Some additional warnings on the reliability of simulators for time-harmonic electromagnetic problems involving innovative media

In this work we show, by a relatively simple modal analysis, that the class of time-harmonic electromagnetic boundary value problems for which the solution does not depend continuously on the source is large and includes problems involving well accepted models of media. In particular, the anomalies pointed out can appear, for example, in the presence of classical models of collisionless cold plasmas. The effects of this analysis on the reliability of numerical simulators are discussed.