The geometry of quantum gravity

我们对现代物理学和物理宇宙的理解建立在两块基石上：量子力学和广义相对论。量子力学使用统计概念来描述亚原子粒子的行为，以预测它们的行为。爱因斯坦的广义相对论描述了时空几何的动力学，它为天文尺度上的物理学提供了极其精确的描述。 将这两种理论统一起来是理论上的必然。将这两种理论及其根本不同的自然观统一在一个数学上一致的框架内是一个巨大的挑战，这仍然是21世纪理论物理学家面临的突出问题。它们是解决这一悬而未决问题的几种方法，其中一种主要方法称为环路量子引力，它关注的是一种与背景无关但不假定额外结构的公式，除非来自量子力学和广义相对论。这是一种纯粹的量子描述，其中时空几何从一开始就被视为量子实体，动力学是非微扰表示的。 我的很多研究都涉及理解这样一个框架如何能够导致量子引力动力学的完全一致的数学公式，以及这如何可能导致物理预测和观测。例如，该提案的要点之一是开发一个几何框架来理解量子引力的物理学，人们期望从这种类型的量子几何中对时空进行基本的非局部描述，这可能会导致相对论原理的惊人修改，这是可以测试的。 70年前，我们不可能预测我们会有展示量子力学行为的显微镜设备，或者对量子力学的理解将导致现代计算机。无法预测量子引力的研究将如何影响我们最终影响我们的社会的意志。对基本理解的永无止境的追求总是带来令人惊讶的好处。

Our understanding of modern physics and the physical universe rests on two corner-stones:quantum mechanics and general relativity. Quantum mechanics describes the behavior of subatomic particle using statistical notions to predict their behavior. Einstein theory of general relativity describes the dynamics of the spacetime geometry, it provides a extremely precise description of physics on astronomical scales. Unifying these two theories is a theoretical necessity. Unifying these two theories and their fundamentally dissimilar views of nature in one mathematically consistent framework is a formidable challenge which remains the outstanding question for theoretical physicists in the 21 st century. They are several approaches to this open question, one of the main approach called loop quantum gravity focus on a formulation which is background independent but do not assume extra structures except from quantum mechanics and general relativity. It is a purely quantum description in which the space time geometry is treated from the onset as a quantum entity and the dynamics expressed non perturbatively. Much of my research involve understanding how such a framework can lead to a fully consistent mathematical formulation of the dynamics of quantum gravity and also how this could lead to physical prediction and observations. For instance, one point of the proposal is to develop a geometrical framework to understand the physics of quantum gravity, and the fundamentally non local description of spacetime that one expect from this type of quantum geometry might lead to surprising modification of the relativity principle that could be tested. Seventy years ago it would have been impossible to predict that we could have mascroscopical devices showing up quantum mechanical behaviors or that understanding quantum mechanics will lead to modern computers. It is impossible to predict how research in quantum gravity could affect our will ultimately impact our society. The never ending quest for fundamental understanding as always led to surprising benefits.