The Cosmology of the Early and Late Universe

宇宙学涵盖了广泛的物理学，从早期宇宙的非常小的尺度和高能量到宇宙后期的星系和星系团。宇宙微波背景（CMB）（大爆炸的残余辐射）和超新星爆炸使我们能够探测宇宙的膨胀历史和组成。这些观测结果表明，宇宙中的大部分物质都是由奇异的暗物质组成的。此外，宇宙的膨胀最近开始加速，而不是像预期的那样继续放缓。这种后期加速可能是由于一种奇异的暗能量成分，或者是爱因斯坦引力定律的修正。晚期宇宙有着丰富的星系和星系团结构。这些结构被认为是由早期宇宙中物质分布的微小初始波动形成的。然而，产生这些波动的机制尚不清楚。将晚期宇宙的观测与早期宇宙和基本粒子物理学联系起来是宇宙学的一个主要突出问题，也是我们工作的主要目标之一。粒子物理学和广义相对论都在极端能量下崩溃，而在极端能量下，统一的量子引力理论有望发挥作用。我们将检验这些理论的观测结果。特别是弦理论允许超弦在宇宙中伸展，改变CMB的波动，产生引力波，发射高能粒子和透镜星系。我们将研究宇宙超弦网络的演化，并对它们的观测特征做出准确的预测。这项工作有可能通过宇宙学为弦理论提供第一个证据。我们还将研究从弦理论产生的模型的宇宙学，包括非常早期的宇宙和结构形成的原始波动的产生。弦理论和其他新的粒子物理模型也为我们提供了一种暗物质候选者，即弱相互作用大质量粒子（WIMPs）。WIMP可以在实验室中直接检测到（通过它们与原子的罕见相互作用），也可以通过它们聚集在一起并湮灭时产生的反粒子和高能伽马射线间接检测到。它们也可以在LHC等粒子对撞机中产生。我们将开发明确探测暗物质并测量其属性所需的工具。我们也将研究特定弦理论暗物质候选者的天体物理学和宇宙学后果。我们将采取双管齐下的方法来理解所观察到的宇宙后期加速的物理基础。我们将开发技术，使我们能够在早期和晚期宇宙中测试引力定律和暗能量模型。我们还将继续探索可能提供加速机制的基本物理模型。我们的研究涵盖了广泛的尺度和能量。这种多样性与一系列相应的技术相结合，以研究各种现象，从量子引力到经典动力学，从分析计算到使用超级计算机的数值模拟。

Cosmology spans a wide range of physics, from the very small scales and high energies of the early Universe to galaxies and galaxy clusters in the late Universe. The Cosmic Microwave Background (CMB) (relic radiation from the big bang) and supernovae explosions allow us to probe the expansion history and constituents of the Universe. These observations suggest that most of matter in the Universe is composed of exotic dark matter. Furthermore the expansion of the Universe recently started accelerating, rather than continuing to slow down as expected. This late time acceleration could be due to an exotic dark energy component, or a modification of Einstein's laws of gravity. The late Universe has a rich structure of galaxies and galaxy clusters. These structures are believed to form from small initial fluctuations in the matter distribution, generated in the early Universe. However the mechanism responsible for producing these fluctuations is not yet understood. Connecting observations of the late time Universe, with the early Universe and fundamental particle physics is a major outstanding issue for cosmology and one of the main goals of our work. Particle physics and general relativity both break down at extreme energies, where a unified theory of quantum gravity is expected to operate. We will test the observational consequences of such theories. In particular string theory allows superstrings to stretch across the Universe, altering the fluctuations in the CMB, producing gravitational waves, emitting high energy particles and lensing galaxies. We will study the evolution of networks of cosmic superstrings and make accurate predictions for their observational signatures. This work could potentially provide the first evidence for string theory through cosmology. We will also study the cosmology of models which arise from string theory, including the very early Universe and the generation of the primordial fluctuations from which structure form. String theory, and other new particle physics models, also provide us with a dark matter candidate in the form of Weakly Interacting Massive Particles (WIMPs). WIMPs can be detected directly in the lab (via their rare interactions with atoms) or indirectly via the antiparticles and high energy gamma-rays that are produced when they come together and annihilate. They can also be produced in particle colliders such as the LHC. We will develop the tools required to unambiguously detect dark matter and measure its properties. We will also study the astrophysical and cosmological consequences of specific string theory dark matter candidates. We will take a two pronged approach to understanding the physics underlying the observed late time acceleration of the Universe. We will develop techniques which will allow us to test the laws of gravity, and models of dark energy, in both the early and late Universe. We will also continue to explore fundamental physics models which may provide a mechanism for the acceleration. Our research encompasses a wide range of scales and energies. This diversity is met with a corresponding array of techniques to study various phenomena, ranging from quantum gravity to classical dynamics and analytic calculations to numerical simulations using supercomputers.