共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Karami M. Jamil M. Roos S. Ghaffari A. Abdolmaleki 《Astrophysics and Space Science》2012,340(1):175-184
We study the entropy-corrected version of the new agegraphic dark energy (NADE) model and dark matter in a spatially non-flat Universe and in the framework of Hořava-Lifshitz cosmology. For the two cases containing noninteracting and interacting entropy-corrected NADE (ECNADE) models, we derive the exact differential equation that determines the evolution of the ECNADE density parameter. Also the deceleration parameter is obtained. Furthermore, using a parametrization of the equation of state parameter of the ECNADE model as ω Λ(z)=ω 0+ω 1 z, we obtain both ω 0 and ω 1. We find that in the presence of interaction, the equation of state parameter ω 0 of this model can cross the phantom divide line which is compatible with the observation. 相似文献
2.
We discuss some aspects of the Horava-Lifshitz cosmology with different matter components considered as dominants at different stages of the cosmic evolution (each stage is represented by an equation of state pressure/density = constant). We compare cosmological solutions from this theory with their counterparts of General Relativity (Friedmann cosmology). At early times, the Horava-Lifshitz cosmology contains a curvature-dependent dominant term which is stiff matter-reminiscent and this fact motivates to discuss, in some detail, this term beside the usual stiff matter component (pressure = density) if we are thinking in the role that this fluid could have played early in the framework of the holographic cosmology. Nevertheless, we show that an early stiff matter component is of little relevance in Horava-Lifshitz cosmology. 相似文献
3.
We present H-band (1.4–1.8 μm) images of Neptune with a spatial resolution of ∼0.06″, taken with the W.M. Keck II telescope
using the slit-viewing camera (SCAM) of the NIRSPEC instrument backed with Adaptive Optics. Images with 60-second integration
times span 4 hours each on UT 20 and 21 August, 2001 and ∼1 hour on UT 1 September, 2001. These images were used to characterize
the overall brightness distribution on Neptune, and to determine rotations periods (which translate into wind speeds) of individual
cloud features. 相似文献
4.
We study the holographic dark energy on the subject of Hořava-Lifshitz gravity with a time dependent gravitational constant
G(t), in the non-flat space-time. We obtain the differential equation that specify the evolution of the dark energy density parameter
based on varying gravitational constant. We find out a relation for the state parameter of the dark energy equation of state
to low red-shifts which containing varying G corrections in the non-flat space-time. 相似文献
5.
In this work, we studied the Logarithmic Entropy-Corrected Holographic Dark Energy (LECHDE) model in a spatially non-flat universe and in the framework of Ho?ava-Lifshitz cosmology. As infrared cutoff of the system we considered the cut-off recently proposed by Granda and Oliveros which contains two terms, one proportional to H 2 and one to $\dot{H}$ . For the two cases containing non-interacting and interacting Dark Energy (DE) and Dark Matter (DM), we obtained the exact differential equation that determines the evolution of the density parameter. Moreover, we derived the expressions of the deceleration parameter q and, using a parametrization of the equation of state (EoS) parameter ω D of our model as ω D (z)=ω 0+ω 1 z, we derived both the expressions of ω 0 and ω 1 for both non-interacting and interacting cases. All derivations made in this work are done in small redshift approximation and for low redshift expansion of the equation of state (EoS) parameter. 相似文献
6.
Farruh Atamurotov Ahmadjon Abdujabbarov Bobomurat Ahmedov 《Astrophysics and Space Science》2013,348(1):179-188
The shadow of rotating Ho?ava-Lifshitz black hole has been studied and it was shown that in addition to the specific angular momentum a, parameters of Ho?ava-Lifshitz spacetime essentially deform the shape of the black hole shadow. For a given value of the black hole spin parameter a, the presence of a parameter Λ W and KS parameter ω enlarges the shadow and reduces its deformation with respect to the one in the Kerr spacetime. We have found a dependence of radius of the shadow R s and distortion parameter δ s from parameter Λ W and KS parameter ω both. Optical features of the rotating Ho?ava-Lifshitz black hole solutions are treated as emphasizing the rotation of the polarization vector along null congruences. A comparison of the obtained theoretical results on polarization angle with the observational data on Faraday rotation measurements provides the upper limit for the δ parameter as δ≤2.1?10?3. 相似文献
7.
Recently, a renormalizable gravity theory has been proposed by Hořava, and it might be an ultraviolet completion of general
relativity or its infrared modification. Particular limit of the theory allows for the Minkowski vacuum. A spherical asymptotically
flat black hole solution that represents the analogy of Schwarzschild solution of general relativity has been obtained. It
will be very interesting to find the difference between traditional general relativity and Hořava-Lifshitz gravity theory.
