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1 The Geometric Meaning of Curvature: Local and Nonlocal Aspects of Ricci Curvature |
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1 | (62) |
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1.1 The Origins of the Concept of Curvature |
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2 | (1) |
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1.2 A Primer on Riemannian Geometry: Not Indispensable |
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3 | (7) |
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1.2.1 Tangent Vectors and Riemannian Metrics |
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3 | (2) |
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1.2.2 Differentials, Gradients, and the Laplace-Beltrami Operator |
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5 | (3) |
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1.2.3 Lengths and Distances |
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8 | (1) |
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9 | (1) |
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1.3 Curvature of Riemannian Manifolds |
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10 | (10) |
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1.3.1 Covariant Derivatives |
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10 | (1) |
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1.3.2 The Curvature Tensor; Sectional and Ricci Curvature |
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11 | (2) |
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1.3.3 The Geometric Meaning of Sectional Curvature |
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13 | (1) |
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1.3.4 The Geometric Meaning of Ricci Curvature |
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14 | (5) |
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19 | (1) |
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1.4 A Nonlocal Approach to Geometry |
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20 | (4) |
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1.5 Generalized Ricci Curvature |
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24 | (7) |
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1.5.1 Forman's Ricci Curvature |
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25 | (2) |
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1.5.2 Ollivier's Ricci Curvature |
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27 | (2) |
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1.5.3 Curvature Dimension Inequality |
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29 | (2) |
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1.6 Ricci Curvature and the Geometry of Graphs |
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31 | (32) |
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1.6.1 Basic Notions from Graph Theory |
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31 | (4) |
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1.6.2 Ricci Curvature and Clustering |
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35 | (13) |
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1.6.3 Curvature Dimension Inequality and Eigenvalue Ratios |
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48 | (3) |
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1.6.4 Exponential Curvature Dimension Inequality on Graphs |
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51 | (1) |
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1.6.5 Li-Yau Gradient Estimate on Graphs and Its Applications |
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52 | (2) |
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1.6.6 Applications to Network Analysis |
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54 | (1) |
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1.6.7 Other Curvature Notions for Graphs |
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55 | (4) |
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59 | (4) |
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2 Metric Curvatures Revisited: A Brief Overview |
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63 | (52) |
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63 | (1) |
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2.2 Metric Curvature for Curves |
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64 | (6) |
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65 | (1) |
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66 | (4) |
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2.3 Metric Curvature for Surfaces: Wald Curvature |
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70 | (10) |
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70 | (10) |
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2.4 Wald Curvature Under Gromov--Hausdorff Convergence |
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80 | (5) |
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2.4.1 Intrinsic Properties and Gromov--Hausdorff Convergence |
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80 | (3) |
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2.4.2 Wald Curvature and Gromov--Hausdorff Convergence |
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83 | (2) |
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2.5 Wald and Alexandrov Curvatures Comparison |
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85 | (3) |
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2.5.1 Alexandrov Curvature |
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85 | (2) |
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2.5.2 Alexandrov Curvature vs. Wald Curvature |
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87 | (1) |
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2.6 A Metric Approach to Ricci Curvature |
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88 | (13) |
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2.6.1 Metric Ricci Flow for PL Surfaces |
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89 | (8) |
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2.6.2 PL Ricci for Cell Complexes |
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97 | (4) |
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2.7 Metric Curvatures for Metric Measure Spaces |
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101 | (14) |
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2.7.1 The Basic Idea: The Snowflaking Operator |
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102 | (9) |
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111 | (4) |
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3 Distances Between Datasets |
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115 | (18) |
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115 | (1) |
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3.1.1 Notation and Background Concepts |
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115 | (1) |
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3.2 The Gromov--Hausdorff Distance |
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116 | (7) |
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117 | (1) |
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118 | (1) |
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119 | (1) |
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3.2.4 The Case of Subsets of Euclidean Space |
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120 | (1) |
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3.2.5 Another Expression and Consequences |
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121 | (2) |
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3.3 The Modified Gromov-Hausdorff and Curvature Sets |
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123 | (4) |
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124 | (1) |
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3.3.2 Comparing Curvature Sets? |
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125 | (1) |
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126 | (1) |
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127 | (4) |
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128 | (1) |
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128 | (1) |
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3.4.3 Other Properties: Geodesics and Alexandrov Curvature |
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129 | (1) |
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3.4.4 The Metric dGW,p in Applications |
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130 | (1) |
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3.5 Discussion and Outlook |
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131 | (2) |
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131 | (2) |
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4 Inference of Curvature Using Tubular Neighborhoods |
