共查询到20条相似文献，搜索用时 393 毫秒
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Artyom V. Astashenok Emilio Elizalde Jaume de Haro Sergei D. Odintsov Artyom V. Yurov 《Astrophysics and Space Science》2013,347(1):1-13
Several simple dark energy models on the brane are investigated. They are compared with corresponding models in the frame of 4d Friedmann-Robertson-Walker cosmology. For constraining the parameters of the models considered, recent observational data, including SNIa apparent magnitude measurements, baryon acoustic oscillation results, Hubble parameter evolution data and matter density perturbations are used. Also, explicit formulas of the so-called state-finder parameters in teleparallel theories are found that could be useful to test these models and compare Loop Quantum Cosmology and Brane Cosmology. The conclusion is reached that a joint analysis as the one developed here allows to estimate, in a very clear way, possible deviation of our cosmology from the standard Friedmann-Robertson-Walker one. 相似文献
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Prabir Rudra 《Astrophysics and Space Science》2012,342(2):579-599
In this work we explore 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 Generalized Cosmic 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 the cosmic coincidence problem is taken. The statefinder parameters are also calculated to classify the dark energy models. Graphs and phase diagrams are drawn to study the variations of these parameters. It is also seen that the background dynamics of Generalized Cosmic Chaplygin gas is consistent with the late cosmic acceleration, but not without satisfying certain conditions. It has been shown that the universe in both the models follows the power law form of expansion around the critical point, which is consistent with the known results. Future singularities were studied and our models were declared totally free from any types of such singularities. Finally, some cosmographic parameters were also briefly studied. Our investigation led to the fact that although Generalized cosmic Chaplygin gas with a far lesser negative pressure compared to other dark energy models, can overcome the relatively weaker gravity of RS II brane, with the help of the negative brane tension, yet for the DGP brane model with much higher gravitation, the incompetency of Generalized cosmic Chaplygin gas is exposed, and it cannot produce the accelerating scenario until it reaches the phantom era. 相似文献
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In the present work we assume that the universe is dominated with a two component mixture which do not evolve separately but interact non-gravitationally with one another. we consider the issue of the tachyon as a source of the dark energy and modified Chaplygin gas as background fluid. So we study the interacting between tachyon field and modified Chaplygin gas in different forms of interactions term Q in both flat and non-flat FRW universe. Then we reconstruct the potential and the dynamics of the tachyon field which describe tachyon cosmology. Also we find a equivalence potential for MCG in this model. Next we study two dark components respect to redshift and we find the conditions that are required for the stability of this model. 相似文献
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Motivated by some previous works of Rudra et al. we set to explore the background dynamics when dark energy in the form of New Variable Modified Chaplygin gas is coupled to dark matter with a suitable interaction in the universe described by brane cosmology. The main idea is to find out the efficiency of New variable modified Chaplygin gas to play the role of DE. As a result we resort to the technique of comparison with standard dark energy models. Here the RSII brane model have been considered as the gravity theory. An interacting model is considered in order to search for a possible solution of the cosmic coincidence problem. A dynamical system analysis is performed because of the high complexity of the system. The statefinder parameters are also calculated to classify the dark energy model. Graphs and phase diagrams are drawn to study the variations of these parameters and get an insight into the effectiveness of the dark energy model. It is also seen that the background dynamics of New Variable Modified Chaplygin gas is consistent with the late cosmic acceleration. After performing an extensive mathematical analysis, we are able to constrain the parameters of new variable modified Chaplygin gas as m<n to produce the best possible results. Future singularities are studied and it is found that the model has a tendency to result in such singularities unlike the case of generalized cosmic Chaplygin gas. Our investigation leads us to the fact that New Variable Modified Chaplygin gas is not as effective as other Chaplygin gas models to play the role of dark energy. 相似文献
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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 the cosmic coincidence
problem is taken. The statefinder parameters are also calculated to classify the dark energy models. Graphs and phase diagrams
are drawn to study the variations of these parameters. It is also seen that the background dynamics of modified Chaplygin
gas is completely consistent with the notion of an accelerated expansion in the late universe. Finally, it has been shown
that the universe in both the models follows the power law form of expansion around the critical point, which is consistent
with the known results. 相似文献
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We consider a self-consistent system of Bianchi type-V cosmology and binary mixture of perfect fluid and dark energy. The perfect fluid is taken to be one obeying the usual equation of state p=γ ρ with γ∈[0,1]. The dark energy is considered to be either the quintessence or Chaplygin gas. Exact solutions to the corresponding Einstein equations are obtained as a quadrature. The cases of disordered radiation and models with power-law and exponential expansion have discussed in detail. For large t, the models tend to be isotropic. 相似文献
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We study FRW cosmology for a double scalar-tensor theory of gravity where two scalar fields are nonminimally coupled to the
geometry. In a framework to study stability and attractor solutions of the model in the phase space, we constrain the model
parameters with the observational data. For an accelerating universe, the model behaves like quintom dark energy models and
predicts a transition from quintessence era to phantom era. 相似文献
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In this work, we have considered the DBI-essence dark energy model in FRW Universe. We have found the exact solutions of potential,
warped brane tension and DBI scalar field. We also calculate the statefinder parameters for our model that make it distinguishable
among numerous dark energy models. Moreover, we establish correspondence between DBI-essence and modified Chaplygin gas (MCG)
and hence reconstruct the potential and warped brane tension. By this reconstruction, we observe that DBI scalar field and
potential increase and warped brane tension decreases during evolution of the Universe. Finally, we investigate the validity
