Bernd Fritzsche – författare

This book is dedicated to Victor Emmanuilovich Katsnelson on the occasion of his 75th birthday and celebrates his broad mathematical interests and contributions.Victor Emmanuilovich’s mathematical career has been based mainly at the Kharkov University and the Weizmann Institute. However, it also included a one-year guest professorship at Leipzig University in 1991, which led to him establishing close research contacts with the Schur analysis group in Leipzig, a collaboration that still continues today.Reflecting these three periods in Victor Emmanuilovich's career, present and former colleagues have contributed to this book with research inspired by him and presentations on their joint work. Contributions include papers in function theory (Favorov-Golinskii, Friedland-Goldman-Yomdin, Kheifets-Yuditskii) , Schur analysis, moment problems and related topics (Boiko-Dubovoy, Dyukarev, Fritzsche-Kirstein-Mädler), extension of linear operators and linear relations (Dijksma-Langer, Hassi-de Snoo, Hassi -Wietsma) and non-commutative analysis (Ball-Bolotnikov, Cho-Jorgensen).

This book is dedicated to Victor Emmanuilovich Katsnelson on the occasion of his 75th birthday and celebrates his broad mathematical interests and contributions.Victor Emmanuilovich’s mathematical career has been based mainly at the Kharkov University and the Weizmann Institute. However, it also included a one-year guest professorship at Leipzig University in 1991, which led to him establishing close research contacts with the Schur analysis group in Leipzig, a collaboration that still continues today.Reflecting these three periods in Victor Emmanuilovich's career, present and former colleagues have contributed to this book with research inspired by him and presentations on their joint work. Contributions include papers in function theory (Favorov-Golinskii, Friedland-Goldman-Yomdin, Kheifets-Yuditskii) , Schur analysis, moment problems and related topics (Boiko-Dubovoy, Dyukarev, Fritzsche-Kirstein-Mädler), extension of linear operators and linear relations (Dijksma-Langer, Hassi-de Snoo, Hassi -Wietsma) and non-commutative analysis (Ball-Bolotnikov, Cho-Jorgensen).

This volume contains translations of six of the original papers of Moshe Livsic on the characteristic operator function, together with a collection of contributions devoted to Moshe Livsic’s theory of the characteristic operator function and its impact on the spectral analysis of non‑selfadjoint operators, a theory first introduced in the 1940s. This theory provides a framework for the spectral analysis of non-selfadjoint and non-unitary operators and has since become a cornerstone of modern operator theory. Over the past seventy‑five years, Livsic’s theory has exerted a lasting influence on analysis, complex analysis, linear systems theory, and a broad range of related topics. The volume examines how Livsic’s theory has shaped the study of pairs of commuting operators, a research direction initiated in the early 1970s with the aim of linking systems theory, non‑selfadjoint operator theory, and Riemannian geometry.The contributions collected here reflect the scope and depth of Livsic’s work at the intersection of operator theory, geometry, and systems theory. This book will be a valuable resource for researchers and advanced graduate students working in operator theory, analysis, systems theory and related areas.A number of recollections from colleagues, students and friends of Moshe Livsic are also included.

About one half of the papers in this volume are based on lectures which were pre­ sented at a conference at Leipzig University in August 1994, which was dedicated to Vladimir Petrovich Potapov. He would have been eighty years old. These have been supplemented by: (1) Historical material, based on reminiscences of former colleagues, students and associates of V.P. Potapov. (2) Translations of a number of important papers (which serve to clarify the Potapov approach to problems of interpolation and extension, as well as a number of related problems and methods) and are relatively unknown in the West. (3) Two expository papers, which have been especially written for this volume. For purposes of discussion, it is convenient to group the technical papers in this volume into six categories. We will now run through them lightly, first listing the major theme, then in parentheses the authors of the relevant papers, followed by discussion. Some supplementary references are listed at the end; OT72 which appears frequently in this volume, refers to Volume 72 in the series Operator Theory: Advances and Applications. It was dedicated to V.P. Potapov. 1. Multiplicative decompositions (Yu.P. Ginzburg; M.S. Livsic, I.V. Mikhailova; V.I. Smirnov).

About one half of the papers in this volume are based on lectures which were pre­ sented at a conference at Leipzig University in August 1994, which was dedicated to Vladimir Petrovich Potapov. He would have been eighty years old. These have been supplemented by: (1) Historical material, based on reminiscences of former colleagues, students and associates of V.P. Potapov. (2) Translations of a number of important papers (which serve to clarify the Potapov approach to problems of interpolation and extension, as well as a number of related problems and methods) and are relatively unknown in the West. (3) Two expository papers, which have been especially written for this volume. For purposes of discussion, it is convenient to group the technical papers in this volume into six categories. We will now run through them lightly, first listing the major theme, then in parentheses the authors of the relevant papers, followed by discussion. Some supplementary references are listed at the end; OT72 which appears frequently in this volume, refers to Volume 72 in the series Operator Theory: Advances and Applications. It was dedicated to V.P. Potapov. 1. Multiplicative decompositions (Yu.P. Ginzburg; M.S. Livsic, I.V. Mikhailova; V.I. Smirnov).

