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xi | |
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xiv | |
Preface |
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xvii | |
Introduction |
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1 | (6) |
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1 Lagrangian and Hamiltonian Formalism for Discrete Equations: Symmetries and First Integrals |
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7 | (43) |
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7 | (2) |
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1.2 Invariance of Euler-Lagrange equations |
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9 | (2) |
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1.3 Lagrangian formalism for second-order difference equations |
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11 | (5) |
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1.4 Hamiltonian formalism for differential equations |
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16 | (5) |
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1.4.1 Canonical Hamiltonian equations |
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16 | (2) |
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1.4.2 The Legendre transformation |
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18 | (1) |
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1.4.3 Invariance of canonical Hamiltonian equations |
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18 | (3) |
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1.5 Discrete Hamiltonian formalism |
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21 | (10) |
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1.5.1 Discrete Legendre transform |
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21 | (2) |
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1.5.2 Variational formulation of the discrete Hamiltonian equations |
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23 | (1) |
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1.5.3 Symplecticity of the discrete Hamiltonian equations |
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24 | (3) |
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1.5.4 Invariance of the Hamiltonian action |
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27 | (1) |
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1.5.5 Discrete Hamiltonian identity and discrete Noether theorem |
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28 | (2) |
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1.5.6 Invariance of the discrete Hamiltonian equations |
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30 | (1) |
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31 | (15) |
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31 | (5) |
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36 | (3) |
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1.6.3 Discrete harmonic oscillator |
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39 | (4) |
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1.6.4 Modified discrete harmonic oscillator (exact scheme) |
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43 | (3) |
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46 | (4) |
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2 Painleve Equations: Continuous, Discrete and Ultradiscrete |
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50 | (33) |
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50 | (1) |
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2.2 A rough sketch of the top-down description of the Painleve equations |
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51 | (6) |
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2.3 A succinct presentation of the bottom-up description of the Painleve equations |
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57 | (7) |
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2.4 Properties of the, continuous and discrete, Painleve equations: a parallel presentation |
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64 | (10) |
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2.4.1 Degeneration cascade |
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64 | (1) |
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65 | (2) |
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2.4.3 Miura and Backlund relations |
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67 | (2) |
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2.4.4 Particular solutions |
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69 | (3) |
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2.4.5 Contiguity relations |
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72 | (2) |
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2.5 The ultradiscrete Painleve equations |
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74 | (6) |
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2.5.1 Degeneration cascade |
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75 | (1) |
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76 | (1) |
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2.5.3 Miura and Backlund relations |
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76 | (2) |
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2.5.4 Particular solutions |
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78 | (1) |
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2.5.5 Contiguity relations |
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78 | (2) |
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80 | (3) |
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3 Definitions and Predictions of Integrability for Difference Equations |
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83 | (32) |
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83 | (5) |
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3.1.1 Points of view on integrability |
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83 | (1) |
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3.1.2 Preliminaries on discreteness and discrete integrability |
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84 | (4) |
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88 | (3) |
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3.2.1 Constants of motion for continuous ODE |
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88 | (1) |
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3.2.2 The standard discrete case |
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89 | (1) |
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3.2.3 The Hirota-Kimura-Yahagi (HKY) generalization |
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90 | (1) |
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3.3 Singularity confinement and algebraic entropy |
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91 | (6) |
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3.3.1 Singularity analysis for difference equations |
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91 | (3) |
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3.3.2 Singularity confinement in projective space |
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94 | (2) |
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3.3.3 Singularity confinement is not sufficient |
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96 | (1) |
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97 | (4) |
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3.4.1 Definitions and examples |
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97 | (1) |
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3.4.2 Quadrilateral lattices |
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98 | (2) |
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100 | (1) |
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100 | (1) |
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3.5 Singularity confinement in 2D |
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101 | (2) |
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3.6 Algebraic entropy for 2D lattices |
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103 | (3) |
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3.6.1 Default growth of degree and factorization |
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103 | (2) |
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3.6.2 Search based on factorization |
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105 | (1) |
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3.7 Consistency around a cube |
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106 | (3) |
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106 | (1) |
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107 | (1) |
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3.7.3 CAC as a search method |
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108 | (1) |
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109 | (3) |
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3.8.1 Background solutions |
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109 | (1) |
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110 | (1) |
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111 | (1) |
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112 | (3) |
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4 Orthogonal Polynomials, their Recursions, and Functional Equations |
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115 | (24) |
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115 | (1) |
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4.2 Orthogonal polynomials |
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116 | (3) |
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119 | (2) |
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4.4 The Freud nonlinear recursions |
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121 | (1) |
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4.5 Differential equations |
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122 | (3) |
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4.6 q-difference equations |
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125 | (3) |
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128 | (2) |
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130 | (4) |
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4.9 The Askey-Wilson polynomials |
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134 | (5) |
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5 Discrete Painleve Equations and Orthogonal Polynomials |
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139 | (21) |
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139 | (7) |
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5.1.1 Orthogonal polynomials |
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140 | (1) |
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5.1.2 Connections to integrable systems |
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140 | (2) |
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5.1.3 The Riemann-Hilbert representation of the orthogonal polynomials |
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142 | (1) |
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5.1.4 Discrete Painleve equations |
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143 | (3) |
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146 | (14) |
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146 | (1) |
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147 | (5) |
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152 | (8) |
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6 Generalized Lie Symmetries for Difference Equations |
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160 | (31) |
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160 | (4) |
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6.1.1 Direct construction of generalized symmetries: an example |
