CSTB反弹宇宙（Coupled Scalar Tachyon Bounce Cosmos）模型的构造、系统分析以及实验

发布时间：2018-04-27 07:46

本文选题：早期宇宙学 + 暴胀宇宙模型　；参考：《南京大学》2014年博士论文

【摘要】：宇宙的起源和早期演化是人类文明肇始以来不断探寻的重要课题,也是人类文明发展的一个原始和持久的推动力。近年来,大量天文观测数据和高能粒子数据及相关的涌现使得当今成为宇宙学研究的黄金时代。在标准宇宙学模型中,人们引入了宇宙加速膨胀--暴胀(Inflation)--的新概念来解决宇宙大爆炸理论存在的“视界问题(Horizon Problem)"和“平坦性问题(Flatness Problem)".通过量子涨落机制产生了与天文观测相符的标度不变原初扰动功率谱,奠定了暴胀的物理基础。然而,暴胀模型仍然未解决宇宙大爆炸的原初奇点问题(Initial Singularity Problem)以及参数精细调节问题(Fine-tuning Problem).因此,人们仍在迫切地寻找可以改进或替代暴胀宇宙学标准模型的新模型。在这篇博士论文中,为了解决暴胀宇宙学标准模型存在的问题和困难,我们提出了全新的基于超弦唯象理论而建立的标量场与快子场耦合的反弹宇宙模型(Coupled Scalar Tachyon Bounce Cosmos),简称CSTB反弹宇宙模型。在CSTB反弹宇宙模型中,由于运用了标量场和快子场的耦合项以及闭合Friedmann-Lemaitre-Robertson-Walker(FLRW)时空的正曲率项,宇宙可以实现光滑的反弹,从而避免了宇宙大爆炸初始奇点问题。同时,CSTB反弹宇宙模型的背景演化是与初始条件无关的动力学吸引子解,因此也避免了参数精细调节问题。相比于其它的反弹宇宙模型,例如Quintom反弹宇宙模型和鬼场凝聚(Ghost Condensation)反弹宇宙模型,CSTB反弹宇宙模型在整个反弹过程中,满足了类光、弱和主导能量条件(Null, Weak, and Dominant Energy Conditions),宇宙在其整个演化过程中不会产生任何非物理的场(Ghost Field). 我们进一步具体地研究了CSTB反弹宇宙模型的原初扰动功率谱并和宇宙观测数据进行比较。通过精确计算CSTB反弹宇宙模型的原初扰动功率谱的谱指数,我们发现这个模型可以产生稳定的和标度不变的原始曲率扰动功率谱,这一结果和宇宙微波背景辐射(Cosmic Microwave Background Radiation (CMBR))目前的观测结果相符。通过对各类暴胀宇宙模型和反弹/循环宇宙模型,特别是CSTB反弹宇宙模型和慢滚暴胀宇宙模型进行更系统的分析,我们提出了一个统一的参数空间(V,m)。这个参数空间包括两个维度：一个是推广的宇宙扰动方程红移-蓝移项的系数m,而V则是宇宙背景演化尺度因子的幂指数因子。在这个统一的参数空间中,我们可以系统地分析各类暴胀宇宙模型、反弹或循环宇宙模型所产生的原初扰动功率谱的性质。我们发现有两组稳定的和标度不变的功率谱解存在：其中一组是在暴胀宇宙模型的加速膨胀过程中产生的,而另外一组则是在反弹/循环宇宙模型的加速收缩过程中产生的。这两组稳定的标度不变的功率谱解存在着一类完整的对偶性使它们一一对应起来。有趣的是CSTB反弹宇宙模型正好通过这个完整的对偶变换被对应到经典的慢滚暴胀宇宙模型--即在标量场驱动的指数膨胀的时空中产生的扰动功率谱与在耦合快子场凝聚物质驱动的物质收缩时空中产生扰动功率谱近似简并。由于不存在参数精细调节问题,因此,相对于慢滚暴胀宇宙模型,CSTB反弹宇宙模型功率谱的标度不变性更加稳定。在本论文的最后部分,我们提出了对反弹,循环宇宙模型框架的直接实验检验的方法：通过测量暗物质粒子质量与散射截面关系,科学家可以判断出宇宙的早期演化是否经历过反弹的过程。通过具体计算暗物质在反弹前的塌缩期和反弹后的膨胀期中的产生过程,我们发现在反弹/循环宇宙模型框架下,存在一类全新的暗物质产生和“冻结(freeze-out)"机制。在这个机制当中,由于极小的散射截面和较大的质量,暗物质在塌缩相和膨胀相中并没有被充分地产生,令其实际丰度远低于热平衡态容许的丰度。随后,暗物质经历了一个微弱的冻结过程,使得“暗物质残留丰度(Cosmic Relic Abundance)"中包含的宇宙早期演化的信息得以保留到今天。我们详细计算了暗物质在这个新机制下整个的产生和冻结过程,并预言了这个新机制下的暗物质散射截面与质量的关系：散射截面与质量的二次方成反比,且暗物质粒子质量大于432电子伏特。如果暗物质探测实验(如中国的锦屏山深地实验室)在将来探测出暗物质粒子的质量与散射截面的关系,那么这个新的暗物质产生-冻结机制以及相应的暗物质散射截面与质量的关系将成为宇宙早期演化是否经历反弹过程的一个重要的直接判据.
[Abstract]:The origin and early evolution of the universe is an important subject since the beginning of human civilization, and it is also a primitive and lasting impetus for the development of human civilization. In recent years, a large number of astronomical observations and high energy particle data and the emergence of related phenomena have become the golden age of research in cosmology.
In the standard cosmological model, the new concept of cosmic accelerated expansion (Inflation) has been introduced to solve the "Horizon Problem" and "Flatness Problem" in the theory of the big bang theory. The scale invariant initial disturbance power spectrum, which is consistent with the astronomical observation, is produced by the quantum fluctuations mechanism. The physical basis of the expansion is laid. However, the expansion model still does not solve the original singularity problem of the big bang (Initial Singularity Problem) and the fine parameter adjustment problem (Fine-tuning Problem). Therefore, people are still looking for a new model that can improve or replace the standard model of the expansion of cosmology.
In this doctoral thesis, in order to solve the problems and difficulties of the standard model of expansion cosmology, we propose a new Coupled Scalar Tachyon Bounce Cosmos, called the CSTB rebound universe model, which is based on the superstring phenomenological theory, for short, the CSTB rebound universe model, in the CSTB rebound universe model. By using the coupling term of the scalar field and the fast subfield and the positive curvature term of the closed Friedmann-Lemaitre-Robertson-Walker (FLRW) space, the universe can achieve a smooth rebound, thus avoiding the initial singularity problem of the big explosion of the universe. At the same time, the background of the CSTB rebound universe model is a dynamic attractor independent of the initial conditions. It also avoids the problem of fine tuning. Compared to other rebound cosmological models, such as the Quintom rebound universe model and the Ghost Condensation rebound universe model, the CSTB rebound universe model satisfies the light like, weak and dominant energy conditions (Null, Weak, and Dominant Energy Conditions) in the whole rebound process. The universe does not produce any Ghost Field in its entire evolution.
