暗物質乃構成宇宙的主要部分。而暗物質，即自身為不可見之物，無論自我湮滅與否，皆可能於各方面影響天體的特性。 / 在本論文中，我們首先研究一個混入非自我湮滅費米子暗物質的核心，並藉二流體方法，探討它如何影響中子星的靜態平衡結構。我們發現若達到足夠大的暗物質質量比重時，便可產生一種新型的致密星一顆由暗物質支配、半徑有數公里的中子星。然後，我們研究該核心導致中子星的線性變化，並應用此星體模型解釋已觀測的特細中子星，也考察此暗物質對中子星的冷卻過程的影響，和不同粒子質量的暗物質的效果。最後，我們討論該核心的徑向震動，從中發現新一種震動模式。 / 接下來，我們集中討論混入暗物質的核心如何干涉主序星的星體演化。一般而言，此核心皆縮短主序星的壽命，並改變演化間唯量，譬如氫融合及氦融合的最低所需質量。但就一個擁有可觀質量的暗物質核心而言，我們發現幾種唯象的改變包括主序星壽命的延長，高質量恆星的橫向分支的消失，以及星體演化的新路徑。由此我們得出，把暗物質放入考慮之列，能令星體演化的討論變得更有系統，也是不可或缺的。再者，我們論證前述的星體，即由暗物質支配的中子星，亦可能從類近的演化中產生。 / 最後，我們轉向研究，在牛頓水動力學中的球體對稱情況下，一個點質量的暗物質核心如何改變白矮星徑向運動的特性。於可行的模擬運算下，此核心的額外引力只局部改變星體的特性，如初始靜態平衡下的密度分佈的外型，而星體的徑向震動模式及震動頻率則不受影響。 / Dark matter constitutes a large proportion of matter in the universe and it is believed that dark matter, self-annihilating or not, can bring observational change to astrophysical objects in different aspects, even though it cannot be observed directly. / In chapter 2, we first study the effect of an admixed dark matter core, consisted of non-self-annihilating fermionic dark matter particles, to the equi-librium structure of a neutron star using the two-fluid formalism. We find that a new subclass of compact star, dark matter dominated neutron star, is formed for a sufficiently large mass fraction of dark matter, which has only a few-kilometer-sized visible radius. Also, we study the linear response of a neutron star towards a dark matter core; we apply the model to explain several observed neutron stars with extraordinary small radii and we study how the dark matter core affects the cooling properties of neutron stars. We examine the effects caused by the choice of dark matter particle mass. Then, we study the radial oscillation modes of a dark matter admixed neutron star, in which a new class of modes is present due to the admixture of dark matter. At last, we extend our study from neutron stars to strange stars, in which we discover that the response of a strange star to the presence of an admixed dark matter core is qualitatively different from a neutron star. / In chapter 3 we focus on the effect of the dark matter core to the stellar evolution of main-sequence stars. We find that in general the existence of a dark matter core reduces the stellar lifetime and quantitative change in the stellar evolution, such as the decrement of the threshold mass for hydro¬gen and helium fusion. But for sufficiently massive dark matter core, several qualitative changes are observed: they include an extension in main-sequence lifetime, absence of horizontal branch for high-mass stars and some new paths in the stellar evolution. From the study we find that the consideration of dark matter is indispensable in a systematic discussion of stellar evolution. Also we argue that dark matter dominated neutron star can be formed following similar stellar evolution processes. / In chapter 4 we turn to the impact of a point-mass dark matter core on the radial oscillation of a white dwarf by doing Newtonian hydrodynamical simulations in spherically symmetric scenarios. We find that, within feasible simulations, the effects of an extra gravity from the dark matter core is highly local. It creates a change in the initial static equilibrium density profile, but its radial oscillation patterns and oscillation frequencies remain unchanged. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Leung, Shing Chi = 非自我湮滅暗物質對致密星及主序星的影響 / 梁成志. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 119-131). / Abstracts also in Chinese. / Leung, Shing Chi = Fei zi wo yan mie an wu zhi dui zhi mi xing ji zhu xu xing de ying xiang / Liang Chengzhi. