Wolfgang Walter – författare

Develops the theory of initial-, boundary-, and eigenvalue problems, real and complex linear systems, asymptotic behavior and stability. Using novel approaches to many subjects, the book emphasizes differential inequalities and treats more advanced topics such as Caratheodory theory, nonlinear boundary value problems and radially symmetric elliptic problems. New proofs are given which use concepts and methods from functional analysis. Applications from mechanics, physics, and biology are included, and exercises, which range from routine to demanding, are dispersed throughout the text. Solutions for selected exercises are included at the end of the book. All required material from functional analysis is developed in the book and is accessible to students with a sound knowledge of calculus and familiarity with notions from linear algebra. This text would be an excellent choice for a course for beginning graduate or advanced undergraduate students.

Develops the theory of initial-, boundary-, and eigenvalue problems, real and complex linear systems, asymptotic behavior and stability. Using novel approaches to many subjects, the book emphasizes differential inequalities and treats more advanced topics such as Caratheodory theory, nonlinear boundary value problems and radially symmetric elliptic problems. New proofs are given which use concepts and methods from functional analysis. Applications from mechanics, physics, and biology are included, and exercises, which range from routine to demanding, are dispersed throughout the text. Solutions for selected exercises are included at the end of the book. All required material from functional analysis is developed in the book and is accessible to students with a sound knowledge of calculus and familiarity with notions from linear algebra. This text would be an excellent choice for a course for beginning graduate or advanced undergraduate students.

The sixthInternational Conference on General Inequalities was held from Dec. 9 to Dec. 15, 1990, at the Mathematisches Forschungsinstitut Oberwolfach (Black Fa­ rest, Germany). The organizing committee was composed of W.N. Everitt (Birm­ ingham), L. Losonczi (Debrecen) and W. Walter (Karlsruhe). Dr. A. Kovacec ( Coimbra) served cheerfully and efficiently as secretary of the meeting. The con­ ference was attended by 44 participants from 20 countries. Yet again the importance of inequalities in both pure and applied mathematics was made evident from the wide range of interests of the individual participants, and from the wealth of new results announced. New inequalities were presented in the usual spread of the subject areas now expected for these meetings: Classical and functional analysis, existence and boundary value problems for both ordinary and partial differential equations, with special contributions to computer science, quantum holography and error analysis. More strongly than ever, the role played by modern electronic computers was made clear in testing out and prohing into the validity and structure of certain inequalities. Here the computer acts not only for numerical calculations of great complexity, but also in symbolic manipulation of complex finite structures. Prob­ lems in inequalities which even a few years ago were intractable, now fall to solution or receive direct and positive guidance as a result of computer applications. The interface between finite and infinite structures in mathematics and the versatility of modern computers is weil developed in the subject of general inequalities.

Inequalities continue to play an essential role in mathematics. The subject is per­ haps the last field that is comprehended and used by mathematicians working in all the areas of the discipline of mathematics. Since the seminal work Inequalities (1934) of Hardy, Littlewood and P6lya mathematicians have laboured to extend and sharpen the earlier classical inequalities. New inequalities are discovered ev­ ery year, some for their intrinsic interest whilst others flow from results obtained in various branches of mathematics. So extensive are these developments that a new mathematical periodical devoted exclusively to inequalities will soon appear; this is the Journal of Inequalities and Applications, to be edited by R. P. Agar­ wal. Nowadays it is difficult to follow all these developments and because of lack of communication between different groups of specialists many results are often rediscovered several times. Surveys of the present state of the art are therefore in­ dispensable not only to mathematicians but to the scientific community at large. The study of inequalities reflects the many and various aspects of mathemat­ ics. There is on the one hand the systematic search for the basic principles and the study of inequalities for their own sake. On the other hand the subject is a source of ingenious ideas and methods that give rise to seemingly elementary but nevertheless serious and challenging problems. There are many applications in a wide variety of fields from mathematical physics to biology and economics.

Aus den Besprechungen: "Wodurch unterscheidet sich das hiermit begonnene Lehrwerk der Analysis von zahlreichen anderen ... exzellenten Werken dieser Art? ... (1) die ausführliche Berücksichtigung des Warum und Woher, der historischen Gesichtspunkte ...; (2) die Anerkennung der Existenz des Computers. Der Autor verschließt sich nicht vor der Tatsache, daß die Computermathematik (hier vor allem verstanden als numerische Mathematik) oft interessante Anwendungen der klassischen Analysis bietet. ... (3) die große Fülle von Beispielen und nicht-trivialen (aber lösbaren) Übungsaufgaben, sowie (4) der häufige Bezug zu den Anwendungen. ... Sogar die Theorie der gewöhnlichen Differentialgleichungen, vor der manche Lehrbuchautoren eine unüberwindliche Scheu zu haben scheinen, ist gut lesbar dargestellt, mit vernünftigen Anwendungen. ... kann das Buch jedem Studierenden der Mathematik wegen der Fülle des Gebotenen und wegen des geschickten didaktischen Aufbaus auf das Wärmste empfohlen werden."ZAMP

