# Quasi-Local Mass and Angular Momentum in General Relativity

R. Penrose

## Abstract

A new approach to defining energy-momentum and angular momentum in general relativity is presented which avoids some of the difficulties of previous definitions and which can be applied quasi-locally. It depends on the construction of a twistor space T$^\alpha$(S) associated with any spacelike topological 2-sphere S. Though several problems of interpretation remain to be solved, the new definition works well at T$^+$, reproducing the Bondimass-momentum as four of the ten precisely determined quantities at each cut of T$^+$. The remaining six quantities provide a definition of angular momentum which appears to be new.