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1.
The big bounce singularity of a simple five-dimensional cosmological model is studied.Contrary to the standard big bang space-time singularity,this big bounce singularity is found to be an event horizon at which the scale factor and the mass density of the universe are finite,while the pressure undergoes a sudden transition from negative infinity to positive infinity.By using coordinate transformation it is also shown that before the bounce the universe contracts deflationary.According to the proper-time,the universe may have existed for an infinitely long time. 相似文献
2.
We propose an idea in spectroscopy to search for extra spatial dimensions as well as to detect the possible deviation from Newton's inverse-square law at small scale, and we take high-Z hydrogenic systems and muonic atoms as illustrations. The relevant experiments might help to explore a more than two extra dimensions scenario in the brane world model proposed by Arkani-Hamed, Dimopoulos, Dvali (ADD) and to set constraints for fundamental parameters such as the size of extra dimensions. 相似文献
3.
Cosmological measurements suggest that our universe contains a dark energy component. In order to study the dark energy evolution, we constrain a parameterized dark energy equation of state ω(z) = ω0 + ω1 1+z/z using the recent observational datasets: 157 Gold type Ia supernovae and the newly released 182 Gold type Ia supernovae by the maximum likelihood method. It is found that the best fit ω(z) crosses -1 in the past and the present best fit value of ω(0) 〈 -1 obtained from 157 Gold-type Ia supernovae. The crossing of-1 is not realized and ω0 = -1 is not ruled out in 1σ confidence level for the 182 Gold-type Ia supernovae. It is also found that the range of parameter ω0 is wide even in 1σ confidence level and the best fit ω(z) is sensitive to the prior of Ωm. 相似文献
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5.
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
6.
本文采用谐和条件下的平面引力波严格解度规作为背景空时的度规,对Dirac方程的解进行了讨论,发现它有一组简单的严格解可描述与引力波同方向运动的m=0中微子;并发现在这种情况下引力波对中微子的能态不发生影响。对于具有任意能量和动量的粒子,其解可展为级数形式。级数前四项的计算结果表明,零阶项为平直空时近似,一阶项为零,二阶项为Einstein弱引力波修正,三阶项和更高阶项为强引力波修正。 相似文献
7.
We investigate the phantom field with potential V(φ) = Voexp(-λφ^2) and dark matter in the spatially flat Friedman-Robertson-Walker model It has been shown by numerical calculation that there is a attractor solution in this model We also apply tile statefinder diagnostic to this phantom model. It is shown that tile evolving trajectories of this scenario in tile s - r diagram is quite different from other dark energy models. 相似文献
8.
Selection statics of the Akaike information criterion (AIC) model and the Bayesian information criterion (BIC) model are applied to the A-cold dark matter (ACDM) cosmological model, the constant equation of state of dark energy, w =constant, and the parametrized equation of state of dark energy, w(z) = wo + wlz/(1 + z), to determine which one is the better cosmological model to describe the evolution of the universe by combining the recent cosmic observational data including She Ia, the size of baryonic acoustic oscillation (BAO) peak from SDSS, the three-year WMAP CMB shift parameter. The results show that AIC, BIC and current datasets are not powerful enough to discriminate one model from the others, though odds suggest differences between them. 相似文献
9.
本文在谐和条件下得到了沿同一方向传播的平面引力波与平面电磁波的混合波严格解,以及与平面引力波同方向传播的圆形截面均匀光束的引力场的内部解与外部解,及多个平行光束的引力场的解。这些解将平面引力波的解和Tolman-Peres-Bonnor等人关于电磁波引力场的解在谐和条件下统一起来,并对他们的若干结论作了进一步的研究和扩展。 相似文献
10.
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