It is hard to learn how gravity and electromagnetism couple

Yi Zen Chu, David M. Jacobs, Yifung Ng, Glenn D. Starkman

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We construct the most general effective Lagrangian coupling gravity and electromagnetism up to mass dimension 6 by enumerating all possible nonminimal coupling terms respecting both diffeomorphism and gauge invariance. In all, there are only two unique terms after field redefinitions: one is known to arise from loop effects in QED, while the other is a parity-violating term which may be generated by weak interactions within the standard model of particle physics. We show that neither the cosmological propagation of light nor, contrary to earlier claims, solar system tests of general relativity are useful probes of these terms. These nonminimal couplings of gravity and electromagnetism may remain a mystery for the foreseeable future.

Original languageEnglish
Article number064022
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number6
StatePublished - 16 Sep 2010


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