共查询到20条相似文献,搜索用时 15 毫秒
1.
Dao-Jun Liu Xin-Zhou Li Jiangang Hao Xing-Hua Jin 《Monthly notices of the Royal Astronomical Society》2008,388(1):275-281
In this paper, we revisit the parametrizations of the equation of state of dark energy and point out that comparing merely the χ2 of different fittings may not be optimal for choosing the 'best' parametrization. Another figure of merit for evaluating different parametrizations based on the area of the w ( z ) − z band is proposed. In light of the analysis of some two-parameter parametrizations and models based on available SNIa data, the area of w ( z ) − z band seems to be a good figure of merit, especially in the situation that the value of χ2 min for different parametrizations are very close. Therefore, we argue that both the area of the w ( z ) − z band and χ2 min should be synthetically considered for choosing a better parametrization of dark energy in the future experiments. 相似文献
2.
Seokcheon Lee 《Astrophysics and Space Science》2014,350(2):785-790
The absence of compelling theoretical model requires the parameterizing the dark energy to probe its properties. The parametrization of the equation of state of the dark energy is a common method. We explore the theoretical optimization of the parametrization based on the Fisher information matrix. As a suitable parametrization, it should be stable at high redshift and should produce the determinant of the Fisher matrix as large as possible. For the illustration, we propose one parametrization which can satisfy both criteria. By using the proper parametrization, we can improve the constraints on the dark energy even for the same data. We also show the weakness of the so-called principal component analysis method. 相似文献
3.
《天文和天体物理学研究(英文版)》2018,(11)
We show that a phenomenological form of energy density for the scalar field can provide the required transition from decelerated(q 0) to accelerated expansion(q 0) phase of the universe.We have used the latest type Ia supernova(SNIa) and Hubble parameter datasets to constrain the model parameters. The best fit values obtained from those datasets are then applied to reconstruct ωφ(z), the equation of state parameter for the scalar field. The results show that the reconstructed forms of q(z) and ω_φ(z) do not differ much from the standard ΛCDM value at the current epoch. Finally, the functional form of the relevant potential V(φ) is derived by a parametric reconstruction. The corresponding V(φ)comes out to be a double exponential potential, which has a number of cosmological implications.Additionally, we have also studied the effect of this particular scalar field dark energy sector on the evolution of matter overdensities. 相似文献
4.
We present dark energy models in an anisotropic Bianchi type-VI0 (B-VI0) space-time with a variable equation of state (EoS). The EoS for dark energy ω is found to be time dependent and its existing range for derived models is in good agreement with the recent observations
of SNe Ia data (Knop et al. in Astrophys. J. 598:102 2003), SNe Ia data with CMBR anisotropy and galaxy clustering statistics (Tegmark et al. in Astrophys. J. 606:702, 2004b) and latest a combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift type
Ia supernovae and galaxy clustering (Hinshaw et al. in Astrophys. J. Suppl. 180:225, 2009; Komatsu et al. in Astrophys. J. Suppl. 180:330, 2009). The cosmological constant Λ is found to be a positive decreasing function of time and it approaches a small positive value
at late time (i.e. the present epoch) which is corroborated by results from recent supernovae Ia observations. The physical
and geometric aspects of the models are also discussed in detail. 相似文献
5.
6.
7.
8.
Andrea V. Macciò Fabio Governato Cathy Horellou 《Monthly notices of the Royal Astronomical Society》2005,359(3):941-948
Using N -body simulations of flat, dark energy-dominated cosmologies, we show that galaxies around simulated binary systems resembling the Local Group (LG) have low peculiar velocities, in good agreement with observational data. We have compared results for LG-like systems selected from large, high-resolution simulations of three cosmologies: a ΛCDM model, a ΛWDM model with a 2-keV warm dark matter candidate, and a quintessence (QCDM) model with an equation-of-state parameter w =−0.6 . The Hubble flow is significantly colder around LGs selected in a flat, Λ-dominated cosmology than around LGs in open or critical models, showing that a dark energy component manifests itself on the scales of nearby galaxies, cooling galaxy peculiar motions. Flows in the ΛWDM and QCDM models are marginally colder than in the ΛCDM one.
