共查询到20条相似文献,搜索用时 31 毫秒
1.
In this work we consider the entropy-corrected version of interacting holographic dark energy (HDE), in the non-flat universe
enclosed by apparent horizon. Two corrections of entropy so-called logarithmic ‘LEC’ and power-law ‘PLEC’ in HDE model with
apparent horizon as an IR-cutoff are studied. The ratio of dark matter to dark energy densities u, equation of state parameter w
D
and deceleration parameter q are obtained. We show that the cosmic coincidence problem is solved for interacting models. By studying the effect of interaction
in EoS parameter of both models, we see that the phantom divide may be crossed and also understand that the interacting models
can drive an acceleration expansion at the present and future, while in non-interacting case, this expansion can happen only
at the early time. The graphs of deceleration parameter for interacting models, show that the present acceleration expansion
is preceded by a sufficiently long period deceleration at past. Moreover, the thermodynamical interpretation of interaction
between LECHDE and dark matter is described. We obtain a relation between the interaction term of dark components and thermal
fluctuation in a non-flat universe, bounded by the apparent horizon. In limiting case, for ordinary HDE, the relation of interaction
term versus thermal fluctuation is also calculated. 相似文献
2.
Singularities in the dark energy universe are discussed, assuming that there is a bulk viscosity in the cosmic fluid. In particular,
it is shown how the physically natural assumption of letting the bulk viscosity be proportional to the scalar expansion in
a spatially flat FRW universe can drive the fluid into the phantom region (w < −1), even if it lies in the quintessence region (w > −1) in the non-viscous case. 相似文献
3.
Recent observations of the Cosmic Microwave Background, Supernovae and Sloan Digital Sky Survey (SDSS) show that our universe has a critical energy density, and roughly 2/3 of it is dark energy, which drives the accelerating expansion of the cosmos. In view of the astrophysical data, we find that the equation of state parameter of the dark energy lies in a narrow range around w = −1. In this paper, we construct a cosmology model with a Rarita-Schwinger field to realize the equation of state parameter w < −1 or w > −1 and discuss its stability. 相似文献
4.
We investigate the QCD ghost model of dark energy in the framework of RS II braneworld. We assume there is an energy flow between the brane and bulk, and hence the continuity equation for the ghost dark energy is violated, while it is still preserved for the dark matter on the brane. We find that with the brane-bulk interaction, the equation of state parameter of ghost dark energy on the brane, can cross the phantom line w D =?1 at the present time, which confirms by some cosmological evidences. This result is in contrast to the standard cosmology where w D of ghost dark energy never cross the phantom line and the universe enters a de Sitter phase at the late time. 相似文献
5.
Yunshuang Du Hongsheng Zhang Xin-Zhou Li 《The European Physical Journal C - Particles and Fields》2011,71(6):1660
Recently, type Ia supernova data appear to support a dark energy whose equation of state w crosses −1, which is a much more amazing problem than the acceleration of the universe. We show that it is possible for the
equation of state to cross the phantom divide by a scalar field in gravity with an additional inverse power-law term of the
Ricci scalar in the Lagrangian. The necessary and sufficient condition for a universe in which the dark energy can cross the
phantom divide is obtained. Some analytical solutions with w<−1 or w>−1 are obtained. A minimally coupled scalar with different potentials, including quadratic, cubic, quantic, exponential and
logarithmic potentials are investigated via numerical methods, respectively. All these potentials lead to the crossing behavior.
We show that it is a robust result which is hardly dependent on the concrete form of the potential of the scalar. 相似文献
6.
In view of the recent observation data indicating that the equation of state of the dark energy might be smaller than −1, this leads to introduction of phantom models featured by their negative kinetic energy to account for the regime of equation of state w < −1. In this paper, we discuss the possibility of using a nonminimally coupled complex scalar field as phantom to realize the equation-of-state parameter w < −1. The main equations which govern the evolution of the universe are obtained. The relations between the potential of the field and red-shift, namely, the reconstruction equations are derived.
PACS 04.40.-b, 98.80.Cq, 98.80.Hw 相似文献
7.
A new dark energy model called “ghost dark energy” was recently suggested to explain the observed accelerating expansion of
the universe. This model originates from the Veneziano ghost of QCD. The dark energy density is proportional to Hubble parameter,
ρ
D
= α H, where α is a constant of order LQCD3{\Lambda_{\rm QCD}^3} and ΛQCD ~ 100 MeV is QCD mass scale. In this Letter, we extend the ghost dark energy model to the universe with spatial curvature
in the presence of interaction between dark matter and dark energy. We study cosmological implications of this model in detail.
