共查询到20条相似文献,搜索用时 0 毫秒
1.
We investigate cosmological models with extended Chaplygin gas (ECG) as a candidate for dark energy and determine the equation of state parameters using observed data namely, observed Hubble data, baryon acoustic oscillation data and cosmic microwave background shift data. Cosmological models are investigated considering cosmic fluid which is an extension of Chaplygin gas, however, it reduces to modified Chaplygin gas (MCG) and also to generalized Chaplygin gas (GCG) in special cases. It is found that in the case of MCG and GCG, the best-fit values of all the parameters are positive. The distance modulus agrees quite well with the experimental Union2 data. The speed of sound obtained in the model is small, necessary for structure formation. We also determine the observational constraints on the constants of the ECG equation. 相似文献
2.
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
3.
M.R. Setare 《The European Physical Journal C - Particles and Fields》2007,52(3):689-692
We employ the generalized Chaplygin gas of interacting dark energy to obtain the equation of state for the generalized Chaplygin
gas energy density in a non-flat universe. By choosing a negative value for B we see that wΛ
eff<-1, which corresponds to a universe dominated by phantom dark energy. 相似文献
4.
We investigate observational constraint on the variable generalized Chaplygin gas (VGCG) model as the unification of dark matter and dark energy by using the Union supernovae sample and the baryon acoustic oscillations data. Based on the best fit parameters for VGCG model it is shown that the current value of equation of state for dark energy is w0de=−1.08<−1, and the universe will not end up with big rip in the future. In addition, we also discuss the evolution of several quantities in VGCG cosmology such as deceleration parameter, fractional density parameters, growth index and sound speed. Finally, the statefinder diagnostic is performed to discriminate the VGCG with other models. 相似文献
5.
Amna Ali Sourish Dutta Emmanuel N. Saridakis Anjan A. Sen 《General Relativity and Gravitation》2012,44(3):657-683
We investigate cosmological scenarios of generalized Chaplygin gas in a universe governed by Hořava-Lifshitz gravity. We consider
both the detailed and non-detailed balance versions of the gravitational background, and we include the baryonic matter and
radiation sectors. We use observational data from Type Ia Supernovae, Baryon Acoustic Oscillations, and Cosmic Microwave Background,
along with requirements of Big Bang Nucleosynthesis, to constrain the parameters of the model, and we provide the corresponding
likelihood contours. We deduce that the present scenario is compatible with observations. Additionally, examining the evolution
of the total equation-of-state parameter, we find in a unified way the succession of the radiation, matter, and dark energy
epochs, consistently with the thermal history of the universe. 相似文献
6.
7.
Shuvendu Chakraborty Ujjal Debnath Chayan Ranjit 《The European Physical Journal C - Particles and Fields》2012,72(8):1-8
We explore the behavior of the holographic superconductors at zero temperature for a charged scalar field coupled to a Maxwell field in higher-dimensional AdS soliton spacetime via analytical way. In the probe limit, we obtain the critical chemical potentials increase linearly as a total dimension d grows up. We find that the critical exponent for condensation operator is obtained as 1/2 independently of d, and the charge density is linearly related to the chemical potential near the critical point. Furthermore, we consider a slightly generalized setup the Einstein–Power–Maxwell field theory, and find that the critical exponent for condensation operator is given as 1/(4?2n) in terms of a power parameter n of the Power–Maxwell field, and the charge density is proportional to the chemical potential to the power of 1/(2?n). 相似文献
8.
R.C. Freitas 《Physics letters. [Part B]》2011,703(3):209-216
We study the generalized Chaplygin gas model (GCGM) using Gamma-ray bursts as cosmological probes. In order to avoid the so-called circularity problem we use cosmology-independent data set and Bayesian statistics to impose constraints on the model parameters. We observe that a negative value for the parameter α is favoured in a flat Universe and the estimated value of the parameter H0 is lower than that found in literature. 相似文献
9.
