Closed surfaces with different shapes that are indistinguishable by the SRNF

Klassen, Eric, and Michor, Peter W.. "Closed surfaces with different shapes that are indistinguishable by the SRNF." Archivum Mathematicum 056.2 (2020): 107-114. <http://eudml.org/doc/297063>.

@article{Klassen2020,
abstract = {The Square Root Normal Field (SRNF), introduced by Jermyn et al. in [5], provides a way of representing immersed surfaces in $\mathbb \{R\}^3$, and equipping the set of these immersions with a “distance function" (to be precise, a pseudometric) that is easy to compute. Importantly, this distance function is invariant under reparametrizations (i.e., under self-diffeomorphisms of the domain surface) and under rigid motions of $\mathbb \{R\}^3$. Thus, it induces a distance function on the shape space of immersions, i.e., the space of immersions modulo reparametrizations and rigid motions of $\mathbb \{R\}^3$. In this paper, we give examples of the degeneracy of this distance function, i.e., examples of immersed surfaces (some closed and some open) that have the same SRNF, but are not the same up to reparametrization and rigid motions. We also prove that the SRNF does distinguish the shape of a standard sphere from the shape of any other immersed surface, and does distinguish between the shapes of any two embedded strictly convex surfaces.},
author = {Klassen, Eric, Michor, Peter W.},
journal = {Archivum Mathematicum},
keywords = {shape space; square root normal field},
language = {eng},
number = {2},
pages = {107-114},
publisher = {Department of Mathematics, Faculty of Science of Masaryk University, Brno},
title = {Closed surfaces with different shapes that are indistinguishable by the SRNF},
url = {http://eudml.org/doc/297063},
volume = {056},
year = {2020},
}

TY - JOUR
AU - Klassen, Eric
AU - Michor, Peter W.
TI - Closed surfaces with different shapes that are indistinguishable by the SRNF
JO - Archivum Mathematicum
PY - 2020
PB - Department of Mathematics, Faculty of Science of Masaryk University, Brno
VL - 056
IS - 2
SP - 107
EP - 114
AB - The Square Root Normal Field (SRNF), introduced by Jermyn et al. in [5], provides a way of representing immersed surfaces in $\mathbb {R}^3$, and equipping the set of these immersions with a “distance function" (to be precise, a pseudometric) that is easy to compute. Importantly, this distance function is invariant under reparametrizations (i.e., under self-diffeomorphisms of the domain surface) and under rigid motions of $\mathbb {R}^3$. Thus, it induces a distance function on the shape space of immersions, i.e., the space of immersions modulo reparametrizations and rigid motions of $\mathbb {R}^3$. In this paper, we give examples of the degeneracy of this distance function, i.e., examples of immersed surfaces (some closed and some open) that have the same SRNF, but are not the same up to reparametrization and rigid motions. We also prove that the SRNF does distinguish the shape of a standard sphere from the shape of any other immersed surface, and does distinguish between the shapes of any two embedded strictly convex surfaces.
LA - eng
KW - shape space; square root normal field
UR - http://eudml.org/doc/297063
ER -