Analysis and Computation of Geodesic Distances on Reductive Homogeneous Spaces

Fuente: arXiv
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Main Authors: Duits, Remco, Bellaard, Gijs, Tumpach, Barbara
Format: Preprint
Published: 2025
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author Duits, Remco
Bellaard, Gijs
Tumpach, Barbara
author_facet Duits, Remco
Bellaard, Gijs
Tumpach, Barbara
contents Many geometric machine learning and image analysis applications, require a left-invariant metric on the 5D homogeneous space of 3D positions and orientations SE(3)/SO(2). This is done in Equivariant Neural Networks (G-CNNs), or in PDE-Based Group Convolutional Neural Networks (PDE-G-CNNs), where the Riemannian metric enters in multilayer perceptrons, message passing, and max-pooling over Riemannian balls. In PDE-G-CNNs it is proposed to take the minimum left-invariant Riemannian distance over the fiber in SE(3)/SO(2), whereas in G-CNNs and in many geometric image processing methods an efficient SO(2)-conjugation invariant section is advocated. The conjecture rises whether that computationally much more efficient section indeed always selects distance minimizers over the fibers. We show that this conjecture does NOT hold in general, and in the logarithmic norm approximation setting used in practice we analyze the small (and sometimes vanishing) differences. We first prove that the minimal distance section is reached by minimal horizontal geodesics with constant momentum and zero acceleration along the fibers, and we generalize this result to (reductive) homogeneous spaces with legal metrics and commutative structure groups.
format Preprint
id arxiv_https___arxiv_org_abs_2504_04878
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analysis and Computation of Geodesic Distances on Reductive Homogeneous Spaces
Duits, Remco
Bellaard, Gijs
Tumpach, Barbara
Differential Geometry
51N30, 53C30
Many geometric machine learning and image analysis applications, require a left-invariant metric on the 5D homogeneous space of 3D positions and orientations SE(3)/SO(2). This is done in Equivariant Neural Networks (G-CNNs), or in PDE-Based Group Convolutional Neural Networks (PDE-G-CNNs), where the Riemannian metric enters in multilayer perceptrons, message passing, and max-pooling over Riemannian balls. In PDE-G-CNNs it is proposed to take the minimum left-invariant Riemannian distance over the fiber in SE(3)/SO(2), whereas in G-CNNs and in many geometric image processing methods an efficient SO(2)-conjugation invariant section is advocated. The conjecture rises whether that computationally much more efficient section indeed always selects distance minimizers over the fibers. We show that this conjecture does NOT hold in general, and in the logarithmic norm approximation setting used in practice we analyze the small (and sometimes vanishing) differences. We first prove that the minimal distance section is reached by minimal horizontal geodesics with constant momentum and zero acceleration along the fibers, and we generalize this result to (reductive) homogeneous spaces with legal metrics and commutative structure groups.
title Analysis and Computation of Geodesic Distances on Reductive Homogeneous Spaces
topic Differential Geometry
51N30, 53C30
url https://arxiv.org/abs/2504.04878