scholarly journals Redshift parametrizations of dark energy and observational constraint on their parameters: Galileon gravity as background

2015 ◽  
Vol 30 (31) ◽  
pp. 1550151 ◽  
Author(s):  
Prabir Rudra ◽  
Chayan Ranjit ◽  
Sujata Kundu
Keyword(s):  
Dark Energy ◽  
Data Analysis ◽  
Theoretical Models ◽  
Acoustic Oscillation ◽  
Model Parameters ◽  
Distance Modulus ◽  
Microwave Background ◽  
Frw Universe ◽  
Type Ia ◽  
Best Fit

In this work, Friedmann–Robertson–Walker (FRW) universe filled with dark matter (DM) (perfect fluid with negligible pressure) along with dark energy (DE) in the background of Galileon gravity is considered. Four DE models with different equation of state (EoS) parametrizations have been employed namely, linear, Chevallier–Polarski–Lindler (CPL), Jassal–Bagla–Padmanabhan (JBP) and logarithmic parametrizations. From Stern, Stern+Baryonic Acoustic Oscillation (BAO) and Stern+BAO+Cosmic Microwave Background (CMB) joint data analysis, we have obtained the bounds of the arbitrary parameters [Formula: see text] and [Formula: see text] by minimizing the [Formula: see text] test. The best fit values and bounds of the parameters are obtained at 66%, 90% and 99% confidence levels which are shown by closed confidence contours in the figures. For the logarithmic model unbounded confidence contours are obtained and hence the model parameters could not be finitely constrained. The distance modulus [Formula: see text](z) against redshift [Formula: see text] has also been plotted for our predicted theoretical models for the best fit values of the parameters and compared with the observed Union2 data sample and SNe Type Ia 292 data and we have shown that our predicted theoretical models permits the observational datasets. From the data fitting it is seen that at lower redshifts [Formula: see text] the SNe Type Ia 292 data gives a better fit with our theoretical models compared to the Union2 data sample. So, from the data analysis, SNe Type Ia 292 data is the more favored data sample over its counterpart given the present choice of free parameters. From the study, it is also seen that the logarithmic parametrization model is less supported by the observational data. Finally, we have generated the plot for the deceleration parameter against the redshift parameter for all the theoretical models and compared the results with the work of Farooq et al., (2013).

scholarly journals Variable Chaplygin gas in Kaluza–Klein framework

2019 ◽  
Vol 97 (2) ◽  
pp. 117-124 ◽  
Author(s):  
M. Salti ◽  
O. Aydogdu ◽  
A. Tas ◽  
K. Sogut ◽  
E.E. Kangal
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Chaplygin Gas ◽  
Model Parameters ◽  
Energy Scenario ◽  
Type Ia ◽  
The Stability ◽  
Best Fit ◽  
Matter Energy ◽  
Kaluza Klein

We investigate cosmological features of the variable Chaplygin gas (VCG) describing a unified dark matter–energy scenario in a universe governed by the five dimensional (5D) Kaluza–Klein (KK) gravity. In such a proposal, the VCG evolves from the dust-like phase to the phantom or the quintessence phases. It is concluded that the background evolution for the KK-type VCG definition is equivalent to that for the dark energy interacting with the dark matter. Next, after performing neo-classical tests, we calculated the proper, luminosity, and angular diameter distances. Additionally, we construct a connection between the VCG in the KK universe and a homogenous minimally coupled scalar field by introducing its self-interacting potential and also we confirm the stability of the KK-type VCG model by making use of thermodynamics. Moreover, we use data from type Ia supernova, observational H(z) dataset and Planck-2015 results to place constraints on the model parameters. Subsequently, according to the best-fit values of the model parameters we analyze our results numerically.

scholarly journals A divergence-free parametrization of deceleration parameter for scalar field dark energy

2016 ◽  
Vol 25 (03) ◽  
pp. 1650032 ◽  
Author(s):  
Abdulla Al Mamon ◽  
Sudipta Das
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Frw Universe ◽  
Potential Term ◽  
Type Ia ◽  
De Formula ◽  
Divergence Free ◽  
Baryonic Acoustic Oscillations

