This self-contained book introduces readers to discrete harmonic analysis with an emphasis on the Discrete Fourier Transform and the Fast Fourier Transform on finite groups and finite fields, as well as their noncommutative versions. It also features applications to number theory, graph theory, and representation theory of finite groups. Beginning with elementary material on algebra and number theory, the book then delves into advanced topics from the frontiers of current research, including spectral analysis of the DFT, spectral graph theory and expanders, representation theory of finite groups and multiplicity-free triples, Tao's uncertainty principle for cyclic groups, harmonic analysis on GL(2,Fq), and applications of the Heisenberg group to DFT and FFT. With numerous examples, figures, and over 160 exercises to aid understanding, this book will be a valuable reference for graduate students and researchers in mathematics, engineering, and computer science.

• Provides a self-contained, unified treatment of finite Abelian Groups, finite fields, Discrete and Fast Fourier Transforms, and applications to number theory, spectral graph theory and expanders, and representation theory of finite groups • Includes a well-rounded set of examples and over 160 exercises • Develops the reader's understanding from the fundamentals to the frontiers of current research

### Contents

Part I. Finite Abelian Groups and the DFT: 1. Finite Abelian groups; 2. The Fourier transform on finite Abelian groups; 3. Dirichlet's theorem on primes in arithmetic progressions; 4. Spectral analysis of the DFT and number theory; 5. The fast Fourier transform; Part II. Finite Fields and Their Characters: 6. Finite fields; 7. Character theory of finite fields; Part III. Graphs and Expanders: 8. Graphs and their products; 9. Expanders and Ramanujan graphs; Part IV. Harmonic Analysis of Finite Linear Groups: 10. Representation theory of finite groups; 11. Induced representations and Mackey theory; 12. Fourier analysis on finite affine groups and finite Heisenberg groups; 13. Hecke algebras and multiplicity-free triples; 14. Representation theory of GL(2,Fq).

### Reviews

'Although the roots of harmonic analysis lie in the continuous world, in the last few decades the field has also started to play a fundamental role in the discrete one. This book gives a panoramic view of Discrete Harmonic Analysis - an area that touches many branches of mathematics, such as number theory, spectral theory, groups and their representations, and graphs. The authors open a door for the reader taking him or her on a beautiful tour of classical and modern mathematics All this is done in a self-contained way that prepares the reader for cutting-edge research.' Alex Lubotzky, Hebrew University of Jerusalem

'This book collects a number of gems in number theory and discrete mathematics that have never been put under the same roof, as far as I know. A distinct feature is that it puts harmonic analysis in the foreground where most textbooks present it as ancillary results. The authors must be complimented for their taste in the selection of topics.' Alain Valette, Université de Neuchâtel, Switzerland

'This impressive book unites the qualities of a textbook and a research monograph into one comprehensive text. The central theme is the character theory of finite groups and fields, along with various applications. It offers careful and self-contained introductions to all required basics, which can serve for a series of courses. At the same time, it conducts the reader through several modern research themes and results, ranging from Tao's uncertainty principle via expander graphs to Hecke algebras and a detailed study of the representation theory of linear groups over finite fields.' Wolfgang Woess, Technische Universität Graz