The results of our simulations have been compared to existing data and to a new data set of 28 nearby galaxies with robust distance measures (Cepheids and surface brightness fluctuations). The measured line-of-sight velocity dispersion is given by σH = (88 ± 20 km s−1 ) × ( R /7 Mpc) . The best agreement with observations is found for LGs selected in the ΛCDM cosmology in environments with −0.1 < δρ/ρ < 0.6 on scales of 7 Mpc, in agreement with existing observational estimates on the local matter density. These results provide new, independent evidence for the presence of dark energy on scales of a few megaparsecs, corroborating the evidence gathered from observations of distant objects and the early Universe. 相似文献
The results of our simulations have been compared to existing data and to a new data set of 28 nearby galaxies with robust distance measures (Cepheids and surface brightness fluctuations). The measured line-of-sight velocity dispersion is given by σ
10.
Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar R, one uses the torsion scalar T for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. (in Phys. Lett. B 704, 384, 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly. 相似文献
11.
Cristian R. Ghezzi 《Astrophysics and Space Science》2011,333(2):437-447
A model of compact object coupled to inhomogeneous anisotropic dark energy is studied. It is assumed a variable dark energy
that suffers a phase transition at a critical density. The anisotropic Λ-Tolman-Oppenheimer-Volkoff equations are integrated
to know the structure of these objects. The anisotropy is concentrated on a thin shell where the phase transition takes place,
while the rest of the star remains isotropic. The family of solutions obtained depends on the coupling parameter between the
dark energy and the fermionic matter. The solutions share several features in common with the gravastar model. There is a
critical coupling parameter that gives non-singular black hole solutions. The mass-radius relations are studied as well as
the internal structure of the compact objects. The hydrodynamic stability of the models is analyzed using a standard test
from the mass-radius relation. For each permissible value of the coupling parameter there is a maximum mass, so the existence
of black holes is unavoidable within this model. 相似文献
12.
This document presents the results from the Distances subgroup of the Cosmic Frontier Community Planning Study (Snowmass 2013). We summarize the current state of the field as well as future prospects and challenges. In addition to the established probes using Type Ia supernovae and baryon acoustic oscillations, we also consider prospective methods based on clusters, active galactic nuclei, gravitational wave sirens and strong lensing time delays. 相似文献
13.
F. Ferrini 《Astrophysics and Space Science》1975,32(1):231-247
We present the results of an improved analysis of the equation of state of matter from metallic to nuclear density which takes into account: (a) in the region of low densities (?<104 g cm?3), the electron correlation energy in the lattice; (b) in the region of medium density (104<4.3×1011 g cm?3) a more refined discussion of the electron energy; (c) in the region of large densities (4.3×1011 g cm?3) a new method for determining the surface nuclear energy based on the Thomas-Fermi method. The equation of state which we obtain shows no discontinuity at the boundaries between the different regions. 相似文献
14.
L. Sh. Grigorian 《Astrophysics and Space Science》1983,89(1):221-228
On the basis of general requirements, the parameters of the hadronic plasma and the state equation of degenerate superdense matter in the whole range of pressures are improved and corrected. 相似文献
15.
We consider the effect on the adiabatic gravitational collapse of stellar cores of large mass due to (1) the use of different equations of state and (2) the inclusion of energy loss of shock. We find that different equations of state give very different central densities at rebounce and amplitudes of rebounce. When shock energy loss is not considered, all the equations discussed here will lead to explosions, but when it is considered, small amplitude rebounces will not do so. 相似文献
16.
In this work we review briefly the origin and history of the cosmological constant and its recent reincarnation in the form of the dark energy component of the universe. We also comment on the fundamental problems associated to its existence and magnitude which require an urgent solution for the sake of the internal consistency of theoretical physics. 相似文献
17.
Here we investigate the holographic dark energy model in the framework of FRW cosmology where the Newtonian gravitational constant, G, is varying with cosmic time. Using the complementary astronomical data which support the time dependency of G, the evolutionary treatment of EoS parameter and energy density of dark energy model are calculated in the presence of time variation of G. It has been shown that in this case, the phantom regime can be achieved at the present time. We also calculate the evolution of G-corrected deceleration parameter for holographic dark energy model and show that the dependency of G on the comic time can influence on the transition epoch from decelerated expansion to the accelerated phase. Finally we perform the statefinder analysis for G-corrected holographic model and show that this model has a shorter distance from the observational point in s–r plane compare with original holographic dark energy model. 相似文献
18.
19.
20.
F. Arévalo P. Cifuentes Samuel Lepe Francisco Peña 《Astrophysics and Space Science》2014,352(2):899-907
In a flat Friedmann–Lemaitre–Robertson–Walker background, a scheme of dark matter–dark energy interaction is studied considering a holographic Ricci-like model for the dark energy. Without giving a priori some specific model for the interaction function, we show that this function can experience a change of sign during the cosmic evolution. The parameters involved in the holographic model are adjusted with Supernova data and we obtained results compatible with the observable universe. 相似文献