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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，由于我们对大爆炸余辉（宇宙微波背景辐射）中微小波动的观测，我们现在有了一个宇宙学的和谐模型，它提供了组成宇宙的物质和能量的数量和类型的精确清单，以及宇宙从几分之一秒开始发展的时间轴。人们普遍认为，宇宙在早期经历了一次被称为暴胀的快速膨胀。然而，在通货膨胀被提出以来的近30年里，我们仍然无法回答关于它的一些基本问题，例如它是如何开始的，它是如何结束的，以及是什么使膨胀继续下去。有无数的模型试图描述通货膨胀，但我们仍然没有一个基本的基础理论来支持它。弦理论是我们目前对“万物理论”的最大希望，但它对暴胀是出了名的敌视，尽管将两者结合起来的尝试仍在进行中。因此，为了取得进展，我们需要找到方法来区分所提出的暴胀模型，所有这些模型都是设计来产生一个类似于我们今天所看到的宇宙。我的方法是找出暴胀模型最显著的特征，以便尽可能多地证实或排除。最诱人的可能性之一是大爆炸遗留物的产生--早期宇宙中产生的实际物理物体，今天可能仍然存在，或者我们可能仍然看到其签名。虽然遗迹是推测性的，但它们的存在将是戏剧性的，无论是发现还是排除它们的回报都是巨大的，使我们能够区分整个类别的模型。我特别研究了三种大爆炸遗迹。首先是原始黑洞。这些微小的黑洞可能是在早期宇宙的稠密环境中产生的，它们要么通过吸入并加热周围的物质而出现，从而发出x射线辐射，要么通过“蒸发”--以伽马射线的形式辐射出去。其次是宇宙弦：在宇宙中伸展的高能弦会使遥远恒星和星系周围的光线发生弯曲，这种现象被称为引力透镜。宇宙弦是特别令人兴奋的搜索，因为它们可能是弦理论的弦，因此是我们直接观察到证实理论的东西的最大希望。第三种遗迹是一种被称为轴子的粒子。如果在暴胀期间存在轴子，它们就可以构成难以捉摸的暗物质，将星系和星系团聚集在一起。然而，我的工作已经表明，如果弦理论和暴胀理论都是正确的，那么轴子就很难与当前的观测结果相吻合。我们了解早期宇宙的最有价值的工具之一是研究宇宙学黑暗时代，这是大爆炸之后的一个时期，但在恒星和星系开始开启之前，当时宇宙主要是中性氢气。它之所以黑暗有两个原因：第一，没有什么东西在发光;第二，中性氢气特别善于吸收辐射。目前正在建造几个雄心勃勃的射电望远镜阵列，以试图更接近黑暗时代中性氢的观测，以便我们可以填补我们从大爆炸中看到的背景辐射与我们今天可以观察到的恒星和星系之间的差距。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。然而，这种精确度需要通过我们所测量的内容的清晰概念来平衡。我希望通过我将早期宇宙物理学与我们今天所能进行的观测联系起来的工作，使我们更接近这种理解。