Probing fundamental physics with multi-wavelength cosmology

宇宙诞生之初发生了什么？所有的结构（如恒星、星系、地球等）是从哪里来的？暗物质的本质是什么？还是加速宇宙膨胀的“暗能量”？我的建议集中于揭示这些深奥的奥秘。首先，通过精确观测天空中的微波辐射，我将比以往任何时候都更早地探索宇宙的历史。这些微波是大约130亿年前由新生宇宙发出的，可能包含非常微弱的模式，称为“B模式”。如果被探测到，这些B模式将是令人信服的证据，证明宇宙在很早的时候就经历了一段快速膨胀的时期，被称为“暴胀”。暴胀将为宇宙的结构提供一个自然的解释：时空结构中的量子涨落将在膨胀过程中被拉伸和放大，产生结构的初始种子，所有其他结构都是从这个种子中生长出来的。对B模式的精确测量也可以告诉我们基础物理学。如果暴胀确实发生过，那么它发生在宇宙非常热和致密的早期。在这种情况下，我们的物理定律还有效吗？探测到B模式将是利用早期宇宙作为“自然实验室”来研究这个问题的第一步。在接下来的5年里，我将分析望远镜的数据，寻找B模式的确凿证据。从观测中梳理出微小的信号将是一个巨大的挑战，因为它预计将比数据中的其他效应弱得多。例如，我们自己的银河系发射的微波比B模式信号强得多。同样重要的是，望远镜设计上的缺陷可能会模拟出真实的信号。因此，我计划开发能够区分真实信号和这些污染效应的新技术。谈到暗能量，探索这个未知的最好方法之一是测量宇宙历史上的结构是如何发展的。因为它是一种排斥力，暗能量抵消了引力，因此抑制了结构的生长。测量这种结构的一种强有力的方法是引力透镜技术。当来自遥远星系的光经过一团物质时，它会被物质的引力场轻微地偏转（或“透镜”）。这种效应会导致观测到的遥远星系的形状发生轻微的扭曲，人们可以用它来推断暗物质的结构。在我的研究期间，我将对新的天空调查进行分析，以了解暗物质和暗能量。特别是我将开发和应用一种新的和创新的技术来测量引力透镜在无线电频段，我最近提出。使用这种技术，我可以确定遥远星系形状的扭曲实际上是由于透镜效应，而不是星系本身固有的。微波B模式和引力透镜都是年轻而又非常令人兴奋的研究领域。它们令人兴奋，因为它们具有探索未知物理的独特潜力。早期宇宙的物理学和暗能量的性质一直被STFC自己的顾问小组和国际机构评为当今宇宙学面临的两个最重要的问题。本建议中所述的研究将在解决这两个科学知识前沿方面发挥重要作用。

What happened at the beginning of our Universe? Where did all the structure (e.g. stars, galaxies, the earth, etc.) come from? What is the nature of dark matter? Or the 'dark energy' responsible for accelerating the expansion of the Universe? My proposal is focused on shedding light on these profound mysteries. First, by making precise observations of the microwave emission across the sky, I will probe earlier into the Universe's history than we have ever reached before. These microwaves, emitted about 13 billion years ago by the nascent Universe, may contain very weak patterns called 'B-modes'. If detected, these B-modes would be compelling evidence that the Universe underwent a period of rapid expansion, known as 'inflation', very early on. Inflation would provide a natural explanation for structure in the Universe: quantum fluctuations in the fabric of space-time would have been stretched and amplified during the expansion, producing the initial seeds of structure from which all others have grown. A precise measurement of B-modes could also tell us about fundamental physics. If inflation did happen, then it happened at very early times when the Universe was extremely hot and dense. Under these conditions, do our laws of physics still work? A detection of B-modes would be the first step on the road to using the early Universe as a 'natural laboratory' to investigate this question. Over the next 5 years, I will analyse the data from telescopes searching for the smoking gun B-mode signature. Teasing out the tiny signal from the observations will be a huge challenge because it is expected to be much weaker than other effects in the data. For example, our own Galaxy emits microwaves which are much stronger than the B-mode signal. Equally important, imperfections in the design of the telescopes can mimic a real signal. I therefore plan to develop new techniques capable of distinguishing between the true signal and these contaminating effects. Turning to the dark energy, one of the best ways to probe this unknown is by measuring how structures have grown over the Universe's history. Because it's a repulsive force, dark energy counteracts gravity and therefore suppresses the growth of structures. A powerful way to measure this structure is the technique of gravitational lensing. As light from a distant galaxy passes by a clump of matter, it is slightly deflected (or 'lensed') by the matter's gravitational field. This effect results in slight distortions in the observed shapes of distant galaxies which one can use to infer the dark matter structure. During my fellowship, I will perform this analysis on new sky surveys in order to learn about the dark matter and dark energy. In particular I will develop and apply a new and innovative technique to measure gravitational lensing in the radio band which I have recently proposed. Using this technique, I can be sure that the distortions in the shapes of distant galaxies are really due to the lensing effect rather than being intrinsic to the galaxies themselves. Both microwave B-modes and gravitational lensing are young and extremely exciting fields of study. They are exciting because of their unique potential to probe unknown physics. The physics of the early Universe and the nature of dark energy are consistently rated, by both STFC's own advisory panels, and by international bodies, as the two most important questions facing cosmology today. The research described in this proposal will play an important role in tackling these two frontiers of scientific knowledge.