Parametrization Of Dark Energy Equation Research Articles

Cosmography for various parametrizations of dark energy equation of state

The concept of dark energy (DE) emerged as a result of confirming the accelerated expansion of the universe. Since then, numerous models have been developed to explore the origin and nature of DE. In this study, we investigate several recent cosmological models (Models 1–9) based on the parametrization of the DE equation of state. Our analysis focuses on a homogeneous, isotropic flat universe comprising DE, dark matter (DM), and radiation. We assume the separate conservation of the dark components (DE and DM) and radiation. By employing various parametrizations of [Formula: see text], we derive the corresponding Hubble function [Formula: see text]. To understand the cosmic expansion history of the universe in a model-independent manner, we employ cosmography as an approach. We express important cosmographic parameters such as deceleration, jerk, snap, and lerk parameters in terms of the Hubble rate [Formula: see text] and its derivative up to the fourth order. Additionally, we examine the statefinder parameter and [Formula: see text] diagnostics to distinguish between different types of DE models. Finally, we compare the physical interpretations of these diagnostic parameters with the standard [Formula: see text]CDM model to assess the viability of each model.

Cosmic expansion with curved dark energy cosmology: Inevitability of cosmic doomsday

In this work, we have constructed deceleration–acceleration and future evolution of cosmic expansion with curved dynamical dark energy models. Closed and open spatial curvatures are calculated by assuming that dark energy density does not exceed 85% of the closure density and by obtaining lower bounds on the ratio of dark energy to matter density, in terms of equation of state of dark energy. The range of transition epoch [Formula: see text] realized for spatial curvature [Formula: see text] is consistent with model independent estimations coming from galactic ages, strong lensing, Type Ia supernovae and recent constraints coming from [Formula: see text] measurements in non-flat dynamical dark energy models. Two novel parametrizations of dark energy equation of state namely the logarithmic and oscillatory, which are singularity free at future point [Formula: see text] are used to study the deceleration parameter q(z). Irrespective of spatial curvature, cosmic doomsday has been found inevitable for both the parametrizations. The time evolution of logarithmic parametrization, being reminiscent of a quintom field (canonical[Formula: see text]phantom), is converted into dynamics of a canonical quintessence and a phantom field for the redshift range ([Formula: see text],[Formula: see text]) and ([Formula: see text], [Formula: see text]). It is found that irrespective of spatial curvature, the quintessence component becomes sub-dominant in future giving it’s way to the phantom component.

A new parametrization of dark energy equation of state leading to double exponential potential

We show that a phenomenological form of energy density for the scalar field can provide the required transition from decelerated (q > 0) to accelerated expansion (q < 0) phase of the universe. We have used the latest type Ia supernova (SNIa) and Hubble parameter datasets to constrain the model parameters. The best fit values obtained from those datasets are then applied to reconstruct ωϕ(z), the equation of state parameter for the scalar field. The results show that the reconstructed forms of q(z) and ωϕ(z) do not differ much from the standard ΛCDM value at the current epoch. Finally, the functional form of the relevant potential V(ϕ) is derived by a parametric reconstruction. The corresponding V(ϕ) comes out to be a double exponential potential, which has a number of cosmological implications. Additionally, we have also studied the effect of this particular scalar field dark energy sector on the evolution of matter overdensities.

Study of non-canonical scalar field model using various parametrizations of dark energy equation of state

In this present work, we try to build up a cosmological model using a non-canonical scalar field within the framework of a spatially flat FRW space–time. In this context, we have considered four different parametrizations of the equation of state parameter of the non-canonical scalar field. Under this scenario, analytical solutions for various cosmological parameters have been found out. It has been found that the deceleration parameter shows a smooth transition from a positive value to some negative value which indicates that the universe was undergoing an early deceleration followed by late time acceleration which is essential for the structure formation of the universe. With these four parametrizations, the future evolution of the models are also discussed. It has been found that one of the models (Generalized Chaplygin gas model, GCG) mimics the concordance $$\Lambda $$ CDM in the near future, whereas two other models (CPL and JBP) diverge due to future singularity. Finally, we have studied these theoretical models with the latest datasets from SN Ia $$+$$ H(z) $$+$$ BAO/CMB.

On the Complementarity of Different Cosmological Probes with SLACS, BELLS and SL2S Strong Gravitational Lensing Data

Accelerating expansion of the Universe is now an indisputable observational fact and became one of the most important issues of both physics and cosmology today, known as dark energy (DE) problem. The nature of this phenomenon is still unknown and from observational point of view the only way to put some light on cosmic expansion history is to combine different methods which are alternative to each other. In this light, we explore the idea that strong gravitational lensing systems offer new opportunity to constrain DE parameters in a way complementary to other cosmological probes. It turns out that the angle of the confidence contour major axis for strong lensing measurements depends on the redshift of the sample what may help to break the degeneracy in the w0–wa parameters plane in the Chevalier–Polarski–Linder parametrization of DE equation of state.