An inequality concerning edges of minor weight in convex 3-polytopes

Igor Fabrici; Stanislav Jendrol'

Displaying similar documents to “An inequality concerning edges of minor weight in convex 3-polytopes”

Isocanted alcoved polytopes

María Jesús de la Puente, Pedro Luis Clavería (2020)

Applications of Mathematics

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Through tropical normal idempotent matrices, we introduce isocanted alcoved polytopes, computing their $f$ -vectors and checking the validity of the following five conjectures: Bárány, unimodality, $3^{d}$ , flag and cubical lower bound (CLBC). Isocanted alcoved polytopes are centrally symmetric, almost simple cubical polytopes. They are zonotopes. We show that, for each dimension, there is a unique combinatorial type. In dimension $d$ , an isocanted alcoved polytope has $2^{d + 1} - 2$ vertices, its face lattice...

Volume thresholds for Gaussian and spherical random polytopes and their duals

Peter Pivovarov (2007)

Studia Mathematica

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Let g be a Gaussian random vector in ℝⁿ. Let N = N(n) be a positive integer and let $K_{N}$ be the convex hull of N independent copies of g. Fix R > 0 and consider the ratio of volumes $V_{N} : = v o l (K_{N} \cap R B ₂ ⁿ) / v o l (R B ₂ ⁿ)$ . For a large range of R = R(n), we establish a sharp threshold for N, above which $V_{N} \to 1$ as n → ∞, and below which $V_{N} \to 0$ as n → ∞. We also consider the case when $K_{N}$ is generated by independent random vectors distributed uniformly on the Euclidean sphere. In this case, similar threshold results are proved for both...

The Cayley Trick, lifting subdivisions and the Bohne-Dress theorem on zonotopal tilings

Birkett Huber, Jörg Rambau, Francisco Santos (2000)

Journal of the European Mathematical Society

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In 1994, Sturmfels gave a polyhedral version of the Cayley Trick of elimination theory: he established an order-preserving bijection between the posets of coherent mixed subdivisions of a Minkowski sum $𝒜_{1} + \dots + 𝒜_{r}$ of point configurations and of coherent polyhedral subdivisions of the associated Cayley embedding $𝒞 (𝒜_{1}, \dots, 𝒜_{r})$ . In this paper we extend this correspondence in a natural way to cover also non-coherent subdivisions. As an application, we show that the Cayley Trick combined with results of Santos...

Approximation of the Euclidean ball by polytopes

Monika Ludwig, Carsten Schütt, Elisabeth Werner (2006)

Studia Mathematica

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There is a constant c such that for every n ∈ ℕ, there is an Nₙ so that for every N≥ Nₙ there is a polytope P in ℝⁿ with N vertices and $v o l ₙ (B ₂ ⁿ △ P) \leq c v o l ₙ (B ₂ ⁿ) N^{- 2 / (n - 1)}$ where B₂ⁿ denotes the Euclidean unit ball of dimension n.

The vertex detour hull number of a graph

A.P. Santhakumaran, S.V. Ullas Chandran (2012)

Discussiones Mathematicae Graph Theory

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For vertices x and y in a connected graph G, the detour distance D(x,y) is the length of a longest x - y path in G. An x - y path of length D(x,y) is an x - y detour. The closed detour interval ID[x,y] consists of x,y, and all vertices lying on some x -y detour of G; while for S ⊆ V(G), $I_{D} [S] = ⋃_{x, y \in S} I_{D} [x, y]$ . A set S of vertices is a detour convex set if $I_{D} [S] = S$ . The detour convex hull ${[S]}_{D}$ is the smallest detour convex set containing S. The detour hull number dh(G) is the minimum cardinality among subsets S of...

