共查询到20条相似文献,搜索用时 31 毫秒
1.
A. Sheykhi K. Karami M. Jamil E. Kazemi M. Haddad 《General Relativity and Gravitation》2012,44(3):623-638
In the derivation of holographic dark energy density, the area law of the black hole entropy plays a crucial role. However,
the entropy-area relation can be modified from the inclusion of quantum effects, motivated from the loop quantum gravity,
string theory and black hole physics. In this paper, we study cosmological implication of the interacting entropy-corrected
holographic dark energy model in the framework of Brans–Dicke cosmology. We obtain the equation of state and the deceleration
parameters of the entropy-corrected holographic dark energy in a non-flat Universe. As system’s IR cutoff we choose the radius
of the event horizon measured on the sphere of the horizon, defined as L = ar(t). We find out that when the entropy-corrected holographic dark energy is combined with the Brans–Dicke field, the transition
from normal state where w
D
> −1 to the phantom regime where w
D
< −1 for the equation of state of interacting dark energy can be more easily achieved for than when resort to the Einstein
field equations is made. 相似文献
2.
A. Sheykhi K. Karami M. Jamil E. Kazemi M. Haddad 《International Journal of Theoretical Physics》2012,51(6):1663-1673
Considering the power-law corrections to the black hole entropy, which appear in dealing with the entanglement of quantum
fields inside and outside the horizon, the holographic energy density is modified accordingly. In this paper we study the
power-law entropy-corrected holographic dark energy in the framework of Brans-Dicke theory. We investigate the cosmological
implications of this model in detail. We also perform the study for the new agegraphic dark energy model and calculate some
relevant cosmological parameters and their evolution. As a result we find that this model can provide the present cosmic acceleration
and even the equation of state parameter of this model can cross the phantom line w
D
=−1 provided the model parameters are chosen suitably. 相似文献
3.
We investigate the QCD ghost model of dark energy in the framework of Brans-Dicke cosmology. First, we study the non-interacting ghost dark energy in a flat Brans-Dicke theory. In this case we obtain the equation of state and the deceleration parameters and a differential equation governing the evolution of ghost energy density. Interestingly enough, we find that the equation of state parameter of the non-interacting ghost dark energy can cross the phantom line (wD=−1) provided the parameters of the model are chosen suitably. Then, we generalize the study to the interacting ghost dark energy in both flat and non-flat Brans-Dicke framework and find out that the transition of wD to phantom regime can be more easily achieved for than when resort to the Einstein field equations is made. 相似文献
4.
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
5.
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
6.
Rong-Jia Yang Jing-Zhao Qi Lihua Feng 《International Journal of Theoretical Physics》2012,51(6):1692-1697
Assuming that the equation of state of dark energy is a constant, we obtain the allowed interval of the equation of state
of dark energy: w
D≥−1, bounded from the generalized second law of thermodynamics, in a universe enveloped by the apparent horizon and containing
a Schwarzschild black hole. 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.
The nature of the dark energy is still a mystery and several models have been proposed to explain it. Here we consider a phenomenological
model for dark energy decay into photons and particles as proposed by Lima (Phys Rev D 54:2571, 1996). He studied the thermodynamic
aspects of decaying dark energy models in particular in the case of a continuous photon creation and/or disruption. Following
his approach, we derive a temperature redshift relation for the cosmic microwave background (CMB) which depends on the effective
equation of state w
eff and on the “adiabatic index” γ. Comparing our relation with the data on the CMB temperature as a function of the redshift obtained from Sunyaev–Zel’dovich
observations and at higher redshift from quasar absorption line spectra, we find w
eff = −0.97 ± 0.03, adopting for the adiabatic index γ = 4/3, in good agreement with current estimates and still compatible with w
eff = −1, implying that the dark energy content being constant in time. 相似文献
9.
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
10.
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
11.
Lixin Xu Wenbo Li Jianbo Lu 《The European Physical Journal C - Particles and Fields》2009,60(1):135-140
In this paper, the holographic dark-energy model is considered in Brans–Dicke theory, where the holographic dark-energy density
ρ
Λ
=3c
2
M
pl2
L
−2 is replaced by ρ
h=3c
2
Φ(t)L
−2. Here
is the time-variable Newton constant. With this replacement, it is found that no accelerated expansion for the universe will
be achieved when the Hubble horizon is taken to play the role of an IR cut-off. When the event horizon is adopted as the IR
cut-off, accelerated expansion for the universe is obtained. In this case, the equation of state of holographic dark energy,
w
h, takes the modified form
. In the limit α→0, the ‘standard’ holographic dark energy is recovered. In the holographic dark-energy dominated epoch, power-law and de
Sitter time-space solutions are obtained. 相似文献
12.
We analyze an oscillating universe model in brane world cenario. The oscillating universe cycles through a series of expansions
and contractions and its energy density is dominated by dust matter at early-time expansion phase and by phantom dark energy
at late-time expansion phase. We find that the period of the oscillating universe is not sensitive to the tension of the brane,
but sensitive to the equation-of-state parameter w of the phantom dark energy, and the ratio of the period to the current Hubble age approximately varies from 3 to 9 when the
parameter w changes from −1.4 to −1.1. The fraction of time that the oscillating universe spends in the coincidence state is also comparable
to the period of the oscillating universe. This result indicates that the coincidence problem can be significantly ameliorated
in the oscillating universe without singularity. 相似文献
13.
