scholarly journals PARAMETRIZATIONS OF THE DARK ENERGY DENSITY AND SCALAR POTENTIALS

2007 ◽  
Vol 22 (12) ◽  
pp. 883-890 ◽  
Author(s):  
ZONG-KUAN GUO ◽  
NOBUYOSHI OHTA ◽  
YUAN-ZHONG ZHANG
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Energy Function ◽  
Theoretical Method ◽  
Chaplygin Gas ◽  
Present Value ◽  
Dark Energy Density ◽  
Generalized Chaplygin Gas ◽  
Scalar Potentials

We develop a theoretical method of constructing the scalar (quintessence or phantom) potential directly from the dimensionless dark energy function X(z), the dark energy density in units of its present value. We apply our method to two parametrizations of the dark energy density, the quiessence-Lambda ansatz and the generalized Chaplygin gas model, and discuss some features of the constructed potentials.

scholarly journals Viscous generalized Chaplygin gas interacting with f(R,T) gravity

2017 ◽  
Vol 14 (04) ◽  
pp. 1750051 ◽  
Author(s):  
E. H. Baffou ◽  
M. J. S. Houndjo ◽  
I. G. Salako
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Graphical Representation ◽  
Input Parameter ◽  
Momentum Tensor ◽  
Chaplygin Gas ◽  
Density Parameter ◽  
Dark Energy Density ◽  
Generalized Chaplygin Gas ◽  
Accelerating Expansion

In this paper, we study in Friedmann–Robertson–Walker universe the interaction between the viscous generalized Chaplygin gas with [Formula: see text] gravity, which is an arbitrary function of the Ricci scalar [Formula: see text] and the trace [Formula: see text] of the energy–momentum tensor. Assuming that the contents of universe are dominated by a generalized Chaplygin gas and dark energy, we obtained the modified Friedmann equations and also the time-dependent energy density and pressure of dark energy due to the shear and bulk viscosities for three interacting models depending on an input parameter [Formula: see text]. Within the simple form of scale factor (power-law), we discuss the graphical representation of dark energy density parameter and investigate the shear and bulk viscosities effects on the accelerating expansion of the universe for each interacting model.

FRW viscous modified cosmic Chaplygin gas cosmology in the presence of cosmological constant

2019 ◽  
Vol 16 (09) ◽  
pp. 1950141 ◽  
Author(s):  
G. S. Khadekar ◽  
Aina Gupta ◽  
Kalpana Pande
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Chaplygin Gas ◽  
Frw Universe ◽  
Dark Energy Density ◽  
Linear Combinations ◽  
Linear Differential ◽  
The Stability ◽  
Cardassian Universe

In this paper, we study viscous Modified Cosmic Chaplygin Gas (MCCG) in the presence of cosmological constant in flat FRW universe. We assume that bulk viscosity [Formula: see text] and cosmological constant [Formula: see text] are the linear combinations of two terms, one is constant and other is a function of dark energy density [Formula: see text]. In this framework, we solve the non-linear differential equation analytically and numerically and obtain time dependent dark energy density. We also consider two separate cases of early and late universe and discussed the evolution of dark energy density. We investigate the effect of viscosity and cosmological constant to the evolution of universe and discuss the stability of the model by square of speed of sound. Finally, we compare our model with Cardassian universe.

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 AGEGRAPHIC CHAPLYGIN GAS MODEL OF DARK ENERGY

2009 ◽  
Vol 18 (13) ◽  
pp. 2023-2034 ◽  
Author(s):  
A. SHEYKHI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Energy Density ◽  
Dark Energy Model ◽  
Chaplygin Gas ◽  
Energy Model ◽  
Generalized Chaplygin Gas ◽  
Agegraphic Dark Energy

We establish a connection between the agegraphic models of dark energy and Chaplygin gas energy density in a nonflat universe. We reconstruct the potential of the agegraphic scalar field as well as the dynamics of the scalar field according to the evolution of the agegraphic dark energy. We also extend our study to the interacting agegraphic generalized Chaplygin gas dark energy model.

scholarly journals GRAVITATIONAL ORIGIN OF PHANTOM DARK ENERGY AND LATE COSMIC ACCELERATION