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy (DE). We have considered a phenomenological parametrization of the deceleration parameter [Formula: see text] and from this, we have reconstructed the equation-of-state (EoS) for DE [Formula: see text]. This divergence-free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the DE EoS given by Barboza and Alcaniz [see E. M. Barboza and J. S. Alcaniz, Phys. Lett. B 666 (2008) 415]. Using the combination of datasets (Type Ia Supernova (SN Ia) + Hubble + baryonic acoustic oscillations/cosmic microwave background (BAO/CMB)), we have constrained the transition redshift [Formula: see text] (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of [Formula: see text]. We have also compared the reconstructed results of [Formula: see text] and [Formula: see text] and have found that the results are compatible with a [Formula: see text]CDM universe if we consider SN Ia + Hubble data, but inclusion of BAO/CMB data makes [Formula: see text] and [Formula: see text] incompatible with [Formula: see text]CDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

scholarly journals COSMIC CONSTRAINT ON RICCI DARK ENERGY MODEL

2009 ◽  
Vol 24 (17) ◽  
pp. 1355-1360 ◽  
Author(s):  
LIXIN XU ◽  
WENBO LI ◽  
JIANBO LU
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Likelihood Method ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Ricci Dark Energy ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit

In this paper, a holographic dark energy model, dubbed Ricci dark energy, is confronted with cosmological observational data from type Ia Supernovae (SN Ia), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB). By using maximum likelihood method, we found that Ricci dark energy model is a viable candidate of dark energy model with the best fit parameters: Ωm0 = 0.34 ± 0.04, α = 0.38 ± 0.03 with 1σ error. Here, α is a dimensionless parameter related to Ricci dark energy ρR and Ricci scalar R, i.e. ρR ∝ αR.

scholarly journals Roles of modified Chaplygin–Jacobi and Chaplygin–Abel gases in FRW universe

2021 ◽  
Author(s):  
Ujjal Debnath
Keyword(s):  
Dark Energy ◽  
Data Analysis ◽  
Scalar Field ◽  
Generating Function ◽  
Information Criteria ◽  
Hyperbolic Function ◽  
Model Parameters ◽  
Jacobi Elliptic Function ◽  
Best Fit ◽  
The Universe

In this paper, we have considered flat Friedmann–Robertson–Walker (FRW) model of the universe and reviewed the modified Chaplygin gas as the fluid source. Associated with the scalar field model, we have determined the Hubble parameter as a generating function in terms of the scalar field. Instead of hyperbolic function, we have taken Jacobi elliptic function and Abel function in the generating function and obtained modified Chaplygin–Jacobi gas (MCJG) and modified Chaplygin–Abel gas (MCAG) equation of states, respectively. Next, we have assumed that the universe is filled in dark matter, radiation, and dark energy. The sources of dark energy candidates are assumed as MCJG and MCAG. We have constrained the model parameters by recent observational data analysis. Using [Formula: see text] minimum test (maximum likelihood estimation), we have determined the best-fit values of the model parameters by OHD[Formula: see text]CMB[Formula: see text]BAO[Formula: see text]SNIa joint data analysis. To examine the viability of the MCJG and MCAG models, we have determined the values of the deviations of information criteria like △AIC, △BIC and △DIC. The evolutions of cosmological and cosmographical parameters (like equation of state, deceleration, jerk, snap, lerk, statefinder, Om diagnostic) have been studied for our best-fit values of model parameters. To check the classical stability of the models, we have examined the values of square speed of sound [Formula: see text] in the interval [Formula: see text] for expansion of the universe.

scholarly journals SNe data analysis in variable speed of light cosmologies without cosmological constant

2014 ◽  
Vol 29 (24) ◽  
pp. 1450103 ◽  
Author(s):  
Pengfei Zhang ◽  
Xinhe Meng
Keyword(s):  
Dark Energy ◽  
Scale Factor ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Distance Modulus ◽  
Data Sets ◽  
Variable Speed ◽  
Speed Of Light ◽  
Type Ia ◽  
Ia Supernovae

