Physics of the Early Universe

宇宙学涵盖了广泛的物理学，从早期宇宙的极小尺度和高能量到星系的大尺度动力学。这种多样性需要一系列相应的技术来研究各种现象，从量子引力到经典动力学，从分析计算到数值模拟。在最大的可观测尺度上，宇宙微波背景（CMB）、大爆炸的遗迹辐射和星系团使我们能够探索宇宙的膨胀历史和成分。这些观察结果表明，宇宙的大部分是由奇异的暗物质和暗能量组成的。了解这些成分的性质，并将宇宙观测与粒子物理学联系起来，是宇宙学的一个重大突出问题，也是我们工作的目标之一。粒子物理学的标准模型在描述各种来源的结果方面非常成功，包括对撞机实验。然而，它确实存在一些概念问题（例如大量自由参数的存在），这激发了对各种扩展的研究。我们将使用非交换几何的思想，它为标准模型的对称性提供了一个自然的框架，来约束自由参数并做出可测试的预测。标准模型的另一个积极的扩展是超对称性，它假设玻色子和费米子之间的对称性。超对称性导致相变时的不同动力学，并且气泡可以成核。这也许可以解释为什么宇宙中物质多于反物质，我们将对这个过程进行数值模拟。标准模型包括强核力，它控制着夸克-胶子等离子体的行为。目前正在对撞机上探索这种新颖的物质状态，但使用传统方法描述它极其复杂。最近人们对使用弦理论技术的可能性产生了极大的兴趣，我们将利用这些见解探索这些等离子体的物理原理。粒子物理学和广义相对论都在极端能量下崩溃，而统一的量子引力理论有望在极端能量下发挥作用。我们将测试弦理论和非度量引力这两种理论的观测结果。弦理论允许超弦在宇宙中延伸，改变宇宙微波背景的波动，产生引力波，发射高能粒子和透镜星系，而非度量引力理论可以成功地再现星系的旋转曲线及其透镜特性。弦理论的另一个特点是它提供了一组新的自由度，称为模域。这些场的行为将导致潜在的可观察后果，这可能为弦理论提供观察证据，或破坏弦理论。我们将计算模量随着宇宙演化的表现，并检查它们与暗能量和暗物质的关系。

Cosmology spans a wide range of physics, from the very small scales and high energies of the early Universe to the large scale dynamics of galaxies. 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. On the largest observable scales the Cosmic Microwave Background (CMB), relic radiation from the big bang, and the clustering of galaxies allow us to probe the expansion history and constituents of the Universe. These observations suggest that most of the Universe is composed of exotic dark matter and dark energy. Understanding the nature of these components, and connecting observations of the Universe with particle physics, is a major outstanding issue for cosmology and one of the goals of our work. The standard model of particle physics is extremely successful at describing the results from various sources, including collider experiments. It does however have some conceptual problems (for instance the existance of a large number of free parameters) which motivate the study of various extensions. We will use ideas from non-commutative geometry, which provides a natural framework for the symmetries of the standard model, to constrain the free parameters and make testable predictions. Another well motivated extension of the standard model is supersymmetry which postulates a symmetry between bosons and fermions. Supersymmetry leads to different dynamics at phase transitions and bubbles can nucleate. This may explain why there is more matter than anti-matter in the Universe and we will perform numerical simulations of this process. The standard model includes the strong nuclear force, which governs the behaviour of a quark-gluon plasma. This novel state of matter is currently being probed at colliders, however it is extremely complicated to describe using orthodox methods. There has recently been great interest in the possibility that techniques derived from string theory can be employed, and we will explore the physics of these plasmas using these insights. 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 two such theories, string theory and non-metric gravity. String theory allows superstrings to stretch across the Universe, altering the fluctuations in the CMB, producing gravitational waves, emmitting high energy particles and lensing galaxies, while non-metric theories of gravity may successfully reproduce the rotation curves of galaxies as well as their lensing properties. Another feature of string theory is that it offers a new set of degrees of freedom called moduli fields. The behaviour of these fields will lead to potentially observable consequences which could provide observational evidence for, or undermine, string theory. We will calculate how the moduli behave as the Universe evolves and examine their relation to dark energy and dark matter.