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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 Tα(S) associated with any spacelike topological 2-sphere S. Though several problems of interpretation remain to be solved, the new definition works well at I+, reproducing the Bondi-mass-momentum as four of the ten precisely determined quantities at each cut of I+. The remaining six quantities provide a definition of angular momentum which appears to be new.
Roger Penrose (1982) studied this question.