“…such a model situation is not as easily accessible. In contrast, to discuss the degeneracy situation considered in , even ϵ and σ are allowed to vanish in a region, requires more general strategies,which are beyond the current framework of assumptions, see for example the problem class discussed in . - It is also noteworthy that we do not assume that M 0 and M 1 are block‐diagonal, as in the classical anisotropic inhomogeneous media case, so general bi‐anisotropic and chiral media are covered by the same description, see , compare for example .
Remark (See‐saw regularity and initial‐value problems) - With the help of the notion of Sobolev lattices, the equation may also be read line by line. The price one has to pay is that even if for some , we only get that the solution U , and belong to the space .
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