Preface |
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ix | |
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1.1 General setting of approximation problems |
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1 | (4) |
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1.2 Existence and uniqueness of best approximation |
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5 | (5) |
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1.3 Schauder bases in Banach spaces |
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10 | (6) |
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16 | (5) |
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2 Lebesgue-type Inequalities for Greedy Approximation with Respect to Some Classical Bases |
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21 | (4) |
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2.2 The trigonometric system |
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25 | (7) |
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32 | (8) |
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40 | (2) |
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42 | (4) |
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2.5.1 Unconditionality does not imply democracy |
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42 | (1) |
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2.5.2 Democracy does not imply unconditionality |
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43 | (1) |
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2.5.3 Superdemocracy does not imply unconditionality |
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43 | (1) |
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2.5.4 A quasi-greedy basis is not necessarily an unconditional basis |
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44 | (2) |
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46 | (8) |
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2.6.1 Direct and inverse theorems |
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46 | (5) |
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2.6.2 Greedy approximation in L1 and L∞ |
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51 | (3) |
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2.7 Some inequalities for the tensor product of greedy bases |
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54 | (7) |
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3 Quasi-greedy Bases and Lebesgue-type Inequalities |
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61 | (3) |
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3.2 Properties of quasi-greedy bases |
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64 | (13) |
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3.3 Construction of quasi-greedy bases |
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77 | (7) |
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3.4 Uniformly bounded quasi-greedy systems |
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84 | (6) |
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3.5 Lebesgue-type inequalities for quasi-greedy bases |
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90 | (4) |
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3.6 Lebesgue-type inequalities for uniformly bounded quasi-greedy bases |
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94 | (5) |
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3.7 Lebesgue-type inequalities for uniformly bounded orthonormal quasi-greedy bases |
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99 | (4) |
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4 Almost Greedy Bases and Duality |
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103 | (2) |
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4.2 Greedy conditions for bases |
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105 | (3) |
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4.3 Democratic and conservative bases |
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108 | (4) |
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112 | (4) |
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4.5 Duality of almost greedy bases |
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116 | (5) |
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5 Greedy Approximation with Respect to the Trigonometric System |
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121 | (6) |
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5.2 Convergence. Conditions on Fourier coefficients |
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127 | (23) |
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127 | (3) |
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5.2.2 Sufficient conditions in terms of Fourier coefficients. Proof of Theorem 5.2.1 |
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130 | (7) |
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5.2.3 Sufficient conditions in terms of the decreasing rearrangement of Fourier coefficients. Proof of Theorem 5.2.2 |
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137 | (3) |
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5.2.4 Convergence in the uniform norm. Proof of Theorems 5.2.3--5.2.5 |
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140 | (10) |
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5.3 Convergence. Conditions on greedy approximants |
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150 | (24) |
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150 | (2) |
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152 | (6) |
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5.3.3 Sufficient conditions in the case p (2, ∞) |
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158 | (3) |
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5.3.4 Necessary conditions in the case p (2, ∞) |
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161 | (8) |
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5.3.5 Necessary and sufficient conditions in the case p = ∞ |
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169 | (5) |
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5.4 An application of WCGA |
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174 | (5) |
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175 | (1) |
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5.4.2 Rate of approximation |
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175 | (2) |
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5.4.3 Constructive approximation of function classes |
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177 | (2) |
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5.5 Constructive nonlinear trigonometric m-term approximation |
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179 | (8) |
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6 Greedy Approximation with Respect to Dictionaries |
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187 | (6) |
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6.2 The Weak Chebyshev Greedy Algorithm |
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193 | (7) |
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6.3 Relaxation. Co-convex approximation |
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200 | (2) |
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202 | (4) |
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206 | (6) |
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6.6 Relaxation. X-greedy algorithms |
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212 | (2) |
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214 | (15) |
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214 | (3) |
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6.7.2 Convergence of the Dual-Based Expansion |
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217 | (4) |
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6.7.3 A modification of the Weak Dual Greedy Algorithm |
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221 | (5) |
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6.7.4 Convergence of WDGA |
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226 | (3) |
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7.1 Lp-spaces and some inequalities |
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229 | (7) |
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7.1.1 Modulus of continuity |
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229 | (2) |
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231 | (5) |
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236 | (3) |
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7.3 Fourier series of functions in Lp |
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239 | (4) |
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7.4 Trigonometric polynomials |
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243 | (6) |
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7.5 Bernstein--Nikol'skii Inequalities. The Marcinkiewicz Theorem |
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249 | (8) |
Bibliography |
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