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

scholarly journals Cosmological models of generalized ghost pilgrim dark energy (GGPDE) in the gravitation theory of Saez–Ballester

2021 ◽  
Author(s):  
Priyanka Garg ◽  
Archana Dixit ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Type I ◽  
Microwave Background ◽  
Light Curve Analysis ◽  
Pilgrim Dark Energy ◽  
Type Ia ◽  
State Formula ◽  
Quintessence Field

In this paper, we study the mechanism of the cosmic model in the presence of generalized ghost pilgrim dark energy (GGPDE) and matter in locally rotationally symmetric (LRS) Bianchi type-I space-time by the utilization of new holographic DE in Saez–Ballester theory. Here, we discuss all the data for three scenarios, the first is supernovae type-Ia union data, the second is SN Ia data in combination with baryon acoustic oscillation and cosmic microwave background observations and the third is a combination with observational Hubble data and joint light-curve analysis observations. From this, we get a model of our universe, where transit state exists from deceleration to acceleration phase. Here, we have observed that the results yielded by cosmological parameters like [Formula: see text] (energy density), equation of state [Formula: see text], squared speed of sound [Formula: see text] and [Formula: see text]–[Formula: see text] are compatible with the recent observations. The [Formula: see text]–[Formula: see text] trajectories lie in both thawing and freezing regions and the correspondence of the quintessence field with GGPDE is also discussed. Some physical aspects of the GGPDE models are mainly highlighted.

scholarly journals Consistency of nonlinear interacting ghost dark energy with recent observations

2017 ◽  
Vol 26 (11) ◽  
pp. 1750124 ◽  
Author(s):  
E. Ebrahimi ◽  
H. Golchin ◽  
A. Mehrabi ◽  
S. M. S. Movahed
Keyword(s):  
Dark Energy ◽  
Observational Data ◽  
Nonlinear Interaction ◽  
Acoustic Oscillation ◽  
Joint Analysis ◽  
Data Sets ◽  
Dark Energy Density ◽  
Ghost Dark Energy ◽  
Interaction Terms ◽  
Best Fit

In this paper, we investigate ghost dark energy model in the presence of nonlinear interaction between dark energy and dark matter. We also extend the analysis to the so-called generalized ghost dark energy (GGDE) which [Formula: see text]. The model contains three free parameters as [Formula: see text] and [Formula: see text] (the coupling coefficient of interactions). We propose three kinds of nonlinear interaction terms and discuss the behavior of equation of state, deceleration and dark energy density parameters of the model. We also find the squared sound speed and search for signs of stability of the model. To compare the interacting GGDE model with observational data sets, we use more recent observational outcomes, namely SNIa from JLA catalog, Hubble parameter, baryonic acoustic oscillation and the most relevant CMB parameters including, the position of acoustic peaks, shift parameters and redshift to recombination. For GGDE with the first nonlinear interaction, the joint analysis indicates that [Formula: see text], [Formula: see text] and [Formula: see text] at 1 optimal variance error. For the second interaction, the best fit values at [Formula: see text] confidence are [Formula: see text], [Formula: see text] and [Formula: see text]. According to combination of all observational data sets considered in this paper, the best fit values for third nonlinearly interacting model are [Formula: see text], [Formula: see text] and [Formula: see text] at [Formula: see text] confidence interval. Finally, we found that the presence of interaction is compatible in mentioned models via current observational datasets.

