This study performs a comparative cosmological analysis of Brans–Dicke theory (BDT) and Formula: see text gravity in the anisotropic Bianchi type-I spacetime. By using a hyperbolic sine form of the scale factor, we constrain the free parameters Formula: see text and Formula: see text against 77 Formula: see text data points via Formula: see text minimization, obtaining Formula: see text and Formula: see text, with a reduced chi-square Formula: see text. The model predicts the present Hubble and deceleration parameters as Formula: see text and Formula: see text, respectively. We derive and examine the dynamical evolution of energy density, pressure, and the equation of state (EoS) parameter. A key outcome is the marked difference in late-time behavior: the Formula: see text model exhibits stronger acceleration with an EoS parameter trending toward phantom regimes, whereas the BDT model shows a distinctive late-time re-acceleration phase driven by the scalar field dynamics. These results highlight how geometric and scalar-field modifications of gravity lead to observationally distinguishable cosmic evolution.
Sharma et al. (Thu,) studied this question.
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