In this work, we establish a correspondence between the interacting holographic, new agegraphic dark energy and generalized Chaplygin gas model in Bianchi type I universe. In continue, we reconstruct the potential of the scalar field which describes the generalized Chaplygin cosmology. Cosmological solutions are obtained when the kinetic energy of the phantom field is order of the anisotropy and dominates over the potential energy of the field. We investigate observational constraints on the generalized Chaplygin gas, holographic and new agegraphic dark energy models as the unification of dark matter and dark energy, by using the latest observational data. To do this we focus on observational determinations of the expansion history $H(z)$. It is shown that the HDE model is better than the NADE and generalized Chaplygin gas models in an anisotropic universe. Then, we calculate the evolution of density perturbations in the linear regime for three models of dark energy and compare the results $Λ$CDM model. Finally, the analysis shows that the increase in anisotropy leads to more correspondence between the dark energy scalar field model and observational data
In this letter we consider a correspondence between holographic dark energy and variable modified Chaplygin gas to obtain a holographic dark energy model of the universe. The corresponding potential of the scalar field has been reconstructed which describes the modified variable Chaplygin gas. The stability of the holographic dark energy in this case is also discussed.
The possibility that the dark energy may be described by the Chaplygin gas is discussed. Some observational constraints are established. These observational constraints indicate that a unified model for dark energy and dark matter through the employement of the Chaplygin gas is favored.
In this letter, we have considered that the universe is filled with normal matter and variable modified Chaplygin gas. Also we have considered the interaction between normal matter and variable modified Chaplygin gas in FRW universe. Then we have considered a correspondence between the holographic dark energy density and interacting variable modified Chaplygin gas energy density. Then we have reconstructed the potential of the scalar field which describes the variable modified Chaplygin cosmology.
In this work, we consider the interacting agegraphic dark energy models with entropy correction terms due to loop quantum gravity. We study the correspondence between the Chaplygin gas energy density with the interacting entropy-corrected agegraphic dark energy models in non-flat FRW universe. We reconstruct the potentials and the dynamics of the interacting entropy-corrected agegraphic scalar field models. This model is also extended to the interacting entropy-corrected agegraphic generalized Chaplygin gas dark energy.
In this work, gravitational collapse of a spherical cloud, consists of both dark matter and dark energy in the form of modified Chaplygin gas is studied. It is found that dark energy alone in the form of modified Chaplygin gas forms black hole. Also when both components of the fluid are present then the collapse favors the formation of black hole in cases the dark energy dominates over dark matter. The conclusion is totally opposite to the usually known results.
In this paper, we consider three different models of dark energy in higher dimensional space-time and discuss about some cosmological parameters numerically. The first model is a single component universe including viscous varying modified Chaplygin gas. In the second model, we consider two-component universe including viscous varying modified Chaplygin gas and ghost dark energy. In the third model, we consider another two-component universe including viscous modified cosmic Chaplygin gas and ghost dark energy. In the cases of two-component fluids we also consider possibility of interaction be…
Recently, it was proposed a new fermionic model of dark energy, the so-called f-essence. In this work, we explicitly reconstruct the different f-essence models. In particular, these models include the fermionic Chaplygin gas and the fermionic generalized Chaplygin gas models of dark energy. We also derive the equation of state parameter of the selected f-essence models.
We consider a universe filled by a modified generalized Chaplygin gas together with a pressureless dark matter component. We get a thermodynamical interpretation for the modified generalized Chaplygin gas confined to the apparent horizon of FRW universe, whiles dark sectors do not interact with each other. Thereinafter, by taking into account a mutual interaction between the dark sectors of the cosmos, we find a thermodynamical interpretation for interacting modified generalized Chaplygin gas. Additionally, probable relation between the thermal fluctuations of the system and the assumed mutual…
We choose a modified Chaplygin Gas Dark energy model for considering some its cosmological behaviors. In this regards, we study different Rip singularity scenarios and bouncing model of the universe in context of this model. We show that by using suitable parameters can explain some cosmological aspects of the model.
Spherically symmetric dark energy structures are investigated in the framework of a generalized Chaplygin gas (GCG), which has an equation of state of the form $P = - A/ρ^α} $. We also study these in a modified GCG equation of state, which includes a matter term, i.e. $P = σ^{2} ρ- A/ρ^α$. The results of the latter are then compared with some observational data on low-surface-brightness galaxies which are supposed to be dominated by dark matter.