Hauptthema dieses zweiten Bandes ist die Differential- und Integralrechnung für Funktionen von mehreren Veränderlichen. Dabei wird auch das Lebesguesche Integral im Rn behandelt. Dem erfolgreichen Konzept von "Analysis 1" folgend, wird viel Wert auf historische Zusammenhänge, Ausblicke und die Entwicklung der Analysis gelegt. Zu den Besonderheiten, die über den kanonischen Stoff des zweiten Semesters hinausgehen, gehören das Morsesche und das Sardsche Lemma, die C?-Approximation von Funktionen (Mollifiers) und die Theorie der absolutstetigen Funktionen. Zahlreiche Beispiele, Übungsaufgaben und Anwendungen, z.B. aus der Physik und Astronomie, runden dieses Lehrbuch ab. Der Abschnitt "Lösungen und Lösungshinweise" wurde für die Neuauflage wesentlich erweitert, so daß die überwiegende Zahl der Aufgaben im Buch nun besprochen oder vollständig gelöst wird.

Das Hauptthema dieses zweiten Bandes ist die Differential- und Integralrechnung f}r Funktionen von mehreren Ver{nderlichen. Dabei wird auchdas Lebesguesche Integral im Rn behandelt. Dem erfolgreichen Konzept von Analysis I folgend, wird viel Wert auf historische Zusammenh{nge, Ausblicke und die Entwicklung der Analysis gelegt. Zu denBesonderheiten, die }ber den kanonischen Stoff des zweiten Semesters hinausgehen, geh|ren das Morsesche und das Sardsche Lemma, die C (unendlich)-Approximation von Funktionen (Mollifiers) und die Theorie der absolutstetigen Funktionen. Die Grundtatsachen }ber die verschiedenen Integralbegriffe werden allesamt aus S{tzen }ber den Netzlimes abgeleitet. Bei den Fourierreihen wird die klassische Theorie in Weiterf}hrung einer von Chernoff und Redheffer entwickelten Methode behandelt. Zahlreiche Beispiele, ]bungsaufgaben und Anwendungen, z.B. aus der Physik und Astronomie, runden dieses Lehrbuch ab.

In der nunmehr 7., neu bearbeiteten und erweiterten Auflage legt W. Walter sein Lehrbuch über Gewöhnliche Differentialgleichungen vor, das schon so etwas wie ein "moderner Klassiker" geworden ist. Das Buch entspricht dem aktuellen Forschungsstand. Es behandelt neben der klassischen Theorie vor allem solche Themen, die für das Studium dynamischer Systeme und des qualitativen Verhaltens gewöhnlicher Differentialgleichungen unentbehrlich sind. Ein Anhang stellt zentrale Begriffe aus Analysis und Topologie bereit. Dieses Lehrbuch bietet dem Studenten eine optimale Einführung in das Gebiet der Differentialgleichungen, die sich durch Übersichtlichkeit im Aufbau und Klarheit in der Beweisführung auszeichnet. Viele instruktive Beispiele mit Lösungen zu ausgewählten Aufgaben runden dieses Werk ab.

In 1964 the author's mono graph "Differential- und Integral-Un­ gleichungen," with the subtitle "und ihre Anwendung bei Abschätzungs­ und Eindeutigkeitsproblemen" was published. The present volume grew out of the response to the demand for an English translation of this book. In the meantime the literature on differential and integral in­ equalities increased greatly. We have tried to incorporate new results as far as possible. As a matter of fact, the Bibliography has been almost doubled in size. The most substantial additions are in the field of existence theory. In Chapter I we have included the basic theorems on Volterra integral equations in Banach space (covering the case of ordinary differential equations in Banach space). Corresponding theorems on differential inequalities have been added in Chapter II. This was done with a view to the new sections; dealing with the line method, in the chapter on parabolic differential equations. Section 35 contains an exposition of this method in connection with estimation and convergence. An existence theory for the general nonlinear parabolic equation in one space variable based on the line method is given in Section 36. This theory is considered by the author as one of the most significant recent applications of in­ equality methods. We should mention that an exposition of Krzyzanski's method for solving the Cauchy problem has also been added. The numerous requests that the new edition include a chapter on elliptic differential equations have been satisfied to some extent.

The field of inequalities is probably the last used by mathematicians in all areas of the discipline. New ones are discovered each year, and some of these come from results obtained in many branches of mathematics, and so the study of inequalities reflects the many aspects of mathematics. There are numerous applications in a variety of fields, from mathematical physics to biology and economics, and this volume not only contains the latest results, but is also a relevant reference for lecturers and researchers.