Jonas, Peter2022-05-112022-05-112003-01-212197-8085https://depositonce.tu-berlin.de/handle/11303/16916http://dx.doi.org/10.14279/depositonce-15694For selfadjoint operators in Krein spaces the notions of spectral points of positive and negative type are basic in the spectral and perturbation theory of these operators. The aim of this paper is to give different characterizations of these sign types of spectral points. Moreover a local variant of definitizability is characterized in various ways.en510 Mathematikselfadjoint and unitary operators in Krein spacesspectral points of positive and negative typespectral functiondefinitizable operatorsselfadjoint linear relationsResearch Paper