String Theory, Black Holes, and the Subatomic Structure of Spacetime

爱因斯坦的广义相对论描述了超重物体的物理学。它是在一个多世纪前发明的，已经成功地解释了各种实验数据。它的主要特征之一是时空结构的流畅性。量子理论描述了非常微小的事物的物理学。它是在不到一个世纪前发明的，也成功地解释了各种实验数据。它的主要特征之一是量子态空间的离散性。在更深的层面上，这两种理论的关键特征是冲突的。对于我们可以想象的大多数系统，如星系或希格斯玻色子，这不是一个令人担忧的问题，因为我们感兴趣的物体要么非常重，要么非常小。但如果我们想要理解黑洞的核心或宇宙的诞生，我们需要一个更好的理论，既能处理平滑的时空，也能处理量子跳跃。即使我们可能永远无法物理接触黑洞或大爆炸，我们仍然可以通过招募理论工具和思维实验来解剖和了解有关它们的有价值的东西。我的主要兴趣是了解量子信息落入黑洞的最终命运，并更多地了解时空的亚原子结构。为了研究这一点，我使用了弦理论，这是目前可用的最发达的量子引力框架。近年来两个相互关联的进步让我的目标变得更容易实现。第一个进展是在弦理论中发现了更高维的引力物体，称为(Mem)膜，它们与一维基本弦共存。薄膜用途广泛，可以用来建造有趣的黑洞。他们还首次从第一原理解释了黑洞的熵，这是一个类似于解体的量，它编码了在引力崩塌中黑洞可能形成的大量方式。自那以来，已经取得了很大进展，但还有更多领域有待了解。关注更细粒度的引力信息是很重要的。为黑洞的微观弦理论建模做出贡献是我研究计划的两个主题之一。第二个进展被称为全息术，这是一个令人惊讶而有力的发现，某些类型的量子引力系统可以替代地用生活在少一个维度的空间中、看起来非常不同的非引力系统来描述。这让人想起全息图，在全息图中，你只从2D全息图获得整个3D图像。全息术最初是使用弦理论发现的，但后来意识到它是一个更一般的概念。它将弦理论、粒子论、引力理论、凝聚态理论、早期宇宙宇宙论和量子信息论的各个方面联系在一起，就像理论物理的微型联合国。为发展全息术做出贡献是我研究计划的另一个主要主题。

Einstein's theory of general relativity describes the physics of very heavy things. Invented a bit over a century ago, it has successfully explained a wide variety of experimental data. One of its key features is the smoothness of the fabric of spacetime. Quantum theory describes the physics of very small things. Invented a bit under a century ago, it has also successfully explained a wide variety of experimental data. One of its key features is the discreteness of the space of quantum states. At a deep level, the key features of these two theories are in conflict. For most systems we can imagine, like galaxies or Higgs bosons, this is not a worry, because our objects of interest are either very heavy or very small. But if we want to understand the heart of a black hole or the birth of the cosmos, we need a better theory that can handle both smooth spacetime and quantum jumps. Even if we may never be able to physically touch black holes or big bangs, we can still dissect and learn valuable things about them by recruiting theoretical tools and thought experiments. My main interest is in understanding the ultimate fate of quantum information falling into black holes and knowing more about the subatomic structure of spacetime. To investigate this, I use string theory, which is currently the best developed quantum gravity framework available. Two interrelated advances in recent years have made my goals more accessible. The first advance was the discovery of higher-dimensional gravitating objects in string theory known as (mem)branes, which co-exist alongside the one-dimensional fundamental strings. Branes are versatile, and can be used to build interesting black holes. They also enabled the first explanation from first principles of the entropy of a black hole, a quantity akin to disorganization which codifies the tremendously large number of ways a black hole could be formed in gravitational collapse. Much progress has been made since then, but more territory remains to be understood. Focusing on more fine-grained gravitational information is important. Contributing to microscopic string theory modelling of black holes is one of the twin themes of my research program. The second advance, known as holography, was a surprising and powerful discovery that certain types of quantum gravity systems can be alternatively described in terms of very different-looking non-gravitational systems living in one less dimension of space. This is reminiscent of a hologram where you get the whole 3D image from only the 2D hologram. Holography was originally found using string theory, but was later realized to be a more general idea. It interconnects aspects of string theory, particle theory, gravity theory, condensed matter theory, early universe cosmology theory, and quantum information theory, like a mini United Nations of theoretical physics. Contributing to developing holography is the other main theme of my research program.