We present a holographic dark energy model of the universe considering modified generalized Chaplygin gas (GCG). The modified GCG behaves as an ordinary barotropic fluid in the early epoch when the universe was tiny but behaves subsequently as a $Λ$CDM model at late epoch. An equivalent model with scalar field is obtained here by constructing the corresponding potential. The holographic dark energy is identified with the modified GCG and we determine the corresponding holographic dark energy field and its potential. The stability of the holographic dark energy in this case is also discussed.
The generalized Chaplygin gas provides an interesting candidate for the present accelerated expansion of the universe. We explore a geometrical explanation for the generalized Chaplygin gas within the context of brane world theories where matter fields are confined to the brane by means of the action of a confining potential. We obtain the modified Friedmann equations, deceleration parameter and age of the universe in this scenario and show that they are consistent with the present observational data.
We consider an anisotropic brane-world model with Bianchi type I and V geometry, without mirror symmetry or any form of junction conditions. The generalized Chaplygin gas, which interpolates between a high density relativistic era and a non-relativistic matter phase, is a popular candidate for the present accelerated expansion of the universe. Considering the generalized Chaplygin gas as a geometrical dark energy, we obtain the general solutions in an exact parametric form for both Bianchi type I and V space-times. Finally, we study the behavior of the observationally important parameters such…
The generalized Chaplygin gas (GCG) model allows for an unified description of the recent accelerated expansion of the Universe and the evolution of energy density perturbations. This dark energy - dark matter unification is achieved through an exotic background fluid whose equation of state is given by $p = - A/ρ^α$, where $A$ is a positive constant and $0 < α\le 1$. Stringent constraints on the model parameters can be obtained from recent WMAP and BOOMERanG bounds on the locations of the first few peaks and troughs of the Cosmic Microwave Background Radiation (CMBR) power spectrum as well as…
Holographic dark energy (HDE), presents a dynamical view of dark energy which is consistent with the observational data and has a solid theoretical background. Its definition follows from the entropy-area relation $S(A)$, where $S$ and $A$ are entropy and area respectively. In the framework of loop quantum gravity, a modified definition of HDE called "entropy-corrected holographic dark energy" (ECHDE) has been proposed recently to explain dark energy with the help of quantum corrections to the entropy-area relation. Using this new definition, we establish a correspondence between modified vari…
In this paper, viscous generalized Chaplygin gas as a model of dark energy considered. We assume non-constant bulk viscous coefficient and study dark energy density. We consider several cases of density-dependent viscosities. We find that, in the special case, the viscous generalized Chaplygin gas is corresponding to modified Chaplygin gas.
The Chaplygin gas has been proposed as a possible dark energy, dark matter candidate. As a working fluid in a Friedmann-Robertson-Walker universe, it exhibits early behavior reminiscent of dark matter, but at later times is more akin to a cosmological constant. In any such universe, however, one can expect local perturbations to form. Here we obtain the general equations for a self-gravitating relativistic Chaplygin gas. We solve these equations and obtain the mass-radius relationship for such structures, showing that only in the phantom regime is the mass-radius relationship large enough to b…
In this paper, we have considered new modified Chaplygin gas (NMCG) model which interpolates between radiation at early stage and $Λ$CDM at late stage. This model is regarded as a unification of dark energy and dark matter (with general form of matter). We have derived the density parameters from the equation of motion for the interaction between dark energy and dark matter. Also we have studied the evolution of the various components of density parameters.
We employ the generalized Chaplygin gas of interacting dark energy to obtain the equation of state for the generalized Chaplygin gas energy density in non-flat universe. By choosing a negative value for $B$ we see that $w_{\rm Λ}^{eff}< -1$, that corresponds to a universe dominated by phantom dark energy.
