12 research outputs found
Constrained evolution of effective equation of state parameter in non-linear dark energy model: Insights from Bayesian analysis of cosmic chronometers and Pantheon samples
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
, where and are model parameters.
This parametric form is applicable within the framework of gravity,
where represents the Ricci scalar and is the matter Lagrangian. Here,
we examine a non-linear model characterized by the functional form
, where is the free parameter of the
model. We examine the evolution of several cosmological parameters, including
the effective EoS parameter , the deceleration parameter , the
density parameter , the pressure , and the statefinder parameters. Our
analysis revealed that the constrained current value of the effective EoS
parameter, for both the CC and Pantheon
datasets, points towards a quintessence phase. Moreover, at redshift , the
deceleration parameter, , indicates that the
present Universe is undergoing accelerated expansion.Comment: The European Physical Journal Plus published versio
Impact of dark energy on the equation of state in light of the latest cosmological data
We reconstruct the effective Equation of State (EoS) within the framework of
General Relativity (GR) theory in a homogeneous and isotropic FLRW Universe,
which is assumed to be composed of matter and Dark Energy (DE). Our analysis
employs a dataset consisting of 31 Cosmic Chronometer (CC) data points, six
data points of Baryon Acoustic Oscillations (BAO), and 1048 Type Ia Supernovae
(SN) from the Pantheon sample, and we determine the best-fit values of the
model parameters through Markov Chain Monte Carlo (MCMC) simulation. We then
use these parameter values to calculate various cosmological parameters, such
as the DE EoS parameter, the energy density, the deceleration parameter, the
state finder parameters, and the diagnostic. All the analyzed
cosmological parameters show behavior consistent with the accelerated Universe
scenario.Comment: PTEP published versio
Modeling cosmic acceleration with a generalized varying deceleration parameter
Understanding the accelerating expansion of the Universe remains a
fundamental challenge in modern cosmology. In this paper, we investigate a
cosmological model parametrized by a generalized variable deceleration
parameter to elucidate the dynamics driving cosmic acceleration. By employing
constraints from the latest observational datasets, including Cosmic
Chronometers (CC), Type Ia Supernovae (SNe), and Baryon Acoustic Oscillations
(BAO), we assess the compatibility of the model with observational data. The
chosen parametrization aligns with thermodynamic constraints on the
deceleration parameter, further validating its reliability. Further, we
estimate the present value of the Hubble parameter, transition redshift,
deceleration parameter, and EoS parameter, which align with observational data.
Lastly, our stability analysis confirms the model's stability against small
perturbations.Comment: Physics of the Dark Universe accepted versio
Square-Root parametrization of dark energy in cosmology
This paper is a parametrization of the equation of state (EoS) parameter of
dark energy (DE), which is parameterized using Square-Root (SR) form i.e.
\omega _{SR}=\text{\omega _{0}}+\text{\omega
_{1}}\frac{z}{\sqrt{z^{2}+1}}, where and are free
constants. This parametrization will be examined in the context of the recently
suggested gravity theory as an alternative to General Relativity (GR),
in which gravitational effects are attributed to the non-metricity scalar
with the functional form , where and are
arbitrary constants. We derived observational constraints on model parameters
using the Hubble dataset with 31 data points and the Supernovae (SNe) dataset
from the Pantheon samples compilation dataset with 1048 data points. For the
current model, the evolution of the deceleration parameter, density parameter,
EoS for DE, and diagnostic have all been investigated. It has been
shown that the deceleration parameter favors the current accelerated expansion
phase. It has also been shown that the EoS parameter for DE has a quintessence
nature at this time.Comment: Communications in Theoretical Physics accepted versio
The Evolution of a Higher-Dimensional FRW Universe with Variable <i>G</i> and Λ and Particle Creation
Using an open thermodynamic systems theory, the effect of particle creation on the evolution and dynamics of the standard cosmological FLRW model in a higher-dimensional spacetime with functionally dependent cosmological and gravitational constants Λ and G is investigated. The gravitational field equations have been transformed into a dimensionless system of non-linear, first-order, coupled differential equations (DEs) as functions of the universe’s density parameters Ωi and rate of particle creation Ψ in redshift space, which can be numerically casted. Two cosmological models are obtained, depending on the choice of particle creation rate—Ψ∼H2 and Ψ∼n2 for dust-, radiation- and dark-energy-dominated universes, respectively. The dynamic behaviour of each model is discussed
Bianchi type–I Model with Time Varying Λ and G: The Generalized Solution
In this paper, we have investigated the homogeneous and anisotropic Bianchi type–I cosmological model with a time-varying Newtonian and cosmological constant. We have analytically solved Einstein’s field equations (EFEs) in the presence of a stiff-perfect fluid. We show that the analytical solution for the average scale factor for the generalized Friedman equation involves the hyper-geometric function. We have studied the physical and kinematical quantities of the model, and it is found that the universe becomes isotropic at late times
The Cosmology of a Non-Minimally Coupled <i>f</i>(<i>R</i>,<i>T</i>) Gravitation
A non-minimally coupled cosmological scenario is considered in the context of f(R,T)=f1(R)+f2(R)f3(T) gravity (with R being the Ricci scalar and T the trace of the energy-momentum tensor) in the background of the flat Friedmann–Robertson–Walker (FRW) model. The field equations of this modified theory are solved using a time-dependent deceleration parameter for a dust. The behavior of the model is analyzed taking into account constraints from recent observed values the deceleration parameter. It is shown that the analyzed models can explain the transition from the decelerating phase to the accelerating one in the expansion of the universe, by staying true to the results of the observable universe. It is shown that the models are dominated by a quintessence-like cosmological dark fluid at the late universe
The Cosmology of a Non-Minimally Coupled f(R,T) Gravitation
A non-minimally coupled cosmological scenario is considered in the context of f(R,T)=f1(R)+f2(R)f3(T) gravity (with R being the Ricci scalar and T the trace of the energy-momentum tensor) in the background of the flat Friedmann–Robertson–Walker (FRW) model. The field equations of this modified theory are solved using a time-dependent deceleration parameter for a dust. The behavior of the model is analyzed taking into account constraints from recent observed values the deceleration parameter. It is shown that the analyzed models can explain the transition from the decelerating phase to the accelerating one in the expansion of the universe, by staying true to the results of the observable universe. It is shown that the models are dominated by a quintessence-like cosmological dark fluid at the late universe