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43. Abstract Harmonic Analysis

This volume extends harmonic analysis to general locally compact groups.

This volume extends harmonic analysis to general locally compact groups. It replaces classical Fourier series and transforms with representation-theoretic and measure-theoretic frameworks.

Part I. Locally Compact Groups

Chapter 1. Topological Groups

1.1 Definitions and examples 1.2 Continuity and group operations 1.3 Subgroups and quotient groups 1.4 Compact and locally compact groups 1.5 Examples

Chapter 2. Haar Measure

2.1 Existence and uniqueness 2.2 Left and right invariance 2.3 Integration on groups 2.4 Modular function 2.5 Examples

Chapter 3. Function Spaces on Groups

3.1 Continuous functions 3.2 Lp spaces on groups 3.3 Convolution algebras 3.4 Approximate identities 3.5 Examples

Part II. Representations of Groups

Chapter 4. Unitary Representations

4.1 Definitions 4.2 Hilbert space representations 4.3 Irreducible representations 4.4 Direct sums and integrals 4.5 Examples

Chapter 5. Dual Objects

5.1 Dual group for abelian groups 5.2 Characters 5.3 Pontryagin duality 5.4 Examples 5.5 Applications

Chapter 6. Non-Abelian Representation Theory

6.1 Representations of non-abelian groups 6.2 Peter–Weyl theorem 6.3 Matrix coefficients 6.4 Applications 6.5 Examples

Part III. Fourier Analysis on Groups

Chapter 7. Fourier Transform on Groups

7.1 Definition 7.2 Properties 7.3 Inversion formula 7.4 Plancherel theorem 7.5 Examples

Chapter 8. Convolution and Algebras

8.1 Convolution operators 8.2 Group algebras 8.3 Banach algebra structure 8.4 Applications 8.5 Examples

Chapter 9. Spectral Theory

9.1 Spectra of operators 9.2 Functional calculus 9.3 Applications 9.4 Examples 9.5 Connections

Part IV. Structure of Groups

Chapter 10. Compact Groups

10.1 Structure theory 10.2 Representations 10.3 Harmonic analysis 10.4 Applications 10.5 Examples

Chapter 11. Abelian Groups

11.1 Structure theorem 11.2 Fourier analysis simplifications 11.3 Duality 11.4 Applications 11.5 Examples

Chapter 12. Non-Abelian Groups

12.1 Structural challenges 12.2 Representation decomposition 12.3 Harmonic analysis 12.4 Applications 12.5 Examples

Part V. Operator Algebras

Chapter 13. Group C*-Algebras

13.1 Definitions 13.2 Representations 13.3 Properties 13.4 Applications 13.5 Examples

Chapter 14. Von Neumann Algebras

14.1 Definitions 14.2 Factors 14.3 Representations 14.4 Applications 14.5 Examples

Chapter 15. Noncommutative Integration

15.1 Operator-valued integration 15.2 Trace and states 15.3 Applications 15.4 Examples 15.5 Connections

Part VI. Applications

Chapter 16. PDE and Analysis

16.1 Harmonic analysis methods 16.2 Differential operators 16.3 Applications 16.4 Examples 16.5 Connections

Chapter 17. Number Theory

17.1 Automorphic forms (overview) 17.2 Representation theory links 17.3 Applications 17.4 Examples 17.5 Connections

Chapter 18. Physics and Engineering

18.1 Symmetry analysis 18.2 Signal processing on groups 18.3 Quantum mechanics 18.4 Applications 18.5 Examples

Part VII. Advanced Topics

Chapter 19. Induced Representations

19.1 Definition 19.2 Mackey theory (overview) 19.3 Applications 19.4 Examples 19.5 Connections

Chapter 20. Noncommutative Harmonic Analysis

20.1 General framework 20.2 Applications 20.3 Examples 20.4 Connections 20.5 Emerging ideas

Chapter 21. Harmonic Analysis on Homogeneous Spaces

21.1 Quotient spaces 21.2 Invariant measures 21.3 Representations 21.4 Applications 21.5 Examples

Part VIII. Research Directions

Chapter 22. Advanced Topics

22.1 Representation theory developments 22.2 Noncommutative geometry 22.3 Harmonic analysis on manifolds 22.4 Modern developments 22.5 Emerging areas

Chapter 23. Open Problems

23.1 Representation classification 23.2 Spectral analysis challenges 23.3 Computational aspects 23.4 Analytical difficulties 23.5 Future directions

Chapter 24. Historical and Conceptual Notes

24.1 Development of abstract harmonic analysis 24.2 Key contributors 24.3 Evolution of ideas 24.4 Cross-disciplinary impact 24.5 Summary

Appendix

A. Standard group examples B. Key theorems summary C. Proof techniques checklist D. Operator algebra reference E. Cross-reference to other MSC branches

This volume generalizes harmonic analysis to abstract group settings. It emphasizes representation theory, operator algebras, and invariant integration.