  Electromagnetic superradiant field coherence exists in a condensed matter
system if the electromagnetic field oscillators undergo a mean displacement.
Transitions into thermal states with ordered superradiant phases have been
shown to theoretically exist in Dicke-Preparata models. The theoretical
validity of these models for condensed matter has been called into question due
to non-relativistic diamagnetic terms in the electronic Hamiltonian. The
microscopic bases of Dicke-Preparata thermal superradiance for realistic
macroscopic systems are explored in this work. The impossibility of diaelectric
correlations in condensed matter systems (via the Landau-Lifshitz theorem)
provides a strong theoretical basis for understanding the physical reality of
condensed matter thermodynamic superradiant phases.
