暗能量问题的数值研究
发布时间：2018-10-09 20:54
【摘要】：自1998年超新星观测发现宇宙加速膨胀,暗能量问题已经成为物理学界最受关注的研究课题之一。暗能量的起源、性质都是谜。它向物理学家们提出了严峻的挑战,即所谓的“宇宙学常数问题”：为什么暗能量的能量密度这么小?为什么当前暗能量的密度与物质在同一个数量级上?为此,理论学家们作了非常多的努力,从各种不同的角度提出了很多暗能量理论模型,但是仍然没能解决暗能量问题。 在没有强有力的理论指导的情况下,我们需要转向实验,希望宇宙学观测能够提供更多解决暗能量问题的线索。幸运的是,目前宇宙学家们已经发展了超新星,重子声学震荡,宇宙微波背景辐射,弱引力透镜等多种暗能量观测手段。这些观测进一步确认了宇宙加速膨胀,并极大地提高了暗能量的观测精度。展望未来,宇宙学家们也在雄心勃勃地筹划LSST, SKA等大型暗能量探测项目,希望通过更加精确的探测帮助我们揭开暗能量的神秘面纱。 研究生期间,我利用宇宙学观测数据对暗能量问题作了一系列数值模拟研究。我们开发了稳定可靠的宇宙学数值模拟程序,能够方便地完成暗能量模型的数据拟合。我们的主要研究工作如下： 我们细致地研究了我的导师李淼老师提出的全息暗能量模型。理论上,我们提出了全息气体模型；数值上,我们作了一系列工作,包括不同红外截断模型的比较,相互作用与曲率的观测限制,全息暗能量的推广,以及全息暗能量与暗物质相互作用问题。 我们也研究了其他一些暗能量模型。我们利用最新的观测数据对九种暗能量模型与五种修改引力模型作了限制、比较,并重构了修改引力模型中的宇宙结构增长历史。我们还研究了一类能够在过去光锥上完全重构宇宙学常数观测的不均匀宇宙模型,并提出利用宇宙年龄检验来鉴别这类模型。 我们详细研究了暗能量重构课题。我们利用红移分段,多项式差值等参数化手段仔细分析了Constitution, Union2以及SNLS3超新星数据。对宇宙膨胀历史、暗能量状态方程、以及暗能量动力学演化作了详细的讨论研究。我们发现,Constitution数据倾向于动力学演化的暗能量,而Union2与SNLS3数据则更倾向于宇宙学常数。 此外,我们还探讨了几个与暗能量相关的小问题。我们初步研究了超新星数据的张力问题。我们还研究了一些古老天体带来的宇宙年龄问题,并试图通过引入暗能量与暗物质相互作用来化解这一问题,我们发现宇宙年龄问题能够得到些许缓和,但仍然没有完全解决。最后,我们还用参数化重构的方法研究了暗能量对宇宙命运的影响,我们发现,在最坏的情况下,宇宙距离大撕裂的时间为16.7Gyr。
[Abstract]:Since supernova observations in 1998 found that the universe is expanding rapidly, dark energy has become one of the most concerned topics in physics. The origin and nature of dark energy are riddles. It poses a serious challenge to physicists, the so-called "cosmological constant problem": why is the energy density of dark energy so small? Why is the current density of dark energy on the same order of magnitude as matter? For this reason, theorists have made a lot of efforts and put forward a lot of dark energy theoretical models from different angles, but they still can not solve the problem of dark energy. In the absence of strong theoretical guidance, we need to turn to experiments in the hope that cosmological observations will provide more clues to the problem of dark energy. Fortunately, cosmologists have developed a variety of dark energy observations such as supernovae, baryon acoustic oscillations, cosmic microwave background radiation, and weak gravitational lensing. These observations further confirm the accelerating expansion of the universe and greatly improve the observation accuracy of dark energy. Looking ahead, cosmologists are also planning ambitious dark energy exploration projects such as LSST, SKA, hoping to help us unravel the mystery of dark energy through more accurate detection. As a graduate student, I made a series of numerical simulations of dark energy using cosmological observations. A stable and reliable numerical simulation program for cosmology has been developed, which can easily fit the dark energy model. Our main research work is as follows: we have carefully studied the holographic dark energy model proposed by my teacher Li Miao. In theory, we propose a holographic gas model, numerically, we do a series of work, including the comparison of different infrared truncation models, the observation limitation of interaction and curvature, the generalization of holographic dark energy. And the interaction between holographic dark energy and dark matter. We have also studied other dark energy models. We use the latest observational data to limit nine dark energy models and five modified gravitational models, and reconstruct the growth history of the universe structure in the modified gravity model. We also study a class of inhomogeneous cosmological models which can completely reconstruct cosmological constant observations on past optical cones and propose to use cosmic age test to identify these models. We study the problem of dark energy reconstruction in detail. Constitution, Union2 and SNLS3 supernova data are carefully analyzed by means of red-shift segmentation, polynomial difference and other parameterization methods. The history of expansion of the universe, the equation of state of dark energy, and the dynamic evolution of dark energy are discussed in detail. We find that the Union2 and SNLS3 data tend to be more cosmological constants, while the Union2 data tend to be the dark energy of dynamical evolution. In addition, we discuss several small problems related to dark energy. We have studied the tension problem of supernova data. We also study the cosmic age problem brought about by some ancient celestial bodies and try to solve this problem by introducing dark energy and dark matter interaction. We find that the cosmic age problem can be alleviated slightly but not completely solved. Finally, we also study the influence of dark energy on the fate of the universe by parameterized reconstruction. We find that in the worst case, the time of large distance tearing is 16.7 Gyr.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P159
