Research in General Relativity and Quantum Gravity

这个项目涉及量子引力-量子理论和广义相对论的统一。 主要研究者对这个问题的方法是基于因果集假设，它断言时空的深层结构是颗粒状的或“原子的”，原子（“因果集元素”）被组织成一个扩展的“家族树”，技术上称为局部有限偏序。 该项目将通过推进基本理论来进一步发展这种方法，同时将其应用于宇宙学常数等问题，最近已经证明宇宙学常数贡献了宇宙有效能量密度的大约三分之二。 该项目的主要重点将是将先前发现的经典序列增长动力学推广到量子因果集的情况。这个问题的解决方案通常被期望告诉我们最小长度尺度上的时空结构，同时，帮助回答为什么宇宙是最大尺度上的宇宙。 该项目还导致了一种新的方式来理解时间作为因果集的新元素的不断诞生。 要开发的算法和代码来实现它们不仅是有用的离散时空过程，但也有一个更普遍的适用性组合的目的，包括在信息技术中的使用。 在基础物理学中获得的知识，如本项目中研究的知识，也吸引了广大公众，并有助于培养受过教育和技术熟练的劳动力。

This project concerns quantum gravity---the unification of quantum theory and general relativity. The Principal Investigator's approach to this problem is based on the causal set hypothesis, which asserts that the deep structure of spacetime is granular or ``atomic'' with the atoms (``causal set elements'') organized into an extended ``family tree'', known technically as a locally finite partial order. The project will develop this approach further by advancing the underlying theory, while at the same time applying it to questions like that of the cosmological constant, which recently has been shown to contribute roughly two thirds of the effective energy density of the universe. A primary focus of the project will be on the development of a generalization of the classical sequential growth dynamics, found previously, to the case of a quantum causal set.A solution of this problem is generally expected to tell us about the structure of spacetime on the smallest length scales and, at the same time, to help answer questions about why the cosmos is as it is on the largest scales. The project also leads to a new way of understanding time as the continual birth of new elements of the causal set. The algorithms to be developed and the codes to implement them are not only useful in connection with discrete spacetime processes but also have a more general applicability for combinatorial purposes including uses in information technology. Knowledge obtained in fundamental physics such as that studied in this project also appeals to members of the public at large and contributes towards an educated and technically skilled labor force.