  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.
