| Preface | 6 |
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| Contents | 10 |
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| 1 Introduction Ill-Posedness of Inverse Problems for Differential and Integral Equations | 13 |
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| 1.1 Some Basic Definitions and Examples | 13 |
| 1.2 Continuity with Respect to Coefficients and Source: Sturm-Liouville Equation | 21 |
| 1.3 Why a Fredholm Integral Equation of the First Kind Is an Ill-Posed Problem? | 25 |
| Part I Introduction to Inverse Problems | 32 |
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| 2 Functional Analysis Background of Ill-Posed Problems | 33 |
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| 2.1 Best Approximation and Orthogonal Projection | 34 |
| 2.2 Range and Null-Space of Adjoint Operators | 41 |
| 2.3 Moore-Penrose Generalized Inverse | 43 |
| 2.4 Singular Value Decomposition | 48 |
| 2.5 Regularization Strategy. Tikhonov Regularization | 55 |
| 2.6 Morozov's Discrepancy Principle | 68 |
| 3 Inverse Source Problems with Final Overdetermination | 73 |
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| 3.1 Inverse Source Problem for Heat Equation | 74 |
| 3.1.1 Compactness of Input-Output Operator and Fréchet Gradient | 77 |
| 3.1.2 Singular Value Decomposition of Input-Output Operator | 82 |
| 3.1.3 Picard Criterion and Regularity of Input/Output Data | 89 |
| 3.1.4 The Regularization Strategy by SVD. Truncated SVD | 94 |
| 3.2 Inverse Source Problems for Wave Equation | 100 |
| 3.2.1 Non-uniqueness of a Solution | 103 |
| 3.3 Backward Parabolic Problem | 106 |
| 3.4 Computational Issues in Inverse Source Problems | 114 |
| 3.4.1 Galerkin FEM for Numerical Solution of Forward Problems | 115 |
| 3.4.2 The Conjugate Gradient Algorithm | 117 |
| 3.4.3 Convergence of Gradient Algorithms for Functionals with Lipschitz Continuous Fréchet Gradient | 122 |
| 3.4.4 Numerical Examples | 126 |
| Part II Inverse Problems for Differential Equations | 130 |
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| 4 Inverse Problems for Hyperbolic Equations | 131 |
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| 4.1 Inverse Source Problems | 131 |
| 4.1.1 Recovering a Time Dependent Function | 132 |
| 4.1.2 Recovering a Spacewise Dependent Function | 134 |
| 4.2 Problem of Recovering the Potential for the String Equation | 136 |
| 4.2.1 Some Properties of the Direct Problem | 137 |
| 4.2.2 Existence of the Local Solution to the Inverse Problem | 141 |
| 4.2.3 Global Stability and Uniqueness | 146 |
| 4.3 Inverse Coefficient Problems for Layered Media | 149 |
| 5 One-Dimensional Inverse Problems for Electrodynamic Equations | 152 |
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| 5.1 Formulation of Inverse Electrodynamic Problems | 152 |
| 5.2 The Direct Problem: Existence and Uniqueness of a Solution | 153 |
| 5.3 One-Dimensional Inverse Problems | 162 |
| 5.3.1 Problem of Finding a Permittivity Coefficient | 162 |
| 5.3.2 Problem of Finding a Conductivity Coefficient | 167 |
| 6 Inverse Problems for Parabolic Equations | 170 |
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| 6.1 Relationships Between Solutions of Direct Problems for Parabolic and Hyperbolic Equations | 170 |
| 6.2 Problem of Recovering the Potential for Heat Equation | 173 |
| 6.3 Uniqueness Theorems for Inverse Problems Related to Parabolic Equations | 175 |
| 6.4 Relationship Between the Inverse Problem and Inverse Spectral Problems for Sturm-Liouville Operator | 178 |
| 6.5 Identification of a Leading Coefficient in Heat Equation: Dirichlet Type Measured Output | 181 |
| 6.5.1 Some Properties of the Direct Problem Solution | 182 |
| 6.5.2 Compactness and Lipschitz Continuity of the Input-Output Operator. Regularization | 184 |
| 6.5.3 Integral Relationship and Gradient Formula | 190 |
| 6.5.4 Reconstruction of an Unknown Coefficient | 193 |
| 6.6 Identification of a Leading Coefficient in Heat Equation: Neumann Type Measured Output | 198 |
| 6.6.1 Compactness of the Input-Output Operator | 200 |
| 6.6.2 Lipschitz Continuity of the Input-Output Operator and Solvability of the Inverse Problem | 204 |
| 6.6.3 Integral Relationship and Gradient Formula | 207 |
| 7 Inverse Problems for Elliptic Equations | 211 |
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| 7.1 The Inverse Scattering Problem at a Fixed Energy | 211 |
| 7.2 The Inverse Scattering Problem with Point Sources | 214 |
| 7.3 Dirichlet to Neumann Map | 219 |
| 8 Inverse Problems for the Stationary Transport Equations | 225 |
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| 8.1 The Transport Equation Without Scattering | 225 |
| 8.2 Uniqueness and a Stability Estimate in the Tomography Problem | 228 |
| 8.3 Inversion Formula | 229 |
| 9 The Inverse Kinematic Problem | 232 |
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| 9.1 The Problem Formulation | 232 |
| 9.2 Rays and Fronts | 233 |
| 9.3 The One-Dimensional Problem | 236 |
| 9.4 The Two-Dimensional Problem | 239 |
| Appendix A Invertibility of Linear Operators | 243 |
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| Appendix B Some Estimates For One-Dimensional Parabolic Equation | 251 |
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| References | 257 |
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| Index | 262 |