Contents

Contents of Basic Algebra I

Preface

Preface to the First Edition

 

INTRODUCTION

       0.1   Zorn’s lemma

       0.2   Arithmetic of cardinal numbers

       0.3   Ordinal and cardinal numbers

       0.4   Sets and classes

       References

1   CATEGORIES

       1.1   Definition and examples of categories

       1.2   Some basic categorical concepts

       1.3   Functors and natural transformations

       1.4   Equivalence of categories

       1.5   Products and coproducts

       1.6   The horn functors. Representable functors

       1.7   Universals

       1.8   Adjoints

       References

2   UNIVERSAL ALGEBRA

       2.1   Ω-algebras

       2.2   Subalgebras and products

       2.3   Homomorphisms and congruences

       2.4   The lattice of congruences. Subdirect products

       2.5   Direct and inverse limits

       2.6   Ultraproducts

       2.7   Free Ω-algebras

       2.8   Varieties

       2.9   Free products of groups

        2.10   Internal characterization of varieties

       References

3   MODULES

       3.1   The categories R-mod and mod-R

       3.2   Artinian and Noetherian modules

       3.3   Schreier refinement theorem. Jordan-Hölder theorem

       3.4   The Krull-Schmidt theorem

       3.5   Completely reducible modules

       3.6   Abstract dependence relations. Invariance of dimensionality

       3.7   Tensor products of modules

       3.8   Bimodules

       3.9   Algebras and coalgebras

      3.10   Projective modules

      3.11   Injective modules. Injective hull

      3.12   Morita contexts

      3.13   The Wedderburn-Artin theorem for simple rings

      3.14   Generators and progenerators

      3.15   Equivalence of categories of modules

       References

4   BASIC STRUCTURE THEORY OF RINGS

       4.1   Primitivity and semi-primitivity

       4.2   The radical of a ring

       4.3   Density theorems

       4.4   Artinian rings

       4.5   Structure theory of algebras

       4.6   Finite dimensional central simple algebras

       4.7   The Brauer group

       4.8   Clifford algebras

       References

5   CLASSICAL REPRESENTATION THEORY OF FINITE GROUPS

       5.1   Representations and matrix representations of groups

       5.2   Complete reducibility

       5.3   Application of the representation theory of algebras

       5.4   Irreducible representations of Sn

       5.5   Characters. Orthogonality relations

       5.6   Direct products of groups. Characters of abelian groups

       5.7   Some arithmetical considerations

       5.8   Burnside’s paqb theorem

       5.9   Induced modules

      5.10   Properties of induction. Frobenius reciprocity theorem

      5.11   Further results on induced modules

      5.12   Brauer’s theorem on induced characters

      5.13   Brauer’s theorem on splitting fields

      5.14   The Schur index

      5.15   Frobenius groups

       References

6   ELEMENTS OF HOMOLOGICAL ALGEBRA WITH APPLICATIONS

       6.1   Additive and abelian categories

       6.2   Complexes and homology

       6.3   Long exact homology sequence

       6.4   Homotopy

       6.5   Resolutions

       6.6   Derived functors

       6.7   Ext

       6.8   Tor

       6.9   Cohomology of groups

      6.10   Extensions of groups

      6.11   Cohomology of algebras

      6.12   Homological dimension

      6.13   Koszul’s complex and Hilbert’s syzygy theorem

       References

7   COMMUTATIVE IDEAL THEORY: GENERAL THEORY AND NOETHERIAN RINGS

       7.1   Prime ideals. Nil radical

       7.2   Localization of rings

       7.3   Localization of modules

       7.4   Localization at the complement of a prime ideal. Local-global relations

       7.5   Prime spectrum of a commutative ring

       7.6   Integral dependence

       7.7   Integrally closed domains

       7.8   Rank of projective modules

       7.9   Projective class group

      7.10   Noetherian rings

      7.11   Commutative artinian rings

      7.12   Affine algebraic varieties. The Hilbert Nullstellensatz

      7.13   Primary decompositions

      7.14   Artin-Rees lemma. Krull intersection theorem

      7.15   Hilbert’s polynomial for a graded module

      7.16   The characteristic polynomial of a noetherian local ring

      7.17   Krull dimension

      7.18   I-adic topologies and completions

       References

8   FIELD THEORY

       8.1   Algebraic closure of a field

       8.2   The Jacobson-Bourbaki correspondence

       8.3   Finite Galois theory

       8.4   Crossed products and the Brauer group

       8.5   Cyclic algebras

       8.6   Infinite Galois theory

       8.7   Separability and normality

       8.8   Separable splitting fields

       8.9   Kummer extensions

      8.10   Rings of Witt vectors

      8.11   Abelian p-extension

      8.12   Transcendency bases

      8.13   Transcendency bases for domains. Affine algebras

      8.14   Luroth’s theorem

      8.15   Separability for arbitrary extension fields

      8.16   Derivations

      8.17   Galois theory for purely inseparable extensions of exponent one

      8.18   Tensor products of fields

      8.19   Free composites of fields

       References

9   VALUATION THEORY

       9.1   Absolute values

       9.2   The approximation theorem

       9.3   Absolute values on images and F(x)

       9.4   Completion of a field

       9.5   Finite dimensional extensions of complete fields. The archimedean case

       9.6   Valuations

       9.7   Valuation rings and places

       9.8   Extension of homomorphisms and valuations

       9.9   Determination of the absolute values of a finite dimensional extension field

      9.10   Ramification index and residue degree. Discrete valuations

      9.11   Hensel’s lemma

      9.12   Local fields

      9.13   Totally disconnected locally compact division rings

      9.14   The Brauer group of a local field

      9.15   Quadratic forms over local fields

       References

10   DEDEKIND DOMAINS

         10.1   Fractional ideals. Dedekind domains

         10.2   Characterizations of Dedekind domains

         10.3   Integral extensions of Dedekind domains

         10.4   Connections with valuation theory

         10.5   Ramified primes and the discriminant

         10.6   Finitely generated modules over a Dedekind domain

         References

11   FORMALLY REAL FIELDS

         11.1   Formally real fields

         11.2   Real closures

         11.3   Totally positive elements

         11.4   Hilbert’s seventeenth problem

         11.5   Pfister theory of quadratic forms

         11.6   Sums of squares in R(x1,…,xn), R a real closed field

         11.7   Artin-Schreier characterization of real closed fields

         References

         INDEX