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We prove new upper and lower bounds on transversal numbers of several classes of simplicial complexes. Specifically, we establish an upper bound on the transversal numbers of pure simplicial complexes in terms of the number of vertices and…

Combinatorics · Mathematics 2025-10-09 Isabella Novik , Hailun Zheng

This paper develops an explicit and implementable framework for constructing spherical designs by lifting point sets from tight fusion frames. By combining existing ingredients, we obtain, in every dimension, explicit spherical $5$-designs…

Combinatorics · Mathematics 2026-02-24 Ryutaro Misawa

We consider the problem of computing a triangulation of the real projective plane P2, given a finite point set S={p1, p2,..., pn} as input. We prove that a triangulation of P2 always exists if at least six points in S are in general…

Computational Geometry · Computer Science 2011-11-10 Mridul Aanjaneya , Monique Teillaud

We present small triangulations of all connected sums of $\mathbb{CP}^2$ and $S^2 \times S^2$ with the standard piecewise linear structure. Our triangulations have $2\beta_2+2$ pentachora, where $\beta_2$ is the second Betti number of the…

Geometric Topology · Mathematics 2025-02-03 Jonathan Spreer , Lucy Tobin

We study triangulations $\cal T$ defined on a closed disc $X$ satisfying the following condition: In the interior of $X$, the valence of all vertices of $\cal T$ except one of them (the irregular vertex) is $6$. By using a flat singular…

Differential Geometry · Mathematics 2018-03-13 Jean-Marie Morvan

For any finite set $\A$ of $n$ points in $\R^2$, we define a $(3n-3)$-dimensional simple polyhedron whose face poset is isomorphic to the poset of ``non-crossing marked graphs'' with vertex set $\A$, where a marked graph is defined as a…

Combinatorics · Mathematics 2007-05-23 David Orden , Francisco Santos

We give a new proof of Steinitz's classical theorem in the case of plane triangulations, which allows us to obtain a new general bound on the grid size of the simplicial polytope realizing a given triangulation, subexponential in a number…

Combinatorics · Mathematics 2013-11-05 Igor Pak , Stedman Wilson

We prove a discrete analogue to a classical isoperimetric theorem of Weil for surfaces with non-positive curvature. It is shown that hexagons in the triangular lattice have maximal volume among all sets of a given boundary in any…

Metric Geometry · Mathematics 2016-04-21 Omer Angel , Itai Benjamini , Nizan Horesh

There exists a bijection between the configuration space of a linear pentapod and all points $(u,v,w,p_x,p_y,p_z)\in\mathbb{R}^{6}$ located on the singular quadric $\Gamma: u^2+v^2+w^2=1$, where $(u,v,w)$ determines the orientation of the…

Robotics · Computer Science 2017-12-20 Arvin Rasoulzadeh , Georg Nawratil

We show that among antipodal $2d$-point configurations on the sphere $S^{d-1}$ in $\mathbb R^d$, the set of vertices of a regular cross-polytope inscribed in $S^{d-1}$ uniquely solves the best-covering problem (this is new for $d\geq 5$)…

Optimization and Control · Mathematics 2022-10-25 Sergiy Borodachov

In our work we focus on the geometry of elliptic normal curves of degree 6 embedded in $\mathbb{P}^5$. We determine the space of quadric hypersurfaces through an elliptic normal curve of degree 6 and find the explicit equations of…

Algebraic Geometry · Mathematics 2022-03-23 Anatoli Shatsila

We construct, for any positive integer n, a family of n congruent convex polyhedra in R^3, such that every pair intersects in a common facet. Previously, the largest such family contained only eight polytopes. Our polyhedra are Voronoi…

Combinatorics · Mathematics 2007-05-23 Jeff Erickson

We construct a sphere-homeomorphic flexible self-intersection free polyhedron in Euclidean 3-space such that all its dihedral angles change during some flex of this polyhedron. The constructed polyhedron has 26 vertices, 72 edges and 48…

Metric Geometry · Mathematics 2024-11-26 Victor Alexandrov , Evgenii Volokitin

Through tropical normal idempotent matrices, we introduce isocanted alcoved polytopes, computing their $f$--vectors and checking the validity of the following five conjectures: B\'{a}r\'{a}ny, unimodality, $3^d$, flag and cubical lower…

Combinatorics · Mathematics 2020-09-30 María Jesús de la Puente , Pedro Luis Clavería

We define some Schnyder-type combinatorial structures on a class of planar triangulations of the pentagon which are closely related to 5-connected triangulations. The combinatorial structures have three incarnations defined in terms of…

Combinatorics · Mathematics 2023-09-01 Olivier Bernardi , Éric Fusy , Shizhe Liang

A degree-regular triangulation is one in which each vertex has identical degree. Our main result is that any such triangulation of a (possibly non-compact) surface $S$ is geometric, that is, it is combinatorially equivalent to a geodesic…

Combinatorics · Mathematics 2017-11-06 Basudeb Datta , Subhojoy Gupta

In 2010 Santos described the construction of a counterexample to the Hirsch conjecture, and in 2012 Santos and Weibel provided the coordinates for the 40 facets of a 20-dimensional counterexample. In this paper we explore technical details…

Combinatorics · Mathematics 2015-03-03 Fred B. Holt

We give several new constructions for moderate rank elliptic curves over $\mathbb{Q}(T)$. In particular we construct infinitely many rational elliptic surfaces (not in Weierstrass form) of rank 6 over $\mathbb{Q}$ using polynomials of…

Number Theory · Mathematics 2010-11-16 Scott Arms , Steven J. Miller , Alvaro Lozano-Robledo

We present novel fully-symmetric quadrature rules with positive weights and strictly interior nodes of degrees up to 84 on triangles and 40 on tetrahedra. Initial guesses for solving the nonlinear systems of equations needed to derive…

Numerical Analysis · Mathematics 2024-09-04 Zelalem Arega Worku , Jason E. Hicken , David W. Zingg

In this paper we describe a methodology for the identification of symmetric quadrature rules inside of quadrilaterals, triangles, tetrahedra, prisms, pyramids, and hexahedra. The methodology is free from manual intervention and is capable…

Numerical Analysis · Mathematics 2014-09-08 F. D. Witherden , P. E. Vincent