In diesem Monat feiern wir den 150. Geburtstag von SOPHUS LIE, einem der größten Mathematiker des vorigen Jahrhunderts. Es ist daher sehr zu begrüßen, daß der Teubner­ Verlag, einer langen Traditionslinie bei der Veröffentlichung von LIES Werken folgend, in seine Reihe "TEUBNER-ARCHIV zur Mathematik" Arbeiten von SOPHUS LIE und seinen Zeitgenossen EDuARD STUDY und FRIEDRICH ENGEL aufgenommen hat. Ausgewählt wurden Beiträge zur Theorie der Differentialinvarianten. Zum einen ist dies ein Gebiet, auf dem alle drei tätig gewesen sind und das als Ausgangspunkt großer Liescher Ideen zur Anwendung gruppentheoretischer Methoden in der Analysis betrachtet werden kann, obwohl es nur einen Ausschnitt aus LIES Schaffen darstellt. Zum anderen vermitteln die hier vorgestellten Arbeiten durch ihren kritischen Stil und durch den Streit um unterschied­ liche mathematische Auffassungen interessante Einblicke in das mathematische Geschehen jener Zeit. Neben der Würdigung dieser drei namhaften Mathematiker stellt der vorliegende Band den Ursprung der Lieschen Theorie, ihre weitere Entwicklung und spätere Ausprägung dar. Wir danken dem Teubner-Verlag und insbesondere Herrn J. WEISS für das freundliche Entgegenkommen und die gute Zusammenarbeit. Greifswald und Leipzig, Dezember 1992 GÜNTER CZICHOWSKI BERND FRITZSCHE SOPHUS LIE Ölgemälde von ERIK THEODOR WERENSKIOLD aus dem Jahre 1902; im Besitz der Universität Oslo (Katalognummer 818) Inhalt S. Lie: Über Gruppen von Transformationen, 1874. (Gesammelte Abhandlungen, Bd. 5 (1924),1-8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 S. Lie: Über Differentialinvarianten, 1884. (Gesammelte Abhandlungen, Bd. 6 (1927), 95-l38) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 . . . . . . . S.Lie: Über die Gruppe der Bewegungen und ihre Differentialinvarianten, 1893. (Gesammelte Abhandlungen, Bd. 6 (1927), 376-383) . . . . . . . . . . . . . . .

This book is devoted primarily to topics in interpolation for scalar, matrix and operator valued functions. About half the papers are based on lectures which were delivered at a conference held at Leipzig University in August 1994 to commemorate the 80th anniversary of the birth of Vladimir Petrovich Potapov. The volume also contains the English translation of several papers relatively unknown in the West, two expository papers written especially for this volume, and historical material based on reminiscences of former colleagues, students and associates of Mr. Potapov. Several examples of interpolation problems of the Nevanlinna-Pick and Caratheodory-Fejer type are included as well as moment problems and problems of integral representation in several settings.The major themes covered include applications of the Potapov method of fundamental matrix inequalities, multiplicative decompositions of J-inner matrix valued functions, the abstract interpolation problem, canonical systems of differential equations and interpolation in spaces with an indefinite metric, and this text should appeal to mathematicians specializing in pure and applied mathematics and engineers who work in systems theory and control.

Dieser Band des "TEUBNER-ARCHIVs zur Mathematik" enthält klassische ma­ thematische Arbeiten, welche im Zeitraum von 1911 bis 1935 von GusTAV HER­ GLOTZ, ISSAI SCHUR, GEORG PICK, ROLF NEVANLINNA und HERMANN WEYL verfaßt wurden und aus heutiger Sicht die Ursprünge einer mathematischen Richtung mar­ kieren, welche sich in den 80er Jahren an der Nahtstelle verschiedener mathemati­ scher Disziplinen herausbildete und nun unter der Bezeichnung "Schur-Analysis" Eingang in die mathematische Literatur gefunden hat. Hervorstechendes Merkmal der Schur-Analysis ist ihr algorithmischer Charakter, der bereits in IssAI ScHURS grundlegender Arbeit "Über Potenzreihen, die im In­ nem des Einheitskreises beschränkt sind", welche 1917 und 1918 in zwei Teilen im "Journal für die reine und angewandte Mathematik" veröffentlicht wurde, prägnant zum Ausdruck kommt. Der dort kreierte tiefsinnige Algorithmus, welcher heute nun unter dem Terminus "Schur-Algorithmus" gefaßt wird, beinhaltet alle haupt­ sächlichen Wesenszüge der Methode und trug wesentlich dazu bei, daß für diese die Begriffsbildung "Schur-Analysis" gewählt wurde. Es ist deshalb nur folgerichtig, daß die oben genannte Arbeit IssAI ScHuRs eine zentrale Stellung einnimmt.