超致密暗物质晕的相关研究

发布时间：2018-11-28 14:48

【摘要】：直到上个世纪Einstein创造广义相对论,我们才第一次真正有了可以用来描述宇宙演化的理论。为了研究的方便Einstein提出了宇宙学原理：物质的分布在足够大的尺度上是均匀各向同性的。同时为得到一个静止的宇宙解,Einstein引进宇宙学常数,然而这样的静态宇宙仍然是不稳定的。随后Hubble观测到邻近24个星系的整体红移,而且红移和距离成正比,这既是宇宙膨胀的直接证据,也暗示了宇宙的均匀各向同性。20年后伽莫夫提出宇宙起源于大爆炸,还计算了遗留的光子背景温度；接着贝尔实验室的工程师彭齐亚斯和威尔斯发现了理论学家正在寻找的宇宙微波背景辐射,从而证实了伽莫夫的预言。另外大爆炸宇宙学还很好的解释了宇宙中轻元素的丰度。20世纪70年代,星系旋转曲线、星系速度弥散和引力透镜等大量观测表明绝大部分物质是暗物质,没有显著的电磁相互作用。1998年Ia超新星的观测数据表明宇宙正在加速膨胀,如果广义相对论在宇宙尺度上是正确的,那么就有一种负压强的暗能量存在。由现代宇宙学的各种观测己经很精确的知道,通常的可见物质(主要是重子)只占据宇宙的4.9%,暗物质占据26.8%,剩下的68.3%是暗能量。本文主要研究一种最近新发现的暗物质结构：超致密暗物质晕(UCMHs)o第一章概述了宇宙学的知识。我们首先简要回顾了宇宙学的发展史,然后介绍了广义相对论的重要概念,最后得到宇宙学的演化方程。对于辐射,物质和暗能量,我们得到能量密度ρ和宇宙尺度因子a的关系,以及宇宙尺度因子随时间演化的方程。第二章系统地描述了暗物质的观测证据,对暗物质候选者进行分类并讨论了探测暗物质的方法。大质量弱相互作用粒子(WIMPs)是理想的冷暗物质的候选者,而研究最多的WIMPs是最轻的超对称粒子。我们给出它们在宇宙中的比例Ωx和参数的关系式,由现代观测我们得到暗物质参数如质量和截面的限制。热暗物质典型的例子是三代中微子,我们对中微子的质量进行了限制。另外我们也讨论了暗物质的非热产生机制,同时给出Ωx依赖于参数的表达式。特别地,我们讨论了最简单的非热产生例子-大质量弱相互作用标量场的凝聚。轴子最初是粒子物理为解决强CP问题而提出的,它是非热产生的一个好的候选者。探测暗物质的方法有测量原子核的核反冲的直接探测,也有测量暗物质粒子湮灭或衰变产生的标准模型粒子的间接探测,当然大型对撞机也试图寻找暗物质存在的迹象。第三章探讨了一种新的暗物质结构-超致密暗物质晕(UCMHs),它是Ricotti Gould在2009年提出的。当存在原初密度扰动δρ0.3的区域时,就有可能形成原初黑洞。但是当密度扰动小于这一临界值但大于10-3时,虽无法形成原初黑洞,却会演化成为超紧致暗物质晕。和一般的暗物质晕相比,UCMHs的密度更大,形成的时间更早。如果暗物质是由WIMP粒子构成的,那么UCMH通过WIMP湮灭或者衰变产生的粒子如γ射线有可能被Fermi卫星或者大气切连科夫探测器(ACTs)观测到,产生的中微子信号被IceCube/DeepCore或其它中微子探测器观测到。对于给定的模型我们计算了来自UCMH的WIMP湮灭产生的γ射线的通量,同时我们也给出了能被探测到的UCMH丰度的下限,以及没有被探测到的UCMH丰度的上限,并把UCMH丰度的限制转化为小尺度上原初曲率扰动的限制。如果暗物质粒子不湮灭的话,衰变将变得很重要。于是我们同时也计算了UCMH中WIMP衰变产生的γ射线信号,得出了相应的UCMH丰度和原初曲率扰动的限制。除了γ射线信号,我们也研究了来自UCMH的中微子信号。虽然没有探测到中微子,我们给出UCMH丰度的限制,并转化为对小尺度上原初曲率扰动的限制。第四章我们总结了本文的工作,并展望了未来的研究。
[Abstract]:Until the last century, Einstein created the general theory of relativity, the first time we really had a theory that could be used to describe the evolution of the universe. For the sake of the study, Einstein proposed the principle of cosmology: the distribution of matter is homogeneous and isotropic on a sufficiently large scale. At the same time, Einstein introduced the cosmological constant to get a static universe solution, but such a static universe is still unstable. The whole red shift of the adjacent 24 galaxies is then observed by Hubble, and the red shift is proportional to the distance, which is not only the direct evidence of the expansion of the universe, but also the uniform isotropy of the universe. Then the engineers of the Bell Labs, Penzias and Wells, have discovered the cosmic microwave background radiation that the theory scientists are looking for, confirming the predictions of the Galov. In addition, big bang cosmology has well explained the abundance of light elements in the universe. A large number of observations such as the galaxy rotation curve, the galaxy velocity dispersion, and the gravitational lens in the 1970s indicate that the vast majority of the materials are dark matter, There is no significant electromagnetic interaction. The observation data of the Ia supernova in 1998 indicate that the universe is accelerating the expansion, and if the general relativity is correct in the cosmic scale, there is a dark energy of negative pressure. The various observations of modern cosmology have been well known, and usually the visible substance (mainly the weight) occupies only 40.9% of the universe, the dark matter occupies 26. 