Symmetries, Supersymmetries, Strings and Spacetime: the search for a fundamental theory of physics.

这项拟议的研究是寻找单一、完整和一致的物理学理论的努力的一部分。虽然自1967年提出所谓的标准模型以来，人们一直在理解电磁力、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，物质和力的行为受量子力学的支配。对于电磁和强弱力的量子力学一致性来说，粒子物理的标准模型包含了大量的对称性是至关重要的。不幸的是，爱因斯坦的广义相对论与量子力学不一致，因此不能简单地与标准模型相结合，提供关于所有四种力的一致理论。人们普遍认为，超对称性将在形成四力统一理论方面发挥重要作用。超对称性是费米子(如电子等物质粒子)与玻色子(光的光子等力载体)交换的对称性。超对称性预示着未知亚原子粒子的存在，而寻找这些粒子是欧洲核子研究中心(CERN)建造大型强子对撞机(LHC)的重要动机，CERN是一个位于日内瓦的大型实验室。弦是沿着一个维度延伸的微小物体，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。我们希望找到并理解弦和膜的基本理论。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已知的四种力。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，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。对称性是潜在的简单和美丽的标志，也是我们今天对物理学的理解的一个可靠的指导原则。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, complete and consistent theory of physics. While the electromagnetic, weak and strong forces have been understood since the formulation of the so-called standard model in 1967, it has so far not been possible also add the more familiar force of gravity in a consistent way. Our current description of gravity is Einstein's very successful theory of general relativity, which describes the motion of planets, stars and galaxies. At small distances the behaviour of matter and forces is governed by quantum mechanics. It is crucial for the quantum mechanical consistency of the electromagnetic and strong and weak forces that the standard model of particle physics incorporates a large amount of of symmetry. Unfortunately, Einstein's theory of general relativity is not consistent with quantum mechanics and so can not be simply combined with the standard model to provide a consistent theory of all the four forces. It is widely believed that supersymmetry, which is a symmetry that exchanges fermions (matter particles such as the electron) with bosons (force carriers such as photons of light) will play an important 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 dimensions 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 theory are unique as a consequence of the large amount of symmetry, and in particular supersymmetry, that they possess. These are the so-called supergravity 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. We wish to find and understand this underlying theory of strings and branes. We propose to investigate this very intricate theory from several points of view. The first is to understand the theory at low energies, where it must produce spacetime and the four forces we know. Secondly, we will investigate the theory at very high energies, where its fundamental constituents behave like vibrating strings and branes and the notion of a smooth spacetime does no longer make sense. Our most important tool will be the enormous amount of symmetry that this theory is thought to possesses. Symmetry is a sign of underlying simplicity and beauty and has been a reliable guiding principle in reaching the understanding of physics we have today. In this process we expect to replace of our usual notion of spacetime by one which is consistent with such symmetries. This illustrates on the one hand the profound effect that a unified theory has on our understanding of nature, and on the other hand the central role played by symmetries.