From the Planck Scale to the Hubble Scale - Theoretical Physics At KCL

我们的研究重点是理论物理学和对我们所居住的宇宙和我们周围所看到的一切的最终规律的追求。我们研究的理论物理有两个方面——量子物理和引力。量子物理学，特别是量子场论，描述了粒子和力，就像那些构成常规物质的粒子和力一样，也描述了那些只能在粒子实验中检测到的粒子和力，比如欧洲核子研究中心的大型强子对撞机。在过去的一个世纪里，量子场论的发展与实验相结合，导致了粒子物理学标准模型的建立。随着希格斯玻色子的发现，这个非常成功的理论在2012年得到了最终的证实。万有引力首先由牛顿提出，然后由爱因斯坦的广义相对论更详细地描述了天体的运动和宇宙的膨胀，这是由于时空的弯曲。多年来，许多观测结果都与爱因斯坦的理论一致。其中最令人兴奋的是2015年引力波的发现，这是该理论的一个关键预测。我们探测时空涟漪的能力从根本上改变了我们对宇宙的了解。虽然在大型强子对撞机上有一些关于新物理学的诱人迹象，但到目前为止，标准模型和广义相对论已经通过了我们能提出的每一个实验测试，而且往往非常准确。我们的研究旨在深入了解这些理论，并解决与观测有关的突出问题。我们正在学习的一些谜题如下。有大量证据表明宇宙中存在暗物质——一种超出标准模型的额外粒子。还有暗能量的证据，暗能量是一种神秘的能量场，它加速了宇宙的膨胀，而且完全不像粒子。宇宙包含的物质比反物质多得多吗？我们知道，一些超越标准引力模型的新物理学必须发生在宇宙之初，以建立我们所居住的宇宙的初始条件。更根本的是，量子理论和广义相对论不能很好地相互配合，在极端情况下，比如在宇宙的开始和黑洞中，会导致不一致。正是这些问题，我们希望用这笔资金来研究。为了找出标准模型之外的东西以及暗物质是什么，我们在粒子对撞机、地下探测器和太空中进行观测。我们可以检查在大型强子对撞机上能观察到什么，不能观察到什么，暗物质在太空星系中做什么，我们越来越多地使用引力波来窥探早期宇宙，比过去更深入。为了调和量子物理和引力，我们研究弦理论和它的许多化身。在基本层面上，弦理论用扩展对象——弦——取代了粒子和量子场。由此产生的理论适应了量子物理学和引力，并揭示了许多新的特征。一个特别的例子是“全息”理论，其中引力提供了量子场论的另一种描述，而不是需要调和的矛盾。我们在不同维度的时空和其中的物体（从粒子到黑洞）中探索大量的理论。对所有可能的物理理论了解得越多，我们就越能理解支配我们宇宙的定律。粗略地说，数学系的理论小组主要研究弦理论、黑洞、量子场论和引力的抽象性质，而物理系的理论小组主要研究粒子物理现象学、暗物质、早期宇宙以及引力与粒子物理的关系。

Our research focuses on theoretical physics and the quest for the ultimate laws governing the Universe we inhabit and everything that we see around us. There are two sides to the kind of theoretical physics we research - quantum physics and gravity. Quantum physics, particularly quantum field theory, describes particles and the forces like those that make up regular matter as well as ones that can only be detected at particle experiments, like the Large Hadron Collider at CERN. The development of quantum field theory in conjunction with experiments have led to the creation of the Standard Model of particle physics over the past century. This hugely successful theory received its final confirmation in 2012 with the discovery of the Higgs boson. Gravity, as first formulated by Newton and then in more detail by Einstein's General Relativity describes the motion of celestial bodies and the expansion of the Universe as being due to the curvature of space-time. There have been multiple observations over the years in agreement with Einstein's theory. One of the most exciting was the discovery in 2015 of gravitational waves, a key prediction of the theory. Our ability to detect these ripples of space-time has fundamentally changed what we can learn about the Universe. While there are some tantalising indications about new physics at the LHC, so far the Standard Model and General Relativity have passed every experimental test we can throw at them, often to amazing accuracy. Our research aims at gaining deeper insights into those theories and resolving outstanding questions in the relation to observations. Some of the puzzles we are studying are as follows. There is plenty of evidence for dark matter in the Universe - an additional particle beyond those in with the standard model. There is also evidence for dark energy, a mysterious energy field which accelerates the Universe's expansion and doesn't behave like a particle at all. And does the Universe contain so much more matter than anti-matter. We know that some new physics beyond just the Standard model with gravity had to take place at the very start of the Universe to set up the initial conditions of the Universe we inhabit. More fundamentally, quantum theory and general relativity don't play well with each other and lead to inconsistencies in extreme situations like at the beginning of the Universe and in black holes. It is precisely these questions that we hope to research with this grant. In order to find out what lies beyond the standard model and what the dark matter is we use observations at particle colliders, underground detectors and in space. We can examine what can and cannot be observed at the Large Hadron collider, what dark matter is doing inside galaxies in space and increasingly we are using gravitational waves to peer deeper into the Early Universe than we have been able to in the past. To reconcile quantum physics and gravity, we study string theory and its many avatars. At a basic level, string theory replaces particles and quantum fields with extended objects - the strings. The resulting theory accommodates both quantum physics and gravity and reveals many new features. One particular example are "holographic" theories where gravity provides an alternative description to quantum field theory, rather than a contradiction that needs to be reconciled. We explore a multitude of theories in varying dimensions of space-time and the objects within them, from particles to black holes. The more learn of all possible physical theories, the better we will understand the laws governing our Universe. Roughly speaking, the Theory Group in the Maths Department works more closely on string theory, black holes, and abstract properties of quantum field theory and gravity while the Theory Group in the Physics Department works on particle physics phenomenology, dark matter, the early Universe and the relation of gravity to particle physics.