In the absence of interaction the equation of state parameter of ghost dark energy is always w
D
> −1 and mimics a cosmological constant in the late time, while it is possible to have w
D
< −1 provided the interaction is taken into account. When k = 0, all previous results of ghost dark energy in flat universe are recovered. For the observational test, we use Supernova
type Ia Gold sample, shift parameter of cosmic microwave background radiation and the correlation of acoustic oscillation
on the last scattering surface and the baryonic acoustic peak from Sloan Digital Sky Survey are used to confine the value
of free parameter of mentioned model. 相似文献
8.
M. Malekjani A. Khodam-Mohammadi 《International Journal of Theoretical Physics》2012,51(10):3141-3151
The interacting polytropic gas dark energy model is investigated from the viewpoint of statefinder diagnostic tool and w−w′ analysis. The dependency of the statefinder parameters on the parameter of the model as well as the interaction parameter between dark matter and dark energy is calculated. We show that different values of the parameters of model and different values of interaction parameter result different evolutionary trajectories in s−r and w−w′ planes. The polytropic gas model of dark energy mimics the standard ΛCDM model at the early time. 相似文献
9.
We find that the expansion of the universe is accelerating by analyzing the recent observation data of type Ia supernova (SN-Ia). It indicates that the equation of state of the dark energy might be smaller than -1, which leads to the introduction of phantom models featured by its negative kinetic energy to account for the regime of equation of state parameter w < -1. In this paper the possibility of using a non-minimally coupled real scalar field as phantom to realize the equation of state parameter w < -1 is discussed. The main equations which govern the evolution of the universe are obtained. Then we rewrite them with the observable quantities. 相似文献
10.
Jianbo Lu Yuting Wang Yabo Wu Tianqiang Wang 《The European Physical Journal C - Particles and Fields》2011,71(11):1800
We use the Markov Chain Monte Carlo method to investigate global constraints on the generalized holographic (GH) dark energy
with flat and non-flat universe from the current observed data: the Union2 dataset of type supernovae Ia (SNIa), high-redshift
Gamma-Ray Bursts (GRBs), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation
(BAO), and the cosmic microwave background (CMB) data. The most stringent constraints on the GH model parameter are obtained.
In addition, it is found that the equation of state for this generalized holographic dark energy can cross over the phantom
boundary w
de
=−1. 相似文献
11.
Esmaeil Ebrahimi Ahmad Sheykhi Hamzeh Alavirad 《Central European Journal of Physics》2013,11(7):949-960
We investigate the generalized Quantum Chromodynamics (QCD) ghost model of dark energy in the framework of Einstein gravity. First, we study the non-interacting generalized ghost dark energy in a flat Friedmann-Robertson-Walker (FRW) background. We obtain the equation of state parameter, w D = p/ρ, the deceleration parameter, and the evolution equation of the generalized ghost dark energy. We find that, in this case, w D cannot cross the phantom line (w D > ?1) and eventually the universe approaches a de-Sitter phase of expansion (w D → ?1). Then, we extend the study to the interacting ghost dark energy in both a flat and non-flat FRW universe. We find that the equation of state parameter of the interacting generalized ghost dark energy can cross the phantom line (w D < ?1) provided the parameters of the model are chosen suitably. Finally, we constrain the model parameters by using the Markov Chain Monte Carlo (MCMC) method and a combined dataset of SNIa, CMB, BAO and X-ray gas mass fraction. 相似文献
12.
Hassan Amirhashchi Anirudh Pradhan H. Zainuddin 《International Journal of Theoretical Physics》2011,50(11):3529-3543
We study the evolution of the dark energy parameter in a spatially homogeneous and isotropic FRW space-time filled with barotropic
fluid and dark energy by considering a time dependent deceleration parameter. Two cases are discussed when the dark energy
is minimally coupled to the perfect fluid as well as direct interaction with it. It is concluded that in both non-interacting
and interacting cases only open and flat universes cross the phantom region. We find that during the evolution of the universe,
the equation of state (EoS) for dark energy ω
D
changes from ω
D
>−1 to ω
D
<−1, which is consistent with recent observations. The cosmic jerk parameter in our derived models is also found to be in
good agreement with the recent data of astrophysical observations. 相似文献
13.
