Космологічна діагностика голографічної темної енергії Всесвіту Барроу типу Біанкі-ІІ

Анотація

In this paper, we investigate a Bianchi type II anisotropic cosmological model in the framework of Barrow holographic dark energy, considering both the Hubble horizon and Granda–Oliveros scale as infrared cutoffs. To obtain exact solutions of the Einstein field equations, we assume a suitable relation between the metric potentials. Using Hubble cosmic chronometer data, we constrain the model parameters and obtain the best-fit values b₄ = −0.091+0.013 −0.012 and H₀ = 72.3±2.7 km s⁻¹Mpc⁻¹. The H(z) fit shows excellent agreement with observational data and overlaps with ΛCDM at low redshifts, with mild deviations at higher z. The physical behaviour of the model is examined through a detailed analysis of cosmological parameters. The deceleration parameter q(z) reveals a smooth transition from an early decelerating phase to the present accelerating epoch. The equation of state parameter ω_de shows quintom-like dynamics, evolving across the cosmological constant boundary and entering the phantom regime, consistent with late-time acceleration. Stability is tested using the squared sound speed v_s² , which remains positive in the recent Universe, ensuring classical stability. The ω_de–ω’_de phase plane indicates that both models lie in the freezing region, corresponding to faster acceleration. The statefinder diagnostics (r,s) and (r,q) further confirm the transition from the standard cold dark matter dominated phase to a de Sitter-like attractor, with trajectories showing clear deviations from ΛCDM.