| Foreword |
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xi | |
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xiii | |
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xv | |
| Preface |
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xvii | |
| Acknowledgment |
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xxi | |
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1 | (50) |
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1 Lie point symmetries of differential equations, their extensions and applications |
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2 | (8) |
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10 | (10) |
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2.1 1-dimensional lattices |
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10 | (1) |
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2.2 2-dimensional lattices |
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10 | (3) |
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2.3 Differential and difference operators on the lattice |
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13 | (1) |
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2.4 Grids and lattices in the description of difference equations |
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14 | (1) |
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14 | (1) |
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2.4.2 Galilei invariant lattice |
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15 | (1) |
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2.4.3 Exponential lattice |
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15 | (1) |
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2.4.4 Polar coordinate systems |
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16 | (2) |
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2.5 Clairaut-Schwarz-Young theorem on the lattices and its consequences |
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18 | (1) |
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2.5.1 Commutativity and non commutativity of difference operators |
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18 | (2) |
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3 What is a difference equation |
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20 | (3) |
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22 | (1) |
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4 How do we find symmetries for difference equations |
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23 | (24) |
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26 | (1) |
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4.1.1 Lie point symmetries of the discrete time Toda lattice |
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26 | (2) |
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4.1.2 Lie point symmetries of DAEs |
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28 | (2) |
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4.1.3 Lie point symmetries of the Toda lattice |
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30 | (2) |
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4.1.4 Classification of DAEs |
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32 | (2) |
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4.1.5 Lie point symmetries of the two dimensional Toda equation |
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34 | (1) |
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4.2 Lie point symmetries preserving discretization of ODEs |
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35 | (3) |
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4.3 Group classification and solution of OAEs |
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38 | (1) |
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4.3.1 Symmetries of second order ODEs |
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38 | (2) |
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4.3.2 Symmetries of the three-point difference schemes |
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40 | (4) |
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4.3.3 Lagrangian formalism and solutions of three-point OAS |
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44 | (3) |
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5 What we leave out on symmetries in this book |
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47 | (1) |
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48 | (3) |
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Chapter 2 Integrability and symmetries of nonlinear differential and difference equations in two independent variables |
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51 | (174) |
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51 | (1) |
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52 | (34) |
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52 | (1) |
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2.2 All you ever wanted to know about the integrability of the KdV equation and its hierarchy |
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53 | (4) |
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2.2.1 The KdV hierarchy: recursion operator |
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57 | (4) |
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2.2.2 The Backlund transformations, Darboux operators and Bianchi identity for the KdV hierarchy |
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61 | (3) |
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2.2.3 The conservations laws for the KdV equation |
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64 | (1) |
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2.2.4 The symmetries of the KdV hierarchy |
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65 | (1) |
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2.2.5 Lie algebra of the symmetries |
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66 | (2) |
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2.2.6 Relation between Backlund transformations and isospectral symmetries |
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68 | (2) |
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2.2.7 Symmetry reductions of the KdV equation |
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70 | (1) |
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2.3 The cylindrical KdV, its hierarchy and Darboux and Backlund transformations |
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71 | (3) |
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2.4 Integrable PDEs as infinite-dimensional superintegrable systems |
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74 | (3) |
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2.5 Integrability of the Burgers equation, the prototype of linearizable PDEs |
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77 | (2) |
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2.5.1 Backlund transformation and Bianchi identity for the Burgers hierarchy of equations |
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79 | (2) |
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2.5.2 Symmetries of the Burgers equation |
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81 | (1) |
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2.5.3 Symmetry reduction by Lie point symmetries |
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81 | (1) |
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2.6 General ideas on linearization |
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82 | (1) |
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2.6.1 Linearization of PDEs through symmetries |
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83 | (3) |
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86 | (43) |
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86 | (1) |
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3.2 The Toda lattice, the Toda system, the Toda hierarchy and their symmetries |
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87 | (5) |
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3.2.1 Symmetries for the Toda hierarchy |
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92 | (1) |
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3.2.2 The Lie algebra of the symmetries for the Toda system and Toda lattice |
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93 | (3) |
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3.2.3 Contraction of the symmetry algebras in the continuous limit |
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96 | (1) |
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3.2.4 Backlund transformations and Bianchi identities for the Toda system and Toda lattice |
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97 | (3) |
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3.2.5 Relation between Backlund transformations and isospectral symmetries |
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100 | (2) |
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3.2.6 Symmetry reduction of a generalized symmetry of the Toda system |
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102 | (1) |
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3.2.7 The inhomogeneous Toda lattices |
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103 | (3) |
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3.3 Volterra hierarchy, its symmetries, Backlund transformations, Bianchi identity and continuous limit |
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106 | (2) |
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3.3.1 Backlund transformations |
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108 | (1) |
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3.3.2 Infinite dimensional symmetry algebra |
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109 | (2) |
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3.3.3 Contraction of the symmetry algebras in the continuous limit |
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111 | (1) |
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3.3.4 Symmetry reduction of a generalized symmetry of the Volterra equation |