Cosmological models with modified Chaplygin gas (MCG) in the framework of Horava–Lifshitz (HL) theory of gravity, both with and without detailed balance, are obtained. The equation of state (EOS) for a MCG contains three unknown parameters namely, A, α, B. The allowed values of some of these parameters of the EOS are determined using the recent astrophysical and cosmological observational data. Using observational data from H(z)-z, baryon acoustic oscillation (BAO) peak parameter and cosmic microwave background (CMB) shift parameter we study cosmologies in detailed-balance and beyond detailed-balance scenario. In this paper we take up the beyond detailed-balance scenario in totality and contribution of dark radiation in detailed-balance scenario on the parameters of the EOS. We explore the effect of dark radiation on the whole range of the effective neutrino parameter (ΔN ν ) to constrain matter contributing parameter B in both the detailed-balance and the beyond detailed-balance scenarios. It has been observed that greater the dark radiation less the matter contribution in the MCG in both the scenario considered here. In order to check the validity of beyond detailed-balance scenario we plot supernovae magnitudes (μ) with red-shift of Union2 data and then the variation of state parameter with redshift is studied. It is noted that beyond detailed-balance scenario is suitable for cosmological model in HL gravity with MCG. 相似文献
10.
New Sr-based Y-type nanocrystalline hexagonal ferrites with a nominal chemical composition of Sr 2Mg 2Fe 12 O 22 (Sr 2Y) were prepared by autocombustion from mixtures of Sr(NO 3) 2, Mg(NO 3) 2?6H 2O and Fe(NO 3) 3?9H 2O. The newly prepared Sr 2Y nanocrystalline particles were characterized by powder X-ray diffraction (XRD). A well crystalline phase of Sr 2Y with hexagonal crystal structure was observed. Fourier transform infrared spectroscopy (FTIR) studies revealed the information about the positions of the ions and their bonds within the lattice structure of the Sr 2Y. The chemical elements and their oxidation states in the Sr 2Y hexaferrites were determined using X-ray photoelectron spectroscopy (XPS). The XRD, FTIR and XPS studies confirmed the formation of Sr 2Mg 2Fe 12 O 22 hexaferrites. The morphology and porosity of the prepared Sr 2Y nanocrystalline Sr 2Y hexaferrite particles were studied by field emission scanning electron microscopy. The magnetic properties of Sr 2Y hexaferrites showed dependence on the methods of preparation conditions and calcination treatments. The values of coercivity, saturation magnetization and retentivity were in the range of 21.33–19.66 kA m ?1, 42.44– 38.72 emu g ?1 and 10.05–13.19 emu g ?1 respectively. 相似文献
11.
Lixin Xu Jianbo Lu Yuting Wang 《The European Physical Journal C - Particles and Fields》2012,72(2):1883
In this paper, we revisit the generalized Chaplygin gas (GCG) model as a unified dark matter and dark energy model. The energy
density of GCG model is given as ρ
GCG/ρ
GCG0=[B
s
+(1−B
s
)a
−3(1+α)]1/(1+α), where α and B
s
are two model parameters which will be constrained by type Ia supernova as standard candles, baryon acoustic oscillation
as standard rulers and the seventh year full WMAP data points. In this paper, we will not separate GCG into dark matter and
dark energy parts any more as adopted in the literature. By using the Markov Chain Monte Carlo method, we find the results
a = 0.00126-0.00126- 0.00126+ 0.000970+ 0.00268\alpha=0.00126_{-0.00126- 0.00126}^{+ 0.000970+ 0.00268} and Bs = 0.775-0.0161- 0.0338+ 0.0161+ 0.0307B_{s}= 0.775_{-0.0161- 0.0338}^{+ 0.0161+ 0.0307}. 相似文献
12.
Peter K. F. Kuhfittig 《General Relativity and Gravitation》2009,41(7):1485-1496
This paper discusses a new variable equation of state parameter leading to exact solutions of the Einstein field equations
describing traversable wormholes. In addition to generalizing the notion of phantom energy, the equation of state generates
a mathematical model that combines the generalized phantom energy and the generalized Chaplygin gas models. 相似文献
13.
