Lagrangian Coupling of Dissipative Electrodynamic Waves with the Thermal Absorption and Emission

Electromagnetic wave dissipation is experienced in radiative absorbing-emitting processes and signal transmissions via media. The absorbed wave initiates thermal processes in the conducting medium. Conversely, thermal processes generate electromagnetic waves in the vacuum–material interface region. The two processes do not take place symmetrically, i.e., the incoming and thermalizing electromagnetic spectrum does not occur in the reverse process. The conservation of energy remains in effect, and the loop process “electromagnetic wave–thermal propagation–electromagnetic wave” is dissipative. In the Lagrangian formalism, we provide a unified description of these two interconnected processes. We point out how it involves the origin of the asymmetry.