  We solve for the exact atom-field eigenstates of a single atom in a three
dimensional spherical cavity, by mapping the problem onto the anisotropic Kondo
model. The spectrum has a rich bound state structure in comparison with models
where the rotating wave approximation is made. It is shown how to obtain the
Jaynes-Cummings model states in the limit of weak coupling. Non-perturbative
Lamb shifts and decay rates are computed. The massive Kondo model is introduced
to model light localization in the form of photon-atom bound states in photonic
crystals.
