排序方式: 共有57条查询结果,搜索用时 15 毫秒
1.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor at a 68% confidence level. 相似文献
2.
Sergey Chervon 《General Relativity and Gravitation》2004,36(7):1547-1553
A new strategy of exact solutions construction in inflationary cosmology within the self-interacting scalar field theory is proposed. It is shown that inflationary models have no restrictions dictated by the slow-roll approximation on the self-interacting potential. The suggested approach makes it possible to compute precisely the e-folds numbers in inflationary scenarios. The scalar field with a logarithmic evolution in time is analyzed in details. Other possible types of scalar field evolution are discussed. 相似文献
3.
In this paper, using the Gravity’s Rainbow theory, we introduce rainbow metric into rainbow Robertson-Walker metric, and obtain
a model which depends on the energy of probe particles. Furthermore, we research on an exact inflationary solution of the
model, and it can be consistent with the conclusions of observation. The results of our research show that some details in
inflation depend on the energy of particles which are observed by observers. 相似文献
4.
马氏定律与哈勃定律的辨析 总被引:2,自引:2,他引:0
本文从理论,实验上论证了“马氏(红移)定律”,同时指出所谓“退行速度Vr”或“星系红移”与“星系间的距离”无必须的关系,从这个意义上来说,哈勃定律是错误的。 相似文献
5.
Palash B Pal 《Pramana》2000,54(1):79-91
I start by defining the cosmological parameters H
0, Θ
m
and ΘA. Then I show how the age of the universe depends on them, followed by the evolution of the scale parameter of the universe
for various values of the density parameters. Then I define strategies for measuring them, and show the results for the recent
determination of these parameters from measurements on supernovas of type 1a. Implications for particle physics is briefly
discussed at the end. 相似文献
6.
With the aim of understanding the cosmic velocity fields at large scale, we investigate the dynamics of a pressureless distribution
of gravitational sources moving under an anisotropic generalization of Hubble expansion and according to Euler-Poisson equations
system. As a result, it turns out that such a behavior requires the distribution to be homogenous, similarly to Hubble law.
Among several solutions, we show a planar kinematics which admits a constant (eternal) and rotational distortion, where the
velocity field is not potential. Within this class, the one with no rotational distortion identifies to a bulk flow. To apply
this model within cosmic structures as the Local Super Cluster, the solutions are interpreted as approximations providing
us with an hint on the behavior of the cosmic flow just after decoupling era up to present date. Such a result suggests that
the observed bulk flow may not be due exclusively to tidal forces but has a primordial origin.
UPRES EA 2596.
Unité Mixte de Recherche (UMR 6207) du CNRS, et des universités Aix-Marseille I, Aix-Marseille II et du Sud Toulon-Var. Laboratoire
affiliéà la FRUMAM (FR 2291). 相似文献
7.
We use the Radial Baryon Acoustic Oscillation (RBAO) measurements, distant type Ia supernovae (SNe Ia), the observational H(z) data (OHD) and the Cosmic Microwave Background (CMB) shift parameter data to constrain cosmological parameters of ΛCDM and XCDM cosmologies and further examine the role of OHD and SNe Ia data in cosmological constraints. We marginalize the likelihood function over h by integrating the probability density P∝e−χ2/2 to obtain the best fitting results and the confidence regions in the Ωm–ΩΛ plane. With the combination analysis for both of the ΛCDM and XCDM models, we find that the confidence regions of 68.3%, 95.4% and 99.7% levels using OHD+RBAO+CMB data are in good agreement with that of SNe Ia+RBAO+CMB data which is consistent with the result of Lin et al.'s (2009) [24] work. With more data of OHD, we can probably constrain the cosmological parameters using OHD data instead of SNe Ia data in the future. 相似文献
8.
以《化学反应原理》中“盖斯定律”这一教学内容为例,基于发展高中生的化学核心素养为目的确立本课时教学目标,将“理解盖斯定律的本质”“应用盖斯定律计算反应热”这2个问题的讨论作为重点,主要从“证据推理与模型认知” “科学态度与社会责任”2个维度,探讨如何在化学课堂上发展高中生的化学核心素养,探索素养为本的有效课堂教学模式。 相似文献
9.
10.
通过第一性原理计算研究了具有锯齿状边沿并且具有反铁磁构型的单层石墨纳米带的自旋极化输运.研究发现,在中心散射区同一位置掺入单个B和N原子,尽管对整个体系磁矩的影响完全相同,但对两个自旋分量电流的影响却完全相反.掺B时,自旋向上的电流显著大于自旋向下的电流;而掺N时,自旋向下的电流显著大于自旋向上的电流.这是由于不管掺B还是掺N都将打破自旋简并,使得导带和价带中自旋向上的能级比自旋向下的能级更高.掺B引入空穴,使完全占据的价带变为部分占据,从而自旋向上的能级正好处于费米能级,使得电子透射能力更强、电流更大,而自旋向下的能级则离费米能级较远使电子透射的能力较弱.掺N则引入电子,使得原来全空的导带变为部分占据,从而费米能级穿过导带中自旋向下的能级,使得自旋向下的电子比自旋向上的电子透射能力更强.
关键词:
自旋极化输运
单层石墨纳米带
第一性原理
非平衡格林函数 相似文献