of the generalized second law (GSL) of thermodynamics in the presence of DBI-essence and modified Chaplygin gas. It is observed
that the GSL breaks down for DBI-essence model but GSL always satisfied for MCG model. 相似文献
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We investigate the bounce cosmology induced by inhomogeneous viscous fluids in FRW space-time (non necessarily flat), taking into account the early-time acceleration after the bounce. Different forms for the scale factor and several examples of fluids will be considered. We also analyze the relation between bounce and finite-time singularities and between the corresponding fluids realizing this scenarios. In the last part of the work, the study is extended to the framework of f(R)-modified gravity, where the modification of gravity may also be considered as an effective (viscous) fluid producing the bounce. 相似文献
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Here we investigate the holographic dark energy model in the framework of FRW cosmology where the Newtonian gravitational constant, G, is varying with cosmic time. Using the complementary astronomical data which support the time dependency of G, the evolutionary treatment of EoS parameter and energy density of dark energy model are calculated in the presence of time variation of G. It has been shown that in this case, the phantom regime can be achieved at the present time. We also calculate the evolution of G-corrected deceleration parameter for holographic dark energy model and show that the dependency of G on the comic time can influence on the transition epoch from decelerated expansion to the accelerated phase. Finally we perform the statefinder analysis for G-corrected holographic model and show that this model has a shorter distance from the observational point in s–r plane compare with original holographic dark energy model. 相似文献
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This paper is aimed to investigate 5D holographic dark energy (HDE) in DGP-Brane cosmology by employing a combination of Sne Ia, BAO and CMB observational data and constraining cosmological parameters. The FRW dynamics for the normal branch (?=+1) solution of induced gravity brane-world model is taken with the assumption that matter in 5D bulk is HDE such that its holographic nature is reproduced effectively in 4D universe. In the HDE model, we used Hubble horizon as IR cutoff instead of future event horizon. This way, while the model predicts current universe acceleration, it also removes the problem of circular reasoning and causality observed in using future event horizon as IR cutoff. 相似文献
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Assuming spherical symmetry we analyse the dynamics of an inhomogeneous dark radiation vaccum on a Randall and Sundrum 3-braneworld.
Under certain natural conditions we show that the effective Einstein equations on the brane form a closed system. On a de
Sitter brane and for negative dark energy density we determine exact dynamical and inhomogeneous solutions which depend on
the brane cosmological constant, on the dark radiation tidal charge and on its initial configuration. We also identify the
conditions leading to the formation of a singularity or of regular bounces inside the dark radiation vaccum.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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It is shown how the techniques that yield anisotropic and inhomogeneous solutions of the Einstein-Liouville equations for Friedmann-Robertson-Walker (FRW) spacetimes can be used to demonstrate the existence of anisotropic and inhomogeneous FRW solutions of the Einstein-Boltzmann equations, thereby providing a possible relativistic kinetic theory basis (and consequently a more self-consistent basis) for tilting imperfect fluid FRW cosmological models (based on a set of phenomenological laws of relativistic thermodynamics). 相似文献
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Jalil Naji 《Astrophysics and Space Science》2014,350(1):385-392
In this paper we consider a correspondence between the holographic dark energy density and interacting generalized cosmic Chaplygin gas energy density in flat FRW universe. Then, we reconstruct the potential of the scalar field which describe the generalized cosmic Chaplygin cosmology. In the special case we obtain time-dependent energy density and study cosmological parameters. We find stability condition of this model which is depend on cosmic parameter. 相似文献
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Suresh Kumar 《Astrophysics and Space Science》2011,332(2):449-454
The paper deals with a spatially homogeneous and isotropic FRW space-time filled with perfect fluid and dark energy components.
The two sources are assumed to interact minimally, and therefore their energy momentum tensors are conserved separately. A
special law of variation for the Hubble parameter proposed by Berman (Nuovo Cimento B 74:182, 1983) has been utilized to solve the field equations. The Berman’s law yields two explicit forms of the scale factor governing
the FRW space-time and constant values of deceleration parameter. The role of dark energy with variable equation of state
parameter has been studied in detail in the evolution of FRW universe. It has been found that dark energy dominates the universe
at the present epoch, which is consistent with the observations. The physical behavior of the universe has been discussed
in detail. 相似文献
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We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon–tachyon cosmology by interaction
between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling
matter Lagrangian in the model rather than being inserted into the formalism as an external source for the interaction. The
correspondence between the tachyon field and the holographic dark energy (HDE) densities allows to reconstruct the tachyon
scalar field and its potential in a flat FRW universe. The model can show the accelerated expansion of the universe and satisfies
the observational data. 相似文献
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V. Fayaz H. Hossienkhani A. Farmany M. Amirabadi N. Azimi 《Astrophysics and Space Science》2014,351(1):299-306
It is shown that the acceleration of the universe can be understood by considering a f(T) gravity models. Modified teleparallel gravity theory with the torsion scalar has recently gained a lot of attention as a possible explanation of dark energy. For these f(T) gravity models, a variant of the accelerating cosmology reconstruction program is developed. We consider spatially homogenous and anisotropic Bianchi type I universe in the context of f(T) gravity. The de Sitter, power-law and general exponential solutions are assumed for the scale factor in each spatial direction and the corresponding cosmological models are reconstructed. We reconstruct f(T) theories from two different holographic dark energy models in different time durations. For the holographic dark energy model, the dark energy dominated era with new setting up is chosen for reconstruction, and the Ricci dark energy model, radiation, matter and dark energy dominated time durations are all investigated. Finally we have obtained a modified gravity action consistent with the holographic dark energy scenario. 相似文献