On some results about convex functions of order $α$

M. Obradović, S. Owa (1986)

Matematički Vesnik

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Counting triangles that share their vertices with the unit $n$ -cube

Brandts, Jan, Cihangir, Apo

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This paper is about $0 / 1$ -triangles, which are the simplest nontrivial examples of $0 / 1$ -polytopes: convex hulls of a subset of vertices of the unit $n$ -cube $I^{n}$ . We consider the subclasses of right $0 / 1$ -triangles, and acute $0 / 1$ -triangles, which only have acute angles. They can be explicitly counted and enumerated, also modulo the symmetries of $I^{n}$ .

Poincaré Inequalities and Moment Maps

Bo’az Klartag (2013)

Annales de la faculté des sciences de Toulouse Mathématiques

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We discuss a method for obtaining Poincaré-type inequalities on arbitrary convex bodies in $ℝ^{n}$ . Our technique involves a dual version of Bochner’s formula and a certain moment map, and it also applies to some non-convex sets. In particular, we generalize the central limit theorem for convex bodies to a class of non-convex domains, including the unit balls of $ℓ_{p}$ -spaces in $ℝ^{n}$ for $0 < p < 1$ .

Convex integration with constraints and applications to phase transitions and partial differential equations

Stefan Müller, Vladimír Šverák (1999)

Journal of the European Mathematical Society

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We study solutions of first order partial differential relations $D u \in K$ , where $u : Ω \subset ℝ^{n} \to ℝ^{m}$ is a Lipschitz map and $K$ is a bounded set in $m \times n$ matrices, and extend Gromov’s theory of convex integration in two ways. First, we allow for additional constraints on the minors of $D u$ and second we replace Gromov’s $P$ −convex hull by the (functional) rank-one convex hull. The latter can be much larger than the former and this has important consequences for the existence of ‘wild’ solutions to elliptic systems. Our...

The Young inequality and the Δ₂-condition

Philippe Laurençot (2002)

Colloquium Mathematicae

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If φ: [0,∞) → [0,∞) is a convex function with φ(0) = 0 and conjugate function φ*, the inequality $x y \leq ε φ (x) + C_{ε} φ * (y)$ is shown to hold true for every ε ∈ (0,∞) if and only if φ* satisfies the Δ₂-condition.

On the null space of a Colin de Verdière matrix

Lászlo Lovász, Alexander Schrijver (1999)

Annales de l'institut Fourier

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Let $G = (V, E)$ be a 3-connected planar graph, with $V = {1, ..., n}$ . Let $M = (m_{i, j})$ be a symmetric $n \times n$ matrix with exactly one negative eigenvalue (of multiplicity 1), such that for $i, j$ with $i \neq j$ , if $i$ and $j$ are adjacent then $m_{i, j} < 0$ and if $i$ and $j$ are nonadjacent then $m_{i, j} = 0$ , and such that $M$ has rank $n - 3$ . Then the null space $ker M$ of $M$ gives an embedding of $G$ in $S^{2}$ as follows: let ${a, b, c}$ be a basis of $ker M$ , and for $i \in V$ let $ϕ (i) : = (a_{i}, b_{i}, c_{i})^{T}$ ; then $ϕ (i) \neq 0$ , and $ψ (i) : = ϕ (i) / ∥ ϕ (i) ∥$ embeds $V$ in $S^{2}$ such that connecting, for any two adjacent vertices $i, j$ , the points $ψ (i)$ and $ψ (j)$ by a shortest geodesic...

Sum labellings of cycle hypergraphs

Hanns-Martin Teichert (2000)

Discussiones Mathematicae Graph Theory

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A hypergraph is a sum hypergraph iff there are a finite S ⊆ IN⁺ and d̲, [d̅] ∈ IN⁺ with 1 < d̲ ≤ [d̅] such that is isomorphic to the hypergraph $_{d ̲, [d ̅]} (S) = (V,)$ where V = S and $= e \subseteq S : d ̲ \leq | e | \leq [d ̅] \land \sum_{v \in e} v \in S$ . For an arbitrary hypergraph the sum number σ = σ() is defined to be the minimum number of isolated vertices $y ₁, . . ., y_{σ} \notin V$ such that $\cup y ₁, . . ., y_{σ}$ is a sum hypergraph. Generalizing the graph Cₙ we obtain d-uniform hypergraphs where any d consecutive vertices of Cₙ form an edge. We determine sum numbers and investigate properties of sum labellings...

