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Steffen’s flexible polyhedron is embedded. A proof via symbolic computations Full article

Journal Journal for Geometry and Graphics
ISSN: 1433-8157
Output data Year: 2025, Volume: 29, Number: 1, Pages: 79--88 Pages count : 10
Tags Euclidean space, flexible polyhedron, embedded polyhedron, symbolic computations
Authors Alexandrov V. 1,2 , Volokitin E. 1,2
Affiliations
1 Sobolev Institute of Mathematics
2 Novosibirsk State University

Funding (1)

1 Министерство науки и высшего образования РФ FWNF-2026-0026

Abstract: A polyhedron is flexible if it can be continuously deformed preserving the shape and dimensions of each face. In the late 1970's Klaus Steffen constructed a sphere-homeomorphic embedded flexible polyhedron with triangular faces and with 9 vertices only, which is well-known in the theory of flexible polyhedra. At about the same time, a hypothesis was formulated that the Steffen polyhedron has the least possible number of vertices among all embedded flexible polyhedra without boundary. A counterexample to this hypothesis was constructed by Matteo Gallet, Georg Grasegger, Jan Legersky, and Josef Schicho in 2024 only. Surprisingly, until now, no proof has been published in the mathematical literature that the Steffen polyhedron is embedded. Probably, this fact was considered obvious to everyone who made a cardboard model of this polyhedron. In this article, we prove this fact using computer symbolic calculations.
Cite: Alexandrov V. , Volokitin E.
Steffen’s flexible polyhedron is embedded. A proof via symbolic computations
Journal for Geometry and Graphics. 2025. V.29. N1. P.79--88.
Dates:
Submitted: Aug 13, 2025
Accepted: Aug 27, 2025
Published print: Sep 12, 2025
Published online: Sep 12, 2025
Identifiers: No identifiers
Citing: Пока нет цитирований