| Preface | 5 |
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| Contents | 9 |
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| Introduction | 16 |
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| A brief history of simple groups | 16 |
| The Classification Theorem | 18 |
| Applications of the Classification Theorem | 19 |
| Remarks on the proof of the Classification Theorem | 20 |
| Prerequisites | 21 |
| Notation | 24 |
| How to read this book | 25 |
| The alternating groups | 26 |
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| Introduction | 26 |
| Permutations | 26 |
| The alternating groups | 27 |
| Transitivity | 28 |
| Primitivity | 28 |
| Group actions | 29 |
| Maximal subgroups | 29 |
| Wreath products | 30 |
| Simplicity | 31 |
| Cycle types | 31 |
| Conjugacy classes in the alternating groups | 31 |
| The alternating groups are simple | 32 |
| Outer automorphisms | 33 |
| Automorphisms of alternating groups | 33 |
| The outer automorphism of S6 | 34 |
| Subgroups of Sn | 34 |
| Intransitive subgroups | 35 |
| Transitive imprimitive subgroups | 35 |
| Primitive wreath products | 36 |
| Affine subgroups | 36 |
| Subgroups of diagonal type | 37 |
| Almost simple groups | 37 |
| The O'Nan--Scott Theorem | 38 |
| General results | 39 |
| The proof of the O'Nan--Scott Theorem | 41 |
| Covering groups | 42 |
| The Schur multiplier | 42 |
| The double covers of An and Sn | 43 |
| The triple cover of A6 | 44 |
| The triple cover of A7 | 45 |
| Coxeter groups | 46 |
| A presentation of Sn | 46 |
| Real reflection groups | 47 |
| Roots, root systems, and root lattices | 48 |
| Weyl groups | 49 |
| Further reading | 50 |
| Exercises | 50 |
| The classical groups | 55 |
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| Introduction | 55 |
| Finite fields | 56 |
| General linear groups | 57 |
| The orders of the linear groups | 58 |
| Simplicity of PSLn(q) | 59 |
| Subgroups of the linear groups | 60 |
| Outer automorphisms | 62 |
| The projective line and some exceptional isomorphisms | 64 |
| Covering groups | 67 |
| Bilinear, sesquilinear and quadratic forms | 67 |
| Definitions | 68 |
| Vectors and subspaces | 69 |
| Isometries and similarities | 70 |
| Classification of alternating bilinear forms | 70 |
| Classification of sesquilinear forms | 71 |
| Classification of symmetric bilinear forms | 71 |
| Classification of quadratic forms in characteristic 2 | 72 |
| Witt's Lemma | 73 |
| Symplectic groups | 74 |
| Symplectic transvections | 75 |
| Simplicity of PSp2m(q) | 75 |
| Subgroups of symplectic groups | 76 |
| Subspaces of a symplectic space | 77 |
| Covers and automorphisms | 78 |
| The generalised quadrangle | 78 |
| Unitary groups | 79 |
| Simplicity of unitary groups | 80 |
| Subgroups of unitary groups | 81 |
| Outer automorphisms | 82 |
| Generalised quadrangles | 82 |
| Exceptional behaviour | 83 |
| Orthogonal groups in odd characteristic | 83 |
| Determinants and spinor norms | 84 |
| Orders of orthogonal groups | 85 |
| Simplicity of Pn(q) | 86 |
| Subgroups of orthogonal groups | 88 |
| Outer automorphisms | 89 |
| Orthogonal groups in characteristic 2 | 90 |
| The quasideterminant and the structure of the groups | 90 |
| Properties of orthogonal groups in characteristic 2 | 91 |
| Clifford algebras and spin groups | 92 |
| The Clifford algebra | 93 |
| The Clifford group and the spin group | 93 |
| The spin representation | 94 |
| Maximal subgroups of classical groups | 95 |
| Tensor products | 96 |
| Extraspecial groups | 97 |
| The Aschbacher--Dynkin theorem for linear groups | 99 |
| The Aschbacher--Dynkin theorem for classical groups | 100 |
| Tensor products of spaces with forms | 101 |
| Extending the field on spaces with forms | 103 |
| Restricting the field on spaces with forms | 104 |
| Maximal subgroups of symplectic groups | 106 |
| Maximal subgroups of unitary groups | 107 |
| Maximal subgroups of orthogonal groups | 108 |
| Generic isomorphisms | 110 |
| Low-dimensional orthogonal groups | 110 |
| The Klein correspondence | 111 |
| Exceptional covers and isomorphisms | 113 |
| Isomorphisms using the Klein correspondence | 113 |
| Covering groups of PSU4(3) | 114 |
| Covering groups of PSL3(4) | 115 |
| The exceptional Weyl groups | 117 |
| Further reading | 119 |
| Exercises | 120 |
| The exceptional groups | 124 |
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| Introduction | 124 |
| The Suzuki groups | 126 |
| Motivation and definition | 126 |
| Generators for Sz(q) | 128 |
| Subgroups | 130 |
| Covers and automorphisms | 131 |
| Octonions and groups of type G2 | 131 |
| Quatern
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