EFFECTIVE QED IN DIELECTRIC MEDIA

A general method, which allows to obtain an effective Hamiltonian for the QED in a dielectric medium, is developed. No unphysical limitation common to usual approaches, like the absence of dispersion, is assume d. In this paper we are interested mainly in the physical interpretati on for the effective theory. We show that the transcription from the f ull theory into the effective one is non-unitary and that it introduce s non-canonical commutation relations among field operators. This fact explains why usually a quantization procedure based on an effective c lassical theory fails.