2007 ◽  
Vol 22 (06) ◽  
pp. 1123-1134 ◽  
Author(s):  
S. K. SRIVASTAVA
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Friedmann Equation ◽  
State Parameter ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Dark Energy Density ◽  
Generalized Chaplygin Gas ◽  
Barotropic Fluid ◽  
Brane Gravity

Here, dark energy is obtained using dual roles of the Ricci scalar (as a physical field as well as geometry). Dark energy density, obtained in this model, mimics phantom and the derived Friedmann equation contains a term [Formula: see text] with ρdebeing the dark energy density and λ, called as cosmic tension. It is like brane-gravity inspired Friedmann equation, which arises here without using the brane-gravity theory. It is found that acceleration is a transient phenomenon for λ< 0, but for λ> 0 accelerated expansion is found to encounter the big-rip problem. It is shown that this problem can be avoided if the dark energy behaves as barotropic fluid and generalized Chaplygin gas simultaneously. Moreover, time for transition (from deceleration to acceleration of the universe) is derived as a function of equation of state parameter wde= pde/ρdewith pdebeing the pressure for dark energy fluid.

scholarly journals Interacting models of generalized Chaplygin gas and modified Chaplygin gas with barotropic fluid

2019 ◽  
Vol 34 (09) ◽  
pp. 1950064 ◽  
Author(s):  
Promila Biswas ◽  
Ritabrata Biswas
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Parameters ◽  
Chaplygin Gas ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Modified Chaplygin Gas ◽  
Interaction Coefficients ◽  
Generalized Chaplygin Gas ◽  
Barotropic Fluid

In this paper, we consider two different models of our present universe. We choose the models which consist of different sets of two separate fluids. The first one of each set tries to justify the late time acceleration and the second one is barotropic fluid. The former model considers our present time universe to be homogeneously filled up by Generalized Chaplygin Gas which is interacting with barotropic fluid. On the other hand, the latter model considers that the cosmic acceleration is generated by Modified Chaplygin Gas which is interacting with matter depicted by barotropic equation of state (EoS). For both the models, we consider the interaction term to vary proportionally with Hubble’s parameter as well as with the exotic matter/dark energy’s energy density. We find an explicit function form of the energy density of the cosmos which is found to depend on different cosmological parameters like scale factor, dark energy and barotropic fluid’s EoS parameters and other constants, like interacting constants, etc. We draw curves of effective EoS-s, different cosmological parameters like deceleration parameter q, statefinder parameters r and s with respect to the redshift z (for different values of dark energy and barotropic fluid parameters) and study them thoroughly. We compare two models as well as the nature of dependencies on these models’ interaction coefficients. We point out the particular redshift for which the universe may transit from a deceleration to acceleration phase. We tally all these values with different observational data. Here, we also analyze how this value of particular redshift does change for different values of interaction coefficients and different dark energy models.

scholarly journals HOLOGRAPHIC DARK ENERGY WITH GENERALIZED CHAPLYGIN GAS IN HIGHER DIMENSIONS

2014 ◽  
Vol 23 (02) ◽  
pp. 1450015 ◽  
Author(s):  
S. GHOSE ◽  
A. SAHA ◽  
B. C. PAUL
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Stable Configuration ◽  
Density Parameter ◽  
Present Value ◽  
Generalized Chaplygin Gas ◽  
The Past ◽  
Phantom Fields ◽  
Kaluza Klein

We investigate holographic dark energy (HDE) correspondence of interacting Generalized Chaplygin Gas (GCG) in the framework of compact Kaluza–Klein (KK) cosmology. The evolution of the modified HDE with corresponding equation of state is obtained here. Considering the present value of the density parameter a stable configuration is found which accommodates Dark Energy (DE). We note a connection between DE and Phantom fields. It reveals that the DE might have evolved from a Phantom state in the past.

scholarly journals Dark Energy Density in Brane World

2005 ◽  
Vol 22 (4) ◽  
pp. 816-819 ◽  
Author(s):  
Wen Hai-Bao ◽  
Huang Xin-Bing
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Brane World ◽  
Dark Energy Density
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