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112 | (1) |
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3.3.5 Inhomogeneous Volterra equations |
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113 | (1) |
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3.4 Discrete Nonlinear Schrodinger equation, its symmetries, Backlund transformations and continuous limit |
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113 | (1) |
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3.4.1 The dNLS hierarchy and its integrability |
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114 | (3) |
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3.4.2 Lie point symmetries of the dNLS |
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117 | (1) |
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3.4.3 Generalized symmetries of the dNLS |
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118 | (2) |
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3.4.4 Continuous limit of the symmetries of the dNLS |
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120 | (1) |
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3.4.5 Symmetry reductions |
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121 | (6) |
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127 | (1) |
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3.5.1 Backlund transformations for the DAE Burgers and its non linear superposition formula |
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128 | (1) |
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3.5.2 Symmetries for the DAE Burgers |
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129 | (1) |
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129 | (96) |
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129 | (2) |
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4.2 Discrete time Toda lattice, its hierarchy, symmetries, Backlund transformations and continuous limit |
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131 | (1) |
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4.2.1 Construction of the discrete time Toda lattice hierarchy |
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131 | (2) |
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4.2.2 Isospectral and non isospectral generalized symmetries for the discrete time Toda lattice |
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133 | (2) |
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4.2.3 Symmetry reductions for the discrete time Toda lattice |
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135 | (1) |
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4.2.4 Backlund transformations and symmetries for the discrete time Toda lattice |
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135 | (1) |
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4.3 Discrete time Volterra equation |
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136 | (1) |
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4.3.1 Continuous limit of the discrete time Volterra equation |
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137 | (1) |
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4.3.2 Symmetries for the discrete Volterra equation |
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137 | (1) |
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4.4 Lattice version of the potential KdV, its symmetries and continuous limit |
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138 | (1) |
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138 | (2) |
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4.4.2 Solution of the discrete spectral problem associated with the IpKdV equation |
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140 | (2) |
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4.4.3 Symmetries of the IpKdV equation |
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142 | (3) |
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4.5 Lattice version of the Schwarzian KdV |
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145 | (1) |
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4.5.1 The integrability of the lSKdV equation |
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146 | (1) |
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4.5.2 Point symmetries of the ISKdV equation |
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147 | (1) |
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4.5.3 Generalized symmetries of the ISKdV equation |
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148 | (3) |
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4.6 Volterra type DAEs and the ABS classification |
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151 | (4) |
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4.6.1 The derivation of the Qv equation |
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155 | (1) |
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4.6.2 Lax pair and Backlund transformations for the ABS equations |
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156 | (2) |
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4.6.3 Symmetries of the ABS equations |
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158 | (4) |
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4.7 Extension of the ABS classification: Boll results |
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162 | (2) |
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4.7.1 Independent equations on a single cell |
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164 | (2) |
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4.7.2 Independent equations on the 2D-lattice |
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166 | (2) |
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168 | (7) |
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4.7.4 The non autonomous Qv equation |
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175 | (2) |
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4.7.5 Symmetries of Boll equations |
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177 | (11) |
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4.7.6 Darboux integrability of trapezoidal H4 and H6 families of lattice equations: first integrals [ 336, 345] |
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188 | (8) |
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4.7.7 Darboux integrability of trapezoidal H4 and H6 families of lattice equations: general solutions [ 336, 344] |
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196 | (5) |
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4.8 Integrable example of quad-graph equations not in the ABS or Boll class |
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201 | (2) |
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4.9 The completely discrete Burgers equation |
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203 | (1) |
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4.10 The discrete Burgers equation from the discrete heat equation |
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204 | (1) |
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4.10.1 Symmetries of the new discrete Burgers |
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205 | (3) |
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4.10.2 Symmetry reduction for the new discrete Burgers equation |
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208 | (2) |
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4.11 Linearization of PAEs through symmetries |
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210 | (2) |
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212 | (5) |
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4.11.2 Necessary and sufficient conditions for a PAE to be linear |
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217 | (3) |
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4.11.3 Four-point linearizable lattice schemes |
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220 | (5) |
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Chapter 3 Symmetries as integrability criteria |
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225 | (210) |
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225 | (5) |
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2 The generalized symmetry method for DΔEs |
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230 | (58) |
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2.1 Generalized symmetries and conservation laws |
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231 | (8) |
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2.2 First integrability condition |
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239 | (4) |
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2.3 Formal symmetries and further integrability conditions |
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243 | (8) |
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2.4 Formal conserved density |
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251 | (5) |
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2.4.1 Why the shape of scalar S-integrable evolutionary DΔEs are symmetric |
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256 | (2) |
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2.4.2 Discussion of PDEs from the point of view of Theorem 34 |
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258 | (1) |
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2.4.3 Discussion of PΔEs from the point of view of Theorem 34 |
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259 | (3) |
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2.5 Discussion of the integrability conditions |
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262 | (1) |
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2.5.1 Derivation of integrability conditions from the existence of conservation laws |
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262 | (1) |
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2.5.2 Explicit form of the integrability conditions |
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263 | (1) |
