. Third, we test the null, strong, and dominant energy conditions to evaluate the physical viability of the best-fit solutions across the cosmic redshift range. Our results show that all three f T , B models are consistent with current observations and exhibit stable behavior under the energy-condition criteria, supporting torsion–boundary modified gravity as a robust and viable alternative of General Relativity.