KMS of Xinjiang Astronomical Observatory, CAS
| 暗能量性质的统计检验和模型研究 | |
| Alternative Title | Studies on statistical test and model of dark energy property |
黄龙
| |
| Subtype | 博士 |
| Thesis Advisor | 刘祥 |
| 2021-12-01 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Name | 理学博士 |
| Degree Discipline | 天体物理 |
| Keyword | 暗能量,模型,状态方程,Ia 型超新星,Planck CMB |
| Abstract | 从 1998 年 Riess 等人使用 Ia 型超新星 (SN Ia) 数据得到的统计结果表明了宇宙正处在加速膨胀状态以来，为了解释宇宙的加速膨胀，物理学家们预测了暗能量的存在。暗能量除了解释宇宙的加速膨胀以外，另一项支持暗能量存在的证据即宇宙微波背景辐射各向异性（CMB Anisotropies）。 暗能量的研究方法主要有两种，一种是约束暗能量物理模型的方法来探讨暗能量密度和压强可能的来源；另一种是不依赖于物理模型直接重构暗能量状态方程来检验暗能量的性质即暗能量密度是否随时间演化。暗能量状态方程的重构包括参数化和非参数化的方法，考虑到参数化的方法并没有找到明显优于LCDM 的模型，我们考虑用非参数化的方法来重构暗能量状态方程。我们提出了一种改进的非参数化方法重构暗能量状态方程，首先考虑使用拉格朗日插值数值积分线性化光度距离红移关系，同时结合基于高斯过程和岭回归分析的主成分分析（PCA）方法重构暗能量状态方程。同时使用不同的暗能量状态参数函数结合光度距离红移关系积分公式抽样获得模拟的光度距离数据，使用模拟的光度距离数据结合该方法检验重构暗能量状态方程，检验该方法的有效性，最后使用 SNIa JLA 样本重构暗能量状态方程。另一方面，我们也考虑从暗能量物理模型的角度来尝试解释暗能量密度和 压强可能的来源。我们探讨了暗能量来自真空标量玻色子的可能性。随着宇宙的膨胀，设想无质量标量玻色子进入宇宙视界内，标量玻色子满足 P 对称，根据时空量子波动和 P 对称，我们可以推导标量玻色子相对位置的不确定性，以及进一步估算标量玻色子和暗能量的密度。最后，我们使用 SNla Pantheon 样本和2018 年 Planck 温度角功率谱数据约束暗能量模型，给出宇宙学参数的统计结果。统计结果显示当我们仅使用 SNla Pantheon 数据时，通过比较最小卡方，我们发现随宇宙年龄演化的暗能量模型相对于 Λ𝐷𝐸𝑁 模型没有明显的优势。但当仅使用 2018 年 Planck CMB 数据时，随宇宙年龄演化的暗能量模型相对于 Λ𝐷𝐸𝑁模型有明显的优势。同时我们给出了哈勃常数的统计平均值，该结果和直接通过对 NGC 4258 测距给出的哈勃常数值一致。考虑到 SNIa 是晚期宇宙学数据(0 < z < 2.26)，而 CMB 是早期宇宙学数据 (z_s = 1089)，我们期望未来能使用中I暗能量性质的统计检验和模型研究性氢 21cm 谱线 (0 < z< 200) 来更进一步约束暗能量模型以及限制宇宙学参数。 |
| Other Abstract | Since cosmic acceleration was first discovered in 1998 , physicists have predicted the existence of dark energy to explain the accelerating expansion of the universe. Meanwhile, the dark energy theory can be used to effectively explain the cosmic microwavebackground (CMB) anisotropies . Dark energy can be studied using two main approaches. The first is to focus on the properties of dark energy, investigating whether or not its density evolves with time; this can be verified by reconstructing the equation of state w(z) of dark energy that is independent of physical models. The reconstruction of the equation of state involves parametric and non-parametric methods, the cosmology models are obviously superior to Λ𝐷𝐸𝑁 model have still not been found by the parametric methods, so we consider using nonparametric methods to reconstruct the dark energy equation of state. We have presented an improved nonparametric reconstruction technique. Firstly, we linearize the luminosity-distance integral formula in near-flat space by adopting Lagrange interpolation for the numerical integral, and then proposing a principal component analysis (PCA) which is based on the Gaussian Process and the ridge regression analysis to reconstruct the equation of state. Meanwhile, we construct hypothetical luminosity-distance data sampled from various w(z) models together with the luminosity-distance integral formula, and use simulated data to reconstruct w(z) , which can be uesd to test the validity of this method. Finally, we use SNla JLA sample to reconstruct w(z). On the other hand, we present a physical model for dark energy and attempt to explain the origin of dark energy density and pressure. We explore the theoretical possibility that the darkenergy density is derivedfromthe massless scalar bosons in vacuum. By assuming massless scalar bosons fall into the horizon boundary of the cosmos with the expansion of the universe, we can deduce the uncertainty in the relative position of scalar bosons based on the quantum fluctuation of space-time and the assumption that scalar bosons satisfy P-symmetry under parity transformation 𝑃Φ(r) = −Φ(r), which can be used to estimate the scalar bosons and dark energy density. Finally, we employ SNIa Pantheon sample and Planck 2018 CMB angular power spectra to constrain the models, and give the statistical results for the cosmology parameters. The statistical results indicate the models that dark energy evolves with age have no evident superiority, compared to LCDM using minimum chi-square when only using SNla Pantheon sample. But when using Planck 2018 CMB data, this models are better than to LCDM. Meanwhile we provide the statistical mean values of Hubble constant H_0 =73.2 ± 1.3km t −1 Mpc −1 , which is consistent with the result obtained using NGC 4258 distance measurement. We consider that SNla are the late universe data (0 < z < 2.26) and CMB are the early universe data (z_s = 1089) , so we hope that 21cm line of atomic hydrogen data (0 < z < 200) can be used to further constrain dark energy models and the cosmology parameters in the future. |
| Pages | 90 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xao.ac.cn/handle/45760611-7/5155 |
| Collection | 研究生学位论文 |
| Affiliation | 中国科学院新疆天文台 |
| First Author Affilication | Xinjiang Astronomical Observatory, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | 黄龙. 暗能量性质的统计检验和模型研究[D]. 北京. 中国科学院大学,2021. |
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| 暗能量性质的统计检验和模型研究_黄龙.p（4084KB） | 学位论文 | 暂不开放 | CC BY-NC-SA | Application Full Text | ||
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