A look inside Feynman's route to gravitation

TL;DR

This paper explores Feynman's unique field-theoretical approach to gravity, emphasizing quantum aspects and his contributions through lectures and unpublished work, highlighting its influence on modern quantum gravity research.

Contribution

It details Feynman's development of a quantum field theory perspective on gravity, including his methods, tools, and unpublished insights from the 1960s.

Findings

Feynman's approach links gravity to quantum field theory principles.

Introduction of concepts like ghosts and the tree theorem in gravity.

Feynman's unpublished lectures reveal additional insights into quantum gravity.

Abstract

In this contribution we report about Feynman's approach to gravitation, starting from the records of his interventions at the Chapel Hill Conference of 1957. As well known, Feynman was concerned about the relation of gravitation with the rest of physics. Probably for this reason, he promoted an unusual, field theoretical approach to general relativity, in which, after the recognition that the interaction must be mediated by the quanta of a massless spin-$2$ field, Einstein's field equations should follow from the general properties of Lorentz-invariant quantum field theory, plus self-consistency requirements. Quantum corrections would then be included by considering loop diagrams. These ideas were further developed by Feynman in his famous lectures on gravitation, delivered at Caltech in 1962-63, and in a handful of published papers, where he also introduced some field theoretical tools which were soon recognized to be of general interest, such as ghosts and the tree theorem. Some original pieces of Feynman's work on gravity are also present in a set of unpublished lectures delivered at Hughes Aircraft Company in 1966-67 and devoted primarily to astrophysics and cosmology. Some comments on the relation between Feynman's approach to gravity and his ideas on the quantum foundations of the fundamental interactions are included.