Classification of Extremal Black Holes

广义相对论是我们研究万有引力的理论。它为我们提供了一个非常精确的大尺度宇宙模型。它最大胆的预测是黑洞的存在，这种巨大的物体形成了一个任何东西都无法逃脱的空间区域。现在人们已经接受黑洞确实存在于我们的宇宙中——这是抽象理论如何具有深远物理意义的一个显著例子。尽管它取得了成功，但GR一直抵制将其与量子力学相一致的尝试，量子力学同样擅长描述自然的基本组成部分。这种“量子引力”理论需要回答一些重大问题，比如我们的宇宙是如何形成的。幸运的是，黑洞提供了一个独特的实验室来研究这个难题——它们的引力场是如此强烈，以至于量子力学和广义相对论的效应都在起作用。我的研究重点是高维黑洞。我们都熟悉四维——一个事件有四个标签，三个代表“在哪里”，一个代表“何时”发生。但是，作为量子引力理论的主要候选理论，弦理论需要不止四个维度。在大尺度上，它降为GR，促使我们研究大于4维的黑洞。人们对四维平衡黑洞了解甚多。它们的形状像一个球的表面，它们的质量和旋转被独特地“标记”了。这些显著的特性在更高的维度中不再成立。最近发现的黑环——甜甜圈形状的黑洞——不仅证明了许多形状都是可能的，而且证明了这种唯一性已经丧失了。我工作的中心目标是对更高维度的黑洞进行分类，检查黑洞非唯一性的程度，并确定如何在量子引力中解决这个问题。为了实现这些具有挑战性的目标，我的策略是瞄准一种特殊类型的黑洞，我已经展示了它是最容易分析的。我的研究将有助于更深入地理解量子引力，并培养具有其他领域所重视的独特定量技能的学生。像大多数基础研究一样，它不太可能立即造福社会。但它可以帮助我们在基本层面上理解自然，我相信这是一个有价值的目标。

General relativity (GR) is our theory to study gravitation. It has led to a very accurate model of our Universe at large scales. Its boldest prediction is the existence of black holes, massive objects that form a region of space from which nothing can escape. It is now accepted that black holes really exist in our Universe - a striking example of how abstract theory can have profound physical significance. Despite its successes, GR has resisted attempts to make it consistent with quantum mechanics, which is equally adept at describing the basic constituents of Nature. Such a theory of `quantum gravity' is needed to answer big questions, like how our Universe formed. Luckily, black holes offer a unique laboratory to study this difficult problem - their gravitational fields are so intense that effects from both quantum mechanics and GR come into play. My research focusses on black holes in higher dimensions. We are all familiar with four dimensions - an event has four labels, three for 'where' and one for `when' it occurred. But string theory, a leading candidate for a theory of quantum gravity, requires more than four dimensions. At large scales, it reduces to GR, impelling us to investigate black holes in dimensions greater than four. Much is known about equilibrium black holes in four dimensions. They are shaped like the surface of a ball, and they are uniquely `labelled' by their mass and spin. These remarkable properties no longer hold in higher dimensions. The recent discovery of black rings - donut shaped black holes - proves not only that many shapes are possible, but that uniqueness is lost. The central goals of my work are to classify black holes in higher dimensions, examine the extent of black hole non-uniqueness, and determine how this issue is resolved within quantum gravity. To achieve these challenging objectives, my strategy is to target a special type of black hole which I have shown are simplest to analyse. My research will contribute significantly to a deeper understanding of quantum gravity, and train students with unique quantitative skills valued in other fields. Like most basic research, it is unlikely to immediately benefit society. But it could help us understand Nature at a fundamental level, which I believe is a worthwhile aim.