Azizov, TomasJonas, Peter2021-12-172021-12-172005-09-082197-8085https://depositonce.tu-berlin.de/handle/11303/15557http://dx.doi.org/10.14279/depositonce-14330For a domain $\Omega$ of the extended complex plane, classes of R-symmetric piecewise meromorphic matrix functions $G$ in $\Omega \setminus \overline{R}$ are studied. If $G$ is locally definitizable in $\Omega$ or a local generalized Nevanlinna function in $\Omega$, then the same is true for the inverse of $G$. The results are applied to an abstract boundary value problem with eigenvalue parameter in the boundary condition.ru510 Mathematikgeneralized Nevanlinna matrix functionsdefinitizable matrix functionslocally definitizable matrix functionsselfadjoint operators in Krein spaceslocally definitizable operatorsResearch Paper