History of MathematicsVolume 21

Essays in the Historyof Lie Groups andAlgebraic Groups

Armand Borel

American Mathematical Society

London Mathematical Society

Contents

Introduction ix

Terminology for Classical Groups and Notation xi

Photo Credits xiii

Chapter I. Overview 1§1. Lie's theory 1§2. Lie algebras 5§3. Globalizations 6

References for Chapter I 8

Chapter II. Pull Reducibility and Invariants for SL2(C) 9§1. Full reducibility, 1890-96 9§2. Averaging. The invariant theorem 11§3. Algebraic proofs of full reducibility 16§4. Appendix: More on some proofs of full reducibility 18

References for Chapter II 26

Chapter III. Hermann Weyl and Lie Groups 29§1. First contacts with Lie groups 29§2. Representations of semisimple Lie groups and Lie algebras 31§3. Impact on E. Cartan 35§4. The Peter-Weyl theorem. Harmonic analysis 37§5. Group theory and quantum mechanics 38§6. Representations and invariants of classical groups 40§7. Two later developments 44

Notes 46References for Chapter III 54

Chapter IV. Elie Cartan, Symmetric Spaces and Lie Groups 59A. Building Up the Theory 60

§1. The spaces £. Local theory 60§2. Spaces £ and semisimple groups. Global theory 64§3. An exposition of Lie group theory from the global point of view 79

B. Further Developments 80§4. Complete orthogonal systems on homogeneous spaces of compact

Lie groups 80

viii CONTENTS

§5. Differential forms and algebraic topology 84§6. Bounded symmetric domains 88

References for Chapter IV 90

Chapter V. Linear Algebraic Groups in the 19th Century 93§1. S. Lie, E. Study, and projective representations 93§2. E. Study, Gordan series and linear representations of SL3 97§3. Emile Picard 99§4. Ludwig Maurer • 102§5. Elie Cartan 114§6. Karl Carda 115

References for Chapter V 117

Chapter VI. Linear Algebraic Groups in the 20th Century 119§1. Linear algebraic groups in characteristic zero. Replicas 119§2. Groups over algebraically closed ground fields I 119§3. Groups over an algebraically closed ground field II 124§4. Rationality properties 126§5. Algebraic groups and geometry. Tits systems and Tits buildings 131§6. Abstract automorphisms 134§7. Merger 142

References for Chapter VI 144

Chapter VII. The Work of Chevalley in Lie Groups and Algebraic Groups 147§1. Lie groups, 1941-1946 147§2. Linear algebraic groups, 1943-1951 150§3. Lie groups, 1948-1955 152§4. Linear algebraic groups, 1954 155§5. Algebraic groups, 1955-1961 156

References for Chapter VII 162

Chapter VIII. Algebraic Groups and Galois Theory in trie-Work of Ellis R.Kolchin 165

§1. The Picard-Vessiot theory 165§2. Linear algebraic groups ' 169§3. Generalization of the Picard-Vessiot theory 170§4. Galois theory of strongly normal extensions 173§5. Foundational work on algebraic sets and groups 176

References for Chapter VIII 179

Name Index 181

Subject Index 183