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 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.

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 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 BAYESIAN ANALYSIS OF THE CHAPLYGIN GAS AND COSMOLOGICAL CONSTANT MODELS USING THE SNe Ia DATA

2004 ◽  
Vol 13 (04) ◽  
pp. 669-693 ◽  
Author(s):  
R. COLISTETE ◽  
J. C. FABRIS ◽  
S. V. B. GONÇALVES ◽  
P. E. DE SOUZA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Confidence Level ◽  
Cold Dark Matter ◽  
Chaplygin Gas ◽  
Type Ia Supernovae ◽  
Λcdm Model ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

The type Ia supernovae observational data are used to estimate the parameters of a cosmological model with cold dark matter and the Chaplygin gas. This exotic gas, which is characterized by a negative pressure varying with the inverse of density, represents in this model the dark energy responsible for the acceleration of the Universe. The Chaplygin gas model depends essentially on four parameters: the Hubble constant, the velocity of the sound of the Chaplygin gas, the curvature of the Universe and the fraction density of the Chaplygin gas and the cold dark matter. The Bayesian parameter estimation yields [Formula: see text] and [Formula: see text]. These and other results indicate that a Universe completely dominated by the Chaplygin gas is favoured, what reinforces the idea that the Chaplygin gas may unify the description for dark matter and dark energy, at least as the type Ia supernovae data are concerned. A closed and accelerating Universe is also favoured. The Bayesian statistics indicates that the Chaplygin gas model is more likely than the standard cosmological constant (ΛCDM) model at 55.3% confidence level when an integration on all free parameters is performed. Assuming the spatially flat curvature, this percentage mounts to 65.3%. On the other hand, if the density of dark matter is fixed at zero value, the Chaplygin gas model becomes more preferred than the ΛCDM model at 91.8% confidence level. Finally, the hypothesis of flat Universe and baryonic matter (Ωb0=0.04) implies a Chaplygin gas model preferred over the ΛCDM at a confidence level of 99.4%.

CONSTRAINTS ON VARIABLE CHAPLYGIN GAS MODEL FROM TYPE IA SUPERNOVAE AND BARYON ACOUSTIC OSCILLATIONS

2010 ◽  
Vol 25 (09) ◽  
pp. 737-747 ◽  
Author(s):  
JIANBO LU ◽  
LIXIN XU
Keyword(s):  
Dark Energy ◽  
Chaplygin Gas ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Acoustic Oscillations ◽  
Confidence Levels ◽  
Energy Models ◽  
Type Ia ◽  
Baryon Acoustic Oscillations ◽  
Ia Supernovae

We apply the type Ia supernovae union dataset and the baryon acoustic oscillations data at z = 0.2 and z = 0.35 to constrain variable Chaplygin gas (VCG) model as the unification of dark matter and dark energy. It is shown that the confidence levels for VCG model parameters are [Formula: see text]. And it indicates that the values of transition redshift and current deceleration parameter are: [Formula: see text]. In addition, we plot the evolution trajectory of the VCG model in the statefinder parameter r–s plane and show the discrimination between this scenario and other dark energy models.

scholarly journals Bayesian analysis of running holographic Ricci dark energy

2020 ◽  
Vol 499 (4) ◽  
pp. 5598-5606
Author(s):  
Paxy George ◽  
Titus K Mathew
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Bayes Factor ◽  
Additive Constant ◽  
Model Parameters ◽  
Acoustic Oscillations ◽  
Ricci Dark Energy ◽  
Relative Significance ◽  
Type Ia

ABSTRACT Holographic Ricci dark energy evolving through its interaction with dark matter is a natural choice for the running vacuum energy model. We have analysed the relative significance of two versions of this model in the light of type Ia supernovae (SN1a), the Cosmic Microwave Background (CMB), the Baryonic Acoustic Oscillations (BAO), and Hubble data sets using the method Bayesian inferences. The first one, model 1, is the running holographic Ricci dark energy (rhrde) having a constant additive term in its density form and the second is one, model 2, having no additive constant, instead the interaction of rhrde with dark matter (ΛCDM) is accounted through a phenomenological coupling term. The Bayes factor of these models in comparison with the standard Lambda cold dark matter have been obtained by calculating the likelihood of each model for four different data combinations, SNIa(307)+CMB+BAO, SNIa(307)+CMB+BAO+Hubble data, SNIa(580)+CMB+BAO, and SNIa(580)+CMB+BAO+Hubble data. Suitable flat priors for the model parameters has been assumed for calculating the likelihood in both cases. Our analysis shows that, according to the Jeffreys scale, the evidence for ΛCDM against both model 1 and model 2 is very strong as the Bayes factor of both models are much less than one for all the data combinations.

scholarly journals Nonlinear evolution of dark matter and dark energy in the Chaplygin-gas cosmology

2004 ◽  
Vol 2004 (11) ◽  
pp. 008-008 ◽  
Author(s):  
Neven Bili ◽  
Robert J Lindebaum ◽  
Gary B Tupper ◽  
Raoul D Viollier
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Nonlinear Evolution ◽  
Chaplygin Gas

scholarly journals Unification of dark matter and dark energy: the inhomogeneous Chaplygin gas

2002 ◽  
Vol 535 (1-4) ◽  
pp. 17-21 ◽  
Author(s):  
Neven Bilić ◽  
Gary B Tupper ◽  
Raoul D Viollier
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Chaplygin Gas

scholarly journals DARK MATTER TO DARK ENERGY TRANSITION IN k-ESSENCE COSMOLOGIES

2005 ◽  
Vol 20 (27) ◽  
pp. 2075-2082 ◽  
Author(s):  
L. P. CHIMENTO ◽  
MÓNICA FORTE ◽  
RUTH LAZKOZ
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Kinetic Energy ◽  
Speed Of Sound ◽  
Energy Transition ◽  
Chaplygin Gas ◽  
Large Set ◽  
Generalized Chaplygin Gas ◽  
General Terms ◽  
Transient Models

We implement the transition from dark matter to dark energy in k-essence cosmologies for a very large set of kinetic functions F, in a way alternative to recent proposals which use generalized Chaplygin gas and transient models. Here we require that the pressure admits a power-law expansion around some value of the kinetic energy where the pressure vanishes. In addition, for suitable values of the parameters of the model, the speed of sound of the dark matter will be low. We first present the discussion in fairly general terms, and later consider for illustration two examples.

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.

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