Stefan Müller-Stach

Inspired by recent developments in dependent type theory and infinity categories, this book presents a history of ideas around the topics of truth, proof, equality and equivalence. Besides selected ideas of Platon, Aristoteles, Leibniz, Kant, Frege and others, the results of Gödel and Tarski on incompleteness, undecidability and truth in deductive systems and their semantic models are covered. The main focus of this textbook is on dependent type theory and its recent variant homotopy type theory. Such theories contain identity types, which give a new understanding of equality, symmetry, equivalence and isomorphism in a conceptual way. The interaction of type theory and infinity category theory yields a new paradigm for a structural view on mathematics. This supports the tendencies towards formalising mathematics with the help of proof assistants. The first edition of this book was first published in German. The translation was done with the help of artificial intelligence. A subsequent human revision was done primarily in terms of content. This second edition has been completely revised and expanded to include a more detailed introduction to Homotopy Type Theory.

Motiviert durch aktuelle Entwicklungen in der abhängigen Typentheorie und bei Unendlichkategorien präsentiert dieses Buch die Ideengeschichte der Begriffe Wahrheit, Beweis, Gleichheit und Äquivalenz. Neben ausgewählten Ideen von Platon, Aristoteles, Leibniz, Kant, Frege und anderen werden Resultate von Gödel und Tarski über Unvollständigkeit, Unentscheidbarkeit und Wahrheit in deduktiven Systemen und ihren semantischen Modellen vorgestellt. Der Hauptgegenstand dieses Textes ist die abhängige Typentheorie und neuere Entwicklungen in der Homotopy Type Theory. Diese Theorien beinhalten Identitätstypen, die neue Möglichkeiten für Gleichheit, Symmetrie, Äquivalenz und Isomorphie auf konzeptuelle Weise eröffnen. Die Interaktion von Typentheorie und Unendlichkategorien ist ein neues Paradigma für eine strukturelle Sichtweise auf die Mathematik. Sie fördert auch den neuen Trend zur Formalisierung von Mathematik in Form von Beweisassistenten. Die vorliegende zweite Auflage ist vollständig durchgesehen und insbesondere zu den Themen Kategorientheorie und Homotopietypentheorie erweitert.

The two works titled "What Are and What Should the Numbers Be?" (1888) and "Continuity and Irrational Numbers" (1872) are Dedekind's contributions to the foundations of mathematics; therein, he laid the groundwork for set theory and the theory of real and natural numbers. These writings are indispensable in modern mathematics. However, Dedekind's achievements have not always been adequately acknowledged, and the content of these books is still little known to many mathematicians today. This volume contains not only the original texts but also a detailed analysis of the two writings and an interpretation in modern language, as well as a brief biography and a transcript of the famous letter to H. Keferstein. The extensive commentary offers a fascinating insight into the life and work of Dedekind's pioneering work and relates the latter to great contemporaries such as Cantor, Dirichlet, Frege, Hilbert, Kronecker, and Riemann. Researchers and students alike will find this work a valuable reference in the history of mathematics.

Inspired by recent developments in dependent type theory and infinity categories, this book presents a history of ideas around the topics of truth, proof, equality and equivalence. Besides selected ideas of Platon, Aristoteles, Leibniz, Kant, Frege and others, the results of Gödel and Tarski on incompleteness, undecidability and truth in deductive systems and their semantic models are covered. The main focus of this textbook is on dependent type theory and its recent variant homotopy type theory. Such theories contain identity types, which give a new understanding of equality, symmetry, equivalence and isomorphism in a conceptual way. The interaction of type theory and infinity category theory yields a new paradigm for a structural view on mathematics. This supports the tendencies towards formalising mathematics with the help of proof assistants. This book was first published in German. The translation was done with the help of artificial intelligence. A subsequent human revision was done primarily in terms of content.

Die beiden Bücher „Was sind und was sollen die Zahlen?“ (1888) und „Stetigkeit und Irrationale Zahlen“ (1872) sind Dedekinds Beiträge zu den Grundlagen der Mathematik; er legte darin die Grundsteine der Mengenlehre und der Theorie der reellen und natürlichen Zahlen. Diese Schriften sind aus der modernen Mathematik nicht mehr wegzudenken. Dennoch wurde die Leistung Dedekinds nicht immer entsprechend gewürdigt und der Inhalt dieser Bücher ist auch heute noch vielen Mathematikerinnen und Mathematikern wenig bekannt. Dieses Buch enthält neben den Originaltexten eine ausführliche Erklärung der beiden Schriften und eine Interpretation in moderner Sprache, sowie eine kurze Biografie und eine Abschrift des berühmten Briefs an H. Keferstein. Dadurch bietet dieses Buch einen faszinierenden Einblick in das Leben und Schaffen dieses wegweisenden Wissenschaftlers und stellt sein Werk in Beziehung zu großen Zeitgenossen wie Cantor, Dirichlet, Frege, Hilbert, Kronecker und Riemann.

