2 research outputs found
The Spectrum Of Periodic Point Perturbations And The Krein Resolvent Formula
this paper that under certain natural conditions the Krein formula works for the case of point perturbations of elliptic operators on a manifold, too. With the help of this formula we prove that the gaps of a periodic point perturbation of such an operator are labelled by the elements of the K 0 -group of an appropriate