ELECTROMAGNETIC WAVE EQUATION IN DIFFERENTIAL-FORM REPRESENTATION

Differential-form formalism has been often applied, in stead of the more commonplace Gibbsian vector calculus, to express the basic electromagnetic equations in simple and elegant form. However, representing higher-order equations has met with unexpected difficulties, in particular, when dealing with general linear electromagnetic media. In the present study, wave equations involving scalar operators of the fourth order are derived for the electromagnetic two-form and the potential one-form, for the general linear bi-anisotropic medium. This generalizes previous coordinatefree approaches valid for certain special classes of media. The analysis is based on some multivector and dyadic identities derived in the Appendix.