排序方式: 共有10条查询结果,搜索用时 31 毫秒
1
1.
2.
Observational constraints on the accelerating universe in the framework of a 5D bounce cosmological model 下载免费PDF全文
In the framework of a five-dimensional (5D) bounce cosmological model, a useful function f(z) is obtained by giving a concrete expression of deceleration parameter q(z)=q1+{q2}/{1+ln (1+ z)}. Then using the obtained Hubble parameter H(z) according to the function f(z), we constrain the accelerating universe from
recent cosmic observations: the 192 ESSENCE SNe Ia and the 9 observational H(z) data. The best fitting values of transition redshift zT and current deceleration parameter q0 are given as zT= 0.65-0.120.25 and q0 = - 0.76-0.15+0.15 (1σ). Furthermore, in the 5D bounce model it can be seen that the evolution of equation of state (EOS) for dark energy wde can cross over -1 at about z=0.23 and the current
value w0de= - 1.15<- 1. On the other hand, by giving a concrete expression of model-independent EOS of dark energy wde, in the 5D bounce model we obtain the best fitting values zT= 0.660.08+0.11 and q0 = - 0.690.10+0.10 (1σ) from the recently observed data: the 192 ESSENCE SNe Ia, the observational H(z) data, the 3-year Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Sky Survey (SDSS) baryon acoustic peak and the x-ray gas mass fraction in clusters. 相似文献
3.
We investigate the interacting new holographic dark energy (HDE) with viscosity. Specifically, we not only study the dynamical evolutions of the new HDE with viscosity and the influences of viscosity as well as the coupling constant on the equation of state for the new HDE, but also establish the correspondence between the new HDE with viscosity and variable generalized Chaplygin gas (VGCG) models in the fiat Friedmann-Robertson-Walker universe. Furthermore, we also reconstruct the potential and the dynamics of VGCG as the scalar field. By analysis we show that for the new holographic Chaplygin gas model, if the related parameters to the potential satisfy some constraints, the accelerated expansion can be achieved. These research results can reduce to the ones without viscosity. 相似文献
4.
In this paper, the properties of dark energy are
investigated according to the parameterized deceleration parameter
q(z), which is used to describe the extent of the accelerating
expansion of the universe. The potential of dark energy V(φ)
and the cosmological parameters, such as the dimensionless energy
density \varOmega_φ, \varOmega_m, and the state parameter
w_φ, are connected to it. Concretely, by giving two kinds of
parameterized deceleration parameters q(z)=a+bz/(1+z) and
q(z)=1/2+(az+b)/(1+z)^2, the evolution of these parameters
and the reconstructed potentials V(φ) are plotted and analysed.
It is found that the potentials run away with the evolution of
universe. 相似文献
5.
将Clifford代数所定义的双曲复空间RH和作用在双曲复空间RH上的双曲相位变换群U4(H)赋予了明确的物理意义. 双曲复空间RH同构于四维Minkowski时空,而其上的双曲相位变换群U4(H)就是四维相对论时空中的洛仑兹(Lorentz)变换群. 进一步,利用U4(H)群的复合变换性质,自然导出了四维Minkowski时空中Lorentz变换和速度变换的一般表达式. 由此,将狭义相对论中的特殊Lorentz变换作为特例包含其中.
关键词:
双曲复数
双曲相位变换
Minkowski时空
Clifford代数 相似文献
6.
7.
By introducing the double complex scalar field, this paper constructs the double Lagrangian with the potential V(Ф(J),Ф(J)) = V(│Ф(J)│), which not only can describe the evolution of quintom Universe, but also can naturally give the spintessence and hessence Universe. Furthermore, the U(1, J) symmetry of the double complex Lagrangian is verified, and the total conserved charge within the physical volume is derived by means of the Norther theorem. Moreover, it can point out that the 'imaginary motion' of the angular parameter in Ref.[14], in fact, is only a real phase displacement in our model. 相似文献
8.
We consider the variable Generalized Chaplygin gas (VGCG) proposal for unification of dark matter and dark energy with p = pdc and ρ= pdm + ρdc. The equation of state of the VGCG is given by p = -A0a^-n/ρ^α, where a is the scale factor. Some cosmological quantities such as the fractional contributions of different components of the universe Ωi (i respectively denotes baryons, dark matter and dark energy) to the critical density, the deceleration parameter q are all obtained. The transition from deceleration to acceleration is described in this model. In addition, we find the behaviour of variable Generalized Chaplgin gas is similar to dust-like matter at early times and will be quiessence or phantom at late stage. 相似文献
9.
Using recently observed data:the Constitution dataset of type supernovae Ia (SNIa),the observational Hubble data (OHD),the measurement results of baryon acoustic oscillation (BAO) from the Sloan Digital Sky Survey (SDSS) and the Two Degree Field Galaxy Redshift Survey (2dFGRS),and the current cosmic microwave background (CMB) data from the five-year Wilkinson Microwave Anisotropy Probe (WMAP),we apply the Markov Chain Monte Carlo method to investigate the observational constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy.For this unified model,the constraints on GCG mixture are discussed by considering the different expressions of current matter density or considering constraints as being independent of the matter quantity Ωm. 相似文献
10.
Some properties related to the NUT--Taub-like spacetime,
such as the surface of infinite red-shift, horizon, singularity
and the area of the NUT--Taub-like black hole are discussed.
Furthermore, the geodesics in the NUT--Taub-like spacetime are
obtained in some special cases. Specifically, the circular orbits
for a massive particle are derived, which can reduce to the cases
of the Schwarzschild spacetime and the NUT--Taub spacetime when
m*=0 and m*\ll M, respectively. 相似文献
1