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We conduct a Bayesian analysis of recent observational datasets, specifically the Cosmic Chronometers (CC) dataset and Pantheon samples, to investigate the evolution of the EoS parameter in dark energy models. Our study focused on the effective EoS parameter, which is described by the parametric form ω eff = - 1 1 + m (1 + z) n , where m and n are model parameters. This parametric form is applicable within the framework of f (R , L m) gravity, where R represents the Ricci scalar and L m is the matter Lagrangian. Here, we examine a non-linear f (R , L m) model characterized by the functional form f (R , L m) = R 2 + L m α , where α is the free parameter of the model. We examine the evolution of several cosmological parameters, including the effective EoS parameter ω eff , the deceleration parameter q, the density parameter ρ , the pressure p, and the statefinder parameters. Our analysis revealed that the constrained current value of the effective EoS parameter, ω eff 0 = - 0.68 ± 0.06 for both the CC and Pantheon datasets, points towards a quintessence phase. Moreover, at redshift z = 0 , the deceleration parameter, q 0 = - 0. 61 - 0.01 + 0.01 , indicates that the present Universe is undergoing accelerated expansion. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new parametrization of dark energy based on the Om(z) diagnostic tool behavior. For this purpose, we investigate a functional form of the Om(z) that predicts the popular dark energy dynamical models, namely phantom and quintessence. We also found the famous cosmological constant for specified values of the model's parameters. We employed the Markov Chain Monte Carlo approach to constrain the cosmological model using Hubble, Pantheon samples, and BAO datasets. Finally, we used observational constraints to investigate the characteristics of dark energy evolution and compare our findings to cosmological predictions. [ABSTRACT FROM AUTHOR]

The paper presents Barrow holographic dark energy (infrared cut-off is the Hubble horizon) suggested by Barrow [The area of a rough black hole, Phys. Lett. B 808 (2020) 135643] recently in an anisotropic Bianchi type-I Universe within the framework of f (Q) symmetric teleparallel gravity, where the non-metricity scalar Q is responsible for the gravitational interaction. We consider two cases: Interacting and non-interacting models of pressureless dark matter and Barrow holographic dark energy by solving f (Q) symmetric teleparallel field equations. To find the exact solutions of the field equations, we assume that the time-redshift relation follows a Lambert function distribution as t (z) = m t 0 l g (z) , where g (z) = Lambert W l m e l − ln (1 + z) m , m and l are non-negative constants and t 0 represents the age of the Universe. Moreover, we discuss several cosmological parameters such as energy density, equation of state (EoS) and skewness parameters, squared sound speed, and (ω B − ω B ′ ) plane. Finally, we found the values of the deceleration parameter (DP) for the Lambert function distribution as q (z = 0) = − 0. 4 5 and q (z = − 1) = − 1 which are consistent with recent observational data, i.e. DP evolves with cosmic time from initial deceleration to late-time acceleration. [ABSTRACT FROM AUTHOR]

Understanding the evolution of dark energy poses a significant challenge in modern cosmology, as it is responsible for the universe's accelerated expansion. In this study, we focus on a specific f (T) cosmological model and analyze its behavior using observational data, including 31 data points from the CC dataset, 1048 points from the Pantheon SNe Ia samples, and 6 points from the BAO dataset. By considering a linear f (T) model with an additional constant term, we derive the expression for the Hubble parameter as a function of cosmic redshift for non-relativistic pressureless matter. We obtain the best-fit values for the Hubble constant, H 0 , and the model parameters α and β , indicating a stable model capable of explaining late-time cosmic acceleration without invoking a dark energy component. This is achieved through modifying field equations to account for the observed accelerated expansion of the universe. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the cosmological implications and constraints of Weyl-type f (Q , T) gravity. This theory introduces a coupling between the non-metricity Q and the trace T of the energy–momentum tensor, using the principles of proper Weyl geometry. In this geometry, the scalar non-metricity Q , which characterizes the deviations from Riemannian geometry, is expressed in its standard Weyl form ∇ μ g α β = − w μ g α β and is determined by a vector field w μ. To study the implications of this theory, we propose a deceleration parameter with a single unknown parameter χ , which we constrain by using the latest cosmological data. By solving the field equations derived from Weyl-type f (Q , T) gravity, we aim to understand the behavior of the energy conditions within this framework. In the present work, we consider two well-motivated forms of the function f (Q , T) : (i) the linear model represented by f (Q , T) = α Q + β 6 κ 2 T , and (ii) the coupling model represented by f (Q , T) = γ 6 H 0 2 κ 2 Q T , where α , β , and γ are free parameters. Here, κ 2 = 1 16 π G represents the gravitational coupling constant. In both of the models considered, the strong energy condition is violated, indicating consistency with the present accelerated expansion. However, the null, weak, and dominant energy conditions are satisfied in these models. [ABSTRACT FROM AUTHOR]

