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Title:
Fourier analysis and approximation of functions
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Dordrecht : Kluwer Academic, 2004
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9781402023415
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30000004598193 QA403.5 T74 2004 Open Access Book Book
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Summary

Summary

In Fourier Analysis and Approximation of Functions basics of classical Fourier Analysis are given as well as those of approximation by polynomials, splines and entire functions of exponential type.
In Chapter 1 which has an introductory nature, theorems on convergence, in that or another sense, of integral operators are given. In Chapter 2 basic properties of simple and multiple Fourier series are discussed, while in Chapter 3 those of Fourier integrals are studied.
The first three chapters as well as partially Chapter 4 and classical Wiener, Bochner, Bernstein, Khintchin, and Beurling theorems in Chapter 6 might be interesting and available to all familiar with fundamentals of integration theory and elements of Complex Analysis and Operator Theory. Applied mathematicians interested in harmonic analysis and/or numerical methods based on ideas of Approximation Theory are among them.
In Chapters 6-11 very recent results are sometimes given in certain directions. Many of these results have never appeared as a book or certain consistent part of a book and can be found only in periodics; looking for them in numerous journals might be quite onerous, thus this book may work as a reference source.
The methods used in the book are those of classical analysis, Fourier Analysis in finite-dimensional Euclidean space Diophantine Analysis, and random choice.


Table of Contents

Dedication
Preface1: Representation Theorems
1.1 Theorems on representation at a point
1.2 Integral operators
Convergence in Lp-norm and almost everywhere
1.3 Multidimensional case
1.4 Further problems and theorems
1.5 Comments to
Chapter 1 2: Fourier Series
2.1 Convergence and divergence
2.2 Two classical summability methods
2.3 Harmonic functions and functions analytic in the disk
2.4 Multidimensional case
2.5 Further problems and theorems
2.6 Comments to
Chapter 2 3: Fourier Integral
3.1 L-Theory
3.2 L2 Theory
3.3 Multidimensional case
3.4 Entire functions of exponential type
The Paley-Wiener theorem
3.5 Further problems and theorems
3.6 Comments to
Chapter 3 4: Discretization
Direct and Inverse Theorems
4.1 Summation formulas of Poisson and Euler-Maclaurin
4.2 Entire functions of exponential type and polynomials
4.3 Network norms
Inequalities of different metrics
4.4 Inverse theorems
Constructive characteristics
Embedding theorems
4.6 Moduli of smoothness
4.7 Approximation on an interval
4.8 Further problems and theorems
4.9 Comments to
Chapter 4 5: Extremal Problems of Approximation Theory
5.1 Best approximation
5.2 The space Lp
Best approximation
5.3 Space C
The Chebyshev alternation
5.4 Extremal properties for algebraic polynomials and splines
5.5 Best approximation of a set by another set
5.6 Further problems and theorems
5.7 Comments to
Chapter 5 6: A Function as the Fourier Transform of a Measure
6.1 Algebras A and úIiú
The Wiener Tauberian theorem
6.2 Positive definate and completely monotone functions
6.3 Positive definate functions depending only on a norm
6.4 Sufficient conditions for belonging to Ap A*
6.5 Further problems and theorems
6.6 Comments to
Chapter 6 7: Fourier Multipliers
7.1 General Properties
7.2 Sufficient conditions
7.3 Multipliers of power series in the Hardy spaces
7.4 Multipliers and comparison of summability methods of orthogonal series
7.5 Further problems and theorems
7.6 Comments to
Chapter 7 8: Summability Methods
Moduli of Smoothness
8.1 Regularity
8.2 Applications of comparison
Two-sided estimates
8.3 Moduli of smoothness and K-functionals
8.4 Moduli of smoothness and strong summability in Hp (D), 0
Further problems and theorems
8.6 Comments to
Chapter 8 9: Lebesgue Constants and Approximation
9.1 Upper and lower estimates
9.2 Examples of Lebesgue constants in the multiple case
9.3 Asymptotics of Lebesgue constants and approximation
9.4 Further problems and theorems
9.5 Comments to
Chapter 9 10: Widths, Polynomial Approximation
10.1 Entrophy numbers
10.2 Polynomials with free spectrum
10.3 Kolmogorov widths
10.4 Further problems and theorems
10.5 Comments to
Chapter 10 11: Functions with Bounded Mixed Derivative
11.1 Hyperbolic cross polynomials
11.2 Estimates of entrophy numbers
11.3 Widths
11.4 Further problems and theorems
11.5 Comments to
Chapter 11 Appendices
Prerequisites
Weierstrass approximation theorems
The modulus of continuity of a function
The Riemann-Stieltjes integral
Summability of series
Analytic functions
Measure and integral. Complex-valued measures
Hilbert spaces. Classical orthonormal systems
Banach spaces and linear operators
Fourier multipliers
Several classical theorems
Polynomials with integral coefficients
Some inequalities
&mathR;m and its subsets
Functional notations
References
Author Index
Topic Index