Color-bounded hypergraphs, V: host graphs and subdivisions

Csilla Bujtás, Zsolt Tuza, Vitaly Voloshin (2011)

Discussiones Mathematicae Graph Theory

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A color-bounded hypergraph is a hypergraph (set system) with vertex set X and edge set = E₁,...,Eₘ, together with integers $s_{i}$ and $t_{i}$ satisfying $1 \leq s_{i} \leq t_{i} \leq | E_{i} |$ for each i = 1,...,m. A vertex coloring φ is proper if for every i, the number of colors occurring in edge $E_{i}$ satisfies $s_{i} \leq | φ (E_{i}) | \leq t_{i}$ . The hypergraph ℋ is colorable if it admits at least one proper coloring. We consider hypergraphs ℋ over a “host graph”, that means a graph G on the same vertex set X as ℋ, such that each $E_{i}$ induces a connected subgraph in G....

Bounds for the number of meeting edges in graph partitioning

Qinghou Zeng, Jianfeng Hou (2017)

Czechoslovak Mathematical Journal

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Let $G$ be a weighted hypergraph with edges of size at most 2. Bollobás and Scott conjectured that $G$ admits a bipartition such that each vertex class meets edges of total weight at least $(w_{1} - Δ_{1}) / 2 + 2 w_{2} / 3$ , where $w_{i}$ is the total weight of edges of size $i$ and $Δ_{1}$ is the maximum weight of an edge of size 1. In this paper, for positive integer weighted hypergraph $G$ (i.e., multi-hypergraph), we show that there exists a bipartition of $G$ such that each vertex class meets edges of total weight at least $(w_{0} - 1) / 6 + (w_{1} - Δ_{1}) / 3 + 2 w_{2} / 3$ , where...

Fires on trees

Jean Bertoin (2012)

Annales de l'I.H.P. Probabilités et statistiques

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We consider random dynamics on the edges of a uniform Cayley tree with $n$ vertices, in which edges are either flammable, fireproof, or burnt. Every flammable edge is replaced by a fireproof edge at unit rate, while fires start at smaller rate $n^{- α}$ on each flammable edge, then propagate through the neighboring flammable edges and are only stopped at fireproof edges. A vertex is called fireproof when all its adjacent edges are fireproof. We show that as $n \to \infty$ , the terminal density of fireproof...

Domination and independence subdivision numbers of graphs

Teresa W. Haynes, Sandra M. Hedetniemi, Stephen T. Hedetniemi (2000)

Discussiones Mathematicae Graph Theory

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The domination subdivision number $s d_{γ} (G)$ of a graph is the minimum number of edges that must be subdivided (where an edge can be subdivided at most once) in order to increase the domination number. Arumugam showed that this number is at most three for any tree, and conjectured that the upper bound of three holds for any graph. Although we do not prove this interesting conjecture, we give an upper bound for the domination subdivision number for any graph G in terms of the minimum degrees of...

On-line ranking number for cycles and paths

Erik Bruoth, Mirko Horňák (1999)

Discussiones Mathematicae Graph Theory

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A k-ranking of a graph G is a colouring φ:V(G) → 1,...,k such that any path in G with endvertices x,y fulfilling φ(x) = φ(y) contains an internal vertex z with φ(z) > φ(x). On-line ranking number $χ *_{r} (G)$ of a graph G is a minimum k such that G has a k-ranking constructed step by step if vertices of G are coming and coloured one by one in an arbitrary order; when colouring a vertex, only edges between already present vertices are known. Schiermeyer, Tuza and Voigt proved that $χ *_{r} (P ₙ) < 3 l o g ₂ n$ for n ≥ 2....