早期宇宙与暗能量若干问题的研究
发布时间：2018-10-26 08:16
【摘要】：本论文对宇宙原初扰动和晚期暗能量的若干问题进行了研究。 我们首先研究了宇宙原初扰动的非高斯性。我们简单介绍了宇宙学扰动理论,然后我们引入了推广的多场暴胀模型。我们计算计算了该模型下原初扰动的四点关联函数。我们发现该模型下四点关联函数的贡献主要来源于两个方面,一个是单顶点图,另一个是中间交换一个标量子的双顶点图。我们发现在一般推广的暴胀模型下,这两个图的贡献都是重要的。我们还分析了该模型下非高斯型的动量位型函数和非线性参数。在研究完四点关联函数之后,我们又介绍了几类暴胀模型五点函数和六点函数的计算,并从中计算出观测上的预言。 我们研究了一类替代暴胀模型,即物质反弹宇宙模型。我们利用“鬼凝聚”标量场来实现物质主导的收缩宇宙到大爆炸膨胀宇宙的反弹。我们计算了含有“鬼凝聚”标量场的物质收缩宇宙的原初扰动谱,发现普通物质产生的扰动谱仍是一个标度不变谱,而“鬼凝聚”标量场产生蓝谱,并且扰动的增长速度要比物质的扰动增长速度要慢。 我们对晚期暗能量进行了唯象上的研究。我们计算了全息暗能量的扰动的稳定性,研究了几种不同的全息暗能量模型下宇宙的命运。我们研究了全息气体模型,该模型下气体的熵正比于该系统的表面积。当我们把这类气体模型运用到宇宙学上,我们发现它可以驱动宇宙加速膨胀,因此,我们的全息气体模型可以作为暗能量的一个候选者之一。
[Abstract]:In this paper, we study some problems of the primary disturbance and late dark energy in the universe. We first study the non-Gao Si nature of the primitive disturbance of the universe. We briefly introduce the cosmological perturbation theory, and then we introduce a generalized multifield inflation model. We calculate the four point correlation function of the primitive disturbance under this model. We find that the contribution of the four-point correlation function under this model mainly comes from two aspects: one is a single-vertex graph and the other is a bivertex graph with a scalar quantum. We find that the contribution of these two graphs is important in the generalized inflation model. We also analyze the momentum potential functions and nonlinear parameters of non Gao Si type in this model. After studying the four-point correlation function, we also introduce the calculation of five-point function and six-point function of several kinds of inflating models, and calculate the observational predictions from them. We study a class of alternative inflation models, namely, the cosmic model of material rebound. We use the "ghost condensation" scalar field to achieve a rebound from the material-dominated shrinking universe to the Big Bang expansion universe. We calculate the original perturbation spectrum of the shrinking universe of matter containing the "ghost condensation" scalar field. It is found that the perturbation spectrum produced by ordinary matter is still a scalar invariant spectrum, while the "ghost condensate" scalar field produces the blue spectrum. And the growth rate of disturbance is slower than that of matter. We have carried out phenomenological studies of late dark energy. We calculate the stability of the perturbation of holographic dark energy and study the fate of the universe under several holographic dark energy models. We study a holographic gas model in which the entropy of the gas is proportional to the surface area of the system. When we apply this kind of gas model to cosmology, we find that it can drive the acceleration of expansion of the universe. Therefore, our holographic gas model can be used as a candidate for dark energy.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：P159
[Abstract]:In this paper, we study some problems of the primary disturbance and late dark energy in the universe. We first study the non-Gao Si nature of the primitive disturbance of the universe. We briefly introduce the cosmological perturbation theory, and then we introduce a generalized multifield inflation model. We calculate the four point correlation function of the primitive disturbance under this model. We find that the contribution of the four-point correlation function under this model mainly comes from two aspects: one is a single-vertex graph and the other is a bivertex graph with a scalar quantum. We find that the contribution of these two graphs is important in the generalized inflation model. We also analyze the momentum potential functions and nonlinear parameters of non Gao Si type in this model. After studying the four-point correlation function, we also introduce the calculation of five-point function and six-point function of several kinds of inflating models, and calculate the observational predictions from them. We study a class of alternative inflation models, namely, the cosmic model of material rebound. We use the "ghost condensation" scalar field to achieve a rebound from the material-dominated shrinking universe to the Big Bang expansion universe. We calculate the original perturbation spectrum of the shrinking universe of matter containing the "ghost condensation" scalar field. It is found that the perturbation spectrum produced by ordinary matter is still a scalar invariant spectrum, while the "ghost condensate" scalar field produces the blue spectrum. And the growth rate of disturbance is slower than that of matter. We have carried out phenomenological studies of late dark energy. We calculate the stability of the perturbation of holographic dark energy and study the fate of the universe under several holographic dark energy models. We study a holographic gas model in which the entropy of the gas is proportional to the surface area of the system. When we apply this kind of gas model to cosmology, we find that it can drive the acceleration of expansion of the universe. Therefore, our holographic gas model can be used as a candidate for dark energy.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：P159
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