本文编号：2260757
[Abstract]:Since supernova observations in 1998 found that the universe is expanding rapidly, dark energy has become one of the most concerned topics in physics. The origin and nature of dark energy are riddles. It poses a serious challenge to physicists, the so-called "cosmological constant problem": why is the energy density of dark energy so small? Why is the current density of dark energy on the same order of magnitude as matter? For this reason, theorists have made a lot of efforts and put forward a lot of dark energy theoretical models from different angles, but they still can not solve the problem of dark energy. In the absence of strong theoretical guidance, we need to turn to experiments in the hope that cosmological observations will provide more clues to the problem of dark energy. Fortunately, cosmologists have developed a variety of dark energy observations such as supernovae, baryon acoustic oscillations, cosmic microwave background radiation, and weak gravitational lensing. These observations further confirm the accelerating expansion of the universe and greatly improve the observation accuracy of dark energy. Looking ahead, cosmologists are also planning ambitious dark energy exploration projects such as LSST, SKA, hoping to help us unravel the mystery of dark energy through more accurate detection. As a graduate student, I made a series of numerical simulations of dark energy using cosmological observations. A stable and reliable numerical simulation program for cosmology has been developed, which can easily fit the dark energy model. Our main research work is as follows: we have carefully studied the holographic dark energy model proposed by my teacher Li Miao. In theory, we propose a holographic gas model, numerically, we do a series of work, including the comparison of different infrared truncation models, the observation limitation of interaction and curvature, the generalization of holographic dark energy. And the interaction between holographic dark energy and dark matter. We have also studied other dark energy models. We use the latest observational data to limit nine dark energy models and five modified gravitational models, and reconstruct the growth history of the universe structure in the modified gravity model. We also study a class of inhomogeneous cosmological models which can completely reconstruct cosmological constant observations on past optical cones and propose to use cosmic age test to identify these models. We study the problem of dark energy reconstruction in detail. Constitution, Union2 and SNLS3 supernova data are carefully analyzed by means of red-shift segmentation, polynomial difference and other parameterization methods. The history of expansion of the universe, the equation of state of dark energy, and the dynamic evolution of dark energy are discussed in detail. We find that the Union2 and SNLS3 data tend to be more cosmological constants, while the Union2 data tend to be the dark energy of dynamical evolution. In addition, we discuss several small problems related to dark energy. We have studied the tension problem of supernova data. We also study the cosmic age problem brought about by some ancient celestial bodies and try to solve this problem by introducing dark energy and dark matter interaction. We find that the cosmic age problem can be alleviated slightly but not completely solved. Finally, we also study the influence of dark energy on the fate of the universe by parameterized reconstruction. We find that in the worst case, the time of large distance tearing is 16.7 Gyr.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P159
【参考文献】
相关期刊论文 前3条
1 ;Holographic Gas as Dark Energy[J];Communications in Theoretical Physics;2009年01期
2 ;Comparison of dark energy models:A perspective from the latest observational data[J];Science China(Physics,Mechanics & Astronomy);2010年09期
3 ;Dark energy and fate of the Universe[J];Science China(Physics,Mechanics & Astronomy);2012年07期
，本文编号：2260757
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