8%, and the remaining 68.3% is dark energy. This paper mainly studies a newly discovered dark matter structure: the first chapter of the ultra-dense dark matter halo (UCMHs) o provides an overview of the knowledge of cosmology. We first briefly review the history of cosmology, then introduce the important concept of general relativity, and finally get the evolution equation of cosmology. For radiation, matter and dark energy, we get the relationship between the energy density factor and the cosmic scale factor a, and the equation of the time evolution of the cosmic scale factor. The second chapter systematically describes the observational evidence of dark matter, classifies the dark matter candidates and discusses the method of detecting dark matter. The large mass of weakly interacting particles (WIMPs) is a candidate for the ideal cold dark matter, and the maximum number of WIMPs is the lightest supersymmetric particle. We give the relation of their proportional omega x and the parameters in the universe, and we get dark matter parameters, such as quality and cross-section, from the modern observation. The typical example of a hot dark matter is the third generation of neutrinos, and we have limited the mass of the neutrino. In addition, we also discuss the non-heat generation mechanism of dark matter, and give the expression of 惟 x depending on the parameter. In particular, we have discussed the simplest non-heat generation examples-the coacervation of a large-mass, weak-interaction scalar field. The axis is originally proposed by the particle physics to solve the problem of strong CP, and it is a good candidate for non-heat generation. The method for detecting dark matter has the direct detection of the nuclear recoil of the nuclei, and the indirect detection of the standard model particles produced by the annihilation or decay of the dark matter particles, of course the large collider also tries to find the evidence of the presence of the dark matter. The third chapter discusses a new dark matter structure, ultra-dense dark matter halo (UCMHs), which is proposed by Ricotti Gould in 2009. It is possible to form the original black hole when the initial density disturbance is in the region of 0.3. However, when the density disturbance is less than this critical value but greater than 10-3, the original black hole can not be formed, but it will evolve into a supertight dark matter halo. Compared with the general dark matter halo, the density of the UCMHs is larger and the formed time is earlier. If the dark matter is composed of WIMP particles, the UCMH can be observed by the Fermi satellite or the atmospheric Cerenkov detector (ACTs) by the particles such as X-rays generated by the annihilation or decay of the WIMP, and the generated neutrino signal is observed by the IceCube/ DeepCore or other neutrino detector. for a given model we calculate the flux of the x-rays generated by the wIMP annihilation from the UCMH, while we also give the lower limit of the UCMH abundance that can be detected, and the upper limit of the UCMH abundance that has not been detected, and the limitation of the UCMH abundance is converted into the limit of the initial curvature disturbance on the small scale. Decay will become important if the dark matter particles are not annihilated. So we also calculated the X-ray signal produced by the decay of WIMP in UCMH, and the limitation of UCMH abundance and initial curvature disturbance was obtained. In addition to the X-ray signal, we have also studied the neutrino signal from UCMH. Although the neutrino is not detected, we present the limitation of the UCMH abundance and transform into the limit of the initial curvature disturbance on the small scale. In the fourth chapter, we sum up the work of this paper and look forward to the future research.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P145.9

【共引文献】