On the relation between Dencker's polarization set and the gauge-fixing in electrodynamics
arXiv:2305.00099
Abstract
The purpose of this short review, based in part on ideas developed in an article by the author and Fagundes [3], is to emphasize that the gauge-fixing condition, necessary to eliminate the spurious degrees of freedom of the electromagnetic field, is elegantly handled by Dencker's work on the propagation of polarization sets for systems of real principal type.
Dedicated to Prof. José Abdalla Helayël-Neto on the occasion of his 70th birthday