Cosmological implications of f(T, B) gravity: constraints from recent observations

In this work, we examine the theoretical framework of modified teleparallel gravity with the inclusion of the boundary term in the action and investigate its cosmological implications by considering the power-law model $f(T, B) = -T + \alpha (-B)^{\beta}$, with the aim of addressing the late-time accelerated expansion and the dark energy. In this context, $T$ denotes the torsion scalar and $B$ represents the boundary term, whose presence allows for departures from standard teleparallel dynamics and provides a unified description that connects torsion and curvature-based formulations, reproducing $f(T)$ and $f(R)$ gravity in appropriate limits. The viability of the model is assessed by confronting its theoretical predictions with observational data while constraining the cosmological and model parameters through a Markov Chain Monte Carlo (MCMC) analysis using cosmic chronometers (CC), the Pantheon Plus sample (PPS), and the DESI baryon acoustic oscillation (BAO) Data Release 2 (DR2) datasets, and comparing its performance with the standard $\Lambda$CDM model. The Akaike Information Criterion (AIC) analysis shows that the combined CC+PPS dataset strongly favors the $f(T, B)$ model, suggesting an improved phenomenological fit to late-time observations relative to $\Lambda$CDM. Our result further shows an alleviation of H0 tensions, although a dedicated analysis is required to establish its full statistical significance. Furthermore, the background cosmological quantities indicate that the model exhibits a dynamical phantom-divide crossing while remaining consistent with late-time observations and yielding a viable expansion history and characteristic dark energy evolution.