General Relativity's energy and positivity -- a brief history

TL;DR

This paper reviews the historical development of defining energy in General Relativity and establishing its positivity, including extensions to cosmology and recent related advances.

Contribution

It provides a concise historical overview of the progress in defining and proving the positivity of energy in GR, highlighting key milestones and recent developments.

Findings

Completion of energy definition in GR after 45 years

Establishment of energy positivity took over 15 years

Extensions to cosmological models and recent offshoots discussed

Abstract

I give a brief review of the search for a proper definition of energy in General Relativity (GR), a far from trivial quest, which was only completed after four and a half decades. The equally (or perhaps more) difficult task of establishing its positivity -- it was to take another fifteen plus years -- will then be summarized. Extension to cosmological GR is included. Mention is made of some recent offshoots.