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133 | (26) |
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134 | (1) |
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4.2 Distance Function and Sets with Positive Reach |
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134 | (5) |
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4.2.1 Gradient of the Distance and Sets with Positive Reach |
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135 | (2) |
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4.2.2 Generalized Gradient and Sets with Positive μ-Reach |
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137 | (2) |
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4.3 Boundary Measures and Federer's Curvature Measures |
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139 | (11) |
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139 | (1) |
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4.3.2 Stability of Boundary Measures |
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140 | (3) |
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4.3.3 Tube Formulas and Federer's Curvature Measures |
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143 | (2) |
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4.3.4 Stability of Federer's Curvature Measures |
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145 | (2) |
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4.3.5 Computation of Boundary Measures and Visualization |
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147 | (3) |
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4.4 Voronoi Covariance Measures and Local Minkowski Tensors |
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150 | (2) |
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4.4.1 Covariance Matrices of Voronoi Cells |
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150 | (1) |
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4.4.2 Voronoi Covariance Measure |
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151 | (1) |
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4.5 Stability of Anisotropic Curvature Measures |
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152 | (7) |
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4.5.1 Anisotropic Curvature Measures of Sets with Positive Reach |
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152 | (1) |
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4.5.2 Stability of the Curvature Measures of the Offsets |
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153 | (1) |
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4.5.3 Computation of the Curvature Measures of 3D Point Clouds |
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154 | (1) |
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4.5.4 Sketch of Proof of Theorem 4.9 |
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155 | (2) |
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157 | (2) |
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5 Entropic Ricci Curvature for Discrete Spaces |
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159 | (16) |
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5.1 Ricci Curvature Lower Bounds for Geodesic Measure Spaces |
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159 | (2) |
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161 | (1) |
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5.2 The Heat Flow as Gradient Flow of the Entropy |
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161 | (2) |
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5.2.1 The Benamou-Brenier Formula |
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162 | (1) |
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5.3 A Gradient Flow Structure for Reversible Markov Chains |
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163 | (4) |
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5.3.1 Discrete Transport Metrics |
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164 | (2) |
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5.3.2 A Riemannian Structure on the Space of Probability Measures |
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166 | (1) |
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5.3.3 The Discrete JKO-Theorem |
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166 | (1) |
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5.4 Discrete Entropic Ricci Curvature |
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167 | (8) |
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5.4.1 Discrete Spaces with Lower Ricci Curvature Bounds |
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169 | (1) |
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170 | (2) |
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172 | (3) |
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6 Geometric and Spectral Consequences of Curvature Bounds on Tessellations |
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175 | (36) |
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175 | (7) |
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177 | (1) |
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6.1.2 Tessellations of Surfaces |
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177 | (1) |
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178 | (3) |
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181 | (1) |
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182 | (12) |
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6.2.1 Gauss--Bonnet Theorem |
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182 | (1) |
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6.2.2 Approximating Flat and Infinite Curvature |
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183 | (1) |
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184 | (1) |
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6.2.4 Absence of Cut Locus |
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185 | (1) |
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186 | (4) |
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6.2.6 Isoperimetric Inequalities |
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190 | (4) |
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194 | (9) |
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6.3.1 The Combinatorial Laplacian |
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194 | (2) |
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6.3.2 Bottom of the Spectrum |
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196 | (2) |
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6.3.3 Discrete Spectrum, Eigenvalue Asymptotics and Decay of Eigenfunctions |
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198 | (2) |
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6.3.4 Unique Continuation of Eigenfunctions |
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200 | (2) |
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202 | (1) |
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6.4 Extensions to More General Graphs |
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203 | (8) |
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6.4.1 Curvature on Planar Graphs |
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203 | (2) |
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6.4.2 Sectional Curvature for Polygonal Complexes |
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205 | (1) |
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206 | (5) |
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7 The Geometric Spectrum of a Graph and Associated Curvatures |
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211 | (48) |
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211 | (3) |
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7.2 The Geometric Spectrum |
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214 | (3) |
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7.3 Invariant Stars and the Lifting Problem |
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217 | (10) |
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218 | (2) |
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220 | (4) |
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7.3.3 The Lifting Problem |
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224 | (3) |
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7.4 Edge Length and the Gauss Map |
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227 | (9) |
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227 | (2) |
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7.4.2 Edge Curvature and Edge Length |
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229 | (5) |
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7.4.3 Path Metric Space Structure and Curvature in the Sense of Alexandrov |
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234 | (2) |
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236 | (8) |
