Particle Theory at the Higgs Centre

自然界中有两种基本力：一种负责亚原子尺度上的粒子相互作用，另一种负责宇宙的大尺度结构。前者由量子场论（QFT）如标准模型（SM）来描述。目前，我们对自然最基本的认识正处于十字路口。2012年，欧洲核子研究中心（CERN）的大型强子对撞机（LHC）以比以往更高的能量碰撞质子，并观察到足够的碰撞，发现了明显的过剩，与SM的希格斯玻色子一致。近年来，事实证明这确实是一个SM希格斯粒子，负责产生矢量玻色子、轻子和夸克的质量。目前，大型强子对撞机正在采集更高能量的数据，我们应该很快就能清楚地知道，在TeV尺度上是否存在更多的物理现象，或者我们是否需要建造能够达到更高能量的机器。在大尺度上，欧洲普朗克卫星提供了宇宙微波背景（CMB）的最精确测量，确定最能描述宇宙大尺度特性背后的物理的粒子物理模型是一个悬而未决的问题。2016年，LIGO宣布探测到引力波，标志着天体物理学新篇章的开始。因此，无论在小尺度还是大尺度上，这都是基础物理学的一个变革时期。我们在爱丁堡希格斯理论物理中心的研究项目旨在走在这些新发现的前沿。具体来说，我们提供了理论计算，使用笔和纸，以及最强大的超级计算机，对已知物理在大型强子对撞机上看到的大量背景过程，以及各种新物理模型中预期的微小信号，以便区分信号和背景，从而最大限度地提高大型强子对撞机的发现潜力。与此同时，我们将试图了解可能开始出现的所有自然力量的更完整的图景。爱因斯坦的广义相对论（GR）描述了大尺度结构的基本力。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，它调和了广义相对论和量子力学。弦理论的低能量极限是超重力（SUGRA），这是广义相对论的非平凡扩展，其中宇宙是由具有附加几何数据的时空来描述的。该小组的成员率先采用了一些方法来推导弦理论的可观测宇宙学结果，并研究了在非常小的（“弦”）距离尺度下预测GR的几何概念是如何变化的。该小组还致力于利用这些理论来改进现有场论的计算。最近发现的QCD振幅和GR之间的关系，被称为“双重复制”，为引力现象提供了新的见解。总之，我们的研究将涉及与探索LHC数据现象学相关的理论和计算方面，并且还将涵盖QFT和弦理论引力方面的广泛主题，涉及宇宙学，粒子物理学和物理学本身的本质。

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 former is described by Quantum Field Theories (QFT) such as the Standard Model(SM). Currently, our understanding of Nature at the most fundamental level is at the crossroads. In 2012, the LHC at CERN collided protons at higher energies than ever before, and observed sufficient collisions to find a significant excess, consistent with the Higgs boson of the SM. Over recent years it has become evident that this is indeed a SM Higgs, responsible for generating masses for vector bosons, leptons and quarks. Currently data at even higher energies is being taken at LHC, and it should soon become clearer whether there is more physics at the TeV scale, or whether we need to build machines capable of going to even higher energies. At large scales the European Planck satellite has given the most precise measurements of the cosmic microwave background (CMB) and it is an open question to determine the particle physics model best capable of describing the physics underlying the large scale properties of the Universe. In 2016 the detection of gravitational waves was announced by LIGO, marking the start of a new chapter in astrophysics. Thus at both small and large scales, this is a transformative time in fundamental physics.Our programme of research at the Higgs Centre for Theoretical Physics in Edinburgh is designed to be at the forefront of these new discoveries. Specifically, we provide theoretical calculations, using pen and paper, and the most powerful supercomputers, of both the huge number of background processes to be seen at LHC due to known physics, and the tiny signals expected in various models of new physics, in order to discriminate between signal and background, and thus maximise the discovery potential of the LHC. In parallel, we will attempt to understand the more complete picture of all the forces of Nature that may begin to emerge. The fundamental force responsible for large scale structure is described by Einstein's General Theory of Relativity (GR). During the last three decades, string theory has emerged as a conceptually rich theoretical framework reconciling both GR and QFT. 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. Members of the group have pioneered approaches to deriving observable cosmological consequences of String Theory, to studying how the geometrical notions on which GR is predicated change at very small ("stringy") distance scales. The group is also engaged in using these theories to improve calculations in existing field theories. Recent discoveries of relationships between QCD amplitudes and GR, known as the 'double copy', offer new insight into gravitational phenomena.In summary, our research will impinge on both theoretical and computational aspects relevant to probing the phenomenology of LHC data, and will also encompass a wide range of topics in QFT and gravitational aspects of String Theory, impinging on cosmology, particle physics and on the very nature of physics itself.