  The static Casimir effect concerns quantum electrodynamic induced Lamb shifts
in the mode frequencies and thermal free energies of condensed matter systems.
Sometimes, the condensed matter constitutes the boundaries of a vacuum region.
The static frequency shift effects have been calculated in the one photon loop
perturbation theory approximation. The dynamic Casimir effect concerns two
photon radiation processes arising from time dependent frequency modulations
again computed in the one photon loop approximation. Under certain conditions
the one photon loop computation may become unstable and higher order terms must
be invoked to achieve stable solutions. This stability calculation is discussed
for a simple example dynamical Casimir effect system.