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Dark Matter: The mysterious piece in the Universe --- p.1 / Chapter 1.1.1 --- The puzzle of missing mass --- p.1 / Chapter 1.1.2 --- Dark Matter in Particle Physics --- p.2 / Chapter 1.1.3 --- Alternatives to Dark Matter --- p.4 / Chapter 1.2 --- Probing the Nature of Dark Matter --- p.5 / Chapter 1.3 --- Neutron Star Astrophysics --- p.8 / Chapter 1.3.1 --- Equilibrium Structure and Radial Oscillation Modes --- p.8 / Chapter 1.3.2 --- Non-radial Oscillation Modes --- p.9 / Chapter 1.3.3 --- Use of NS as a DM probe --- p.10 / Chapter 1.3.4 --- Rotating Neutron Stars --- p.11 / Chapter 1.4 --- Hydrodynamical Simulation --- p.12 / Chapter 1.4.1 --- Algorithm --- p.12 / Chapter 1.4.2 --- Applications in Astrophysics --- p.14 / Chapter 1.5 --- Structure of the thesis --- p.15 / Chapter 2 --- Astrophysical Properties of DANS --- p.17 / Chapter 2.1 --- Formalism --- p.17 / Chapter 2.1.1 --- Static Equilibrium Structure of DANS --- p.17 / Chapter 2.1.2 --- Choice of EOS --- p.19 / Chapter 2.1.3 --- Moment of inertia --- p.20 / Chapter 2.1.4 --- Equations for radial oscillations --- p.21 / Chapter 2.1.5 --- Equations for NS cooling --- p.23 / Chapter 2.1.6 --- EOS for strange quark matter --- p.32 / Chapter 2.2 --- Static Equilibrium Properties of DANS --- p.35 / Chapter 2.2.1 --- General Properties of DANS --- p.35 / Chapter 2.2.2 --- Linear Response of DANS --- p.39 / Chapter 2.2.3 --- Effects of DM particle mass --- p.41 / Chapter 2.3 --- Radial Oscillations of DANS --- p.44 / Chapter 2.3.1 --- One-fluid limit --- p.44 / Chapter 2.3.2 --- Oscillation modes of DANS --- p.45 / Chapter 2.3.3 --- Effects of DM particle mass --- p.51 / Chapter 2.4 --- Neutron Star Cooling --- p.52 / Chapter 2.4.1 --- Introduction --- p.52 / Chapter 2.4.2 --- Numerical Result in Neutrino Emission --- p.53 / Chapter 2.4.3 --- Time-dependent calculation --- p.54 / Chapter 2.4.4 --- Discussion --- p.58 / Chapter 2.5 --- Strange Star --- p.59 / Chapter 2.5.1 --- Introduction --- p.59 / Chapter 2.5.2 --- Strange Star Properties --- p.60 / Chapter 2.5.3 --- Discussion --- p.63 / Chapter 2.6 --- Chapter Summary --- p.65 / Chapter 3 --- Effects of Non-self-annihilating Dark Matter on Stellar Evolution --- p.66 / Chapter 3.1 --- Formulation --- p.66 / Chapter 3.1.1 --- Effect of Dark Matter --- p.66 / Chapter 3.1.2 --- Convergence test --- p.67 / Chapter 3.2 --- Results --- p.72 / Chapter 3.2.1 --- High mass stars --- p.74 / Chapter 3.2.2 --- Intermediate mass stars --- p.76 / Chapter 3.2.3 --- Low mass stars --- p.79 / Chapter 3.2.4 --- Brown Dwarfs --- p.82 / Chapter 3.3 --- Discussion --- p.85 / Chapter 3.3.1 --- Absence of Horizontal Branch --- p.85 / Chapter 3.3.2 --- Extended Main-sequence Lifetime --- p.87 / Chapter 3.3.3 --- Lower Mass Thresholds for Hydrogen Fusion and Helium Fusion --- p.88 / Chapter 3.3.4 --- New Stellar Evolution Path --- p.90 / Chapter 3.4 --- Chapter Summary --- p.91 / Chapter 4 --- Dynamical Simulation of Hybrid White Dwarf --- p.93 / Chapter 4.1 --- Formalism --- p.93 / Chapter 4.2 --- Convergence Test --- p.94 / Chapter 4.3 --- Numerical Results --- p.96 / Chapter 4.4 --- Chapter summary --- p.98 / Chapter 5 --- Conclusion --- p.101 / Chapter A --- DANS as an Alternative to Strange Stars --- p.105 / Chapter B --- Verification of separated TOV equations --- p.107 / Chapter C --- Code for numerical evolution --- p.109 / Chapter D --- Notation Convention and Units --- p.111 / Chapter E --- Discussion on the smearing of DM core --- p.113 / Chapter F --- Unit conversion --- p.118 / Bibliography --- p.119
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328574 |
| Date | January 2012 |
| Contributors | Leung, Shing Chi., Chinese University of Hong Kong Graduate School. Division of Physics. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (iv, iii, 131 leaves) : ill. |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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