Observation constraints on scalar field cosmological model in Anisotropic universe
Vinod Kumar Bhardwaj, Anil Kumar Yadav
TL;DR
This work investigates a scalar-field dark energy model in an anisotropic LRS Bianchi type-I universe and constrains its parameters using MCMC with observational data from OHD, BAO, and Pantheon. Employing a CPL-Linder parametrization for the scalar field equation of state and including a shear-driven anisotropy term, the authors extract best-fit values such as $H_0$, $Ω_{m0}$, $Ω_{φ0}$, and $Ω_{σ0}$, finding a transition from deceleration to acceleration at $z_t \approx 0.70$ and a present $q_0$ in the phantom/quintessence regime. The model yields a present age around $t_0 \sim 13.7$–$13.8$ Gyr, a particle horizon scale $R_p \sim 2.386\,H_0^{-1}$ at high redshift, and a jerk parameter $j$ that signals deviation from $\Lambda$CDM. Diagnostics such as Om indicate phantom-like dynamics, and energy conditions reveal a consistent acceleration with NEC/SEC violation, while WEC/DEC hold. Overall, the results support the viability of a scalar-field cosmology in an anisotropic background as compatible with current observations and predictive of distinctive late-time behavior.
Abstract
In this study, we have explored a scalar field cosmological model in the axially symmetric Bianchi type-I universe. In this study, our aim is to constrain the scalar field dark energy model in an anisotropic background. For this purpose, the explicit solution of the developed field equations for the model is determined and analysed. Constraints on the cosmological model parameters are established utilizing Markov Chain Monte Carlo (MCMC) analysis and using the latest observational data sets of OHD, BAO, and Pantheon. For the combined dataset (OHD, BAO, and Pantheon), the best-fit values of Hubble and density parameters are estimated as $ H_{0} = 71.54\pm 0.28$, $Ω_{m0}=0.2622\pm0.0021$ $Ω_{\phi0} = 0.7331\pm0.0046$, and $Ω_{σ0} = 0.000162\pm0.000063$. The model shows a flipping nature and redshift transition occurs at $z_{t} = 0.6964^{+0.0136}_{-0.0006}$, and the present value of decelerated parameter is computed to be $q_{0} = -0.6964\pm0.028$ for the combined dataset. We have explored characteristics like the universe's age, particle horizon, deceleration parameter, and jerk parameter. The dynamical properties such as energy density $ρ_φ$, scalar field pressure $p_φ$, and equation of state parameter $ω_φ$ are analyzed and presented. We have also described the behavior of the scalar potential $V(φ)$ and scalar fields. Furthermore, the authors also described the behavior of energy conditions in scalar-tensor cosmology. The scenario of the present accelerated expansion of the universe is described by the contribution of the scalar field.