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7.5.1 The Theorem of Descartes |
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236 | (1) |
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237 | (7) |
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244 | (15) |
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257 | (2) |
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8 Discrete Minimal Surfaces of Koebe Type |
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259 | (34) |
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259 | (1) |
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8.2 Discrete Minimal Surfaces |
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260 | (9) |
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8.2.1 Discrete Curvatures |
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263 | (1) |
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8.2.2 Characterization of Discrete Minimal Surfaces |
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264 | (5) |
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8.3 Construction of Koebe Polyhedra and Discrete Minimal Surfaces |
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269 | (6) |
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8.3.1 Construction of Koebe Polyhedra and Spherical Circle Patterns |
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270 | (2) |
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8.3.2 Construction of S-Isothermic Discrete Minimal Surfaces with Special Boundary Conditions |
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272 | (3) |
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8.4 Examples of Discrete Minimal Surfaces |
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275 | (11) |
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275 | (2) |
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8.4.2 Schwarz's CLP Surface |
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277 | (1) |
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8.4.3 Schwarz's D Surface |
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278 | (1) |
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279 | (1) |
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8.4.5 Schwarz's H Surface |
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280 | (1) |
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8.4.6 Schoen's I-6 Surface and Generalizations |
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281 | (1) |
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8.4.7 Polygonal Boundary Frames |
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282 | (4) |
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8.5 Weierstrass Representation and Convergence of Discrete Minimal Surfaces |
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286 | (7) |
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8.5.1 Discrete Weierstrass Representation |
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287 | (1) |
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8.5.2 Convergence of Discrete Minimal Surfaces |
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287 | (3) |
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290 | (3) |
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9 Robust and Convergent Curvature and Normal Estimators with Digital Integral Invariants |
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293 | (56) |
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9.1 Curvature Estimation on Discrete Data |
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294 | (3) |
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9.2 Background: Multigrid Convergence and Integral Invariants |
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297 | (6) |
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9.2.1 Digital Space and Digitizations Operators |
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297 | (3) |
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9.2.2 Multigrid Convergence of Global and Local Geometric Estimators |
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300 | (1) |
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9.2.3 Integral Invariants in the Continuous Setting |
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301 | (2) |
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303 | (11) |
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9.3.1 Moments and Digital Moments |
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303 | (1) |
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9.3.2 General Results for Volume Estimation Errors |
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304 | (2) |
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9.3.3 Volume Approximation Within a Ball of Radius R |
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306 | (5) |
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9.3.4 Errors on Volume and Moment Estimation Within a Ball of Radius R |
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311 | (2) |
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313 | (1) |
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9.4 Multigrid Convergence of Mean Curvature in 2D and 3D |
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314 | (6) |
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9.4.1 Definition of Mean Curvature Estimators |
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314 | (1) |
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9.4.2 Convergence at Points of X (Weak Formulation) |
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315 | (2) |
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9.4.3 Multigrid Convergence for Smooth Enough Shapes |
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317 | (3) |
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9.5 Multigrid Convergence of Curvature Tensor in 3D |
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320 | (11) |
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9.5.1 Digital Covariance Matrix and Digital Principal Curvature Estimators |
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320 | (1) |
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9.5.2 Some Properties of Covariance Matrix and Moments |
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321 | (1) |
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9.5.3 Multigrid Convergence of Digital Covariance Matrix |
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322 | (4) |
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9.5.4 Useful Results of Matrix Perturbation Theory |
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326 | (1) |
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9.5.5 Multigrid Convergence of Integral Principal Curvature Estimators |
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327 | (4) |
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9.6 Parameter-Free Digital Curvature Estimation |
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331 | (3) |
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9.6.1 Asymptotic Laws of Straight Segments Along the Boundary of Digitized Shapes and Scale Determination |
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331 | (1) |
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9.6.2 Parameter-Free Digital Curvature Estimators |
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332 | (1) |
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9.6.3 Local Parameter-Free Digital Curvature Estimator and 3D Case |
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333 | (1) |
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9.7 Experimental Evaluation |
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334 | (7) |
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9.7.1 Implementation Details |
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334 | (2) |
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9.7.2 Multigrid Convergence Analysis |
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336 | (2) |
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9.7.3 Parameter-Free Estimators |
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338 | (3) |
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9.8 Discussion, Applications and Further Works |
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341 | (8) |
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9.8.1 Robustness to Noise |
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341 | (2) |
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9.8.2 Feature Detection with Multiscale Approach |
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343 | (1) |
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9.8.3 Current Limitations and Possible Research Directions |
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344 | (1) |
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345 | (4) |
Index |
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349 | |