Testing the equivalence principle in the quantum domain

Abstract

Metric theories of gravity offer the singular beauty of endowing spacetime with a symmetric, second-rank tensor field g"" that couples universally to all non-gravitational fields. This unique operational geometry is embodied in the validity of the Einstein Equivalence Principles (EEP).

Although the empirical evidence in support of EEP has reached an impressive level of precision, it has only probed effects that are sensitive to nuclear electromagnetic interactions (i.e., the baryon/photon sector of the standard model). In this thesis we provide the theoretical framework to confront EEP with the interaction realm of quantum electrodynamics (QED).

We reformulate QED within the context of non-metric theories of gravity and calculate the main radiative corrections affecting the atomic energy levels (Lamb shift) and the gyromagnetic ratio of fermions (anomalous magnetic moment).

We find that a non-metric spacetime structure induces qualitatively new effects in the behavior of radiative corrections that leave distinctive physical signatures. Such effects allow the possibility of setting new bounds on the validity of the EEP. In fact from present experiments, we obtain the most stringent bound yet noted for the non-metric parameters related to leptonic matter.