The Effective Action for a Relativistic Jaynes-Cummings Model

We describe an effective field theory for atomic lasers which reduces to the Jaynes-Cummings model in the non-relativistic, single mode limit. Our action describes a multi-mode system, with general polarizations and Lorentz invariance and can therefore be used in all contexts from the astrophysical to the laboratory. We show how to compute the effective action for this model and perform the calculation explicitly at the one loop level. Our model provides a way of analyzing a many-particle, two-state model with arbitrary boundary conditions.