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2.5.3 Construction of conservation laws from the integrability conditions |
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264 | (1) |
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2.5.4 Left and right order of generalized symmetries |
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265 | (1) |
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2.6 Hamiltonian equations and their properties |
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266 | (3) |
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2.7 Discrete Miura transformations and master symmetries |
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269 | (6) |
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2.8 Generalized symmetries for systems of lattice equations: Toda type equations |
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275 | (6) |
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2.9 Integrability conditions for relativistic Toda type equations |
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281 | (7) |
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288 | (28) |
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3.1 Volterra type equations |
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288 | (1) |
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3.1.1 Examples of classification |
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288 | (4) |
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3.1.2 Lists of equations, transformations and master symmetries |
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292 | (5) |
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297 | (4) |
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3.3 Relativistic Toda type equations |
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301 | (1) |
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3.3.1 Non point connection between Lagrangian and Hamiltonian equations, and properties of Lagrangian equations |
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302 | (4) |
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3.3.2 Hamiltonian form of relativistic lattice equations |
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306 | (2) |
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3.3.3 Lagrangian form of relativistic lattice equations |
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308 | (2) |
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3.3.4 Relations between the presented lists of relativistic equations |
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310 | (2) |
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3.3.5 Master symmetries for the relativistic lattice equations |
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312 | (4) |
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4 Explicit dependence on the discrete spatial variable n and time t |
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316 | (14) |
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4.1 Dependence on n in Volterra type equations |
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316 | (1) |
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4.1.1 Discussion of the general theory |
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316 | (4) |
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320 | (4) |
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4.2 Toda type equations with an explicit n and t dependence |
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324 | (4) |
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4.3 Example of relativistic Toda type |
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328 | (2) |
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5 Other types of lattice equations |
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330 | (9) |
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5.1 Scalar evolutionary DΔEs of an arbitrary order |
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330 | (5) |
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335 | (4) |
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6 Completely discrete equations |
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339 | (21) |
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6.1 Generalized symmetries for PΔEs and integrability conditions |
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339 | (1) |
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6.1.1 Preliminary definitions |
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339 | (3) |
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6.1.2 Derivation of the first integrability conditions |
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342 | (3) |
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6.1.3 Integrability conditions for five point symmetries |
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345 | (5) |
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6.2 Testing PΔEs for the integrability and some classification results |
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350 | (1) |
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6.2.1 A simple classification problem |
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350 | (3) |
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6.2.2 Further application of the method to examples and classes of equations |
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353 | (7) |
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7 Linearizability through change of variables in PΔEs |
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360 | (37) |
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7.1 Three-point PΔEs linearizable by local and non local transformations |
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362 | (1) |
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7.1.1 Linearizability conditions |
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363 | (3) |
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7.1.2 Classification of complex multilinear equations defined on a three-point lattice linearizable by one-point transformations |
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366 | (3) |
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7.1.3 Linearizability by a Cole--Hopf transformation |
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369 | (2) |
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7.1.4 Classification of complex multilinear equations defined on three points linearizable by Cole--Hopf transformation |
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371 | (1) |
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7.2 Nonlinear equations on a quad-graph linearizable by one-point, two-point and generalized Cole--Hopf transformations |
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372 | (1) |
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7.2.1 Linearization by one-point transformations |
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372 | (2) |
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7.2.2 Two-point transformations |
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374 | (5) |
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7.2.3 Linearization by a generalized Cole--Hopf transformation to an homogeneous linear equation |
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379 | (4) |
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383 | (9) |
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7.3 Results on the classification of multilinear PΔEs linearizable by point transformation on a square lattice |
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392 | (1) |
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7.3.1 Quad-graph PΔEs linearizable by a point transformation |
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392 | (2) |
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7.3.2 Classification of complex autonomous multilinear quad-graph PΔEs linearizable by a point transformation |
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394 | (3) |
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Appendix A Construction of lattice equations and their Lax pair |
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397 | (10) |
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Appendix B Transformation groups for quad lattice equations |
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407 | (6) |
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Appendix C Algebraic entropy of the non autonomous Boll equations |
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413 | (8) |
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1 Algebraic entropy test for H4 and H6 trapezoidal equations |
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413 | (3) |
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2 Algebraic entropy for the non autonomous YdKN equation and its subcases |
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416 | (5) |
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Appendix D Translation from Russian of RI Yamilov, On the classification of discrete equations, reference [ 841] |
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421 | (12) |
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1 Proof of the conditions (D.2--D.4) |
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422 | (2) |
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2 Nonlinear differential difference equations satisfying conditions (D.2--D.4) |
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424 | (1) |
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3 List of non linear differential difference equations of type I satisfying conditions (D.2, D.4) |
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425 | (8) |
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Appendix E No quad-graph equation can have a generalized symmetry given by the Narita-Itoh-Bogoyavlensky equation |
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433 | (2) |
| Bibliography |
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435 | (38) |
| Subject Index |
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473 | |