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1.
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
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
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.
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
10.
Mubasher Jamil K. Karami A. Sheykhi E. Kazemi Z. Azarmi 《International Journal of Theoretical Physics》2012,51(2):604-611
Motivated by the recent works of one of us (Karami and Fehri, Int. J. Theor. Phys. 49:1118, 2010; Phys. Lett. B 684:61, 2010), we study the holographic dark energy in Brans-Dicke gravity with the Granda-Oliveros cut-off proposed recently in literature.
We find out that when the present model is combined with 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 dark energy can be more easily achieved for than when resort to the Einstein field equations
is made. Furthermore, the phantom crossing is more easily achieved when the matter and the holographic dark energy undergo
an exotic interaction. We also calculate some relevant cosmological parameters and their evolution. 相似文献
11.
Ronald F. Bruner 《International Journal of Theoretical Physics》2009,48(9):2704-2714
It is shown that if a volume element V, of space is assumed to have intrinsic energy E, then basic principles of mechanics, thermodynamics and special relativity lead to the equation of state: E=pV, where p is the pressure. When this equation of state is incorporated in the Einstein equations it leads to the prediction that the
orbital speed of matter circling a visible galaxy embedded in a spherical galactic halo should be relativistic, in disagreement
with observations. However, it also leads directly to the interesting notion that the inertial mass of such a medium can be
understood as a resistance to being compressed via Lorentz contraction. It is then shown that the mathematical structure of
thermodynamics suggests another plausible definition of pressure if we allow for the possibility that the intrinsic energy
of spacetime may not be described by the same work-energy relationship as ordinary matter. This additional possibility leads
to the equation of state: E=−pV. While both of these equations of state describe forms of energy that are quite unlike ordinary energy, neither alone is
able to account for observed rotational velocity curves of matter orbiting visible galaxies. Therefore, the possibility that
space has two distinct components of energy is investigated. This results in a plausible, two-component equation of state
in which the former equation of state is tentatively identified as the “dark matter” (DM) component, the latter as the “dark
energy” (DE) component. The effective equation of state of space, accounting for the presence of both components, may then
be written in the form: p=w
ε, where ε is the total energy density, p the total pressure, and w represents the fractional excess of DM over DE (and therefore satisfies: −1≤w≤+1). Given the wide range of possible spacetime properties implied by this equation it appears to be a viable candidate for
explaining observations presently attributed to the presence of both DM and DE. Specifically, the static, spherically symmetric
solution of Einstein’s field equations, neglecting effects of ordinary matter, predicts the inverse r
2 distribution of intrinsic space energy required to explain observed constant rotational velocity curves for matter in circular
orbits around visible galaxies embedded within spherically symmetric galactic halos. The proposed equation of state is also
capable of describing regions of space undergoing accelerated expansion as regions where DE is dominant (i.e., w<−1/3). 相似文献
12.
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
13.
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
14.
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
15.
A modified Chaplygin gas (MCG) model of unifying dark energy and dark matter is considered in this paper, in which dark energy
interacts with dark matter. Concretely, the evolution of such a unified dark sectors model is studied and the statefinder
diagnostic to the MCG model is performed in our model. By analysis, it is shown that the effective equation of state (EoS)
parameter of dark energy can cross the so-called phantom divide ω = −1, the behavior of MCG will be like ΛCDM in the future and therefore our Universe will not end up with Big Rip in the
future. Furthermore, we plot the evolution trajectories of the MCG model in the statefinder parameter r–s plane and illustrate the discrimination between this scenario and the generalized Chaplygin gas (GCG) model. 相似文献
16.
The Bianchi Type-I Universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for
the dark energy component of the Universe has been used. It is modeled on the equation of state p = γ(ρ − ρ*) which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in
quadrature form. The solution for constant deceleration parameter have been studied in detail for both power-law and exponential
forms. The cases γ = 1 and γ = 0 have also been analysed.
相似文献
17.