The generalized Chaplygin gas, characterized by the equation of state $p=-\mathcal{A}/ρ^α$, has been considered as a model for dark energy due its dark-energy-like evolution at late times. When dissipative processes are taken account, within the framework of the standard Eckart theory of relativistic irreversible thermodynamics, cosmological analytical solutions are found. Using the truncated causal version of the Israel-Stewart formalism, a suitable model was constructed which cross the $w=-1$ barrier. The future-singularities encounter in both approaches are of a new type, not included in th…
In this work, we investigate the holographic dark energy model with new infrared cut-off (new HDE model) proposed by Granda and Oliveros. Using this new definition for infrared cut-off, we establish the correspondence between new HDE model and standard Chaplygin gas (SCG), generalized Chaplygin gas (GCG) and modified Chaplygin gas (MCG) scalar field models in non-flat universe. The potential and dynamics for these scalar field models, which describe the accelerated expansion of the universe are reconstructed. According to the evolutionary behavior of new HDE model, we derive the same form of d…
The modified Chaplygin gas (MCG) is a strong candidate for the unified model of dark matter and dark energy. The equation of state of this modified model is valid from the radiation era to the $Λ$CDM model. In early epoch (when $ρ$ was large), dark matter had the dominant role while at later stages (when $ρ$ is small), the MCG model behaves as dark energy. In this work, we have found exact solution of static spherically symmetric Einstein equations describing a wormhole for an inhomogeneous distribution of modified Chaplygin gas. For existence of wormhole solution, there are some restrictions …
In this paper we investigate the role played by dark energy in the form of Generalized cosmic Chaplygin gas in an accelerating universe described by FRW cosmology. We have tried to describe the model from the theoretical point of view of a field, by introducing a scalar field $ϕ$ and a self interacting potential $V(ϕ)$. The corresponding expressions for the field are obtained for the given model. Statefinder parameters have been used to characterize the dark energy model. Plots have been generated for characterizing different phases of universe diagrammatically and a comparative study is perfo…
The goal of this paper is to discuss phase space analysis of some interacting Chaplygin gas models in General Relativity. Chaplygin gas is one of the fluids actively considered in modern cosmology due to the fact that it is a joint model of dark energy and dark matter. In this paper we have considered various forms of interaction term Q including linear and non linear sign changeable interactions. For each case late time attractors for the field equations are found.
In the context of brane cosmology, we investigate exact solution of the gravitational field equations in the Randall-Sundrum model for an anisotropic brane with Bianchi V geometry, with a generalized Chaplygin gas, which plays the role of dark energy and interacts with dark matter particles. Also, the behavior of the observationally important parameters like expansion and anisotropy is examined.
In this paper, we reexamine the generalized Chaplygin gas (GCG) cosmology with the sign-changeable interaction. The dynamical analysis show that there exists de-Sitter attractors in this model, which means that the late-time behaviors of the model is insensitive to the initial condition and thus alleviates the coincidence problem. Furthermore, we find that this interaction oscillates and tends to zero finally by numerical calculations of the nonlinear equations. In some specific cases of initial conditions, the interaction is positive (the energy transition from dark energy to dark matter) at …
The correspondence of the Gauss-Bonnet (GB) and its modification (MGB) models of dark energy with the standard and generalized Chaplygin gas-scalar field models (SCG and GCG) have been studied in a °at universe. The exact solution of potentials and scalar fields, which describe the accelerated expansion of the universe, are reconstructed. According to the evolutionary behavior of the GB and MGB models, the same form of dynamics of scalar field and potential for different SCG and GCG models are derived. By calculating the squared sound speed of the MGB, GB model as well as the SCG, GCG, and inv…
We investigate the correspondence between the ghost and Chaplygin scalar field dark energy models in the framework of Einstein gravity. We consider a spatially non-flat FRW universe containing the interacting dark energy with dark matter. We reconstruct the potential and the dynamics for the Chaplygin scalar field model according to the evolutionary behavior of the ghost dark energy which can describe the phantomic accelerated expansion of the universe.
In this paper, the model of holographic Chaplygin gas has been extended to two general cases: first is the case of modified variable Chaplygin gas and secondly of the viscous generalized Chaplygin gas. The dynamics of the model are expressed by the use of scalar fields and the scalar potentials.
We examine observational constraints on the generalized Chaplygin gas (GCG) model for dark energy from the 9 Hubble parameter data points, the 115 SNLS Sne Ia data and the size of baryonic acoustic oscillation peak at redshift, $z=0.35$. At a 95.4% confidence level, a combination of three data sets gives $0.67\leq A_s\leq 0.83$ and $-0.21\leq α\leq 0.42$, which is within the allowed parameters ranges of the GCG as a candidate of the unified dark matter and dark energy. It is found that the standard Chaplygin gas model ($α=1$) is ruled out by these data at the 99.7% confidence level.
