共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
3.
A new dark energy model, named “agegraphic dark energy”, has been proposed recently, based on the so-called Károlyházy uncertainty
relation, which arises from quantum mechanics together with general relativity. In this note, we extend the original agegraphic
dark energy model by including the interaction between agegraphic dark energy and pressureless (dark) matter. In the interacting
agegraphic dark energy model, there are many interesting features different from the original agegraphic dark energy model
and holographic dark energy model. The similarity and difference between agegraphic dark energy and holographic dark energy
are also discussed. 相似文献
4.
Mubasher Jamil Muneer Ahmad Rashid 《The European Physical Journal C - Particles and Fields》2008,56(3):429-434
We have investigated the model of dark energy interacting with dark matter by choosing inhomogeneous equations of state for
the dark energy and a nonlinear interaction term for the underlying interaction. The equations of state have dependencies
either on the energy densities, the redshift, the Hubble parameter or the bulk viscosity. We have considered these possibilities
and have derived the effective equations of state for the dark energy in each case. 相似文献
5.
A NUT-like metric is obtained by means of a complex coordinate transformation in the Brans-Dicke theory. 相似文献
6.
Guang-Wen Ma 《International Journal of Theoretical Physics》1995,34(11):2331-2339
The Kerr-type solution in the Brans-Dicke theory should contain three parameters: a massm, a rotational parametera
0, and a coupling parameter It goes over to the Kerr solution in Einstein's theory of general relativity in the limit 8. Using these conditions, we construct a special solution from Bruckman's solutions which can be regarded as a Kerr-type solution in the Brans-Dicke theory. 相似文献
7.
We present a Euclidean wormhole solution in vacuum Brans-Dicke theory, which is different from that obtained by Accetta et al. This wormhole appears to have the feature that its throat dimension increases linearly with Euclidean cosmic time, although this increase may not be measurable. It also requires a negative Brans-Dicke parameter. 相似文献
8.
In the derivation of Holographic Dark Energy (HDE), the area law of the black hole entropy assumes a crucial role. However, the entropy-area relation can be modified including some quantum effects, motivated from the Loop Quantum Gravity (LQG), string theory and black hole physics. In this paper, we study the cosmological implications of the interacting logarithmic entropy-corrected HDE (LECHDE) model in the framework of Brans-Dicke (BD) cosmology. As system’s infrared (IR) cut-off, we choose the average radius of Ricci scalar curvature, i.e. R ?1/2. We obtain the Equation of State (EoS) parameter ω D , the deceleration parameter q and the evolution of energy density parameter $\varOmega'_{D}$ of our model in a non-flat universe. Moreover, we study the limiting cases corresponding to our model without corrections and to the Einstein’s gravity. 相似文献
9.
Li Yuanjie Luo Shijun Ma Weichan 《International Journal of Theoretical Physics》1993,32(11):2173-2176
We show that an inflationary phase may occur at a sufficiently early epoch in the Robertson-Walker universe model in Brans-Dicke theory with torsion. Some features of this inflationary scenario are briefly discussed. 相似文献
10.
Kang G 《Physical review D: Particles and fields》1996,54(12):7483-7489
11.
The static perfect fluid in Brans-Dicke theory with spherical symmetry and conformal flatness leads to a differential equation in terms of the scalar field only. We obtain a unique exact solution for the casep=, but density and pressure are singular at the center. We further consider the metric corresponding to a static nonrotating space-time with two mutually orthogonal spacelike Killing vectors in Brans-Dicke theory. We obtain a differential equation involving only the scalar field for the equation of statep= The general solution is found as a transcendental function. Finally, we generalize a theorem given by Bronnikov and Kovalchuk (1979) for perfect fluid in Einstein's theory.On leave from Jadavpur University, Calcutta-32, India. 相似文献
12.
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
13.
H. A. Buchdahl 《General Relativity and Gravitation》1973,4(4):319-326
In the general theory of relativity the active mass M of a static source can be written exactly as an integral over a certain
linear combination of the diagonal components of the stress-energy tensor. Two corresponding integrals are found within the
framework of the Brans-Dicke theory which give the values of those two constants characterizing the source which alone enter
into the metric tensor at points sufficiently remote from the source. After dealing with some concomitant results it is shown
that the Brans-Dicke equations do not admit everywhere regular, static, asymptotically flat vacuum solutions. 相似文献
14.
An attempt has been made to construct nonsingular cosmological models in Brans-Dicke theory by taking vacuum field as the long-range interacting scalar field which tends to avert the occurrence of initial singularity in a homogeneous and isotropic cosmological model. Such a model will possess an extremely small value of coupling parameter , as such they will be characteristically different from the usual Brans-Dicke models with 6. A justification for the estimated value of coupling parameter in the present paper has been given with particular reference to the helium problem. The model satisfies the initial conditions as proposed by Salam, Sinha, etc. However, it predicts a larger value of the energy density at the present epoch. 相似文献
15.
16.
Marcelo Samuel Berman 《International Journal of Theoretical Physics》1992,31(2):321-323
A static universe with position-dependent rest-energy density, pressure, and scalar field is considered in Brans-Dicke theory. A perfect-gas equation of state is obtained with the solution to the field equations for the Euclidean case with Robertson-Walker metric. 相似文献
17.
The behaviour of gravitational energy and scalar field during the evolution of the universe within the framework of Brans-Dicke
theory has been discussed. With help of the Landau-Lifshitz pseudo-tensor for the flat Friedmann-Robertson-Walker model, it
is found that (i) the total energy of the universe is always zero, (ii) the Brans-Dicke scalar field for all Ω >-0 contributes
energy to the negative energy of gravitational field and this gets transferred to the vacuum energy which accelerates the
expansion of the universe. 相似文献
18.
We study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this, we take the FRW universe model with a viscous fluid (without potential) and the Bianchi type-I universe model with a barotropic fluid (with and without a potential). We evaluate the deceleration parameter and the Brans-Dicke parameter to explore cosmic acceleration. It is concluded that accelerated expansion of the universe can also be achieved for higher values of the Brans-Dicke parameter in some cases. 相似文献
19.
A recent investigation showed that a local gauge string with a phenomenological energy momentum tensor, as prescribed by Vilenkin,
is inconsistent in Brans-Dicke theory. In this work it has been shown that such a string is indeed consistent if one introduces
time dependences in the metric. A set of solutions of full non-linear Einstein’s equations for the interior region of such
a string are presented. 相似文献
20.
Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological
observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet. Explanations
of cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models
are nearly all based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but
all share one feature in common—an inability to account for the gravitational properties of the vacuum energy. Speculative
ideas from string theory may hold some promise, but it is fair to say that no convincing model has yet been proposed. An alternative
to dark energy is that gravity itself may behave differently from general relativity on the largest scales, in such a way
as to produce acceleration. The alternative approach of modified gravity (or dark gravity) provides a new angle on the problem,
but also faces serious difficulties, including in all known cases severe fine-tuning and the problem of explaining why the
vacuum energy does not gravitate. The lack of an adequate theoretical framework for the late-time acceleration of the universe
represents a deep crisis for theory—but also an exciting challenge for theorists. It seems likely that an entirely new paradigm
is required to resolve this crisis. 相似文献