Browsing NTNU Open by Author "Nichols, Roger"
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Dirichlet-to-Neumann maps, abstract Weyl–Titchmarsh M-functions, and a generalized index of unbounded meromorphic operator-valued functions
Behrndt, Jussi; Gesztesy, Fritz; Holden, Helge; Nichols, Roger (Journal article; Peer reviewed, 2016)We introduce a generalized index for certain meromorphic, unbounded, operator-valued functions. The class of functions is chosen such that energy parameter dependent Dirichlet-to-Neumann maps associated to uniformly elliptic ... -
On the index of meromorphic operator-valued functions and some applications
Berndt, Jussi; Gesztesy, Fritz; Holden, Helge; Nichols, Roger (Chapter, 2017)We revisit and connect several notions of algebraic multiplicities of zeros of analytic operator-valued functions and discuss the concept of the index of meromorphic operator-valued functions in complex, separable Hilbert ...