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13. Commutative Algebra

This volume studies commutative rings, ideals, modules, and their structural properties.

This volume studies commutative rings, ideals, modules, and their structural properties. It forms the algebraic foundation for algebraic geometry and number theory.

Part I. Rings and Ideals

Chapter 1. Commutative Rings

1.1 Definitions and examples 1.2 Ring homomorphisms 1.3 Subrings and quotient rings 1.4 Units and zero divisors 1.5 Basic constructions

Chapter 2. Ideals

2.1 Definition and examples 2.2 Prime and maximal ideals 2.3 Operations on ideals 2.4 Ideal quotient and radical 2.5 Correspondence theorems

Chapter 3. Ring Constructions

3.1 Polynomial rings 3.2 Localization 3.3 Product rings 3.4 Extension and contraction 3.5 Examples

Part II. Noetherian Rings

Chapter 4. Chain Conditions

4.1 Ascending chain condition 4.2 Noetherian rings 4.3 Finitely generated ideals 4.4 Hilbert basis theorem 4.5 Applications

Chapter 5. Modules over Rings

5.1 Definitions and examples 5.2 Submodules and quotient modules 5.3 Homomorphisms 5.4 Exact sequences 5.5 Free and projective modules

Chapter 6. Primary Decomposition

6.1 Primary ideals 6.2 Decomposition theorems 6.3 Associated primes 6.4 Uniqueness properties 6.5 Applications

Part III. Dimension Theory

Chapter 7. Krull Dimension

7.1 Chains of prime ideals 7.2 Definition of dimension 7.3 Examples 7.4 Dimension of polynomial rings 7.5 Applications

Chapter 8. Integral Extensions

8.1 Integral elements 8.2 Integral closure 8.3 Going-up and going-down 8.4 Normal domains 8.5 Applications

Chapter 9. Valuation Theory

9.1 Valuation rings 9.2 Discrete valuations 9.3 Valuation ideals 9.4 Completions 9.5 Applications

Part IV. Local Algebra

Chapter 10. Local Rings

10.1 Definition and examples 10.2 Maximal ideals 10.3 Localization revisited 10.4 Residue fields 10.5 Applications

Chapter 11. Nakayama’s Lemma

11.1 Statement and proof 11.2 Consequences 11.3 Applications to modules 11.4 Generators and relations 11.5 Structural insights

Chapter 12. Completions

12.1 Adic topology 12.2 Completion of rings 12.3 Formal power series 12.4 Applications 12.5 Examples

Part V. Homological Methods

Chapter 13. Exact Sequences

13.1 Short and long exact sequences 13.2 Diagram chasing 13.3 Snake lemma 13.4 Five lemma 13.5 Applications

Chapter 14. Derived Functors

14.1 Tor functor 14.2 Ext functor 14.3 Projective and injective resolutions 14.4 Homological dimension 14.5 Applications

Chapter 15. Depth and Regularity

15.1 Regular sequences 15.2 Depth of modules 15.3 Cohen–Macaulay rings 15.4 Regular local rings 15.5 Applications

Part VI. Advanced Ring Theory

Chapter 16. Integral Domains

16.1 Unique factorization domains 16.2 Principal ideal domains 16.3 Dedekind domains 16.4 Class groups 16.5 Applications

Chapter 17. Completion and Formal Methods

17.1 Formal schemes (overview) 17.2 Adic rings 17.3 Flatness 17.4 Completion techniques 17.5 Applications

Chapter 18. Flatness and Tensor Products

18.1 Tensor products 18.2 Flat modules 18.3 Faithful flatness 18.4 Base change 18.5 Applications

Part VII. Connections and Applications

Chapter 19. Algebraic Geometry Interface

19.1 Coordinate rings 19.2 Spec of a ring 19.3 Zariski topology 19.4 Sheaf perspective (overview) 19.5 Applications

Chapter 20. Number Theory Interface

20.1 Rings of integers 20.2 Localization in number theory 20.3 Valuations and primes 20.4 Ideal factorization 20.5 Applications

Chapter 21. Computational Commutative Algebra

21.1 Gröbner bases 21.2 Buchberger algorithm 21.3 Polynomial ideals 21.4 Computational complexity 21.5 Software tools

Part VIII. Research Directions

Chapter 22. Advanced Topics

22.1 Tight closure (overview) 22.2 Homological conjectures 22.3 Singularities 22.4 Derived algebraic geometry (overview) 22.5 Emerging areas

Chapter 23. Open Problems

23.1 Dimension theory questions 23.2 Homological bounds 23.3 Classification problems 23.4 Computational challenges 23.5 Future directions

Chapter 24. Historical and Conceptual Notes

24.1 Development of commutative algebra 24.2 Key contributors 24.3 Evolution of methods 24.4 Cross-disciplinary impact 24.5 Summary

Appendix

A. Common identities and lemmas B. Standard examples reference C. Proof techniques checklist D. Algorithm templates E. Cross-reference to other MSC branches

This volume provides the algebraic core used in geometry and number theory. It emphasizes structure, local behavior, and homological methods.