Accelerating Five-Dimensional Bianchi Type-I Cosmology in Saez–Ballester Theory with Hyperbolic Expansion
Abstract
We present a five-dimensional anisotropic Bianchi type-I cosmological model in Saez--Ballester scalar--tensor theory employing the hyperbolic expansion law α(t)=sinhα(βt). Exact solutions of the field equations are derived and their cosmological behavior is examined. The model evolves from an initial singular state to a late-time accelerated phase, with anisotropy diminishing and isotropization achieved asymptotically. The deceleration parameter approaches (q = - 1), while (ωde ≈ -1.308) indicates phantom dark-energy behavior. The null, weak, and dominant energy conditions remain satisfied, whereas the strong energy condition is violated, supporting the observed cosmic acceleration. Furthermore, the statefinder and Om diagnostics reveal that the model asymptotically approaches the ΛCDM scenario.
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