Motiviert durch aktuelle Entwicklungen in der abhängigen Typentheorie und bei Unendlichkategorien präsentiert dieses Buch die Ideengeschichte der Begriffe Wahrheit, Beweis, Gleichheit und Äquivalenz. Neben ausgewählten Ideen von Platon, Aristoteles, Leibniz, Kant, Frege und anderen werden Resultate von Gödel und Tarski über Unvollständigkeit, Unentscheidbarkeit und Wahrheit in deduktiven Systemen und ihren semantischen Modellen vorgestellt. Der Hauptgegenstand dieses Textes ist die abhängige Typentheorie und neuere Entwicklungen in der Homotopy Type Theory. Diese Theorien beinhalten Identitätstypen, die neue Möglichkeiten für Gleichheit, Symmetrie, Äquivalenz und Isomorphie auf konzeptuelle Weise eröffnen. Die Interaktion von Typentheorie und Unendlichkategorien ist ein neues Paradigma für eine strukturelle Sichtweise auf die Mathematik. Sie fördert auch den neuen Trend zur Formalisierung von Mathematik in Form von Beweisassistenten.

This book casts the theory of periods of algebraic varieties in the natural setting of Madhav Nori’s abelian category of mixed motives. It develops Nori’s approach to mixed motives from scratch, thereby filling an important gap in the literature, and then explains the connection of mixed motives to periods, including a detailed account of the theory of period numbers in the sense of Kontsevich-Zagier and their structural properties. Period numbers are central to number theory and algebraic geometry, and also play an important role in other fields such as mathematical physics. There are long-standing conjectures about their transcendence properties, best understood in the language of cohomology of algebraic varieties or, more generally, motives. Readers of this book will discover that Nori’s unconditional construction of an abelian category of motives (over fields embeddable into the complex numbers) is particularly well suited for this purpose. Notably, Kontsevich's formal period algebra represents a torsor under the motivic Galois group in Nori's sense, and the period conjecture of Kontsevich and Zagier can be recast in this setting. Periods and Nori Motives is highly informative and will appeal to graduate students interested in algebraic geometry and number theory as well as researchers working in related fields. Containing relevant background material on topics such as singular cohomology, algebraic de Rham cohomology, diagram categories and rigid tensor categories, as well as many interesting examples, the overall presentation of this book is self-contained.

This up-to-date introduction to Griffiths' theory of period maps and period domains focusses on algebraic, group-theoretic and differential geometric aspects. Starting with an explanation of Griffiths' basic theory, the authors go on to introduce spectral sequences and Koszul complexes that are used to derive results about cycles on higher-dimensional algebraic varieties such as the Noether–Lefschetz theorem and Nori's theorem. They explain differential geometric methods, leading up to proofs of Arakelov-type theorems, the theorem of the fixed part and the rigidity theorem. They also use Higgs bundles and harmonic maps to prove the striking result that not all compact quotients of period domains are Kähler. This thoroughly revised second edition includes a new third part covering important recent developments, in which the group-theoretic approach to Hodge structures is explained, leading to Mumford–Tate groups and their associated domains, the Mumford–Tate varieties and generalizations of Shimura varieties.

This up-to-date introduction to Griffiths' theory of period maps and period domains focusses on algebraic, group-theoretic and differential geometric aspects. Starting with an explanation of Griffiths' basic theory, the authors go on to introduce spectral sequences and Koszul complexes that are used to derive results about cycles on higher-dimensional algebraic varieties such as the Noether–Lefschetz theorem and Nori's theorem. They explain differential geometric methods, leading up to proofs of Arakelov-type theorems, the theorem of the fixed part and the rigidity theorem. They also use Higgs bundles and harmonic maps to prove the striking result that not all compact quotients of period domains are Kähler. This thoroughly revised second edition includes a new third part covering important recent developments, in which the group-theoretic approach to Hodge structures is explained, leading to Mumford–Tate groups and their associated domains, the Mumford–Tate varieties and generalizations of Shimura varieties.

This book casts the theory of periods of algebraic varieties in the natural setting of Madhav Nori’s abelian category of mixed motives. It develops Nori’s approach to mixed motives from scratch, thereby filling an important gap in the literature, and then explains the connection of mixed motives to periods, including a detailed account of the theory of period numbers in the sense of Kontsevich-Zagier and their structural properties. Period numbers are central to number theory and algebraic geometry, and also play an important role in other fields such as mathematical physics. There are long-standing conjectures about their transcendence properties, best understood in the language of cohomology of algebraic varieties or, more generally, motives. Readers of this book will discover that Nori’s unconditional construction of an abelian category of motives (over fields embeddable into the complex numbers) is particularly well suited for this purpose. Notably, Kontsevich's formal period algebra represents a torsor under the motivic Galois group in Nori's sense, and the period conjecture of Kontsevich and Zagier can be recast in this setting. Periods and Nori Motives is highly informative and will appeal to graduate students interested in algebraic geometry and number theory as well as researchers working in related fields. Containing relevant background material on topics such as singular cohomology, algebraic de Rham cohomology, diagram categories and rigid tensor categories, as well as many interesting examples, the overall presentation of this book is self-contained.

Das Buch wendet sich an alle, die in die klassischen Themen der Zahlentheorie einsteigen wollen. Viel Wert wird auf die konkrete Berechenbarkeit bei allen Problemlösungen gelegt. So gibt es auch Abschnitte über moderne Primzahltests und Faktorisierungsalgorithmen und am Ende des Buches wird ein Weg zur Bestimmung der Klassenzahl der quadratischen Zahlkörper aufgezeigt. Im Rahmen der Bachelor-/Master-Studiengänge eignet sich das Buch als Grundlage für zwei Semester: ein Aufbaumodul in elementarer Zahlentheorie mit einem Vertiefungsmodul in algebraischer Zahlentheorie.