Research in General Relativity and Quantum Gravity

WPCP 2 B V P Z Courier 10cpi 2 x x x, x @ 8；X @ BOND - HP Laserjet II HPLASERJ。PRS x @, t 0# BmX @ 2 N (#| x 3 ' 3 ‘ ’标准3 ' 3 ‘ ’标准= rJet系列II Y (WPCN 2 B V P Z Courier 10cpi 2 x x x, x @ 8；X @ BOND - HP Laserjet II HPLASERJ。这个项目将进行“量子引力”的研究，这是一个重要的问题，即寻找一个理论，在这个理论中，引力场的行为是以量子随机性而不是经典爱因斯坦理论的确定性进化为特征的。人们知道，这种随机性对于一致性是必要的，因为已知的物质的不可预测性（例如，发生在原子内部的量子跃迁）必然会在物质产生的引力场中引起相应的不可预测性。当量子引力理论被发现时，人们可能会期望理解落入黑洞的物体发生了什么，并理解是什么使宇宙“大爆炸”采取了它所做的形式。索尔金教授将采用的方法是基于时空具有“原子”结构的假设，即技术上所谓的因果集。在这一理论发展的当前阶段，理解时空“原子”如何相互作用的一个中心问题是，了解哪种相互作用可以避免产生远距离作用的印象（这将与既定的物理定律相冲突）。索尔金教授将利用计算机模拟电磁场在因果集上的传播来研究这个问题。这项工作的进展将是朝着使用费曼历史和方法全面制定因果集动力学迈出的重要一步。它还可能提供一种新的方法，可以应用于计算机模拟其他重要的物理问题，比如预测质子等基本粒子的质量。＊＊＊

WPCP 2 B V P Z Courier 10cpi 2 x x x , x @ 8 ; X @ BOND - HP Laserjet II HPLASERJ.PRS x @ , t 0# BmX @ 2 N ( #| x 3 ' 3 ' Standard 3 ' 3 ' Standard = rJet Series II Y ( WPCN 2 B V P Z Courier 10cpi 2 x x x , x @ 8 ; X @ BOND - HP Laserjet II HPLASERJ.PRS x @ , t 0# BmX @ 2 L #| x 9307570 Sorkin This project will pursue research in "quantum gravity", which is the important problem of finding a theory in which the behavior of the gravitational field is characterized by a quantum randomness instead of by the deterministic evolution of the classical Einstein theory. One knows such randomness is necessary for consistency, since the known unpredictability of matter (for example, the quantum jumps which occur within atoms) must necessarily give rise to a corresponding unpredictability in the gravitational fields produced by the matter. When a theory of quantum gravity is found one may expect to understand what happens to objects which fall into black holes, and to understand what made the cosmological "big bang" take the form that it did. The approach Prof. Sorkin will follow is based on the hypothesis that spacetime has an "atomic" structure, being what technically is called a causal set. At the current stage of development of this theory a central question in understanding how the spacetime "atoms" interact with each other, is that of l earning which sort of interaction can avoid producing the impression of action at a distance (which would conflict with established physical laws). Prof. Sorkin will study this question using computer simulations of fields like the electromagnetic field propagating on a causal set. Progress in this effort will be a significant step toward a full formulation of causal set dynamics using Feynman's sum over histories method. It might also provide a novel method which one could apply to computer simulations of other problems of physical importance, such as predicting the masses of e lementary particles like the proton. ***