A Green's function formalism of energy and momentum transfer in fluctuational electrodynamics

TL;DR

This paper develops a Green's function formalism to describe energy and momentum transfer in fluctuational electrodynamics, applicable to arbitrary-shaped objects with various dielectric and magnetic properties, advancing understanding of thermal radiation and non-equilibrium effects.

Contribution

It introduces a general Green's function approach linking surface integrals of electromagnetic fields to energy and momentum transfer for complex objects.

Findings

Derived relations between non-equilibrium transfer and Green's functions.

Formulated generalized transmissivity and conductance expressions.

Confirmed reciprocity and consistency with black body radiation theory.

Abstract

Radiative energy and momentum transfer due to fluctuations of electromagnetic fields arising due to temperature difference between objects is described in terms of the cross-spectral densities of the electromagnetic fields. We derive relations between thermal non-equilibrium contributions to energy and momentum transfer and surface integrals of tangential components of the dyadic Green's functions of the vector Helmholtz equation. The expressions derived here are applicable to objects of arbitrary shapes, dielectric functions, as well as magnetic permeabilities. For the case of radiative transfer, we derive expressions for the generalized transmissivity and generalized conductance that are shown to obey reciprocity and agree with theory of black body radiative transfer in the appropriate limit.