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach 总被引:1,自引:0,他引:1
We use the Markov Chain Monte Carlo method to investigate a global constraints on the modified Chaplygin gas (MCG) model as
the unification of dark matter and dark energy from the latest observational data: the Union2 dataset of type supernovae Ia
(SNIa), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and
the cosmic microwave background (CMB) data. In a flat universe, the constraint results for MCG model are, Wbh2 = 0.02263+0.00184-0.00162 (1s)+0.00213-0.00195 (2s){\Omega_{b}h^{2}\,{=}\,0.02263^{+0.00184}_{-0.00162} (1\sigma)^{+0.00213}_{-0.00195} (2\sigma)}, Bs = 0.7788+0.0736-0.0723(1s)+0.0918-0.0904 (2s){B_{s}\,{=}\,0.7788^{+0.0736}_{-0.0723}(1\sigma)^{+0.0918}_{-0.0904} (2\sigma)}, a = 0.1079+0.3397-0.2539 (1s)+0.4678-0.2911 (2s){\alpha\,{=}\,0.1079^{+0.3397}_{-0.2539} (1\sigma)^{+0.4678}_{-0.2911} (2\sigma)}, B = 0.00189+0.00583-0.00756(1s)+0.00660-0.00915 (2s){B\,{=}\,0.00189^{+0.00583}_{-0.00756}(1\sigma)^{+0.00660}_{-0.00915} (2\sigma)}, and H0=70.711+4.188-3.142 (1s)+5.281-4.149(2s){H_{0}=70.711^{+4.188}_{-3.142} (1\sigma)^{+5.281}_{-4.149}(2\sigma)}. 相似文献
14.
In this article, the three-point QCD sum rules are used to compute the strong coupling constants of vertices containing the strange bottomed (charmed) mesons with the pion. The coupling constants are calculated when both the bottom (charm) and the pion states are off-shell. A comparison of the obtained results of the coupling constants with existing predictions is also made. 相似文献
15.
16.
We consider a new generalized Chaplygin gas model that includes the original Chaplygin gas model as a special case. In such a model the generalized Chaplygin gas evolves as from dust to quiescence or phantom. We show that the background evolution for the model is equivalent to that for a coupled dark energy model with dark matter. The constraints from the current type Ia supernova data favour a phantom-like Chaplygin gas model. 相似文献
17.
Abdul Jawad Amara Ilyas Shamaila Rani 《The European Physical Journal C - Particles and Fields》2017,77(2):131
In this paper, we examine the possible realization of a new inflation family called “shaft inflation” by assuming the modified Chaplygin gas model and a tachyon scalar field. We also consider the special form of the dissipative coefficient \(\Gamma ={a_0}\frac{T^{3}}{\phi ^{2 }}\) and calculate the various inflationary parameters in the scenario of strong and weak dissipative regimes. In order to examine the behavior of inflationary parameters, the \(n_s \)–\( \phi ,\, n_s \)–r, and \(n_s \)–\( \alpha _s\) planes (where \(n_s,\, \alpha _s,\, r\), and \(\phi \) represent the spectral index, its running, tensor-to-scalar ratio, and scalar field, respectively) are being developed, which lead to the constraints \(r< 0.11\), \(n_s=0.96 \pm 0.025\), and \(\alpha _s =-0.019 \pm 0.025\). It is quite interesting that these results of the inflationary parameters are compatible with BICEP2, WMAP \((7+9)\) and recent Planck data. 相似文献
18.
19.
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
20.
L. N. Granda E. Torrente-Luján J. J. Fernandez-Melgarejo 《The European Physical Journal C - Particles and Fields》2011,71(7):1704
In the frame of the scalar field model with non-minimal kinetic coupling to gravity, we study the cosmological solutions of
the Chaplygin gas model of dark energy. By appropriately restricting the potential, we found the scalar field, the potential
and coupling giving rise to the Chaplygin gas solution. Extensions to the generalized and modified Chaplygin gas have been
made. 相似文献