The three classical tests of general relativity including gravitational red-shift, perihelion precession of the planet Mercury,
and light deflection in gravitational field in the spherical asymptotically flat black hole solution of infrared modified
Hořava-Lifshitz gravity are investigated. The first order corrections from the standard general relativity is obtained. The
result can be used to limit the parameters in Hořava-Lifshitz gravity and to show the viability of the theory. 相似文献
8.
Hassan Amirhashchi 《中国天文和天体物理学报》2014,(9)
We study the evolution of the equation of state of viscous dark energy in the scope of Bianchi type III space-time. We consider a case where the dark energy is minimally coupled to the perfect fluid, as well as in direct interaction with it. The viscosity and the interaction between the two fluids are parameterized by constants ζ0and σ, respectively. We have made a detailed investigation of the cosmological implications of this parametrization. To differentiate between different dark energy models,we have performed a geometrical diagnostic by using the statefinder pair {s, r}. 相似文献
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Using the third-order WKB approximation, we evaluate the quasinormal frequencies of massless Dirac field perturbation around
a deformed black hole in the Hořava-Lifshitz gravity with coupling constant λ=1. Our result shows that the Hořava-Lifshitz parameter α plays an important role for the quasinormal frequencies and we discuss the variation of quasinormal frequencies with α. Moreover, we find that the massless Dirac field perturbations decay more slowly in the deformed Hořava-Lifshitz gravity. 相似文献
11.
Martin Nekola René Hudec Martin Jelínek Matůš Kocka Petr Kubánek Filip Münz Cyril Polášek Vojtěch Šimon Jan Štrobl 《Experimental Astronomy》2010,28(1):79-85
We report on two small aperture robotic telescopes called BART and D50 operated in Ondřejov. Both telescopes are capable of
automatic observation of gamma ray burst (GRB) optical afterglows. Coordinates of GRBs are taken from alerts distributed via
Internet. Telescopes observe other interesting high energy sources when there is not any alert. The smaller telescope BART
has aperture D = 254 mm. The bigger telescope D50 has a primary mirror of diameter D = 500 mm. Both telescopes are controlled
by free software package RTS2 and are accessible through Internet. We describe the two telescopes and related software and
show some results such as our first observed optical counterpart of GRB. 相似文献
12.
This work is devoted to the investigation of new holographic dark energy (infrared cutoff is the Hubble radius) in locally rotationally symmetric Bianchi type-\(I\) universe within the framework of Saez–Ballester (Phys. Lett. A 113:467, 1986) scalar–tensor theory of gravitation. We construct interacting and non-interacting dark energy models by solving the field equations using a relationship between the metric potentials. This leads to a variable deceleration parameter model which exhibits a transition of the universe from deceleration to acceleration. We evaluate various cosmological parameters of our models. We have observed that the energy density parameters, equation of state and important cosmological planes (\(\omega _{\mathit{de}} - \omega _{\mathit{de}}'\) and \(r - s\)) yield the results compatible with the modern observational data. We have, also, discussed the stability analysis of our models. 相似文献
13.
Dragan Slavkov Hajdukovic 《Astrophysics and Space Science》2010,326(1):3-5
I present three relations, striking in their simplicity and fundamental appearance. The first one connects the Compton wavelength of a pion and the dark energy density of the Universe; the second one connects the Compton wavelength of a pion and the mass distribution of non-baryonic dark matter in a galaxy; the third one relates the mass of a pion to fundamental physical constants and cosmological parameters. All these relations are in excellent numerical agreement with observations. 相似文献
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A locally rotationally symmetric Bianchi type-II (LRS B-II) space-time with variable equation of state (EoS) parameter and
constant deceleration parameter have been investigated in the scalar-tensor theory proposed by Saez and Ballester (Phys. Lett.
A 113:467, 1986). The scalar-tensor field equations have been solved by applying variation law for generalized Hubble’s parameter given by
Bermann (Nuovo Cimento 74:182, 1983). The physical and kinematical properties of the model are also discussed. 相似文献
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To reconstruct dark energy models the redshift z eq , marking the end of radiation era and the beginning of matter-dominated era, can play a role as important as z t , the redshift at which deceleration parameter experiences a signature flip. To implement the idea we propose a variable equation of state for matter that can bring a smooth transition from radiation to matter-dominated era in a single model. A popular Λ∝ ρ dark energy model is chosen for demonstration but found to be unacceptable. An alternative Λ∝ ρ a 3 model is proposed and found to be more close to observation. 相似文献
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