Cosmological simulations of large scale structure and general relativity

大尺度结构和广义相对论的宇宙学模拟

• 批准号: 2322273
• 金额: --
• 依托单位: University of Portsmouth
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2322273
• 关键词: Cosmological; simulations; large; scale; structure

The current standard model of cosmology, LCDM, assumes Cold Dark Matter and a cosmologicalconstant Lambda as Dark Energy, and is based on three main ingredients:1) the Universe is isotropic and homogeneous on the largest scales and thus well described theFriedmann-Lemaitre-Robertson-Walker (FLRW) metric;2) large-scale structure can be modelled by perturbative methods, linear and non-linear;3) fully nonlinear structure formation can be described by Newtonian N-body simulations.This project will address the question of how good this last assumption is. The modern theory ofgravity is, after all, General Relativity. With state-of-the-art cosmological observations reaching aprecision of 1% or better and even more improvement expected in the near future, it is extremelytimely to investigate how accurate the current theoretical predictions are.There are now publicly available Newtonian N-body codes, as well as N-body codes that includecorrections from General Relativity, that can be used to model large-scale structure in cosmology.However, it is far from clear that these codes including some relativistic corrections capture all theimportant effects. On the other hand, we recently successfully applied numerical relativity codes (i.e.codes that are fully relativistic) in cosmology for the first time, albeit in a very simplified setting andusing a fluid description of matter, rather than the particle description of N-body codes. This PhDproject will build on these first pioneering works to further develop a fully relativistic approach to thestudy of large-scale structure. One important goal is to establish how accurate Newtonian and "GRcorrected" codes are; another is to test various general-relativist approximations used to modelstructure formation in the mildly-non-linear regime; these issues can be addressed by using existingnumerical relativity codes as benchmark. Another open problem to address is that of accuratelyimplementing relativistic initial conditions derived from perturbation theory into the nonlinear evolution.There is a number of physical questions that need investigation in full GR, from the collapse of the firstcosmological objects to the formation of large voids, to how the formation of nonlinear structuresaffects light propagation in cosmology, ultimately affecting observations.

当前的宇宙学标准模型 LCDM 假设冷暗物质和宇宙常数 Lambda 作为暗能量，并基于三个主要成分：1）宇宙在最大尺度上是各向同性和均匀的，因此很好地描述了弗里德曼-勒梅特-罗伯逊-沃克（FLRW）度量；2）大尺度结构可以通过微扰方法、线性和 非线性；3）完全非线性结构的形成可以通过牛顿 N 体模拟来描述。该项目将解决最后一个假设有多好的问题。毕竟，现代引力理论是广义相对论。随着最先进的宇宙学观测精度达到 1% 或更高，并且预计在不久的将来会有更大的改进，研究当前理论预测的准确性非常及时。现在有公开的牛顿 N 体代码，以及包含广义相对论修正的 N 体代码，可用于模拟宇宙学中的大规模结构。然而，目前还不清楚这些代码是否有效。 包括一些相对论修正捕获了所有重要的影响。另一方面，我们最近首次在宇宙学中成功应用了数值相对论代码（即完全相对论的代码），尽管是在非常简化的环境中并使用物质的流体描述，而不是 N 体代码的粒子描述。该博士项目将以这些开创性工作为基础，进一步开发一种完全相对论的方法来研究大规模结构。一个重要目标是确定牛顿码和“GR 校正”码的准确度；另一个是测试用于模拟轻度非线性状态下结构形成的各种广义相对论近似；这些问题可以通过使用现有的数值相对论代码作为基准来解决。另一个需要解决的开放问题是如何准确地将微扰理论导出的相对论初始条件应用到非线性演化中。在完整的广义相对论中，有许多物理问题需要研究，从第一个宇宙学物体的坍缩到大空洞的形成，到非线性结构的形成如何影响宇宙学中的光传播，最终影响观测。