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.

Ghost dark energy in Rastall theory

2021 ◽  
pp. 2150090
Author(s):  
E. E. Kangal ◽  
M. Salti ◽  
O. Aydogdu
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Text Analysis ◽  
Functional Form ◽  
Expansion Rate ◽  
Dark Energy Density ◽  
Cosmic Expansion ◽  
Astrophysical Data ◽  
Ghost Dark Energy ◽  
History Of

Making use of the generalized form of the Ghost dark energy density, which has the functional form [Formula: see text] where [Formula: see text] represents the Hubble expanding rate, the present accelerated enlargement behavior of the cosmos is investigated from the Rastall theory perspective. After finding a relation for the Hubble cosmic expansion rate, we consider recent cosmology-independent measurements calculated for the expansion history of the cosmos to fit the model via the [Formula: see text]-analysis. Moreover, we discuss the cosmographic properties of the model with the help of some cosmological quantities. We show that our model is stable and consistent with the recent astrophysical data. Also, for our model, we investigate cosmological interpretations of thermodynamics.

scholarly journals VISCOUS MODIFIED COSMIC CHAPLYGIN GAS COSMOLOGY

2013 ◽  
Vol 22 (09) ◽  
pp. 1350061 ◽  
Author(s):  
B. POURHASSAN
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Nonlinear Equation ◽  
Observational Data ◽  
Function Method ◽  
Chaplygin Gas ◽  
Time Dependent ◽  
Dark Energy Density ◽  
Hubble Expansion ◽  
Exponential Function Method

In this paper, we construct viscous modified cosmic Chaplygin gas as a model of dark energy. We use exponential function method to solve nonlinear equation and obtain time-dependent dark energy density. Then, we discuss Hubble expansion parameter and scale factor and fix them by using observational data. Effect of viscosity to the evolution of Universe is investigated. We also investigate stability of this theory.

scholarly journals GENERALIZED HOLOGRAPHIC DARK ENERGY AND ITS OBSERVATIONAL CONSTRAINTS

2012 ◽  
Vol 27 (20) ◽  
pp. 1250115 ◽  
Author(s):  
ZHENHUI ZHANG ◽  
MIAO LI ◽  
XIAO-DONG LI ◽  
SHUANG WANG ◽  
WEN-SHUAI ZHANG
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Joint Analysis ◽  
Observational Constraints ◽  
Dark Energy Density ◽  
Cosmological Constraints ◽  
Dimensionless Constant ◽  
The Future ◽  
Type C ◽  
Physical Quantities

In the original holographic dark energy (HDE) model, the dark energy density is proposed to be [Formula: see text], with c a dimensionless constant characterizing the properties of the HDE. In this work, we propose the generalized holographic dark energy (GHDE) model by considering the parameter c as a redshift-dependent function c(z). We derive all the physical quantities of the GHDE model analytically, and fit the c(z) by trying four kinds of parametrizations. The cosmological constraints of the c(z) are obtained from the joint analysis of the present SNLS3+BAO+CMB +H0data. We find that, compared with the original HDE model, the GHDE models can provide a better fit to the data. For example, the GHDE model with JBP-type c(z) can reduce the [Formula: see text] of the HDE model by 2.16. We also find that, unlike the original HDE model with a phantom-like behavior in the future, the GHDE models can present many more different possibilities, i.e. it allows the GHDE in the future to be either quintessence-like, cosmological constant-like, or phantom-like, depending on the forms of c(z).

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).

Probing kinematics and fate of Bianchi type I universe in Brans–Dicke theory

2020 ◽  
Vol 35 (21) ◽  
pp. 2050174
Author(s):  
Nishant Singla ◽  
Anil Kumar Yadav ◽  
M. K. Gupta ◽  
G. K. Goswami ◽  
Rajendra Prasad
Keyword(s):  
Observational Data ◽  
Bianchi Type ◽  
Statistical Test ◽  
Data Sets ◽  
Type I ◽  
Bianchi Type I Universe ◽  
Age Of The Universe ◽  
Best Fit ◽  
The Universe ◽  
Good Agreement

In this paper, we examine the existence of Bianch type I Brans–Dicke universe by performing statistical test from [Formula: see text] and SN Ia observational data sets. We find that anisotropic Brans-Dicke ([Formula: see text] BD) model provides a reasonable fit with observational data. In addition to [Formula: see text], we also use Akaike information creation (AIC) and Bayes information creation (BIC) to determine the values of best fit parameters. The model under consideration represents a transitioning universe from early decelerating phase to current accelerating phase. We obtain the present age of the universe as 13.732 Gyrs, which is in good agreement with WMAP observations. The physical behavior of particle horizon and [Formula: see text] parameter of the derived model are also discussed.

scholarly journals MODELING TIME-VARYING DARK ENERGY WITH CONSTRAINTS FROM LATEST OBSERVATIONS

2012 ◽  
Vol 27 (10) ◽  
pp. 1250030 ◽  
Author(s):  
QING-JUN ZHANG ◽  
YUE-LIANG WU
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Local Extremum ◽  
Joint Analysis ◽  
Type I ◽  
Time Varying ◽  
Two Parameters ◽  
Best Fit ◽  
Two Parameter ◽  
Extra Parameter

