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String Theory Scotland

苏格兰弦理论

基本信息

批准号：
ST/G000514/1
负责人：
Richard Joseph Szabo
金额：
$ 4.32万
依托单位：
Heriot-Watt University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FG000514%2F1
关键词：
String Theory Scotland

项目摘要

There are two types of fundamental forces in Nature: those responsible for particle interactions at subatomic scales and those responsible for the large scale structure of the universe. The latter is described by Einstein's General Theory of Relativity (GR) and the former by Quantum Field Theories (QFTs) such as the Standard Model. Einstein's theory is conceptually simple, but is classical and breaks down when the force of gravity is strong, as it is at very small scales, whereas QFTs are effective theories which ignore the gravitational interactions and which cannot be trusted at very high energies. During the last three decades, String Theory has emerged as a conceptually rich theoretical framework reconciling both GR and QFT. In particular, it is a theory of quantum gravity and our group's research programme is firmly focused on a wide range of quantum gravitational aspects of String Theory. The expansion of the universe is incontrovertible. In String Theory, the universe is described via the notion of a string background. Thus if String Theory is to make contact with cosmology, one has to come to grips with time-dependent backgrounds, which are not directly amenable to investigation using the standard perturbative formulation of string theory. Our group have pioneered the study of time-dependent string backgrounds and an important part of our research activities is centred on this topic. Our goal is to understand the general structure of string perturbation theory in time-dependent backgrounds in order to be able to answer questions such as 'Does string theory resolve Big-Bang-type singularities?'---a natural question in view of the fact that string theory is known to resolve other types of singularities. Another important goal of our research is to derive observable cosmological consequences of string theory in an effort to falsify it or at least to constraint the landscape of possible string backgrounds. String theory challenges the geometrical notions of spacetime on which GR is predicated. At very small ('stringy') scales the nature of spacetime is believed to be fundamentally different from GR---its continuous structures thought to be replaced by discrete, algebraic structures which no longer distinguish individual spacetime events. Noncommutative Geometry (NCG) is a branch of modern mathematics dealing with such discrete structures. There are strong hints that NCG appears naturally in String Theory and a thorough investigation of this expectation is another of the main focal points of our group's research. Perturbative string theory is described in terms of two-dimensional conformal field theory (CFT) and one of our main goals in this area is the emergence of NCG on the important class of quasi-rational conformal field theories. The low-energy limit of String Theory is supergravity (SUGRA), a nontrivial extension of GR, in which the universe is described by a spacetime with additional geometric data ? the signature of stringy physics. As the energy increases, these backgrounds are believed to receive corrections, and determining which types of corrections is one of the main questions we will address. As in GR, SUGRA admits solutions describing gravitating objects such as black holes, branes,... We known from Hawking's work that black holes obey the laws of thermodynamics and this prompts the natural question: 'Which microstates are responsible for the entropy of a black hole?' Our group have pioneered the systematic approach to the classification of SUGRA backgrounds and we are well poised to answer some of the more pressing questions in this area, such as 'what are the possible branes in a SUGRA background?', an important question in the gauge/gravity correspondence. In summary, our research encompasses a wide range of gravitational aspects of String Theory, impinging on cosmology, particle physics and on the very nature of String Theory itself.

自然界中有两种基本力：一种是在亚原子尺度上负责粒子相互作用的力，另一种是负责宇宙大尺度结构的力。后者由爱因斯坦的广义相对论（GR）描述，前者由量子场论（QFT）如标准模型描述。爱因斯坦的理论在概念上很简单，但却是经典的，当引力很强时（因为它是在非常小的尺度上），它就会崩溃，而QFT是有效的理论，它忽略了引力相互作用，并且在非常高的能量下不能被信任。在过去的三十年里，弦理论已经成为一个概念丰富的理论框架，调和了GR和QFT。特别是，它是一个量子引力理论，我们小组的研究计划坚定地集中在弦理论的量子引力方面。宇宙的膨胀是无可争议的。在弦论中，宇宙是通过弦背景的概念来描述的。因此，如果弦理论要与宇宙学建立联系，就必须掌握依赖于时间的背景，而这些背景不能直接用弦理论的标准微扰表述来研究。我们的团队开创了与时间相关的弦背景的研究，我们的研究活动的一个重要组成部分是围绕这个主题。我们的目标是了解弦微扰理论在时间相关背景下的一般结构，以便能够回答诸如“弦理论能解决大爆炸型奇点吗？这是一个自然的问题，因为弦理论可以解决其他类型的奇点。我们研究的另一个重要目标是导出弦理论的可观测宇宙学结果，以证伪它，或者至少限制可能的弦背景的景观。弦理论挑战了GR所预言的时空几何概念。在非常小的尺度上，时空的性质被认为与GR有着根本的不同--它的连续结构被离散的代数结构所取代，不再区分单个的时空事件。非对易几何（NCG）是研究这种离散结构的现代数学的一个分支。有强烈的暗示表明，NCG自然地出现在弦论中，对这种期望的彻底调查是我们小组研究的另一个主要焦点。微扰弦理论描述的二维共形场论（CFT），我们在这方面的主要目标之一是出现NCG的重要类准有理共形场论。弦论的低能极限是超引力（SUGRA），它是GR的一个非平凡的扩展，其中宇宙是由一个具有额外几何数据的时空来描述的。弦物理学的标志随着能量的增加，这些背景被认为会得到修正，确定哪种类型的修正是我们将要解决的主要问题之一。与GR一样，SUGRA承认描述引力物体的解决方案，如黑洞，膜，…我们从霍金的工作中知道，黑洞遵守热力学定律，这就引出了一个自然的问题：“哪些微观状态对黑洞的熵负责？”“我们的团队开创了对SUGRA背景进行分类的系统方法，我们已经准备好回答这一领域中一些更紧迫的问题，例如'SUGRA背景中可能的膜是什么？'这是规范/重力对应中的一个重要问题。总之，我们的研究涵盖了弦理论的广泛引力方面，影响了宇宙学，粒子物理学和弦理论本身的本质。