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Let $D$ be a space of $2\times n$ matrices. Then the face of the cone of all completely positive maps from $M_2$ into $M_n$ given by $D$ is an exposed face of the bigger cone of all decomposable positive linear maps if and only if the set…

Mathematical Physics · Physics 2011-06-08 Hyun-Suk Choi , Seung-Hyeok Kye

Generalized polyhedral convex sets, generalized polyhedral convex functions on locally convex Hausdorff topological vector spaces, and the related constructions such as sum of sets, sum of functions, directional derivative, infimal…

Optimization and Control · Mathematics 2017-05-22 Nguyen Ngoc Luan , Jen-Chih Yao , Nguyen Dong Yen

We briefly introduce several problems: (1) a generalization of the convex fair partition conjecture, (2) on non-trivial invariants among polyhedrons that can be formed from the same set of face polygons, (3) two questions on assembling…

Metric Geometry · Mathematics 2015-02-16 R. Nandakumar

Let $K, L$ be convex sets in the plane. For normalization purposes, suppose that the area of $K$ is $1$. Suppose that a set $K_n$ of $n$ points are chosen independently and uniformly over $K$, and call a subset of $K$ a {\em hole} if it…

Metric Geometry · Mathematics 2015-06-16 Octavio Arizmendi , Gelasio Salazar

The largest discs contained in a regular tetrahedron lie in its faces. The proof is closely related to the theorem of Fritz John characterising ellipsoids of maximal volume contained in convex bodies.

Metric Geometry · Mathematics 2009-09-25 Keith Ball

We analyze polyhedra composed of hexagons and triangles with three faces around each vertex, and their 3-regular planar graphs of edges and vertices, which we call "trihexes". Trihexes are analogous to fullerenes, which are 3-regular planar…

Combinatorics · Mathematics 2025-07-01 Linda Green , Stellen Li

A polyhedral map is called $\{p, q\}$-equivelar if each face has $p$ edges and each vertex belongs to $q$ faces. In 1983, it was shown that there exist infinitely many geometrically realizable $\{p, q\}$-equivelar polyhedral maps if $q > p…

Geometric Topology · Mathematics 2007-05-23 Basudeb Datta

In the article, a series of neigbourly polyhedra is constructed. They have $N=2d+4$ vertices and are embedded in $\mathbb R^{2d}$. Their (affine) Gale diagrams in $\mathbb R^2$ have $d+3$ black points that form a convex polygon. These Gale…

Combinatorics · Mathematics 2015-10-12 Rostislav Devyatov

A new notion of face relative interior for convex sets in topological real vector spaces is introduced in this work. Face relative interior is grounded in the facial structure, and may capture the geometry of convex sets in topological…

Optimization and Control · Mathematics 2024-07-02 Reinier Díaz Mill án , Vera Roshchina

The faces of a convex set owe their relevance to an interplay between convexity and topology that is systematically studied in the work of Rockafellar. Infinite-dimensional convex sets are excluded from this theory as their relative…

Metric Geometry · Mathematics 2026-01-01 Stephan Weis

A convex polyhedron, that is, a compact convex subset of $\mathbb{R}^3$ which is the intersection of finitely many closed half-spaces, can be rectified by taking the convex hull of the midpoints of the edges of the polyhedron. We derive…

Metric Geometry · Mathematics 2016-04-05 Samuel Reid

Given a set of radii measured from a fixed point, the existence of a convex configuration with respect to the set of distinct radii in the two-dimensional case is proved when radii are distinct or repeated at most four points. However, we…

Computational Geometry · Computer Science 2025-08-22 Supanut Chaidee , Kokichi Sugihara

We prove that the number of dissections of a given polygon into triangles with fixed areas of faces is finite and that an equidissection is algebraic as long as the vertices of the original polygon have algebraic coordinates.

Combinatorics · Mathematics 2024-02-13 Ivan Frolov

This paper extends the Pythagorean Theorem to positive and negative real exponents to take the form a^n + b^n = c^n and makes use of the definition gamma = b/a >= 1. For the case of n in the set of positive real numbers, n greater than or…

General Mathematics · Mathematics 2023-01-09 Jeffrey S. Lee , Gerald B. Cleaver

A classic theorem by Steinitz states that a graph G is realizable by a convex polyhedron if and only if G is 3-connected planar. Zonohedra are an important subclass of convex polyhedra having the property that the faces of a zonohedron are…

Computational Geometry · Computer Science 2008-11-04 Muhammad Abdullah Adnan , Masud Hasan

A {\em convex hole} (or {\em empty convex polygon)} of a point set $P$ in the plane is a convex polygon with vertices in $P$, containing no points of $P$ in its interior. Let $R$ be a bounded convex region in the plane. We show that the…

Computational Geometry · Computer Science 2012-06-06 József Balogh , Hernán González-Aguilar , Gelasio Salazar

This note introduces the class of basic $r$-ball polyhedra in the $d$-dimensional Euclidean space $\mathbb{E}^{d}$ for $d>1$ and $r>0$. We investigate their face structure and, for given integers $0\leq i\leq d-1$, $n\geq d+1\geq 3$…

Metric Geometry · Mathematics 2026-02-18 Károly Bezdek

We define a centrally symmetric analogue of the cyclic polytope and study its facial structure. We conjecture that our polytopes provide asymptotically the largest number of faces in all dimensions among all centrally symmetric polytopes…

Combinatorics · Mathematics 2007-05-23 Alexander Barvinok , Isabella Novik

Let $\mathcal{P}_n$ be the convex hull in $\mathbb{R}^n$ of all parking functions of length $n$. Stanley found the number of vertices and the number of facets of $\mathcal{P}_n$. Building upon these results, we determine the number of faces…

Combinatorics · Mathematics 2022-02-10 Aruzhan Amanbayeva , Danielle Wang

Eberhard proved that for every sequence $(p_k), 3\le k\le r, k\ne 5,7$ of non-negative integers satisfying Euler's formula $\sum_{k\ge3} (6-k) p_k = 12$, there are infinitely many values $p_6$ such that there exists a simple convex…

Combinatorics · Mathematics 2010-05-07 Matt DeVos , Agelos Georgakopoulos , Bojan Mohar , Robert Šámal