scholarly journals Constraints on interacting dark energy models through cosmic chronometers and Gaussian process

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Muhsin Aljaf ◽  
Daniele Gregoris ◽  
Martiros Khurshudyan
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Gaussian Process ◽  
Cold Dark Matter ◽  
Hubble Constant ◽  
Energy Coupling ◽  
Chaplygin Gas ◽  
History Of ◽  
Friedmann Cosmological Models ◽  
Interacting Dark Energy Models

AbstractIn this paper, after reconstructing the redshift evolution of the Hubble function by adopting Gaussian process techniques, we estimate the best-fit parameters for some flat Friedmann cosmological models based on a modified Chaplygin gas interacting with dark matter. In fact, the expansion history of the Universe will be investigated because passively evolving galaxies constitute cosmic chronometers. An estimate for the present-day values of the deceleration parameter, adiabatic speed of sound within the dark energy fluid, effective dark energy, and dark matter equation of state parameters is provided. By this, we mean that the interaction term between the two dark fluids, which breaks the Bianchi symmetries, will be interpreted as an effective contribution to the dark matter pressure similarly to the framework of the “Generalized Dark Matter”. We investigate whether the estimates of the Hubble constant and of the present-day abundance of dark matter are sensitive to the dark matter–dark energy coupling. We will also show that the cosmic chronometers data favor a cold dark matter, and that our findings are in agreement with the Le Châtelier–Braun principle according to which dark energy should decay into dark matter.

scholarly journals TOWARDS CLASSIFICATION OF SIMPLE DARK ENERGY COSMOLOGICAL MODELS

2007 ◽  
Vol 04 (02) ◽  
pp. 313-323 ◽  
Author(s):  
MAREK SZYDLOWSKI ◽  
ALEKSANDRA KUREK
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Friedmann Equation ◽  
Chaplygin Gas ◽  
Generalized Chaplygin Gas ◽  
Cosmological Time ◽  
Energy Models ◽  
State Formula ◽  
The Universe

We characterize a class of simple FRW models filled by both dark energy and dark matter in notion of a single potential function of the scale factor a(t); t is the cosmological time. It represents the potential of a fictitious particle — Universe moving in 1-dimensional well V(a) which the positional variable mimics the evolution of the Universe. Then the class of all dark energy models (called a multiverse) can be regarded as a Banach space naturally equipped in the structure of the Sobolev metric. In this paper, we explore the notion of C1 metric introduced in the multiverse which measures distance between any two dark energy models. If we choose cold dark matter as a reference, then we can find how far apart are different models offering explanation of the present accelerating expansion phase of the Universe. We consider both models with dark energy (models with the generalized Chaplygin gas, models with variable coefficient equation of state [Formula: see text] parameterized by redshift z, models with phantom matter) as well as models based on some modification of Friedmann equation (Cardassian models, Dvali–Gabadadze–Porrati brane models). We argue that because observational data still favor the ΛCDM model, all reasonable dark energy models should belong to the nearby neighborhood of this model.

scholarly journals ON THE WIDTH OF THE LAST SCATTERING SURFACE

2004 ◽  
Vol 13 (07) ◽  
pp. 1425-1429
Author(s):  
NILZA PIRES ◽  
MARIA ASSUNTA S. NOBRE ◽  
JOSÉ A. S. LIMA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Chaplygin Gas ◽  
Microwave Background ◽  
Energy Plus ◽  
Microwave Background Radiation ◽  
Physical Effects ◽  
Weakly Dependent

We discuss the physical effects of some accelerated world models on the width of the last scattering surface (LSS) of the cosmic microwave background radiation (CMBR). The models considered in our analysis are X-matter (XCDM) and a Chaplygin type gas. The redshift of the LSS does not depend on the kind of dark energy (if XCDM of Chaplygin). Further, for a Chaplygin gas, the width of the LSS is also only weakly dependent on the kind of scenario (if we have dark energy plus cold dark matter or the unified picture).

THE GENERALIZED CHAPLYGIN GAS MODEL WITH INTERACTION

2007 ◽  
Vol 16 (10) ◽  
pp. 1601-1609 ◽  
Author(s):  
YABO WU ◽  
SONG LI ◽  
HAI YANG ZHONG ◽  
LEI LI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Generalized Chaplygin Gas ◽  
Phantom Divide ◽  
Big Rip ◽  
The Future ◽  
Two Fluid

A two-fluid generalized Chaplygin gas (GCG) model including two different cases is considered in this paper. Concretely, the evolution of the GCG model with interaction is discussed and the statefinder diagnostic for the GCG models is performed, respectively. By analysis, we show that the effective state parameter of dark energy can cross the so-called phantom divide ω = -1, the behavior of GCG will be like ΛCDM in the future and therefore our Universe will not end up with the Big Rip in the future. In addition, we find that the statefinder diagnostic can differentiate the GCG model with or without interaction. Also, trajectories of both the GCG model mixed with cold dark matter (CDM) and the pure GCG model in the parameter plane are illustrated to be significantly different.

