The Dipole Coupling of Atoms and Light in Gravitational Fields

TL;DR

This paper derives the form of the dipole coupling between atoms and electromagnetic fields in a weak gravitational field, showing it remains consistent with flat space-time when expressed properly, and discusses its relation to minimal coupling.

Contribution

It provides a derivation of the dipole coupling in gravitational fields and clarifies its relation to minimal coupling, extending understanding to curved space-time.

Findings

Dipole coupling form remains unchanged in weak gravitational fields when using proper time.

The relation between minimal and dipole coupling is clarified.

Coupling expressions are consistent with flat space-time results in the appropriate limit.

Abstract

The dipole coupling term between a system of N particles with total charge zero and the electromagnetic field is derived in the presence of a weak gravitational field. It is shown that the form of the coupling remains the same as in flat space-time if it is written with respect to the proper time of the observer and to the measurable field components. Some remarks concerning the connection between the minimal and the dipole coupling are given.