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 delta-function potentials) is calculated within QED perturbation theory. It is found to be of order ct like the known radiative correction for ideally reflecting miners 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(alpha(2)) 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. [S0031-9007(98)07449-3].