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On locally definitizable matrix functions

Azizov, Tomas; Jonas, Peter

Inst. Mathematik

For 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.