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161 | (3) |
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6.2 Generalized symmetries from the integrability properties |
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164 | (13) |
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164 | (4) |
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6.2.2 The symmetry algebra for the Toda Lattice |
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168 | (2) |
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6.2.3 The continuous limit of the Toda symmetry algebras |
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170 | (2) |
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6.2.4 Backlund transformations for the Toda equation |
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172 | (1) |
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6.2.5 Backlund transformations vs. generalized symmetries |
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173 | (2) |
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6.2.6 Generalized symmetries for PΔE's |
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175 | (2) |
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6.3 Formal symmetries and integrable lattice equations |
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177 | (14) |
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6.3.1 Formal symmetries and further integrability conditions |
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182 | (3) |
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6.3.2 Why integrable equations on the lattice must be symmetric |
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185 | (3) |
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6.3.3 Example of classification problem |
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188 | (3) |
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7 Four Lectures on Discrete Systems |
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191 | (16) |
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191 | (1) |
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7.2 Discrete symmetries and completely integrable systems |
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191 | (2) |
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7.3 Discretization of linear operators |
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193 | (2) |
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7.4 Discrete GLn connections and triangle equation |
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195 | (3) |
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7.5 New discretization of complex analysis |
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198 | (9) |
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8 Lectures on Moving Frames |
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207 | (40) |
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207 | (2) |
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8.2 Equivariant moving frames |
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209 | (2) |
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8.3 Moving frames on jet space and differential invariants |
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211 | (2) |
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8.4 Equivalence and signatures |
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213 | (2) |
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8.5 Joint invariants and joint differential invariants |
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215 | (3) |
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8.6 Invariant numerical approximations |
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218 | (6) |
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8.7 The invariant bicomplex |
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224 | (7) |
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8.8 Generating differential invariants |
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231 | (4) |
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8.9 Invariant variational problems |
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235 | (2) |
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8.10 Invariant curve flows |
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237 | (10) |
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9 Lattices of Compact Semisimple Lie Groups |
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247 | (12) |
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247 | (1) |
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248 | (2) |
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9.3 Simple Lie groups and simple Lie algebras |
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250 | (4) |
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250 | (1) |
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9.3.2 Standard bases in Rn |
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251 | (1) |
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9.3.3 Reflections and affine reflections in Rn |
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252 | (1) |
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9.3.4 Weyl group and Affine Weyl group |
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252 | (2) |
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9.4 Lattice grids FM ⊂ F ⊂ Rn |
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254 | (2) |
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255 | (1) |
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9.5 W-invariant functions orthogonal on FM |
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256 | (1) |
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9.6 Properties of elements of finite order |
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257 | (2) |
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10 Lectures on Discrete Differential Geometry |
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259 | (33) |
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260 | (4) |
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10.2 Backlund transformations |
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264 | (2) |
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266 | (2) |
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268 | (3) |
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271 | (2) |
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273 | (3) |
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276 | (5) |
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281 | (2) |
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283 | (3) |
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10.10 Hirota equation for K-nets |
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286 | (6) |
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11 Symmetry Preserving Discretization of Differential Equations and Lie Point Symmetries of Differential-Difference Equations |
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292 | |
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11.1 Symmetry preserving discretization of ODEs |
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294 | (6) |
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11.1.1 Formulation of the problem |
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294 | (1) |
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11.1.2 Lie point symmetries of ordinary difference schemes |
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295 | (4) |
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11.1.3 The continuous limit |
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299 | (1) |
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11.2 Examples of symmetry preserving discretizations |
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300 | (6) |
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11.2.1 Equations invariant under SL1(2, R) |
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300 | (3) |
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11.2.2 Equations invariant under SL2(2, R) |
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303 | (1) |
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11.2.3 Equations invariant under the similitude group of the Euclidean plane |
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304 | (2) |
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11.3 Applications to numerical solutions of ODEs |
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306 | (8) |
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11.3.1 General procedure for testing the numerical schemes |
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306 | (1) |
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11.3.2 Numerical experiments for a third-order ODE invariant under SL1(2, R) |
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307 | (3) |
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11.3.3 Numerical experiments for ODEs invariant under SL2(2, R) |
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310 | (3) |
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11.3.4 Numerical experiments for third-order ODE invariant under Sim(2) |
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313 | (1) |
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11.4 Exact solutions of invariant difference schemes |
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314 | (12) |
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11.4.1 Lagrangian formulation for second-order ODEs |
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315 | (3) |
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11.4.2 Lagrangian formulation for second order difference equations |
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318 | (3) |
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11.4.3 Example: Second-order ODE with three-dimensional solvable symmetry algebra |
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321 | (5) |
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11.5 Lie point symmetries of differential-difference equations |
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326 | (8) |
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11.5.1 Formulation of the problem |
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326 | (1) |
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11.5.2 The evolutionary formalism and commuting flows for differential equations |
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327 | (1) |
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11.5.3 The evolutionary formalism and commuting flows for differential-difference equations |
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328 | (2) |
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11.5.4 General algorithm for calculating Lie point symmetries of a differential-difference equation |
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330 | (1) |
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11.5.5 Theorems simplifying the calculation of symmetries of DΔE |
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330 | (1) |
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11.5.6 Volterra type equations and their generalizations |
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331 | (2) |
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11.5.7 Toda type equations |
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333 | (1) |
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11.5.8 Toda field theory type equations |
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333 | (1) |
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11.6 Examples of symmetries of DΔE |
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334 | |
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335 | (1) |
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336 | (1) |
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11.6.3 The two-dimensional Toda lattice equation |
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336 | |