A relativistic QFT description for the interaction of a spin with a magnetic field*

We present a derivation of a spin interacting with a magnetic field (the Zeeman effect) for a hydrogen-like atom from a fully relativistic quantum field theory. We then repeat the derivation starting from a quantum field theory in curved space to compute corrections to the Zeeman Hamiltonian that are leading order in curvature. Applications to test quantum field theory on experimental platforms are discussed.