Simple quantum field theory of the retarded image potential of a slowly moving charge

By using a recently developed retarded field quantization of the normal modes of a metallic slab the image potential of a slowly moving charge is calculated. It is explicitly shown that there is no contradiction between the classical and quantum result, respectively. In the quantized retarded theory the main contribution to the image potential at very large distances from the surface is provided by the volume polarition continuum and not by the two surface polaritons. Thereby, a longstanding controversy is resolved.