Time evolution in string theory

爱因斯坦的广义相对论描述了大物体之间的引力，例如地球和太阳之间的吸引力，将银河系保持在一起的力量以及自大爆炸以来决定宇宙膨胀速度的力量。这是一个精确的理论，它的预言已经在实验和观察中得到了检验。量子力学是关于小的理论：原子，以及原子的组成部分。 它支配着半导体、化学反应和基本粒子的行为，从日常的电子到奇异的顶夸克。 这个理论与实验以前所未有的精确度相吻合。这两种理论似乎没有什么共同之处，然而，对某些对象和现象的研究需要我们同时使用这两种理论。 这包括试图了解黑洞的内部，例如被认为存在于我们银河系中心的黑洞。 另一个例子是大爆炸后的瞬间，当时我们刚刚诞生的宇宙非常小，密度和热量。 弦理论是我们最好的候选框架，在这个框架中，这两个理论可以结合在一起。 在过去的三十年里，弦理论在我们对引力和量子力学之间相互作用的理解上取得了巨大的进步。 实验和观测继续挑战这个理论;最近的一次挑战是宇宙学通过测量一个正的宇宙学常数提出的，还没有得到回答。在我的工作中，我专注于那些我认为在回答这个挑战时必不可少的问题：解决弦理论中时间演化的方法。 我的工作的影响范围从整个宇宙的演化问题到黑洞如何衰变的问题。

Einstein's theory of general relativity describes gravitational forces between large objects, forces such as the attraction between the Earth and the Sun, those holding the Milky Way galaxy together and those forces determining the rate of expansion of the Universe since the Big Bang. It is an accurate theory and its predictions have been tested in experiment and observation. Quantum Mechanics is the theory of the small: the atom, as well as the atom's constituents.  It governs the behaviour of semiconductors, of chemical reactions and of elementary particles, from the every-day electrons to the exotic top quark.  The theory agrees with experiments with an unprecedented accuracy. These two theories seem to have little in common; however, the study of some objects and phenomena requires us to use of both of them.  This includes attempts to understand the interior of a black hole, such as the one believed to exists at the center of our Galaxy.  Another example is the split-second after the Big Bang, when our just-born Universe was incredibly small, dense and hot.  String theory is our best candidate for a framework in which these two theories can be brought together.  In the last three decades, string theory has made great advances in our understanding of the interplay between Gravity and Quantum Mechanics.  Experiment and observations continue to challenge the theory; the most recent such challenge, issued by Cosmology through the measurement of a positive cosmological constant, has yet to be answered. In my work, I focus on those problems I believe are going to be essential in answering this challenge: the methods for addressing time evolution in String theory.  The implications of my work range from the problems of evolution of the Universe as a whole to the questions of how black holes decay.