The modified Chaplygin gas (MCG) cosmological model is derived by using the geometrothermodynamics (GTD) formalism. We show that the MCG corresponds to a system with internal thermodynamic interaction and describes the current accelerated expansion of the universe. Moreover, we also show that the MCG can be interpreted as a unified model for dark energy and dark matter that is perfectly consistent with the current SNe observations and CMB anisotropy measurements.
We investigate the possibility of constraining Chaplygin dark energy models with current Integrated Sachs Wolfe effect data. In the case of a flat universe we found that generalized Chaplygin gas models must have an energy density such that $Ω_c >0.55$ and an equation of state $w <-0.6$ at 95% c.l.. We also investigate the recently proposed Silent Chaplygin models, constraining $Ω_c >0.55$ and $w <-0.65$ at 95% c.l.. Better measurements of the CMB-LSS correlation will be possible with the next generation of deep redshift surveys. This will provide independent and complementary constraints on u…
In this work we investigate the background dynamics when dark energy is coupled to dark matter with a suitable interaction in the universe described by brane cosmology. Here DGP and the RSII brane models have been considered separately. Dark energy in the form of modified Chaplygin gas is considered. A suitable interaction between dark energy and dark matter is considered in order to at least alleviate (if not solve) the cosmic coincidence problem. The dynamical system of equations is solved numerically and a stable scaling solution is obtained. A significant attempt towards the solution of th…
The hypothesis that dark matter and dark energy are unified through the Chaplygin gas is reexamined. Using generalizations of the spherical model which incorporate effects of the acoustic horizon we show that an initially perturbative Chaplygin gas evolves into a mixed system containing cold dark matter-like gravitational condensate.
This paper is devoted to the investigation of modified Chaplygin gas model in the context of solvable k-essence cosmologies. For this purpose, we construct equations of state parameter of this model for some particular values of the parameter $n$. The graphical behavior of these equations are also discussed by using power law form of potential. The relationship between k-essence and modified Chaplygin gas model shows viable results in the dark energy scenario. We conclude that the universe behaves as a cosmological constant, quintessence phase or phantom phase depending upon $n$.
In this paper, we study in Friedmann-Robertson-Walker universe the interaction between the viscous generalized Chaplygin gas with $f(R,T)$ gravity, which is an arbitrary function of the Ricci scalar $R$ and the trace $T$ of the energy-momentum tensor. Assuming that the contents of universe is 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 $Q$. Within the simple form of sc…
Even though many scalar field models of dark energy have been considered in the literature, there is another interesting class of dark energy models involving a fluid known as a Chaplygin gas. In addition to describing the dark energy, both scalar-tensor model and the Chaplygin gas model are suitable candidates for explaining the spherical cosmological collapse. One of the most well-known scalar field models is the quintessence model, which was first introduced to explain an accelerating expanding universe. Using a special form of the quintessence model that is equivalent to Chaplygin gas, we …
We review the essential features of the Chaplygin gas cosmological models and provide some examples of appearance of the Chaplygin gas equation of state in modern physics. A possible theoretical basis for the Chaplygin gas in cosmology is discussed. The relation with scalar field and tachyon cosmological models is also considered.
We consider the scenario emerging from the dynamics of a generalized $d$-brane in a $(d+1, 1)$ spacetime. The equation of state describing this system is given in terms of the energy density, $ρ$, and pressure, $p$, by the relationship $p = - A/ρ^α$, where $A$ is a positive constant and $0 < α\le 1$. We discuss the conditions under which homogeneity arises and show that this equation of state describes the evolution of a universe evolving from a phase dominated by non-relativistic matter to a phase dominated by a cosmological constant via an intermediate period where the effective equation of …
A new model describing the dark sector of the universe is established. The model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an excited state above it as dark matter (DM). The condensate is assumed to have a negative pressure and is embodied as an exotic fluid with Chaplygin equation of state. Excitations are described as a quasiparticle gas. It is shown that the model is not in disagreement with the current observations of the cosmic acceleration. The model predicts increase of the effective cosmological constant and a complete disappearance of the matter at the far future…
The present work employs the Linder parametrization of a constant growth index \cite{linder/index} to investigate the evolution of growth rate of clustering and the dissipation of configurational entropy in some of the most widely studied Chaplygin gas models, such as the generalized Chaplygin gas and the modified Chaplygin gas. The model parameters of the Chaplygin gas models are found to play a vital role in the evolution of growth rate, dark energy density parameter, EoS parameter, and configurational entropy. Furthermore, the work communicates the rate of change of configurational entropy …
Recently developed Generalized Cosmic Chaplygin gas (GCCG) is studied as an unified model of dark matter and dark energy. To explain the recent accelerating phase, the Universe is assumed to have a mixture of radiation and GCCG. The mixture is considered for without or with interaction. Solutions are obtained for various choices of the parameters and trajectories in the plane of the statefinder parameters and presented graphically. For particular choice of interaction parameter, we have shown the role of statefinder parameters in various cases for the evolution of the Universe.
