In a large class of scalar-tensor theories that are potential candidates for dark energy, a non-minimal coupling between the scalar and the photon is possible. The presence of such an interaction grants us the exciting prospect of directly observing dark sector phenomenology in the electromagnetic spectrum. This paper investigates the behavior of one-electron atoms in this class of modified gravity models, exploring their viability as probes of deviations from general relativity in both laboratory and astrophysical settings. Building heavily on earlier studies, our main contribution is threefold: a thorough analysis finds additional fine structure corrections previously unaccounted for, which now predict a contribution to the Lamb shift larger by nearly four orders of magnitude. Secondly, we include the effects of the nuclear magnetic moment, allowing for the study of hyperfine structure and the 21 cm line, which hitherto have been unexplored in this context. Finally, we also examine how a background scalar leads to equivalence principle violations.
L. Wong and A. Davis
Fri, 17 Mar 17
Comments: 10 pages, 2 figures. Submitted to PRD