The classicallossless inverse scattering (LIS) problem of network theory is to find all possible representations of a given Schur function s(z) (i. e. , a function which is analytic and contractive in the open unit disc D) in terms of an appropriately restricted class of linear fractional transformations. These linear fractional transformations corre- spond to lossless, causal, time-invariant two port networks and from this point of view, s(z) may be interpreted as the input transfer function of such a network with a suitable load. More precisely, the sought for representation is of the form...

These papers from the Workshop on Operator Theory and Complex Analysis review advances in operator theory and complex analysis, and their interplay in applications to mathematical system theory and control. Special attention is paid to different extension and interpolation problems for matrix and operator valued functions. Other topics include: operator inequalities and operator means; matrix completion problems; operators in spaces with indefinite scalar products and non-selfadjoint operators; and scattering and inverse spectral problems. The book should be useful to both pure and applied...

This careful selection of participant contributions reflects the focus of the 14th International Conference on Operator Theory, held in Timisoara (Romania) in June 1992, centring on the problems of extensions of operators and their connections with interpolation of analytic functions and with the spectral theory of differential operators. Other topics concern operator inequalities, spectral theory in general spaces and operator theory in Krein spaces.

This volume is dedicated to Tsuyoshi Ando, a- foremost expert in operator theory, matrix theory, complex analysis, and their applications, on the occasion of his 60th birthday. The book opens with his biography and list of publications. It contains a selection of papers covering a broad spectrum of topics ranging from abstract operator theory to various concrete problems and applications. The majority of the papers deal with topics in modern operator theory and its applications. This volume also contains papers on interpolation and completion problems, factorisation problems and problems...

This - book offers a panoptic view of operator theory. It treats a variety of classes of linear operators which illustrate the richness of the theory, both in its theoretical developments and its applications. For each of the classes various differential and integral operators motivate or illustrate the main results. The topics have been updated and enhanced by new developments, many of which appear here for the first time. Interconnections appear frequently and unexpectedly. This second volume consists of five parts: triangular representations, classes of Toeplitz operators, contractive...

This volume consists of eight papers on new advances in interpolation theory for matrix functions and completion theory for matrices and operators. Much emphasis is placed on different interpolation and completion problems when the interpolant is estimated in two different norms . The book also focuses on the study of the spectra of different completions of 2 x 2 block matrices when originally all entries are specified except the lower left corner. A third theme concerns two-sided tangential interpolation problems for real rational matrix functions, and also for the time varying case. A...

native settlement, in 1950 he graduated - as an extramural studen- from Groznyi Teachers College and in 1957 from Rostov University. He taught mathematics in Novocherkask Polytechnic Institute and its branch in the town of Shachty. That was when his mathematical talent blossomed and he obtained the main results given in the present monograph. In 1969 N. V. Govorov received the degree of Doctor of Mathematics and the aca- demic rank of a Professor. From 1970 until his tragic death on 24 April 1981, N. V. Govorov worked as Head of the Department of Mathematical Anal- ysis of Kuban' University...

CHAPTER 1 - OPERATORS IN FINITE-DIMENSIONAL NORMED SPACES 1 l. Norms of vectors, linear functionals, and linear operators. 1 2. Survey of spectral theory 14 3. Spectral radius . 17 4. One-parameter groups and semigroups of operators. 25 Appendix. Conditioning in general computational problems 28 CHAPTER 2 - SPECTRAL PROPERTIES OF CONTRACTIONS 33 l. Contractive operators and isometries. 33 2. Stability theorems. 46 3. One-parameter semigroups of contractions and groups of isometries. 48 4. The boundary spectrum of extremal contractions. 52 5. Extreme points of the unit ball in the space of...