极早期宇宙相关问题的研究
发布时间：2018-10-05 16:12
【摘要】： 宇宙学标准模型在物理学的发展中扮演着重要的角色,因为它预言了一系列关于宇宙演化的理论结果,而这些结果被随后的观测所证实。然而,标准模型中也存在着许多问题在理论上无法给出合理的解释。通过引入暴胀假说,某些问题如视界疑难、平直性疑难以及磁单极子疑难等得到或部分得到解决。与此不同的是,另一些问题如大爆炸奇点问题,暗能量问题以及宇宙大尺度结构的起源和形成等问题一般认为纯粹在经典引力论的框架内是无法给出圆满解决的方案的。 本文首先简单地回顾了标准宇宙理论和暴胀模型的基本内容,然后主要介绍了大爆炸奇点和几类半经典量子宇宙学中给出的解决方案。 其次,我们通过引入一个特殊的修正色散关系研究了它对宇宙的背景动力学的影响。通过引力理论与视界上的热力学的一种对应,我们推导出了一个含有反弹解的修正的弗里德曼方程。然后探讨了产生反弹所需的条件和可能性,我们发现在高能区域,当粒子能量趋近于普朗克能标时,大反弹的确能够产生。因此,在我们的模型里大爆炸奇点问题不复存在。 在第三部分,我们首先回顾了宇宙早期热扰动假说的一些基本内容,比如热功率谱的计算以及非高斯性的相关简介。此后我们也简单地回顾了三类比较流行的半经典模型中热扰动的研究情况,这些模型的引入使得标准宇宙学中无法得到谱的标度不变性的困难得以克服。最后,我们研究了热扰动在粘滞宇宙中的情况。我们发现,由于粘滞性的存在,各种热扰动模在穿越视界以后的演化行为将与理想流体时的情况很不一样。这样,标准模型中的困难被打破,当粘滞流体的状态参量满足w≈α-1或是w≈-1/3的时候,我们得到的功率谱是标度不变的。同时,我也讨论了扰动的非高斯性。我们发现,对于德西特膨胀,即状态参数满足w≈α-1时,非高斯性被压低；而对于phantom like w≈-1/3的情况,如果我们选取粘滞系数α≈4/3,则非高斯性具有标度不变性且是可以被观测到的。
[Abstract]:The standard cosmological model plays an important role in the development of physics because it predicts a series of theoretical results on the evolution of the universe, which are confirmed by subsequent observations. However, there are many problems in the standard model which can not be explained in theory. By introducing the inflation hypothesis, some problems such as horizon problem, flatness problem and magnetic monopole problem are solved or partially solved. In contrast, other problems, such as the singularity of the Big Bang problem, the dark energy problem and the origin and formation of the large-scale structure of the universe, are generally considered to be impossible to give a satisfactory solution purely within the framework of classical gravitation theory. In this paper, the basic contents of the standard cosmic theory and the inflation model are briefly reviewed, and then the solutions of the Big Bang singularity and several kinds of semi-classical quantum cosmology are introduced. Secondly, we study its influence on the background dynamics of the universe by introducing a special modified dispersion relation. By means of a correspondence between the theory of gravity and thermodynamics on the horizon, we derive a modified Friedman equation with a bouncing solution. Then we discuss the conditions and the possibility of producing the rebound. We find that in the high energy region, when the particle energy approaches the Planck energy scale, the large rebound can indeed occur. Therefore, the big bang singularity problem no longer exists in our model. In the third part, we first review some basic contents of the early cosmic thermal disturbance hypothesis, such as the calculation of thermal power spectrum and the introduction of non-Gao Si. After that, we also briefly review the study of thermal perturbation in three popular semi-classical models. The introduction of these models makes it possible to overcome the difficulty of scale invariance of spectrum in standard cosmology. Finally, we study the thermal perturbation in the viscous universe. It is found that due to the existence of viscosity, the evolution behavior of various thermal disturbance modes after crossing the horizon will be very different from that of the ideal fluid. In this way, the difficulty in the standard model is broken. When the state parameters of the viscous fluid satisfy w 鈮，
本文编号：2254030
[Abstract]:The standard cosmological model plays an important role in the development of physics because it predicts a series of theoretical results on the evolution of the universe, which are confirmed by subsequent observations. However, there are many problems in the standard model which can not be explained in theory. By introducing the inflation hypothesis, some problems such as horizon problem, flatness problem and magnetic monopole problem are solved or partially solved. In contrast, other problems, such as the singularity of the Big Bang problem, the dark energy problem and the origin and formation of the large-scale structure of the universe, are generally considered to be impossible to give a satisfactory solution purely within the framework of classical gravitation theory. In this paper, the basic contents of the standard cosmic theory and the inflation model are briefly reviewed, and then the solutions of the Big Bang singularity and several kinds of semi-classical quantum cosmology are introduced. Secondly, we study its influence on the background dynamics of the universe by introducing a special modified dispersion relation. By means of a correspondence between the theory of gravity and thermodynamics on the horizon, we derive a modified Friedman equation with a bouncing solution. Then we discuss the conditions and the possibility of producing the rebound. We find that in the high energy region, when the particle energy approaches the Planck energy scale, the large rebound can indeed occur. Therefore, the big bang singularity problem no longer exists in our model. In the third part, we first review some basic contents of the early cosmic thermal disturbance hypothesis, such as the calculation of thermal power spectrum and the introduction of non-Gao Si. After that, we also briefly review the study of thermal perturbation in three popular semi-classical models. The introduction of these models makes it possible to overcome the difficulty of scale invariance of spectrum in standard cosmology. Finally, we study the thermal perturbation in the viscous universe. It is found that due to the existence of viscosity, the evolution behavior of various thermal disturbance modes after crossing the horizon will be very different from that of the ideal fluid. In this way, the difficulty in the standard model is broken. When the state parameters of the viscous fluid satisfy w 鈮，
本文编号：2254030
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