W. Scharlau – författare

This book arose from a course of lectures given by the first author during the winter term 1977/1978 at the University of Münster (West Germany). The course was primarily addressed to future high school teachers of mathematics; it was not meant as a systematic introduction to number theory but rather as a historically motivated invitation to the subject, designed to interest the audience in number-theoretical questions and developments. This is also the objective of this book, which is certainly not meant to replace any of the existing excellent texts in number theory. Our selection of topics and examples tries to show how, in the historical development, the investigation of obvious or natural questions has led to more and more comprehensive and profound theories, how again and again, surprising connections between seemingly unrelated problems were discovered, and how the introduction of new methods and concepts led to the solution of hitherto unassailable questions. All this means that we do not present the student with polished proofs (which in turn are the fruit of a long historical development); rather, we try to show how these theorems are the necessary consequences of natural questions. Two examples might illustrate our objectives.

This book arose from a course of lectures given by the first author during the winter term 1977/1978 at the University of Münster (West Germany). The course was primarily addressed to future high school teachers of mathematics; it was not meant as a systematic introduction to number theory but rather as a historically motivated invitation to the subject, designed to interest the audience in number-theoretical questions and developments. This is also the objective of this book, which is certainly not meant to replace any of the existing excellent texts in number theory. Our selection of topics and examples tries to show how, in the historical development, the investigation of obvious or natural questions has led to more and more comprehensive and profound theories, how again and again, surprising connections between seemingly unrelated problems were discovered, and how the introduction of new methods and concepts led to the solution of hitherto unassailable questions. All this means that we do not present the student with polished proofs (which in turn are the fruit of a long historical development); rather, we try to show how these theorems are the necessary consequences of natural questions. Two examples might illustrate our objectives.

This book arose from a course of lectures given by the first author during the winter term 1977/1978 at the University of Münster (West Germany). The course was primarily addressed to future high school teachers of mathematics; it was not meant as a systematic introduction to number theory but rather as a historically motivated invitation to the subject, designed to interest the audience in number-theoretical questions and developments. This is also the objective of this book, which is certainly not meant to replace any of the existing excellent texts in number theory. Our selection of topics and examples tries to show how, in the historical development, the investigation of obvious or natural questions has led to more and more comprehensive and profound theories, how again and again, surprising connections between seemingly unrelated problems were discovered, and how the introduction of new methods and concepts led to the solution of hitherto unassailable questions. All this means that we do not present the student with polished proofs (which in turn are the fruit of a long historical development); rather, we try to show how these theorems are the necessary consequences of natural questions. Two examples might illustrate our objectives.

Felix Hausdorff gehört zu den herausragenden Mathematikern der ersten Hälfte des 20. Jahrhunderts. Eine Gesamtausgabe seiner Werke galt lange als Desideratum. Die auf 8 Bände veranschlagte Edition wird Hausdorffs gesamtes publiziertes Opus enthalten, ferner eine Reihe bemerkenswerter Stücke aus dem umfangreichen wissenschaftlichen Nachlaß. Alle Texte werden von Fachleuten auf den einzelnen Gebieten sorgfältig kommentiert; an dieser Arbeit sind mehr als 20 Mathematiker, Mathematikhistoriker, Astronomen, Philosophen und Literaturwissenschaftler aus vier Staaten beteiligt. Der vorliegende Band IV enthält Hausdorffs Arbeiten zur Analysis, Algebra und Zahlentheorie, darunter die klassischen auch heute noch vielzitierten Texte zu Hausdorff-Maß und Hausdorff-Dimension und zum Hausdorffschen Kugelparadoxon. Aus dem Nachlaß werden 19 Faszikel publiziert, ferner einige interessante Briefe.

Felix Hausdorff gehört zu den herausragenden Mathematikern der ersten Hälfte des 20. Jahrhunderts. Eine Gesamtausgabe seiner Werke galt lange als Desideratum. Die auf 8 Bände veranschlagte Edition wird Hausdorffs gesamtes publiziertes Opus enthalten, ferner eine Reihe bemerkenswerter Stücke aus dem umfangreichen wissenschaftlichen Nachlaß. Alle Texte werden von Fachleuten auf den einzelnen Gebieten sorgfältig kommentiert; an dieser Arbeit sind mehr als 20 Mathematiker, Mathematikhistoriker, Astronomen, Philosophen und Literaturwissenschaftler aus vier Staaten beteiligt. Der vorliegende Band IV enthält Hausdorffs Arbeiten zur Analysis, Algebra und Zahlentheorie, darunter die klassischen auch heute noch vielzitierten Texte zu Hausdorff-Maß und Hausdorff-Dimension und zum Hausdorffschen Kugelparadoxon. Aus dem Nachlaß werden 19 Faszikel publiziert, ferner einige interessante Briefe.

For a long time - at least from Fermat to Minkowski - the theory of quadratic forms was a part of number theory. Much of the best work of the great number theorists of the eighteenth and nineteenth century was concerned with problems about quadratic forms. On the basis of their work, Minkowski, Siegel, Hasse, Eichler and many others crea­ ted the impressive "arithmetic" theory of quadratic forms, which has been the object of the well-known books by Bachmann (1898/1923), Eichler (1952), and O''Meara (1963). Parallel to this development the ideas of abstract algebra and abstract linear algebra introduced by Dedekind, Frobenius, E. Noether and Artin led to today''s structural mathematics with its emphasis on classification problems and general structure theorems. On the basis of both - the number theory of quadratic forms and the ideas of modern algebra - Witt opened, in 1937, a new chapter in the theory of quadratic forms. His most fruitful idea was to consider not single "individual" quadratic forms but rather the entity of all forms over a fixed ground field and to construct from this an algebra­ ic object. This object - the Witt ring - then became the principal object of the entire theory. Thirty years later Pfister demonstrated the significance of this approach by his celebrated structure theorems.