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
14.
M. Hamani Daouda Manuel E. Rodrigues M. J. S. Houndjo 《The European Physical Journal C - Particles and Fields》2012,72(2):1893
We develop the reconstruction of the f(T) gravity model according to the holographic dark energy. T is the torsion scalar and its initial value from the teleparallel gravity is imposed for fitting the initial value of the
function f(T). The evolutionary nature of the holographic dark energy is essentially based on two important parameters, Ω
V
and ω
V
, respectively, the dimensionless dark energy and the parameter of the equation of state, related to the holographic dark
energy. The result shows a polynomial function for f(T), and we also observe that, when Ω
V
→1 at the future time, ω
V
may cross −1 for some values of the input parameter b. Another interesting aspect of the obtained model is that it provides a unification scenario of dark matter with dark energy. 相似文献
15.
We study cosmological application of interacting holographic energy density in the framework of Brans–Dicke cosmology. We obtain the equation of state and the deceleration parameter of the holographic dark energy in a non-flat universe. As system's IR cutoff we choose the radius of the event horizon measured on the sphere of the horizon, defined as L=ar(t). We find that the combination of Brans–Dicke field and holographic dark energy can accommodate wD=−1 crossing for the equation of state of noninteracting holographic dark energy. When an interaction between dark energy and dark matter is taken into account, the transition of wD to phantom regime can be more easily accounted for than when resort to the Einstein field equations is made. 相似文献
16.
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
17.
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
18.
Jianbo Lu Yuanxing Gui Li xin Xu 《The European Physical Journal C - Particles and Fields》2009,63(3):349-354
We investigate observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and
dark energy from the latest observational data: the Union SNe Ia data, the observational Hubble data, the SDSS baryon acoustic
peak and the five-year WMAP shift parameter. The result is obtained that the best-fit values of the GCG model parameters with
their confidence level are A
s=0.73−0.06+0.06 (1σ) −0.09+0.09 (2σ), α=−0.09−0.12+0.15 (1σ) −0.19+0.26 (2σ). Furthermore, in this model, we can see that the evolution of equation of state (EOS) for dark energy is similar to quiessence,
and its current best-fit value is w
0de=−0.96 with the 1σ confidence level −0.91≥w
0de≥−1.00. 相似文献
19.
Lixin Xu Jianbo Lu Wenbo Li 《The European Physical Journal C - Particles and Fields》2009,64(1):89-95
In this paper, we consider generalized holographic and Ricci dark energy models where the energy densities are given as ρ
R
=3c
2
M
pl2
Rf(H
2/R) and ρ
h
=3c
2
M
pl2
H
2
g(R/H
2), respectively; here f(x), g(y) are positive defined functions of the dimensionless variables H
2/R or R/H
2. It is interesting that holographic and Ricci dark energy densities are recovered or recovered interchangeably when the function
f(x)=g(y)≡1 or f(x)=Id and g(y)=Id are taken, respectively (for example f(x),g(x)=1−ε(1−x), ε=0or1, respectively). Also, when f(x)≡xg(1/x) is taken, the Ricci and holographic dark energy models are equivalent to a generalized one. When the simple forms f(x)=1−ε(1−x) and g(y)=1−η(1−y) are taken as examples, by using current cosmic observational data, generalized dark energy models are considered. As expected,
in these cases, the results show that they are equivalent (ε=1−η=1.312), and Ricci-like dark energy is more favored relative to the holographic one where the Hubble horizon was taken as
an IR cut-off. And the suggested combination of holographic and Ricci dark energy components would be 1.312R−0.312H
2, which is
2.312H2+1.312[(H)\dot]2.312H^{2}+1.312\dot{H}
in terms of H
2 and
[(H)\dot]\dot{H}
. 相似文献
20.
Building on our earlier work (Misra and Shukla, Nucl. Phys. B 827:112, 2010; Phys. Lett. B 685:347–352, 2010), we show the possibility of generating “light” fermion mass scales of MeV–GeV range (possibly related to the first two generations
of quarks/leptons) as well as eV (possibly related to first two generations of neutrinos) in type IIB string theory compactified
on Swiss-Cheese orientifolds in the presence of a mobile space-time filling D3-brane restricted to (in principle) stacks of fluxed D7-branes wrapping the “big” divisor Σ
B
. This part of the paper is an expanded version of the latter half of Sect. 3 of a published short invited review (Misra,
Mod. Phys. Lett. A 26:1, 2011) written by one of the authors [AM]. Further, we also show that there are no SUSY GUT-type dimension-five operators corresponding
to proton decay, and we estimate the proton lifetime from a SUSY GUT-type four-fermion dimension-six operator to be 1061 years. Based on GLSM calculations in (Misra and Shukla, Nucl. Phys. B 827:112, 2010) for obtaining the geometric K?hler potential for the “big divisor,” using further the Donaldson’s algorithm, we also briefly
discuss in the first of the two appendices the metric for the Swiss-Cheese Calabi–Yau used, which we obtain and which becomes
Ricci flat in the large-volume limit. 相似文献