Quantum classical correspondence in nonrelativistic electrodynamics

A form of classical electrodynamic field exists which gives exact agreement with the operator field of quantum electrodynamics (QED) for the Lamb shif t of a harmonically bound point electron. Here it is pointed out that this form of classical theory, with its physically acceptable interpretation, is the result of an unconventional resolution of a mathematically ambiguous t erm in classical field theory. Finally, a quantum classical correspondence principle is shown to exist in the sense that the classical field and expec tation value of the QED operator field are identical, if retardation is neg lected in the latter. (C) 1999 John Wiley & Sons, Inc.