Semiclassical stochastic radiation theory

Abstract

The basic concept of classical, stochastic electrodynamics is the assumption that there exists a classical, fluctuating, electromagnetic ground-state radiation, even at absolute zero of temperature, with energy density $(\frac{1}{2})\ensuremath{\hbar}\ensuremath{\omega}$ per mode. This ground-state radiation is incorporated into the semiclassical radiation theory in which particle systems are quantized and radiation is a classical field. It is shown that the ground-state radiation removes the difficulties associated with spontaneous emission, and that all radiation processes can be treated by one single perturbation scheme which closely resembles that of quantum electrodynamics. The transition probabilities for various first- and second-order radiation processes and the Lamb shift for energy levels are calculated in agreement with the results of quantum electrodynamics. Small deviations from the latter are found only in two processes which are probably inobservable in principle. Processes in which ground-state radiation is spontaneously absorbed by an atom have to be excluded by postulate. However, it is suggested that radiation-reaction effects of the type introduced by Crisp and Jaynes could provide a mechanism for the exclusion of spontaneous absorption.