Holomorphic Operator Functions of One Variable and Applications

This is a book on holomorphic operator functions of a single variable and their - plications,whichisfocussedontherelationsbetweenlocalandglobaltheories.Itis based on methods and technics of Complex analysis of scalar and matrix functions of several variables. The applications concern: interpolation, holomorphic families of subspaces and frames, spectral theory of polynomials with operator coe?cients, holomorphic equivalence and diagonalization, and Plemelj-Muschelishvili fact- ization. The book also contains a theory of Wiener-Hopf integral equations with operator-valued kernels and a theory of in?nite Toplitz ¿ matrices with operator entries. We started to work on these topics long ago when one of us was a Ph.D. s- dent of the other in Kishinev (now Cisinau) University. Then our main interests were in problems of factorization of operator-valued functions and singular in- gral operators. Working in this area, we realized from the beginning that di?erent methods and tools from Complex analysis of several variables and their modi?- tions are very useful in obtaining results on factorization for matrix and operator functions. We have in mind di?erent methods and results concerning connections between local and global properties of holomorphic functions. The ?rst period was very fruitful and during it we obtained the basic results presented in this book.

"This is a book on holomorphic operator functions of a single variable and applications, which is focused on the relations between local and global theories. It is based on methods and technics of complex analysis of several variables.The first part of the theory starts with a straightforward generalization of some results from the basics of analysis of scalar functions of one complex variable. In the second part, which is the main part of the theory, results are obtained by methods and tools adapted from complex analysis of functions of several variables. We have in mind the theory of holomorphic cocycles (fiber bundles) with values in infinite-dimensional non-commutative groups. As a rule, these results do not appear in traditional complex analysis of one variable, not even for matrix valued cocycles. The third part consists of applications to operator theory. Here applications are presented for holomorphic families of subspaces and Plemelj-Muschelishvili factorization. The fourth part presents a generalization of the theory of cocycles to cocycles with restrictions. This part contains also applications to interpolation problems, to the problem of holomorphic equivalence and diagonalization."

Elementary properties of holomorphic functions.- Solution of and applications.- Splitting and factorization with respect to a contour.- The Rouché theorem for operator functions.- Multiplicative cocycles ( -cocycles).- Families of subspaces.- Plemelj-Muschelishvili factorization.- Wiener-Hopf operators, Toeplitz operators and factorization.- Multiplicative cocycles with restrictions ( -cocycles).- Generalized interpolation problems.- Holomorphic equivalence, linearization and diagonalization.