In this paper, we present a spatially homogeneous and anisotropic Bianchi type-I cosmological model with a viscous bulk fluid in f (R , T) gravity where R and T are the Ricci scalar and trace of the energy-momentum tensor, respectively. The field equations are solved explicitly using the hybrid law of the scale factor, which is related to the average Hubble parameter and gives a time-varying deceleration parameter (DP). We found the deceleration parameter describing two phases in the universe, the early deceleration phase (q > 0) and the current acceleration phase (q < 0). We have calculated some physical and geometric properties and their graphs, whether in terms of time or redshift. Note that for our model, the bulk viscous pressure (p ¯) is negative and the energy density (ρ) is positive. The energy conditions and the Om (z) analysis for our spatially homogeneous and anisotropic Bianchi type-I model are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the parametrization of the effective equation of state (EoS) parameter within the framework of f (Q) symmetric teleparallel gravity. Here, the gravitational action is represented by an arbitrary function of the non-metricity scalar Q. By utilizing a specific parametrization of the effective EoS parameter and a power-law model of f (Q) theory, namely f (Q) = β Q m + 1 (where β and m are arbitrary constants), we derive the cosmological solution of the Hubble parameter H (z). To constrain model parameters, we employ recent observational data, including the Observational Hubble parameter Data (O H D), Baryon Acoustic Oscillations data (B A O), and Type Ia supernovae data (S N e Ia). The current constrained value of the deceleration parameter is found to be q 0 = − 0. 5 0 − 0. 01 + 0. 01 , indicating that the current Universe is accelerating. Furthermore, we examine the evolution of the density, EoS, and O m (z) diagnostic parameters to deduce the accelerating nature of the Universe. Finally, we perform a stability analysis with linear perturbations to confirm the model's stability. [ABSTRACT FROM AUTHOR]

We present a new f (Q) cosmological model capable of reproducing late-time acceleration, i.e. f Q = λ 0 λ + Q n by supporting certain parametrization of the Hubble parameter. By using observational data from Hubble, Pantheon, and Baryonic Acoustic Oscillations (BAO) dataset, we investigate the constraints on the proposed quadratic Hubble parameter H (z). This proposal caused the Universe to transition from its decelerated phase to its accelerated phase. Further, the current constrained value of the deceleration parameter from the combined Hubble+Pantheon+BAO dataset is q 0 = − 0. 285 ± 0. 021 , which indicates that the Universe is accelerating. We also analyze the evolution of energy density, pressure, and EoS parameters to infer the Universe's accelerating behavior. Finally, we use a stability analysis with linear perturbations to assure the model's stability. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Bianchi type-I space–time with perfect fluid as matter content of the Universe in the framework of f (Q) gravity (where Q is the non-metricity scalar) recently proposed by Jiménez et al. (2018). We find exact solutions of the field equations using the anisotropic property of space–time for volumetric hybrid expansion. The cosmological parameters for the linear form of non-metricity scalar i.e. f Q = α Q + β (where α and β are free model parameters) are discussed and compared with recent Hubble measurements. Also, we have obtained the best fitting values of the model parameters k , n and H 0 by constraining our model with updated Hubble datasets consisting of 57 data points (31 (DA) and 26 (BAO+other)) along with also examined the stability of the model and test its validity by energy conditions. [ABSTRACT FROM AUTHOR]