O(α) Radiative Correction to the Casimir Energy for Penetrable Mirrors

The leading radiative correction to the Casimir energy for two parallel penetrable mirrors (realized by δ-function potentials) is calculated within QED perturbation theory. It is found to be of order α like the known radiative correction for ideally reflecting mirrors from which it differs, for a mirror distance much larger than the electron Compton wavelength, only by a monotonic, powerlike function of the frequency at which the mirrors become transparent. This shows that the O(α²) radiative correction calculated recently by Kong and Ravndal for ideally reflecting mirrors on the basis of effective field theory methods remains subleading even for the physical case of penetrable mirrors.