Methods of Approximation Theory

Author: Alexander I. Stepanets  

Publisher: De Gruyter‎

Publication year: 2005

E-ISBN: 9783110195286

P-ISBN(Paperback): 9789067644273

Subject: O174.41 Approximation Theory

Language: ENG

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Chapter

PREFACE

pp.:  1 – 11

PART I

pp.:  11 – 19

1. Introduction

pp.:  19 – 19

8. Corollaries of Theorem 7.1. Regularity of Linear Methods of Summation of Fourier Series

pp.:  61 – 84

2. SATURATION OF LINEAR METHODS

pp.:  84 – 97

2. Sufficient Conditions for Saturation

pp.:  97 – 99

1. Statement of the Problem

pp.:  97 – 97

3. Saturation Classes

pp.:  99 – 102

4. Criterion for Uniform Boundedness of Multipliers

pp.:  102 – 108

5. Saturation of Classical Linear Methods

pp.:  108 – 116

3. CLASSES OF PERIODIC FUNCTIONS

pp.:  116 – 119

2. Classes Hω[a,b] and Hω

pp.:  119 – 126

1. Sets of Summable Functions. Moduli of Continuity

pp.:  119 – 119

3. Moduli of Continuity in Spaces Lp. Classes Hωp

pp.:  126 – 128

4. Classes of Differentiable Functions

pp.:  128 – 130

5. Conjugate Functions and Their Classes

pp.:  130 – 134

6. Weyl-Nagy Classes

pp.:  134 – 137

7. Classes LψϐN

pp.:  137 – 138

8. Classes CψϐN

pp.:  138 – 144

9. Classes LψϐN

pp.:  144 – 148

10. Order Relation for (ψ,ϐ) -Derivatives

pp.:  148 – 151

11. ψ-Integrals of Periodic Functions

pp.:  151 – 155

12. Sets M0, M∞, and Mc

pp.:  155 – 165

13. Set F

pp.:  165 – 171

14. Two Counterexamples

pp.:  171 – 174

15. Function ηa(t) and Sets Defined by It

pp.:  174 – 178

16. Sets B and M0

pp.:  178 – 180

4. INTEGRAL REPRESENTATIONS OF DEVIATIONS OF POLYNOMIALS GENERATED BY LINEAR PROCESSES OF SUMMATION OF FOURIER SERIES

pp.:  180 – 183

2. Second Integral Representation

pp.:  183 – 185

1. First Integral Representation

pp.:  183 – 183

3. Representation of Deviations of Fourier Sums on Sets CψM and Lψ

pp.:  185 – 191

5. APPROXIMATION BY FOURIER SUMS IN SPACES C AND L1

pp.:  191 – 205

1. Simplest Extremal Problems in Space C

pp.:  205 – 207

2. Simplest Extremal Problems in Space L1

pp.:  207 – 216

3. Approximations of Functions of Small Smoothness by Fourier Sums

pp.:  216 – 221

4. Auxiliary Statements

pp.:  221 – 225

5. Proofs of Theorems 3.1-3.3'

pp.:  225 – 243

6. Approximation by Fourier Sums on Classes Hω

pp.:  243 – 253

7. Approximation by Fourier Sums on Classes Hω

pp.:  253 – 257

8. Analogs of Theorems 3.1-3.3' in Integral Metric

pp.:  257 – 261

9. Analogs of Theorems 6.1 and 7.1 in Integral Metric

pp.:  261 – 270

10. Approximations of Functions of High Smoothness by Fourier Sums in Uniform Metric

pp.:  270 – 271

11. Auxiliary Statements

pp.:  271 – 277

12. Proofs of Theorems 10.1-10.3'

pp.:  277 – 289

13. Analogs of Theorems 10.1-10.3' in Integral Metric

pp.:  289 – 296

14. Remarks on the Solution of Kolmogorov-Nikol’skii Problem

pp.:  296 – 297

15. Approximation of ψ-Integrals That Generate Entire Functions by Fourier Sums

pp.:  297 – 302

16. Approximation of Poisson Integrals by Fourier Sums

pp.:  302 – 312

17. Corollaries of Telyakovskii Theorem

pp.:  312 – 321

18. Solution of Kolmogorov-Nikol’skii Problem for Poisson Integrals of Continuous Functions

pp.:  321 – 328

19. Lebesgue Inequalities for Poisson Integrals

pp.:  328 – 356

20. Approximation by Fourier Sums on Classes of Analytic Functions

pp.:  356 – 363

21. Convergence Rate of Group of Deviations

pp.:  363 – 381

22. Corollaries of Theorems 21.1 and 21.2. Orders of Best Approximations

pp.:  381 – 392

23. Analogs of Theorems 21.1 and 21.2 and Best Approximations in Integral Metric

pp.:  392 – 396

24. Strong Summability of Fourier Series

pp.:  396 – 401

BIBLIOGRAPHICAL NOTES (Part I)

pp.:  401 – 411

REFERENCES (Part I)

