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We show that a realization of a closed connected PL-manifold of dimension n-1 in n-dimensional Euclidean space (n>2) is the boundary of a convex polyhedron (finite or infinite) if and only if the interior of each (n-3)-face has a point,…

计算几何 · 计算机科学 2007-05-23 Konstantin Rybnikov

We show that every ridge unfolding of an $n$-cube is without self-overlap, yielding a valid net. The results are obtained by developing machinery that translates cube unfolding into combinatorial frameworks. Moreover, the geometry of the…

组合数学 · 数学 2020-07-28 Kristin DeSplinter , Satyan L. Devadoss , Jordan Readyhough , Bryce Wimberly

Symmetric edge polytopes, also called adjacency polytopes, are lattice polytopes determined by simple undirected graphs. We introduce the integer array \(\mathrm{maxf}(n,m)\) giving the maximum number of facets of a symmetric edge polytope…

组合数学 · 数学 2023-07-07 Benjamin Braun , Kaitlin Bruegge

We prove that any finite polyhedral manifold in 3D can be continuously flattened into 2D while preserving intrinsic distances and avoiding crossings, answering a 19-year-old open problem, if we extend standard folding models to allow for…

计算几何 · 计算机科学 2021-05-25 Zachary Abel , Erik D. Demaine , Martin L. Demaine , Jason S. Ku , Jayson Lynch , Jin-ichi Itoh , Chie Nara

We extend the notion of a star unfolding to be based on a simple quasigeodesic loop Q rather than on a point. This gives a new general method to unfold the surface of any convex polyhedron P to a simple, planar polygon: shortest paths from…

计算几何 · 计算机科学 2008-12-15 Jin-ichi Itoh , Joseph O'Rourke , Costin Vîlcu

A $0/1$-polytope in $\mathbb{R}^n$ is the convex hull of a subset of $\{0,1\}^n$. The graph of a polytope $P$ is the graph whose vertices are the zero-dimensional faces of $P$ and whose edges are the one-dimensional faces of $P$. A…

组合数学 · 数学 2025-09-15 Asaf Ferber , Michael Krivelevich , Marcelo Sales , Wojciech Samotij

Ghomi proved that every convex polyhedron could be stretched via an affine transformation so that it has an edge-unfolding to a net [Gho14]. A net is a simple planar polygon; in particular, it does not self-overlap. One can view his result…

计算几何 · 计算机科学 2023-02-17 Joseph O'Rourke

Polygons are described as almost-convex if their perimeter differs from the perimeter of their minimum bounding rectangle by twice their `concavity index', $m$. Such polygons are called \emph{$m$-convex} polygons and are characterised by…

组合数学 · 数学 2007-10-26 W. R. G. James , I. Jensen , A. J. Guttmann

We prove that, for any two polyhedral manifolds $\mathcal P,\mathcal Q$, there is a polyhedral manifold $\mathcal I$ such that $\mathcal P,\mathcal I$ share a common unfolding and $\mathcal I,\mathcal Q$ share a common unfolding. In other…

计算几何 · 计算机科学 2025-11-18 Lily Chung , Erik D. Demaine , Jenny Diomidova , Tonan Kamata , Jayson Lynch , Ryuhei Uehara , Hanyu Alice Zhang

We approximate boundaries of convex polytopes by smooth hypersurfaces $Y=Y_\varepsilon$ with {\it positive mean curvatures} and, by using basic geometric relations between the scalar curvatures of Riemannin manifolds and the mean curvatures…

微分几何 · 数学 2023-03-24 Misha Gromov

This addendum to [O'R17] establishes that a nearly flat acutely triangulated convex cap in the sense of that paper can be edge-unfolded even if closed to a polyhedron by adding the convex polygonal base under the cap.

计算几何 · 计算机科学 2017-09-11 Joseph O'Rourke

This note proves that every polar zonohedron has an edge-unfolding to a non-overlapping net.

计算几何 · 计算机科学 2023-02-17 Joseph O'Rourke

This note establishes that every polyhedron that has a Hamiltonian quasigeodesic can be edge-unfolded to a net, and shows that the class of such polyhedra is infinite.

计算几何 · 计算机科学 2025-06-24 Joseph O'Rourke

We prove that, for any two polyhedral manifolds $\mathcal P, \mathcal Q$, there is a polyhedral manifold $\mathcal I$ such that $\mathcal P, \mathcal I$ share a common unfolding and $\mathcal I,\mathcal Q$ share a common unfolding. In other…

计算几何 · 计算机科学 2025-10-08 Lily Chung , Erik D. Demaine , Jenny Diomidova , Tonan Kamata , Jayson Lynch , Ryuhei Uehara , Hanyu Alice Zhang

Piecewise Euclidean structures (identified solid Euclidean polyhedra) on topological 3-dimensional manifolds and pseudo-manifolds are constructed so that they admit pseudo-foliations, a generalized type of foliation. The construction of…

微分几何 · 数学 2007-05-23 Simon P Morgan

Given a convex n-gon P in the Euclidean plane, it is well known that the simplicial complex \theta(P) with vertex set given by diagonals in P and facets given by triangulations of P is the boundary complex of a polytope of dimension n-3. We…

组合数学 · 数学 2010-07-23 Benjamin Braun , Richard Ehrenborg

A drawing of a graph in the plane is a thrackle if every pair of edges intersects exactly once, either at a common vertex or at a proper crossing. Conway's conjecture states that a thrackle has at most as many edges as vertices. In this…

离散数学 · 计算机科学 2019-09-18 Oswin Aichholzer , Linda Kleist , Boris Klemz , Felix Schröder , Birgit Vogtenhuber

We investigate asymptotically flat manifolds with cone structure at infinity. We show that any such manifold M has a finite number of ends. For simply connected ends we classify all possible cones at infinity, except for the 4-dimensional…

微分几何 · 数学 2016-07-22 Anton Petrunin , Wilderich Tuschmann

A monotone cylindrical graph is a topological graph drawn on an open cylinder with an infinite vertical axis satisfying the condition that every vertical line intersects every edge at most once. It is called simple if any pair of its edges…

组合数学 · 数学 2014-12-15 Andres J. Ruiz-Vargas

We prove two results about transforming any convex polyhedron, modeled as a linkage L of its edges. First, if we subdivide each edge of L in half, then L can be continuously flattened into a plane. Second, if L is equilateral and we again…

计算几何 · 计算机科学 2024-12-20 Erik D. Demaine , Martin L. Demaine , Markus Hecher , Rebecca Lin , Victor H. Luo , Chie Nara