A PARAMETRIZED VARIABLE DARK ENERGY MODEL: STRUCTURE FORMATION AND OBSERVATIONAL CONSTRAINTS

2006 ◽  
Vol 15 (09) ◽  
pp. 1455-1472 ◽  
Author(s):  
S. ARBABI BIDGOLI ◽  
M. SADEGH MOVAHED ◽  
S. RAHVAR
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Large Scale ◽  
High Redshift ◽  
Growth Index ◽  
Energy Model ◽  
Linear Perturbation ◽  
Model Parameters ◽  
Type Ia ◽  
Parametrization Scheme

In this paper we investigate a simple parametrization scheme of the quintessence model given by Wetterich [Phys. Lett. B594, 17 (2004)]. The crucial parameter of this model is the bending parameter b, which is related to the amount of dark energy in the early universe. Using the linear perturbation and the spherical infall approximations, we investigate the evolution of matter density perturbations in the variable dark energy model, and obtain an analytical expression for the growth index f. We show that increasing b leads to less growth of the density contrast δ, and also decreases the growth index. Giving a fitting formula for the growth index at the present time, we verify that the approximation relation [Formula: see text] also holds in this model. To compare predictions of the model with observations, we use the Supernovae type Ia (SNIa) Gold Sample and the parameters of the large scale structure determined by the 2-degree Field Galaxy Redshift Survey (2dFGRS). The best fit values for the model parameters by marginalizing on the remained ones, are [Formula: see text], [Formula: see text] and [Formula: see text] at 1σ confidence level. As a final test we calculate the age of universe for different choices of the free parameters in this model and compare it with the age of old stars and some high redshift objects. Then we show that the predictions of this variable dark energy model are consistent with the age observation of old star and can solve the "age crisis" problem.

scholarly journals RECONSTRUCTION OF 5D COSMOLOGICAL MODELS FROM RECENT OBSERVATIONS

2007 ◽  
Vol 16 (10) ◽  
pp. 1573-1579
Author(s):  
CHENGWU ZHANG ◽  
LIXIN XU ◽  
YONGLI PING ◽  
HONGYA LIU
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Solution ◽  
Type Ia Supernovae ◽  
Shift Parameter ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit ◽  
The Universe

We use a parameterized equation of state (EOS) of dark energy to a 5D Ricci-flat cosmological solution and suppose the universe contains two major components: dark matter and dark energy. Using the recent observational datasets: the latest 182 type Ia Supernovae Gold data, the three-year WMAP CMB shift parameter and the SDSS baryon acoustic peak, we obtain the best fit values of the EOS and two major components' evolution. We find that the best fit EOS crosses -1 in the near past where z ≃ 0.07, the present best fit value of wx(0) < -1 and for this model, the universe experiences the acceleration at about z ≃ 0.5.

scholarly journals Astronomical bounds on the modified Chaplygin gas as a unified dark fluid model

2019 ◽  
Vol 623 ◽  
pp. A28
Author(s):  
Hang Li ◽  
Weiqiang Yang ◽  
Liping Gai
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Fluid Model ◽  
Chaplygin Gas ◽  
Linear Perturbation ◽  
Model Parameters ◽  
Modified Chaplygin Gas ◽  
Dark Fluid ◽  
Type Ia ◽  
Linear Perturbation Theory

The modified Chaplygin gas could be considered to abide by the unified dark fluid model because the model might describe the past decelerating matter dominated era and at present time it provides an accelerating expansion of the Universe. In this paper, we have employed the Planck 2015 cosmic microwave background anisotropy, type-Ia supernovae, observed Hubble parameter data sets to measure the full parameter space of the modified Chaplygin gas as a unified dark matter and dark energy model. The model parameters Bs, α, and B determine the evolutional history of this unified dark fluid model by influencing the energy density ρMCG = ρMCG0[Bs + (1 − Bs)a−3(1 + B)(1 + α)]1/(1 + α). We assumed the pure adiabatic perturbation of unified modified Chaplygin gas in the linear perturbation theory. In the light of Markov chain Monte Carlo method, we find that Bs = 0.727+0.040+0.075−0.039−0.079, α = −0.0156+0.0982+0.2346−0.1380−0.2180, B = 0.0009+0.0018+0.0030−0.0017−0.0030 at 2σ level. The model parameters α and B are very close to zero and the nature of unified dark energy and dark matter model is very similar to cosmological standard model ΛCDM.

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