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The Cosmology of the Early and Late Universe

早期和晚期宇宙的宇宙学

基本信息

批准号：
ST/L000393/1
负责人：
Edmund Copeland
金额：
$ 84.56万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FL000393%2F1
关键词：
Cosmology Early Late Universe

项目摘要

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. Specific features in our Universe such as the Cosmic Microwave Background (CMB) (relic radiation from the big bang) and individual supernovae explosions allow us to probe the expansion history and constituents of the Universe. These observations suggest that most of the matter in the Universe is composed of exotic dark matter. Furthermore the expansion of the Universe recently started accelerating (by recent we mean a few billion years ago actually, but recent compared to the Universe's age of 13.7 billion years), 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. Moreover, we also have in the late Universe rich structures of galaxies and galaxy clusters which are believed to have grown from small initial fluctuations in the matter distribution, which in turn were generated in the very early Universe. However the mechanism responsible for producing these fluctuations is not yet fully 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. We will study the evolution of networks of cosmic strings and superstrings and make accurate predictions for their observational signatures. We will then test these predictions directly against data from the Planck satellite and thereby constrain the allowed form these strings could take in our Universe. This work could potentially provide the first evidence for string theory through cosmology. 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 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. One exciting proposal we will investigate involves a Harry Potter like invisibility cloak. In a class of modified gravity models we have developed, the cosmological constant can be arbitrarily large as it is hidden from the background geometry of the Universe by the presence of a scalar field which acts like the cloak. There are many interesting facets to this proposal which we will investigate in depth, not least among them, is it observationally consistent?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.

宇宙学涵盖了广泛的物理学领域，从早期宇宙的非常小的尺度和高能量到晚期宇宙中的星系和星系团。我们宇宙的特定特征，如宇宙微波背景（CMB）（大爆炸遗留的辐射）和单个超新星爆炸，使我们能够探索宇宙的膨胀历史和组成。这些观测表明，宇宙中的大部分物质都是由外来的暗物质组成的。此外，宇宙的膨胀最近开始加速（我们说的最近是指几十亿年前，但与宇宙137亿年的年龄相比，最近），而不是像预期的那样继续减速。这种晚时间的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。此外，我们在晚期宇宙中也有丰富的星系和星系团结构，它们被认为是从物质分布的微小初始波动中成长起来的，而这些波动又在非常早期的宇宙中产生。然而，产生这些波动的机制尚不完全清楚。将晚期宇宙、早期宇宙和基本粒子物理学的观测联系起来，是宇宙学的一个重大突出问题，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失效，在极端能量下，统一的量子引力理论有望起作用。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。我们将研究宇宙弦和超弦网络的演化，并对它们的观测特征做出准确的预测。然后，我们将直接根据普朗克卫星的数据来测试这些预测，从而约束这些弦在我们的宇宙中可能采取的允许形式。这项工作有可能通过宇宙学为弦理论提供第一个证据。弦理论和其他新的粒子物理模型也以弱相互作用大质量粒子（wimp）的形式为我们提供了暗物质的候选者。wimp可以在实验室中直接探测到（通过它们与原子罕见的相互作用），也可以通过反粒子和高能伽马射线间接探测到（当它们聚集在一起并湮灭时产生的反粒子和高能伽马射线）。它们也可以在粒子对撞机中产生，比如大型强子对撞机。我们将开发出明确探测暗物质并测量其特性所需的工具。我们将采取双管齐下的方法来理解观测到的宇宙晚期加速的物理基础。我们将开发技术，使我们能够在早期和晚期的宇宙中测试重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。我们将研究的一个令人兴奋的提议涉及一件类似哈利波特的隐形斗篷。在我们开发的一类修正重力模型中，宇宙常数可以任意大，因为它被隐藏在宇宙的背景几何中，因为标量场的存在就像斗篷一样。这个建议有很多有趣的方面，我们将深入研究，尤其是其中，它在观测上是一致的吗？我们的研究涵盖了广泛的尺度和能量。这种多样性需要相应的一系列技术来研究各种现象，从量子引力到经典动力学，从分析计算到使用超级计算机的数值模拟。