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42. Harmonic Analysis

This volume studies representation of functions via oscillatory components such as Fourier series and transforms.

This volume studies representation of functions via oscillatory components such as Fourier series and transforms. It connects analysis, PDEs, number theory, and signal processing.

Part I. Fourier Analysis on ℝ

Chapter 1. Fourier Transform

1.1 Definition 1.2 Basic properties 1.3 Inversion formula 1.4 Plancherel theorem 1.5 Examples

Chapter 2. Convolution

2.1 Definition 2.2 Properties 2.3 Convolution theorem 2.4 Approximate identities 2.5 Applications

Chapter 3. Distributions (Overview)

3.1 Generalized functions 3.2 Fourier transform of distributions 3.3 Examples 3.4 Applications 3.5 Connections

Part II. Fourier Series

Chapter 4. Fourier Series on the Circle

4.1 Periodic functions 4.2 Fourier coefficients 4.3 Convergence 4.4 Parseval identity 4.5 Examples

Chapter 5. Convergence Theory

5.1 Pointwise convergence 5.2 Uniform convergence 5.3 Gibbs phenomenon 5.4 Applications 5.5 Examples

Chapter 6. Summability Methods

6.1 Cesàro summation 6.2 Fejér kernels 6.3 Convergence improvement 6.4 Applications 6.5 Examples

Part III. Lp Spaces and Inequalities

Chapter 7. Lp Spaces

7.1 Definitions 7.2 Norms and completeness 7.3 Duality 7.4 Interpolation (overview) 7.5 Examples

Chapter 8. Inequalities

8.1 Hölder inequality 8.2 Minkowski inequality 8.3 Young’s inequality 8.4 Hausdorff–Young inequality 8.5 Applications

Chapter 9. Singular Integrals (Overview)

9.1 Definition 9.2 Calderón–Zygmund theory (overview) 9.3 Boundedness results 9.4 Applications 9.5 Examples

Part IV. Fourier Analysis on Groups

Chapter 10. Fourier Analysis on ℝⁿ

10.1 Multidimensional transforms 10.2 Radial functions 10.3 Applications 10.4 Examples 10.5 Extensions

Chapter 11. Fourier Analysis on Compact Groups

11.1 Characters 11.2 Peter–Weyl theorem (overview) 11.3 Representation theory links 11.4 Applications 11.5 Examples

Chapter 12. Abstract Harmonic Analysis (Overview)

12.1 Locally compact groups 12.2 Haar measure 12.3 Fourier transform on groups 12.4 Applications 12.5 Examples

Part V. Time-Frequency Analysis

Chapter 13. Short-Time Fourier Transform

13.1 Definitions 13.2 Window functions 13.3 Time-frequency localization 13.4 Applications 13.5 Examples

Chapter 14. Wavelet Transform

14.1 Basic concepts 14.2 Multiresolution analysis 14.3 Continuous and discrete wavelets 14.4 Applications 14.5 Examples

Chapter 15. Frames and Bases

15.1 Frame theory 15.2 Redundant representations 15.3 Stability 15.4 Applications 15.5 Examples

Part VI. Applications

Chapter 16. PDE Applications

16.1 Fourier methods for PDEs 16.2 Heat and wave equations 16.3 Regularity analysis 16.4 Applications 16.5 Examples

Chapter 17. Signal Processing

17.1 Filtering 17.2 Sampling theory 17.3 Compression 17.4 Applications 17.5 Examples

Chapter 18. Number Theory Connections

18.1 Exponential sums 18.2 Fourier methods in number theory 18.3 Applications 18.4 Examples 18.5 Connections

Part VII. Advanced Topics

Chapter 19. Multiplier Theory

19.1 Fourier multipliers 19.2 Boundedness criteria 19.3 Applications 19.4 Examples 19.5 Connections

Chapter 20. Oscillatory Integrals

20.1 Definitions 20.2 Stationary phase method 20.3 Applications 20.4 Examples 20.5 Connections

Chapter 21. Nonlinear Harmonic Analysis

21.1 Nonlinear transforms 21.2 Applications 21.3 Examples 21.4 Connections 21.5 Emerging ideas

Part VIII. Research Directions

Chapter 22. Advanced Topics

22.1 Time-frequency analysis developments 22.2 Connections to geometry 22.3 Harmonic analysis on manifolds 22.4 Modern developments 22.5 Emerging areas

Chapter 23. Open Problems

23.1 Convergence questions 23.2 Boundedness of operators 23.3 High-dimensional analysis 23.4 Computational challenges 23.5 Future directions

Chapter 24. Historical and Conceptual Notes

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

Appendix

A. Fourier transform identities B. Kernel formulas C. Proof techniques checklist D. Example catalog E. Cross-reference to other MSC branches

This volume develops harmonic analysis as the study of oscillatory structure. It emphasizes decomposition, transforms, and applications across mathematics and engineering.