pp.:  411 – 417

PART II

pp.:  417 – 447

0. Introduction

pp.:  447 – 447

6. CONVERGENCE RATE OF FOURIER SERIES AND THE BEST APPROXIMATIONS IN THE SPACES Lp

pp.:  447 – 447

1. Approximations in the Space L2

pp.:  447 – 450

2. Direct and Inverse Theorems in the Space L2

pp.:  450 – 455

3. Extension to the Case of Complete Orthonormal Systems

pp.:  455 – 457

4. Jackson Inequalities in the Space L2

pp.:  457 – 462

5. Marcinkiewicz, Riesz, and Hardy-Littlewood Theorems

pp.:  462 – 466

6. Imbedding Theorems for the Sets LψLP

pp.:  466 – 470

7. Approximations of Functions from the Sets LψLp by Fourier Sums

pp.:  470 – 473

8. Best Approximations of Infinitely Differentiable Functions

pp.:  473 – 484

9. Jackson Inequalities in the Spaces C and Lp

pp.:  484 – 499

7. BEST APPROXIMATIONS IN THE SPACES C AND L

pp.:  499 – 507

1. Chebyshev and de la Vallée Poussin Theorems

pp.:  507 – 508

2. Polynomial of the Best Approximation in the Space L

pp.:  508 – 510

3. General Facts on the Approximations of Classes of Convolutions

pp.:  510 – 513

4. Orders of the Best Approximations

pp.:  513 – 523

5. Exact Values of the Upper Bounds of Best Approximations

pp.:  523 – 528

6. Dzyadyk-Stechkin-Xiung Yungshen Theorem. Korneichuk Theorem

pp.:  528 – 540

7. Serdyuk Theorem

pp.:  540 – 543

8. Bernstein Inequalities for Polynomials

pp.:  543 – 557

9. Inverse Theorems

pp.:  557 – 563

8. INTERPOLATION

pp.:  563 – 571

2. Lebesgue Constants and Nikol’skii Theorems

pp.:  571 – 575

1. Interpolation Trigonometric Polynomials

pp.:  571 – 571

3. Approximation by Interpolation Polynomials in the Classes of Infinitely Differentiable Functions

pp.:  575 – 578

4. Approximation by Interpolation Polynomials on the Classes of Analytic Functions

pp.:  578 – 590

5. Summable Analog of the Favard Method

pp.:  590 – 604

9. APPROXIMATIONS IN THE SPACES OF LOCALLY SUMMABLE FUNCTIONS

pp.:  604 – 615

1. Spaces Lp

pp.:  615 – 616

2. Order Relation for (ψ, ß)-Derivatives

pp.:  616 – 619

3. Approximating Functions

pp.:  619 – 625

4. General Estimates

pp.:  625 – 633

5. On the Functions ψ(•) Specifying the Sets Lψß

pp.:  633 – 642

6. Estimates of the Quantities ║ȓcσ(t, ß)║1 for c = σ - h and h > 0

pp.:  642 – 644

7. Estimates of the Quantities ║ȓcσ(t, ß)║1 for c = θσ, 0 ≤θ≤ 1, and ψ ∈ Uc

pp.:  644 – 650

8. Estimates of the Quantities ║ȓcσ(t, ß)║1 for c = 2σ - η(σ) and ψ ∈ U∞

pp.:  650 – 652

9. Estimates of the Quantities ║ȓcσ(t, 0)║1 for c = θσ, 0 ≤ θ ≤ 1, and ψ ∈ U0

pp.:  652 – 653

10. Estimates of the Quantities ║δσ,c(t,ß)║1

pp.:  653 – 654

11. Basic Results

pp.:  654 – 657

12. Upper Bounds of the Deviations ρσ(f;•) in the Classes Ĉψß,∞ and ĈψßHω

pp.:  657 – 666

13. Some Remarks on the Approximation of Functions of High Smoothness

pp.:  666 – 684

14. Strong Means of Deviations of the Operators Fσ(f;x)

pp.:  684 – 686

10. APPROXIMATION OF CAUCHY-TYPE INTEGRALS

pp.:  686 – 697

1. Definitions and Auxiliary Statements

pp.:  697 – 698

2. Sets of ψ-Integrals

pp.:  698 – 714

3. Approximation of Functions from the Classes Cψ(T)+

pp.:  714 – 720

4. Landau Constants

pp.:  720 – 731

5. Asymptotic Equalities

pp.:  731 – 734

6. Lebesgue-Landau Inequalities

pp.:  734 – 741

7. Approximation of Cauchy-Type Integrals

pp.:  741 – 745

11. APPROXIMATIONS IN THE SPACES SP

pp.:  745 – 759

2. ψ-Integrals and Characteristic Sequences

pp.:  759 – 763

1. Spaces

pp.:  759 – 759

3. Best Approximations and Widths of p-Ellipsoids

pp.:  763 – 765

4. Approximations of Individual Elements from the Sets

pp.:  765 – 768

5. Best n-Term Approximations

pp.:  768 – 773

6. Best n-Term Approximations (q>p)

pp.:  773 – 789

7. Proof of Lemma 6.1

pp.:  789 – 795

8. Best Approximations by q-Ellipsoids in the Spaces Spφ

pp.:  795 – 826

9. Application of Obtained Results to Problems of Approximation of Periodic Functions of Many Variables

pp.:  826 – 829

10. Remarks

pp.:  829 – 835

11. Theorems of Jackson and Bernstein in the Spaces Sp

pp.:  835 – 840

12. APPROXIMATIONS BY ZYGMUND AND DE LA VALLÉE POUSSIN SUMS

pp.:  840 – 865

1. Fejér Sums: Survey of Known Results

pp.:  865 – 866

2. Riesz Sums: A Survey of Available Results

pp.:  866 – 878

3. Zygmund Sums: A Survey of Available Results

pp.:  878 – 881

4. Zygmund Sums on the Classes Cψß,∞

pp.:  881 – 884

5. De la Vallée Poussin Sums on the Classes Wrß and WrßHw

pp.:  884 – 889

6. De la Vallée Poussin Sums on the Classes CψßN and CψN

pp.:  889 – 895

BIBLIOGRAPHICAL NOTES (Part II)

pp.:  895 – 899

REFERENCES (Part II)

pp.:  899 – 903

Index

pp.:  903 – 935

LastPages

pp.:  935 – 941

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