We consider the oscillating dark energy with periodic equation of state in two equivalent formulations: ideal fluid or scalar–tensor theory. It is shown that such dark energy suggests the natural way for the unification of early-time inflation with late-time acceleration. We demonstrate how it describes the transition from deceleration to acceleration or from non-phantom to phantom era and how it solves the coincidence problem. The occurrence of finite-time future singularity for the oscillating (phantom) universe is also investigated. 相似文献
14.
K. Karami S. Ghaffari J. Fehri 《The European Physical Journal C - Particles and Fields》2009,64(1):85-88
By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas
energy density in a non-flat universe. We show that for an even polytropic index by choosing
$K>Ba^{\frac{3}{n}}$K>Ba^{\frac{3}{n}}
, one can obtain ω
Λ
eff<−1, which corresponds to a universe dominated by phantom dark energy. 相似文献
15.
M.R. Setare 《The European Physical Journal C - Particles and Fields》2007,52(3):689-692
We employ the generalized Chaplygin gas of interacting dark energy to obtain the equation of state for the generalized Chaplygin
gas energy density in a non-flat universe. By choosing a negative value for B we see that wΛ
eff<-1, which corresponds to a universe dominated by phantom dark energy. 相似文献
16.
Iver Brevik 《The European Physical Journal C - Particles and Fields》2008,56(4):579-583
We consider a modified gravity fluid on a Randall–Sundrum II brane situated at y=0, the action containing a power α of the scalar curvature. As is known from 4D spatially flat modified gravity, the presence of bulk viscosity may drive the
cosmic fluid into the phantom region (w<−1) and thereafter inevitably into the Big Rip singularity, even if it is initially nonviscous and lies in the quintessence
region (w>−1). The condition for this to occur is that the bulk viscosity contains the power (2α−1) of the scalar expansion. We combine this with the 5D RS II model, and we find that the Big Rip, occurring for α>1/2, carries over to the metric for the bulk metric, |y|>0. Actually, the scale factors on the brane and in the bulk become simply proportional to each other. 相似文献
17.
M. Malekjani A. Khodam-Mohammadi M. Taji 《International Journal of Theoretical Physics》2011,50(10):3112-3124
The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model
including the evolution of EoS parameter w
Λ, energy density ΩΛ and deceleration parameter q are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence
or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of q in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase
later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic
gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are
reconstructed according to the evolution of interacting polytropic gas. 相似文献
18.
The unifying approach to early-time and late-time universe based on phantom cosmology is proposed. We consider gravity-scalar system which contains usual potential and scalar coupling function in front of kinetic term. As a result, the possibility of phantom–non-phantom transition appears in such a way that universe could have effectively phantom equation of state at early time as well as at late time. In fact, the oscillating universe may have several phantom and non-phantom phases. Role in each of two phase and can be absorbed into the redefinition of the scalar field. Right on the transition point, however, the factor cannot be absorbed into the redefinition and play the role to connect two phases smoothly. Holographic dark energy where infrared cutoff is identified with combination of FRW parameters: Hubble constant, particle and future horizons, cosmological constant and universe life-time (if finite). Depending on the specific choice of the model the number of interesting effects occur: the possibility to solve the coincidence problem, crossing of phantom divide and unification of early-time inflationary and late-time accelerating phantom universe. The bound for holographic entropy which decreases in phantom era is also discussed. 相似文献
19.
20.
We discuss observational constraints coming from supernovae Ia imposed on the behaviour of the Randall-Sundrum models. In the case of dust matter on the brane, the difference between the best-fit Perlmutter model with a -term and the best-fit brane models becomes detectable for redshifts z > 1.2. It is interesting that brane models predict brighter galaxies for such redshifts which is in agreement with the measurement of the z = 1.7 supernova. We also demonstrate that the fit to supernovae data can also be obtained, if we admit the super-negative dark energy (phantom matter) p = – (4/3) on the brane, where the dark energy in a way mimics the influence of the cosmological constant. It also appears that the dark energy enlarges the age of the universe which is demanded in cosmology. Finally, we propose to check for dark radiation and brane tension by the application of the angular diameter of galaxies minimum value test. We point out the existence of coincidence problem for the brane tension parameter. 相似文献