This book gives a thorough introduction on classical Fourier transforms in a compact and self-contained form. Chapter I is devoted to the L1-theory: basic properties are proved as well as the Poisson summation formula, the central limit theorem and Wiener's general tauberian theorem. As an illustration of a Fourier transformation of a function not belonging to L1-theory an integral due to Ramanujan is given. Chapter II is devoted to the L2-theory, including Plancherel's theorem, Heisenberg's inequality, the Paley-Wiener theorem, Hardy's interpolation formula and two inequalities due to Bernstein. Chapter III deals with Fourier-Stieltjes transforms. After the basic properties are explained, distribution functions, positive-definite functions and the uniqueness theorem of Offord are treated. The book is intended for undergraduate students and requires of them basic knowledge in real and complex analysis.
I. Fourier transforms on L1 (-?,?).- §1. Basic properties and examples.- §2. The L1 -algebra.- §3. Differentiability properties.- §4. Localization, Mellin transforms.- §5. Fourier series and Poisson's summation formula.- §6. The uniqueness theorem.- §7. Pointwise summability.- §8. The inversion formula.- §9. Summability in the L1-norm.- §10. The central limit theorem.- §11. Analytic functions of Fourier transforms.- §12. The closure of translations.- §13. A general tauberian theorem.- §14. Two differential equations.- §15. Several variables.- II. Fourier transforms on L2(-?,?).- §1. Introduction.- §2. Plancherel's theorem.- §3. Convergence and summability.- §4. The closure of translations.- §5. Heisenberg's inequality.- §6. Hardy's theorem.- §7. The theorem of Paley and Wiener.- §8. Fourier series in L2(a,b).- §9. Hardy's interpolation formula.- §10. Two inequalities of S. Bernstein.- §11. Several variables.- III. Fourier-Stieltjes transforms (one variable).- §1. Basic properties.- §2. Distribution functions, and characteristic functions.- §3. Positive-definite functions.- §4. A uniqueness theorem.- Notes.- References.