Connecting Early Universe Physics to Modern Advances in Observational Astronomy

将早期宇宙物理学与现代观测天文学进展联系起来

基本信息

批准号：
ST/G007306/1
负责人：
Katherine Mack
金额：
$ 23.32万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FG007306%2F1
关键词：
Connecting Early Universe Physics Modern

项目摘要

We are living in a golden age for cosmology. Thanks in large part to our observations of the tiny fluctuations in the afterglow of the Big Bang, the cosmic microwave background, we now have a concordance model of cosmology which provides a precise inventory of the amount and type of matter and energy that makes up the Universe and a timeline of the Universe's development from a fraction of a second on. However, a few nagging uncertainties remain. It has become largely accepted that at early times the Universe underwent a rapid expansion known as inflation. However, in the nearly three decades since inflation was proposed, we are still unable to answer some basic questions about it, such as how it started, how it ended, and what kept the expansion going. There are countless models attempting to describe inflation, but we still don't have a basic underlying theory to ground it in. String theory, our current best hope for a 'theory of everything,' is notoriously hostile to inflation, though attempts to unite the two are ongoing. In order to make progress, therefore, we need to find ways to distinguish among the inflationary models being proposed, all of which, by design, produce a universe similar to what we see today . My approach is to seek out the most distinctive features of inflationary models so as to confirm or rule out as much as possible. One of the most enticing possibilities is the production of relics from the Big Bang -- actual physical objects produced in the early universe that may still exist today, or whose signatures we might still see. Although relics are speculative, their presence would be dramatic enough that the pay-off for either discovering or ruling them out would be huge, allowing us to distinguish among entire classes of models. I have been looking in particular at three kinds of Big Bang relics. First are primordial black holes. These tiny black holes, which could have been produced in the dense environment of the early universe, would show up either by pulling in and heating up the matter around them, which puts out x-ray radiation, or by 'evaporating' -- radiating themselves away as gamma rays. Second are cosmic strings: strings of high energy stretching across the universe would bend the light of distant stars and galaxies around them in a phenomenon known as gravitational lensing. Cosmic strings are particularly exciting to search for because they could be the very strings of string theory, and are therefore our best hope for directly observing something that would confirm the theory. A third type of relic is a particle known as an axion. If axions existed during inflation, they could make up the elusive dark matter that holds galaxies and clusters of galaxies together. However, my work has shown that axions are difficult to fit in with current observations if both string theory and inflation are correct. One of the most valuable tools we have for learning about the early universe is the study of the cosmological Dark Ages, a period after the Big Bang, but before stars and galaxies started to turn on, when the Universe was mostly neutral hydrogen gas. It was dark for two reasons: first, nothing much was shining; and second, neutral hydrogen gas is particularly good at absorbing radiation. Several ambitious radio telescope arrays are currently being built in order to try to get closer to observations of the neutral hydrogen in the Dark Ages so we can fill in the gap between the background radiation we see from the Big Bang and the stars and galaxies we can observe today. Cosmology, which was once the work of philosophers and theologians, is now a precision science. However, that precision needs to be balanced by a clear conceptual picture of what it is we're measuring. I hope to bring us closer to that understanding through my work of connecting early universe physics to the observations we can make today.

我们生活在宇宙学的黄金时代。在很大程度上要感谢我们观察到大爆炸余潮中微小的波动，宇宙微波背景，我们现在拥有宇宙学的一致性模型，该模型提供了构成宇宙的物质和类型和能量的精确清单，这些库存构成了宇宙的数量和类型，以及宇宙的时间表，从第二的一小部分开始。但是，仍然存在一些na不确定的问题。在很大程度上，在早期，宇宙经历了一种被称为通货膨胀的快速扩张。但是，在提出通货膨胀以来的近三十年中，我们仍然无法回答有关它的一些基本问题，例如它的开始，结局的结局以及使扩张的发展是什么。有无数的模型试图描述通货膨胀，但是我们仍然没有基本的基本理论来基础。弦理论，我们目前对“一切理论”的最大希望，众所周知，这对通货膨胀是敌对的，尽管试图将两者团结在一起。因此，为了取得进步，我们需要找到方法来区分所提出的通货膨胀模型，所有这些模型都通过设计产生与我们今天所看到的类似的宇宙。我的方法是寻找通货膨胀模型的最独特的特征，以便尽可能确认或排除。最吸引人的可能性之一是从大爆炸中生产遗物 - 早期宇宙中可能仍然存在的实际物理物体，或者我们仍然可能看到其签名。尽管文物是投机性的，但它们的存在将是足够的，以至于发现或排除它们的回报将是巨大的，从而使我们能够区分整个模型。我一直在寻找三种大爆炸遗物。首先是原始黑洞。这些可能是在早期宇宙茂密的环境中产生的微小的黑洞，可以通过拉进并加热周围的物质来出现，从而散发出X射线辐射，或者“蒸发” - 作为伽马射线散发出来。其次是宇宙弦：在整个宇宙中伸展的高能弦会以一种称为引力透镜的现象弯曲远处的恒星和星系的光。宇宙弦特别令人兴奋，因为它们可能是弦理论的一系列弦，因此是我们直接观察可以证实这一理论的事物的最大希望。第三种遗物是一种称为轴的粒子。如果在通货膨胀期间存在轴，则可以构成将星系和星系簇融合在一起的难以捉摸的暗物质。但是，我的工作表明，如果弦理论和通货膨胀均正确，轴很难与当前观察结果相适应。我们为早期宇宙学习的最有价值的工具之一是对宇宙黑暗时代的研究，这是大爆炸后的一个时期，但是在恒星和星系开始开启之前，宇宙主要是中性氢气。天黑的原因有两个：首先，什么都没有光芒。其次，中性氢气特别擅长吸收辐射。目前正在建造几个雄心勃勃的射电望远镜阵列，以试图近距离观察到黑暗时代的中性氢气，以便我们可以填补从大爆炸中看到的背景辐射之间的间隙，而我们今天可以观察到的恒星和星系。宇宙学曾经是哲学家和神学家的工作，现在是一门精确的科学。但是，需要通过清晰的概念图表来平衡我们正在测量什么。我希望通过将早期宇宙物理学与今天可以进行的观察联系起来的工作使我们更接近这种理解。