We further study the original perturbation power spectrum of the CSTB rebound universe model and compare with the cosmic observation data. By accurately calculating the spectral exponents of the original perturbation power spectrum of the CSTB rebound universe model, we find that the model can produce stable and scale-invariant original curvature disturbance power spectrum, which is the result and the result of this model. The observed results of cosmic microwave background radiation (Cosmic Microwave Background Radiation (CMBR)) coincide.
Through a more systematic analysis of the various expansion of the universe model and the rebound / circular universe model, especially the CSTB rebound universe model and the slow rolling universe model, we have proposed a unified parameter space (V, m). This parameter space includes two dimensions: one is the coefficient m of the red shift blue term of the universal perturbation equation, and V In this unified parameter space, we can systematically analyze the properties of the original perturbation power spectrum of all kinds of expansion of the universe model, bounce or circular universe model. We find that there are two groups of stable and scale invariant power spectral solutions, one of which is in the same group. In the accelerated expansion of the expansion of the universe model, the other is produced during the accelerated contraction of the rebound / circular universe model. These two sets of stable scale invariant power spectral solutions have a complete duality that makes them correspond to one one. Interestingly, the CSTB rebound universe model just passes this integrity. The dual transformation is corresponded to the classical slow rolling bulge universe model, that is, the disturbance power spectrum produced in the exponential expansion of the scalar field is approximately degenerate with the generation disturbance power spectrum in the time and space of the matter driven material contraction in the coupling fast subfield condensed matter. The scale invariance of the power spectrum of the CSTB rebound universe model is more stable.
In the final part of this paper, we propose a direct experimental test of a rebound, circular universe model framework: by measuring the relationship between the mass of the dark matter particles and the scattering cross section, scientists can determine whether the early evolution of the universe has experienced a rebound. In the expansion period after the projectile, we found a new kind of dark matter production and "freeze-out" mechanism under the framework of the rebound / circular universe model. In this mechanism, the dark matter is not fully produced in the collapse phase and the expansion phase due to the small scattering cross section and the larger mass, which makes it practical. The abundance is much lower than the allowable abundance of the heat equilibrium state. Subsequently, the dark matter has experienced a weak freezing process, making the information of the early evolution of the universe contained in the "Cosmic Relic Abundance" "the information of the early evolution of the universe preserved to the present. The relationship between the cross section of the dark matter scattering and the mass of the new mechanism is predicted: the scattering cross section is inversely proportional to the two mass of the mass, and the mass of the dark matter particles is greater than 432 electron volt. If the dark matter detection experiment (such as the Jinping deep Laboratory in China) detects the relationship between the mass of the dark matter particles and the scattering cross section in the future, This new dark matter production - freezing mechanism and the corresponding relation between the cross section of dark matter and the mass of the dark matter will be an important direct criterion for whether the early evolution of the universe has experienced a rebound process.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P159

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