Constraining hybrid potential scalar field cosmological model in Lyra's geometry with recent observational data

TL;DR

This paper investigates a scalar-field dark-energy model within Lyra's geometry, using a time-dependent displacement vector to modify the Friedmann equations in a flat FRW universe. A hybrid scalar-field density $\rho_{\phi}=\rho_{\phi0}\,(1+z)^{\alpha}\,e^{n z}$ is adopted, and model parameters are constrained via a joint analysis of Pantheon SN Ia, BAO/CMB, and OHD data using an MCMC approach. The study finds a late-time transition at $z_t\approx0.756$ with $q_0\approx-0.625$, $\omega_{\phi0}\approx-1.042$, and a near-unity total density today, with statefinder $\{r_0,s_0\}=(1.09673,-0.02877)$ and jerk $j_0\approx1.11$, indicating a quintom-like evolution that is close to $\Lambda$CDM at present but diverges at late times. The results demonstrate that Lyra-based scalar-field cosmologies can fit current observations and replicate the observed transition from deceleration to acceleration, while offering distinctive late-time dynamics through the Lyra displacement vector and hybrid energy density. These findings provide a viable alternative framework for dark energy with testable predictions for future observational probes.

Abstract

In the current study, we investigate a scalar field cosmological model with Lyra's geometry to explain the present cosmic expansion in a homogeneous and isotropic flat FRW universe. In Einstein's field equations, we presupposed a variable displacement vector as an element of Lyra's geometry. In the context of the conventional theory of gravity, we suggest a suitable parameterization of the scalar field's dark energy density in the hybrid function of redshift $z$, confirming the essential transition behavior of the universe from a decelerating era to the present accelerated scenario. We present constraints on model parameters using the most recent observational data sets from OHD, BAO/CMB, and Pantheon, taking Markov Chain Monte Carlo (MCMC) analysis into account. For the proposed model, the best estimated values of parameters for the combined dataset (OHD, BAO/CMB, and Pantheon) are $ H_0 = 71.15\pm 0.26$ km/s/Mpc, $ Ω_{m0}=0.2625\pm 0.0024$, $ Ω_{\phi0} = 0.676\pm0.038$, $ α=-0.22\pm0.13$, $n = 0.096\pm0.079$, and $k = 0.38\pm0.32$. The model exhibits a flipping nature, and the redshift transition occurs at $z_t = 0.756^{+0.005}_{-0.015}$. The current value of the decelerated parameter for the proposed model is calculated as $q_0 = -0.625^{+0.067}_{-0.085}$ for the combined dataset. Some dynamical properties of the model like energy density ($ρ_φ$), scalar field pressure ($p_φ$), EoS parameter of scalar field ($ω_φ$), and effective EoS parameter ($ω_{eff}$) are analyzed and presented. Further, we have also examined the statefinder diagnosis and jerk parameters of the derived model. The total density parameter for the derived model is found to be unity which is in nice agreement with recent standard findings.

Figures (8)

• Figure 1: Confidence contour plot for joint data set of OHD, Pantheon and BAO.
• Figure 2: (a) Plot of Hubble rate $H(z)/(1+z)$ vs $z$ for $H_0 = 71.15\pm 0.26$ km/s/Mpc , (b) Distance modulus plot versus $z$ for $H_0 = 71.15\pm 0.26$ km/s/Mpc.
• Figure 3: Deceleration parameter $q$ as a function of $z$ for OHD + Pantheon + BAO data sets.
• Figure 4: (a) Energy density, (b) EoS.
• Figure 5: Deceleration parameter $q$ as a function of $z$ for OHD + Pantheon + BAO data sets.