The goal of this paper is to study new cosmological models where the dark energy is a varying Chaplygin gas. This specific dark energy model with non-linear EoS had been often discussed in modern cosmology. Contrary to previous studies, we consider new forms of non-linear non-gravitational interaction between dark matter and assumed dark energy models. We applied the phase space analysis allowing understanding the late time behavior of the models. It allows demonstrating that considered non-gravitational interactions can solve the cosmological coincidence problem. On the other hand, we applied…
Facultad de Física, Universidad Veracruzana（韦拉克鲁斯大学物理学院）；Centro de Investigación en Ciencias del Espacio y Física Teórica (CICEF), Universidad Central de Chile（智利中央大学空间科学与理论物理研究中心）；Instituto de Física y Astronomía, Universidad de Valparaíso（瓦尔帕莱索大学物理与天文研究所）
In this note two cosmological models representing the flat Friedmann Universe filled with a Chaplygin fluid, with or without dust, are analyzed in terms of the recently proposed "statefinder" parameters. Trajectories of both models in the parameter plane are shown to be significantly different w.r.t. "quiessence" and "tracker" models. The generalized Chaplygin gas model with an equation of state of the form $p = -A/ρ^α$ is also analyzed in terms of the statefinder parameters.
We clarify thermodynamics of the Chaplygin gas by introducing the integrability condition. All thermal quantities are derived as functions of either volume or temperature. Importantly, we find a new general equation of state, describing the Chaplygin gas completely. We confirm that the Chaplygin gas could show a unified picture of dark matter and energy which cools down through the universe expansion without any critical point (phase transition).
In this paper we construct modified cosmic Chaplygin gas which has viscosity. We use exponential function method to solve non-linear equation and obtain time-dependent dark energy density. Then discuss Hubble expansion parameter and scale factor and fix them by using observational data. We also investigate stability of this theory.
We extend the world model of Kamenshchik et al. to large perturbations by formulating a Zeldovich-like approximation. We sketch how this model unifies dark matter with dark energy in a geometric setting reminiscent of M-theory.
The Friedmann-Robertson-Walker(FRW) model with dynamical Dark Energy(DE) in the form of modified Chaplygin gas(MCG) has been investigated. The evolution equations are reduced to an autonomous system on the two dimensional phase plane and it can be interpreted as the motion of the particle in an one dimensional potential.
The models that unify dark matter and dark energy based upon the Chaplygin gas fail owing to the suppression of structure formation by the adiabatic speed of sound. Including string theory effects, in particular the Kalb-Ramond field, we show how nonadiabatic perturbations allow a successful structure formation.
We investigate Holographic Dark Energy Correspondence of Interacting Generalized Chaplygin Gas model in the framework of compact Kaluza-Klein cosmology. The evolution of the modified holographic dark energy and the equation of state parameter is obtained here.Using the present observational value of density parameter a stable configuration is formed which accommodates Dark Energy. we note a connection between Dark Energy and Phantom field and have shown that Dark Energy might have evolved from a Phantom state in the past.
Both scalar fields and (generalized) Chaplygin gases have been widely used separately to characterize the dark sector of the Universe. Here we investigate the cosmological background dynamics for a mixture of both these components and quantify the fractional abundances that are admitted by observational data from supernovae of type Ia and from the evolution of the Hubble rate. Moreover, we study how the growth rate of (baryonic) matter perturbations is affected by the dark-sector perturbations.