Jianbo Lu Lixin Xu Molin Liu Yuanxing Gui 《The European Physical Journal C - Particles and Fields》2008,58(2):311-324
We use recent data: the 192 ESSENCE type Ia supernovae (SNe Ia), the 182 Gold SNe Ia, the three-year WMAP, the SDSS baryon
acoustic peak, the X-ray gas mass fraction in clusters and the observational H(z) data, to constrain models of the accelerating universe. Combining the 192 ESSENCE data with the observational H(z) data to constrain the parameterized deceleration parameter, we obtain the best-fit values of the transition redshift and
current deceleration parameter z
T=0.632−0.127+0.256 and q
0=−0.788−0.182+0.182. Furthermore, using the ΛCDM model and two model-independent equations of state of the dark energy, we find that the combined
constraint from the 192 ESSENCE data and four other cosmological observations gives smaller values for Ω
0m and q
0, but a larger value for z
T than the combined constraint from the 182 Gold data with four other observations. Finally, according to the Akaike information
criterion it is shown that the recently observed data equally support three dark energy models: ΛCDM, w
de(z)=w
0 and w
de(z)=w
0+w
1ln (1+z). 相似文献
18.
Molin Liu Jianbo Lu Yuanxing Gui 《The European Physical Journal C - Particles and Fields》2009,59(1):107-116
On the basis of the 4D momentum, the influence of quintessence on the gravitational frequency shift and the deflection of
light are examined in modified Schwarzschild space. We find that the frequency of a photon depends on the state parameter
of the quintessence w
q: the frequency increases for −1<w
q<−1/3 and decreases for −1/3<w
q<0. Meanwhile, we adopt an integral power number a (a=3ω
q+2) to solve the orbital equation of photon. The photon’s potentials become higher with the decrease of ω
q. The behavior of the bending light sensitively depends on the state parameter ω
q. In particular, for the case of ω
q=−1, there is no influence on the deflection of light by quintessence. Furthermore, according to the H-masers of the GP-A
redshift experiment and long-baseline interferometry, the constraints on the quintessence field in the solar system are presented
here. 相似文献
19.
Recent observations on Type-Ia supernovae and low density (Ω
m
=0.3) measurement of matter including dark matter suggest that the present-day universe consists mainly of repulsive-gravity
type ‘exotic matter’ with negative-pressure often said ‘dark energy’ (Ω
x
=0.7). But the nature of dark energy is mysterious and its puzzling questions, such as why, how, where and when about the
dark energy, are intriguing. In the present paper the authors attempt to answer these questions while making an effort to
reveal the genesis of dark energy and suggest that ‘the cosmological nuclear binding energy liberated during primordial nucleo-synthesis
remains trapped for a long time and then is released free which manifests itself as dark energy in the universe’. It is also
explained why for dark energy the parameter
w=-\frac23w=-\frac{2}{3}
. Noting that w=1 for stiff matter and
w=\frac13w=\frac{1}{3}
for radiation;
w=-\frac23w=-\frac{2}{3}
is for dark energy because “−1” is due to ‘deficiency of stiff-nuclear-matter’ and that this binding energy is ultimately
released as ‘radiation’ contributing “
+\frac13+\frac{1}{3}
”, making
w=-1+\frac13=-\frac23w=-1+\frac{1}{3}=-\frac{2}{3}
. When dark energy is released free at Z=80,
w=-\frac23w=-\frac{2}{3}
. But as on present day at Z=0 when the radiation-strength-fraction (δ), has diminished to δ→0, the
w=-1+d\frac13=-1w=-1+\delta\frac{1}{3}=-1
. This, almost solves the dark-energy mystery of negative pressure and repulsive-gravity. The proposed theory makes several
estimates/predictions which agree reasonably well with the astrophysical constraints and observations. Though there are many
candidate-theories, the proposed model of this paper presents an entirely new approach (cosmological nuclear energy) as a
possible candidate for dark energy. 相似文献
20.
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