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%.

scholarly journals Study of thermal stability for different dark energy models

2019 ◽  
Vol 16 (11) ◽  
pp. 1950171
Author(s):  
Abdulla Al Mamon ◽  
Pritikana Bhandari ◽  
Subenoy Chakraborty
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Point Of View ◽  
Frw Universe ◽  
Generalized Chaplygin Gas ◽  
Dark Fluid ◽  
Energy Models

In this work, we have made an attempt to investigate the dark energy possibility from the thermodynamical point of view. For this purpose, we have studied thermodynamic stability of three popular dark energy models in the framework of an expanding, homogeneous, isotropic and spatially flat FRW Universe filled with dark energy and cold dark matter. The models considered in this work are Chevallier–Polarski–Linder (CPL) model, Generalized Chaplygin Gas (GCG) model and Modified Chaplygin Gas (MCG) model. By considering the cosmic components (dark energy and cold dark matter) as perfect fluid, we have examined the constraints imposed on the total equation of state parameter ([Formula: see text]) of the dark fluid by thermodynamics and found that the phantom nature ([Formula: see text]) is not thermodynamically stable. Our investigation indicates that the dark fluid models (CPL, GCG and MCG) are thermodynamically stable under some restrictions of the parameters of each model.

INTERACTING GENERALIZED CHAPLYGIN GAS MODEL WITH HOLOGRAPHIC DARK ENERGY

2009 ◽  
Vol 24 (25) ◽  
pp. 2013-2024 ◽  
Author(s):  
YA BO WU ◽  
HUAN HUAN FU ◽  
FANG YUAN CHENG ◽  
JUN WANG ◽  
WEI QIANG YANG ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Density Parameter ◽  
Coupling Constant ◽  
Generalized Chaplygin Gas ◽  
Dark Energy Component ◽  
Evolution Laws

In this paper we consider the interacting generalized Chaplygin gas model as a unified scheme, in which the holographic dark energy as the dark energy component interacts with the cold dark matter with wdm= 0. Concretely, we mainly discuss the two kinds of interactions between the dark energy and dark matter, and give the evolution trajectories of density parameter and equation of state of dark energy as well as the decelerate parameter. By analysis, we show that in both cases of Q = 3bHρdeand Q = 3bHρGCG, the evolution laws and the present values of Ωde, wdeand q are compatible with the astronomical observations, but the effects of the coupling constant and holographic constant on them are completely different.

scholarly journals BAYESIAN STATISTICS AND PARAMETER CONSTRAINTS ON THE GENERALIZED CHAPLYGIN GAS MODEL USING SNeIa DATA

2005 ◽  
Vol 14 (05) ◽  
pp. 775-796 ◽  
Author(s):  
R. COLISTETE ◽  
J. C. FABRIS ◽  
S. V. B. GONÇALVES
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Hubble Constant ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Accelerating Universe ◽  
Generalized Chaplygin Gas ◽  
Age Of The Universe ◽  
Parameter Constraints ◽  
The Universe

The type Ia supernovae ( SNe Ia ) observational data are used to estimate the parameters of a cosmological model with cold dark matter and the generalized Chaplygin gas model (GCGM). The GCGM depends essentially on five parameters: the Hubble constant, the parameter [Formula: see text] related to the velocity of the sound, the equation of state parameter α, the curvature of the Universe and the fraction density of the generalized Chaplygin gas (or the cold dark matter). The parameter α is allowed to take negative values and to be greater than one. The Bayesian parameter estimation yields [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], where t0 is the age of the Universe and q0 is the value of the deceleration parameter today. Our results indicate that a Universe completely dominated by the generalized Chaplygin gas is favored, which reinforces the idea that the this gas may unify the description for dark matter and dark energy, at least as far as the SNe Ia data is concerned. A closed and accelerating Universe is also favored. The traditional Chaplygin gas model (CGM), α = 1 is not ruled out, even if it does not give the best-fitting. Particular cases with four or three independent free parameters are also analyzed.

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 Kinematical & Chemical Characteristics of the Thin and Thick Disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 179-190 ◽  
Author(s):  
Rosemary F. G. Wyse
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Observational Evidence ◽  
Chemical Characteristics ◽  
Chemical Abundance ◽  
The Galaxy ◽  
History Of ◽  
Thin And Thick Disks ◽  
Thick Disks

AbstractI discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.

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
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