排序方式: 共有18条查询结果,搜索用时 31 毫秒
1.
2.
3.
We study linear perturbations about a dust filled Bianchi type-I model with the vorticity set to zero. In comparisonto linear perturbations about the Friedmann-Lemaitre Robertson Walker models, modes of perturbations about the Bianchi type-I models are coupled. We find that the tensor that represents the background shear needs to be degenerate in order for the scalar-mode perturbations to decouple from the rest of the flow. 相似文献
4.
Mechanical properties of the thermal equilibrium Friedmann–Robertson–Walker universe model
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The mechanical property of the thermal-equilibrium Friedmann-Robertson-Walker (TEFRW) universe is first studied. The equation of state and the scale factor of the TEFRW universe take the forms ofw = w(a;zT) and a = a(a;zT,Ho). For the universe consisting of the nonrelativistic matter and the dark energy, the behavior of the dark energy depends on the value of the present-day matter fraction. For the TEFRW universe consisting of N ingredients, the effective temperature is introduced. Lastly, a simple TEFRW universe model is analyzed. 相似文献
5.
The universe content is considered as a non-perfect fluid with bulk viscosity and can be described by a general equation of state (endowed some deviation from the conventionally assumed cosmic perfect fluid model). An explicitly bulk viscosity dark energy model is proposed to confront consistently with the current observational data sets by statistical analysis and is shown consistent with (not deviated away much from) the concordant A Cold Dark Matter (CDM) model by comparing the decelerating parameter. Also we compare our relatively simple viscosity dark energy model with a more complicated one by contrast with the concordant ACDM model and find our model improves for the viscosity dark energy model building. Finally we discuss the perspectives of dark energy probes for the coming years with observations. 相似文献
6.
It has been shown [Chin. Phys. Lett.25 (2008) 4199] that the generalized second law of thermodynamics holds in Einstein gravity. Here we extend this procedure for Gauss-Bonnet and Lovelock gravities. It is shown that by employing the general expression for temperature Th =|κ|/2π= 1/2πτA (1-τA/2HτA) associated with the apparent horizon of a Friedman Robertson-Walker (FRW) universe and assuming Tm = bTh, we are able to construct conditions for which the generalized second law holds in Gauss Bonnet and Lovelock gravities, where Tm and Th are the temperatures of the source and the horizon respectively. 相似文献
7.
量子纠缠作为量子信息理论中最核心的部分,代表量子态一种内在的特性,是微观物质的一种根本的性质,它是以非定域的形式存在于多子量子系统中的一种神奇的物理现象.熵也是量子信息理论的重要概念之一,纠缠熵作为量子信息的一个测度已经成为一种重要的理论工具,为物理学中的各类课题提供了新的研究方法.本文主要考虑量子纠缠的宇宙学应用,试图更好地从纠缠的角度来理解宇宙动力学.本文研究了量子信息理论的概念和宇宙学之间的深层联系,利用费米正则坐标和共形费米坐标构建了弗里德曼- 勒梅特-罗伯逊-沃尔克宇宙学弗里德曼方程和纠缠之间的联系.假设小测地球(a geodesic ball)的纠缠熵在给定体积下是最大的,可以从量子纠缠第一定律推导出弗里德曼方程.研究表明引力与量子纠缠之间存在着某种深刻的联系,这种联系对引力场方程的解是成立的. 相似文献
8.
9.
In this paper, proceeding from the relation between the Cardassian model and the accelerated expansion of the universe, adopting a parametric method which does not depend on a precise mechanism for gravitational baryo/leptogenesis and using the model parameter of CPT-violating interaction, we study the role of the modified Friedmann equation which plays a role in the matter asymmetry of the early epoch and the accelerated expansion of the present universe. Thus the appropriate Cardassian component in the radiation-dominated era or in the matter-dominated universe can be obtained. The results indicate that early CPT-violation is included in the Cardassian term. In the same way, the present Cardassian term that belongs to a quintessence-like model can drive the universe towards a flat, matter-dominated and accelerating expansion. 相似文献
10.
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