Particles, Fields and Spacetime

粒子物理学进入了一个新的关键阶段。欧洲核子研究中心（CERN）的大型强子对撞机（Large Hadron Collider）使我们能够通过实验来检验粒子物理学标准模型（如希格斯机制）背后的理论概念，并将继续寻找被认为可以统一物理定律的更深层次的结构。量子场论是表达标准模型的数学语言，它将粒子视为点状物体。只有特定种类的量子场论，即规范理论，在我们生活的四维世界中是一致的。这些理论包括并概括了描述光与电荷相互作用的电动力学理论。为了能够解释实验结果，我们需要能够解决规范理论，至少是近似的。这是一个很难的问题，但最近在这个问题上取得了非常显著的进展，这是由于最初在完全不同的背景下为解决非常不同的理论而发展起来的思想的融合。该项目的主要推动力将是进一步推动这一研究方向，以便能够更全面地理解规范理论并能够计算其性质。大尺度的物质受引力支配，这是爱因斯坦广义相对论所描述的。它支配着行星、恒星、星系的运动以及宇宙本身的演化。统一广义相对论和粒子物理的标准模型是理论物理学面临的最重要的挑战。尽管不是所有人都相信弦理论提供了这样一种统一。弦理论用扩展对象取代了量子场论中的点状粒子，扩展对象的不同振动模式解释了不同种类的基本粒子。正是这种信念导致了超对称性的期望，超对称性是所有现实弦理论的一个特性，在自然界中发挥着作用，并且很可能在大型强子对撞机上被发现。展示大自然如何隐藏这种属性是项目的另一部分。弦理论还导致了不同物理理论之间的许多意想不到的关系，最显著的是AdS/CFT对应关系，它表明某些引力理论与相应的规范理论之间是等价的，使我们能够通过研究另一种理论中较简单的问题来解决一种理论中的难题。我们将用它来研究重力问题，否则将是棘手的，也模型强耦合的物理过程在不同的领域，从凝聚态物理到等离子体重力。我们还将使用另一种方法来研究强子，这种方法特别适合描述大量的强子结合成原子核甚至中子星。这是基于有效的场理论，如Skyrme模型，我们将使用计算机进行数值研究。作为一种量子引力理论，弦对宇宙学有许多影响，特别是它们承认了这样一种可能性，即我们所看到的物理宇宙只是一个被称为膜的低维子空间，在更高维度的空间中运动。我们将继续寻找直接的实验和观测特征来验证这一设想。

Particle Physics has entered a new and crucial phase. The Large Hadron Collider at CERN has enabled us to examine experimentally theoretical concepts that underly the standard model of particle physics, such as the Higgs mechanism, and it will go on to search for the deeper structures that are believed to unify the laws of physics.Quantum field theory is the mathematical language in which the standard model is expressed, and it treats particles as point-like objects. Only certain kinds of quantum field theories, known as gauge theories, are consistent in the four dimensional world we live in. These include, and are generalisations of, the theory of electrodynamics that describes light interacting with electric charge. To be able to interpret the results of experiments we need to be able to solve gauge theories, at least approximately. This is a hard problem, but one in which there has recently been very remarkable progress due to a convergence of ideas originally developed in quite disparate contexts for solving very different kinds of theories. A major thrust of the project will be to push this line of enquiry further so as to be able to more fully understand gauge theories and be able to compute their properties.Matter at large scales is dominated by gravity which is described by Einstein's theory of General Relativity. This governs the motion of planets, stars, galaxies, and the evolution of the Universe itself. Uniting General Relativity and the standard model of particle physics is the most important challenge facing theoretical physics. It is widely, though not universally, believed that string theory provides such a unification. String theory replaces the point-like particles of quantum field theory with extended objects whose different vibrational modes account for the different species of fundamental particles. It is this belief that leads to the expectation that supersymmetry, a property of all realistic string theories, plays a role in nature, and may well be discovered at the LHC. Showing how nature contrives to hide this property is another part of the project.String theory has also led to many unexpected relations between different kinds of physical theories, most notably in the AdS/CFT correspondence which states equivalences between certain gravity theories and corresponding gauge theories, enabling us to solve difficult problems in one theory by studying simper ones in the other. We will use this to study problems in gravity that would otherwise be intractable and also model strongly coupled physical processes in diverse areas ranging from condensed matter physics to plasmas by gravity. We will also use another method for studying hadrons that is particularly appropriate to describing large numbers of thembound into nuclei or even neutron stars. This is based on effective field theories such as the Skyrme model which we will investigate numerically using computers.Being a theory of quantum gravity strings have many implications for cosmology, in particular they admit the possibility that what we see as the physical universe is only a low dimensional subspace called a brane, moving in a space of higher dimensions. We will continue the quest to find direct experimental and observational signatures that will test this scenario.