We introduce a set of two-parameter models for the dark energy equation of state (EOS) w(z) to investigate time-varying dark energy. The models are classified into two types according to their boundary behaviors at the redshift z = (0, ∞) and their local extremum properties. A joint analysis based on four observations ( SNe + BAO + CMB + H0) is carried out to constrain all the models. It is shown that all models get almost the same [Formula: see text] and the cosmological parameters (ΩM, h, Ωbh2) with the best-fit results (0.28, 0.70, 2.24), although the constraint results on two parameters (w0, w1) and the allowed regions for the EOS w(z) are sensitive to different models and a given extra model parameter. For three of Type I models which have similar functional behaviors with the so-called CPL model, the constrained two parameters w0 and w1 have negative correlation and are compatible with the ones in CPL model, and the allowed regions of w(z) get a narrow node at z~0.2. The best-fit results from the most stringent constraints in Model Ia give [Formula: see text] which may compare with the best-fit results [Formula: see text] in the CPL model. For four of Type II models which have logarithmic function forms and an extremum point, the allowed regions of w(z) are found to be sensitive to different models and a given extra parameter. It is interesting to obtain two models in which two parameters w0 and w1 are strongly correlative and appropriately reduced to one parameter by a linear relation w1∝(1+w0).

scholarly journals Nonlinearly interacting ghost dark energy in Brans–Dicke cosmology

2016 ◽  
Vol 94 (10) ◽  
pp. 1001-1007 ◽  
Author(s):  
E. Ebrahimi ◽  
H. Golchin
Keyword(s):  
Dark Energy ◽  
Nonlinear Interaction ◽  
Sound Speed ◽  
Statefinder Parameters ◽  
Acceleration Phase ◽  
Coincidence Problem ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Interaction Term ◽  
The Universe

In this paper we extend the form of interaction term into the nonlinear regime in the ghost dark energy model. A general form of the nonlinear interaction term is presented and cosmic dynamic equations are obtained. Next, the model is detailed for two special choices of the nonlinear interaction term. According to this the universe transits at suitable time (z ∼ 0.8) from deceleration to acceleration phase, which alleviate the coincidence problem. Squared sound speed analysis revealed that for one class of nonlinear interaction term [Formula: see text] can become positive. This point is an impact of the nonlinear interaction term and we never find such behavior in non-interacting and linearly interacting ghost dark energy models. Also, statefinder parameters are introduced for this model and we found that for one class the model meets the ΛCDM while in the second choice although the model approaches the ΛCDM, but never matches it.

scholarly journals Some models of holographic dark energy on the Randall–Sundrum brane and observational data

2019 ◽  
Vol 29 (01) ◽  
pp. 1950176 ◽  
Author(s):  
A. V. Astashenok ◽  
A. S. Tepliakov
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Observational Data ◽  
Energy Analysis ◽  
Holographic Dark Energy ◽  
Brane Tension ◽  
Dark Energy Density ◽  
Energy Models ◽  
Current Energy ◽  
The Universe

Some models of holographic dark energy for Randall–Sundrum brane are considered. For the first class of dark energy models, we take energy density in the form [Formula: see text], where [Formula: see text] is size of event horizon in universe and [Formula: see text] is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of [Formula: see text] ([Formula: see text] is current energy density in the universe and [Formula: see text] is brane tension). Then we investigate models for which dark energy density has the form [Formula: see text] where [Formula: see text] is Hubble parameter.

scholarly journals Testing the consistency between cosmological data: the impact of spatial curvature and the dark energy EoS

2021 ◽  
Vol 2021 (11) ◽  
pp. 060
Author(s):  
Javier E. Gonzalez ◽  
Micol Benetti ◽  
Rodrigo von Marttens ◽  
Jailson Alcaniz
Keyword(s):  
Dark Energy ◽  
Joint Analysis ◽  
Data Sets ◽  
Acoustic Oscillations ◽  
Spatial Curvature ◽  
Eos Parameter ◽  
Flat Universe ◽  
Type Ia ◽  
Cosmological Data ◽  
The Impact

Abstract The results of joint analyses of available cosmological data have motivated an important debate about a possible detection of a non-zero spatial curvature. If confirmed, such a result would imply a change in our present understanding of cosmic evolution with important theoretical and observational consequences. In this paper we discuss the legitimacy of carrying out joint analyses with the currently available data sets and explore their implications for a non-flat universe and extensions of the standard cosmological model. We use a robust tension estimator to perform a quantitative analysis of the physical consistency between the latest data of Cosmic Microwave Background, type Ia supernovae, Baryonic Acoustic Oscillations and Cosmic Chronometers. We consider the flat and non-flat cases of the ΛCDM cosmology and of two dark energy models with a constant and varying dark energy EoS parameter. The present study allows us to better understand if possible inconsistencies between these data sets are significant enough to make the results of their joint analyses misleading, as well as the actual dependence of such results with the spatial curvature and dark energy parameterizations. According to our results, we conclude that a joint analysis in the context of a non-flat universe including the CMB data is only possible if the CMB Lens is taken into account, otherwise, it potentially leads to misleading conclusions.

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