Quantum theory of radiative transfer

Abstract

Stemming from the classic work of Planck, classical radiative transfer theory works with pencils of light rays streaming in straight lines in any homogeneous medium. But light is described by Maxwell's equations in classical and quantum electrodynamics, and so we need to find a bundle of rays equivalent to the electromagnetic waves. In this paper we realize such a pencils of light rays. Their properties and the equations obeyed by the ray density function are deduced. We need to generalize radiative transfer theory for this purpose appropriately. For homogeneous statistical wave fields radiative transfer theory obtains rigorously. Particular attention is paid to the polarization properties of light rays. These concepts have some relation with the phase-space picture of quantum mechanics. Also, other general questions including possible further developments are discussed.