Equivalence Principle in Classical and Quantum Gravity

• Published in: Universe (Basel) Vol. 8; no. 11; p. 598
• Main Authors: Paunkovic, Nikola, Vojinovic, Marko
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-11-2022
• Subjects: Electromagnetism; equivalence principle; general relativity; General relativity (Physics); Geometry; Gravity; Partial differential equations; Quantum gravity; Quantum physics; Quantum theory; Spacetime; String theory; Theory of relativity; Portugal
• ISSN: 2218-1997; 2218-1997
• DOI: 10.3390/universe8110598

We give a general overview of various flavours of the equivalence principle in classical and quantum physics, with special emphasis on the so-called weak equivalence principle, and contrast its validity in mechanics versus field theory. We also discuss its generalisation to a theory of quantum gravity. Our analysis suggests that only the strong equivalence principle can be considered fundamental enough to be generalised to a quantum gravity context since all other flavours of equivalence principle hold only approximately already at the classical level.