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A colloquium on operator theory was held in Vienna, Austria, in March 2004, on the occasion of the retirement of Heinz Langer, a leading expert in operator theory and indefinite inner product spaces. The book contains fifteen refereed articles reporting on recent and original results in various areas of operator theory, all of them related with the work of Heinz Langer. The topics range from abstract spectral theory in Krein spaces to more concrete applications, such as boundary value problems, the study of orthogonal functions, or moment problems. The book closes with a historical survey paper.
List of contents
Research articles.- General Solution of the Stieltjes Truncated Matrix Moment Problem.- Q-functions of Quasi-selfadjoint Contractions.- A Class of Abstract Boundary Value Problems with Locally Definitizable Functions in the Boundary Condition.- Riesz Bases of Root Vectors of Indefinite Sturm-Liouville Problems with Eigenparameter Dependent Boundary Conditions, I.- Minimal Models for -functions.- Generalized Friedrichs Extensions Associated with Interface Conditions for Sturm-Liouville Operators.- Spectral Properties of Operator Polynomials with Nonnegative Coefficients.- Szeg? Pairs of Orthogonal Rational Matrix-valued Functions on the Unit Circle.- Singularities of Generalized Strings.- Orthogonal Polynomials on the Unit Circle with Respect to a Rational Weight Function.- Bi-dimensional Moment Problems and Regular Dilations.- Isospectral Vibrating Systems, Part 2: Structure Preserving Transformations.- A Functional Description for the Commutative WJ*-algebras of the D?+-class.- On Normal Extensions of Unbounded Operators: IV. A Matrix Construction.- Directing Mappings in Krein Spaces.- Survey Article.- The Extension Problem for Positive Definite Functions. A Short Historical Survey.
Summary
A colloquium on operator theory was held in Vienna, Austria, in March 2004, on the occasion of the retirement of Heinz Langer, a leading expert in operator theory and indefinite inner product spaces. The book contains fifteen refereed articles reporting on recent and original results in various areas of operator theory, all of them related with the work of Heinz Langer. The topics range from abstract spectral theory in Krein spaces to more concrete applications, such as boundary value problems, the study of orthogonal functions, or moment problems. The book closes with a historical survey paper.
