Characteristic Matrices and Spectral Properties of Evolutionary Systems
M. A. Kaashoek, Sjoerd M. Verduyn Lunel · Transactions of the American Mathematical Society · 1992
In this paper we introduce the notion of a characteristic matrix for a large class of unbounded operators and study the precise connection between characteristic matrices and spectral properties of evolutionary systems. In particular, we study so-called multiplicity theorems. Several examples will illustrate our results.