Applied Mathematics and Optimization, Vol.31, No.2, 177-187, 1995
On a Generalization of the Kalman-Yakubovic Lemma
In this paper we generalize the Kalman-Yakubovic lemma to infinite dimensions - or, more precisely, to semigroups of operators over a Hilbert space. The proof differs substantially from the finite-dimensional version and is based on the Paley-Wiener-Helson-Lowdenslager factorization theorem.