Symmetry, supersymmetry, strings, branes and gauge theories; physics from the Planck to the QCD scale.

这项拟议的研究是寻找一个单一、完整和一致的物理学理论的努力的一部分。虽然自1967年标准模型形成以来，人们就已经了解了电磁力、弱力和强力，但到目前为止，还不可能以一致的方式添加更常见的引力。我们目前对引力的描述是爱因斯坦非常成功的广义相对论，它描述了行星、恒星和星系的运动。在很小的距离内，物质和力的行为是由量子力学控制的。粒子物理的标准模型包含了大量的对称性，这对于电磁和强弱力的量子力学一致性是至关重要的。不幸的是，爱因斯坦的广义相对论与量子力学不一致，因此不能简单地结合标准模型来提供所有四种力的一致理论。人们普遍认为，超对称性，即费米子(物质粒子，如电子)与玻色子(力载体，如光的光子)交换的对称性，将在形成四种力的统一理论方面发挥重要作用。超对称性预示着未知亚原子粒子的存在，对这些粒子的探索是欧洲核子研究中心建造大型强子对撞机(LHC)的重要动机。欧洲核子研究中心是一个位于日内瓦的大型实验室。弦是沿着一维延伸的微观物体，可以振动，就像小提琴上的弦一样。到目前为止，还没有一个完整的弦理论，但这种理论的最低能量效应是独一无二的，因为它们具有大量的对称性，特别是超对称性。这些就是所谓的超引力理论。通过对这些理论的研究，人们认识到膜和一种称为U-对偶的对称性是整个理论的重要组成部分。类似地，薄膜可以被认为是弦在一个以上维度上延伸的对象的微观推广。这个完整的理论被称为M-理论。虽然在微观层面上对它知之甚少，但已知它涉及11维，延伸了超弦的10维时空。我们希望找到并理解这一潜在的弦和膜理论。我们建议从几个角度来研究这一非常复杂的理论。首先是在低能量下理解这个理论，在那里它必须产生时空和我们所知道的四种力。其次，我们将在非常高的能量下研究这一理论，在那里，它的基本成分就像振动的弦和膜，而平滑时空的概念不再有意义。我们最重要的工具将是这个理论被认为拥有的巨大对称性。对称性是简约和美丽的标志，是我们今天理解物理学的可靠指导原则。在这个过程中，我们希望用与这种对称性一致的时空概念来取代我们通常的时空概念。这一方面说明了统一理论对我们理解自然的深刻影响，另一方面也说明了对称性所起的中心作用。

The proposed research is part of a quest to find a single, completeand consistent theory of physics. While the electromagnetic, weakand strong forces have been understood since the formulation of thestandard model in 1967, it has so far not been possibleto add the more familiar force of gravity in a consistent way. Ourcurrent description of gravity is Einstein's very successful theoryof general relativity, which describes the motion of planets, starsand galaxies. At small distances the behaviour of matter and forces is governedby quantum mechanics. It is crucial for the quantum mechanicalconsistency of the electromagnetic and strong and weak forces thatthe standard model of particle physics incorporates a large amountof of symmetry. Unfortunately, Einstein's theory of general relativity isnot consistent with quantum mechanics and so cannot be simplycombined with the standard model to provide a consistent theory ofall the four forces.It is widely believed that supersymmetry, which is a symmetry thatexchanges fermions (matter particles such as the electron) withbosons (force carriers such as photons of light) will play animportant role in formulating a unified theory of the four forces. Supersymmetry predicts the existence of yet unknown subatomic particles, and the search for these is an important motivation behind the construction of the `Large Hadron Collider' (LHC) at CERN, a vast laboratory situated in Geneva.Strings are microscopic objects which are extended along one dimension and can vibrate, just like strings on a violin. To date there does not exist a complete theory of strings, but the lowest energy effects of such a theoryare unique as a consequence of the large amount of symmetry, and inparticular supersymmetry, that they possess. These are the so-calledsupergravity theories. By studying these theories it has been realised that branes and a symmetry called U-duality are an important part of the full theory. Branes can similarly be thought of as microscopic generalizations of strings to objects that are extended along more than one dimension. This complete theory is known as M-theory. Although little is known about it on microscopic level it is known to involve eleven-dimensions, extending the ten-dimensional space-time of superstrings.We wish to find and understand this underlying theory of string andbranes. We propose to investigate this very intricate theory fromseveral points of view. The first is to understand the theory at lowenergies, where it must produce space-time and the four forces weknow. Secondly, we will investigate the theory at very highenergies, where its fundamental constituents behave like vibratingstrings and branes and the notion of a smooth space-time does nolonger make sense. Our most important tool will be the enormous amount of symmetry thatthis theory is thought to possesses. Symmetry is a sign ofunderlying simplicity and beauty and has been a reliable guidingprinciple in reaching the understanding of physics we have today. Inthis process we expect to replace of our usual notion of space-timeby one which is consistent with such symmetries. This illustrates onthe one hand the profound effect that a unified theory has on ourunderstanding of nature, and on the other hand the central roleplayed by symmetries.