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Stratidistance in stratified graphs

Gary Chartrand, Heather Gavlas, Michael A. Henning, Reza Rashidi (1997)

Mathematica Bohemica

A graph G is a stratified graph if its vertex set is partitioned into classes (each of which is a stratum or a color class). A stratified graph with k strata is k -stratified. If G is a connected k -stratified graph with strata S i ( 1 i ...

Strong asymmetric digraphs with prescribed interior and annulus

Steven J. Winters (2001)

Czechoslovak Mathematical Journal

The directed distance d ( u , v ) from u to v in a strong digraph D is the length of a shortest u - v path in D . The eccentricity e ( v ) of a vertex v in D is the directed distance from v to a vertex furthest from v in D . The center and periphery of a strong digraph are two well known subdigraphs induced by those vertices of minimum and maximum eccentricities, respectively. We introduce the interior and annulus of a digraph which are two induced subdigraphs involving the remaining vertices. Several results concerning...

Strong Chromatic Index Of Planar Graphs With Large Girth

Gerard Jennhwa Chang, Mickael Montassier, Arnaud Pêche, André Raspaud (2014)

Discussiones Mathematicae Graph Theory

Let Δ ≥ 4 be an integer. In this note, we prove that every planar graph with maximum degree Δ and girth at least 1 Δ+46 is strong (2Δ−1)-edgecolorable, that is best possible (in terms of number of colors) as soon as G contains two adjacent vertices of degree Δ. This improves [6] when Δ ≥ 6.

Strong Equality Between the Roman Domination and Independent Roman Domination Numbers in Trees

Mustapha Chellali, Nader Jafari Rad (2013)

Discussiones Mathematicae Graph Theory

A Roman dominating function (RDF) on a graph G = (V,E) is a function f : V −→ {0, 1, 2} satisfying the condition that every vertex u for which f(u) = 0 is adjacent to at least one vertex v for which f(v) = 2. The weight of an RDF is the value f(V (G)) = P u2V (G) f(u). An RDF f in a graph G is independent if no two vertices assigned positive values are adjacent. The Roman domination number R(G) (respectively, the independent Roman domination number iR(G)) is the minimum weight of an RDF (respectively,...

Strong sequences and the weight of regular spaces

Marian Turzański (1992)

Commentationes Mathematicae Universitatis Carolinae

It will be shown that if in a family of sets there exists a strong sequence of the length ( κ λ ) + then this family contains a subfamily consisting of λ + pairwise disjoint sets. The method of strong sequences will be used for estimating the weight of regular spaces.

Strong sequences, binary families and Esenin-Volpin's theorem

Marian Turzański (1992)

Commentationes Mathematicae Universitatis Carolinae

One of the most important and well known theorem in the class of dyadic spaces is Esenin-Volpin's theorem of weight of dyadic spaces. The aim of this paper is to prove Esenin-Volpin's theorem in general form in class of thick spaces which possesses special subbases.

Strong ƒ-Star Factors of Graphs

Zheng Yan (2015)

Discussiones Mathematicae Graph Theory

Let G be a graph and f : V (G) → {2, 3, . . .}. A spanning subgraph F is called strong f-star of G if each component of F is a star whose center x satisfies degF (x) ≤ ƒ(x) and F is an induced subgraph of G. In this paper, we prove that G has a strong f-star factor if and only if oddca(G − S) ≤ ∑x∊S ƒ(x) for all S ⊂ V (G), where oddca(G) denotes the number of odd complete-cacti of G.

Stronger bounds for generalized degrees and Menger path systems

R.J. Faudree, Zs. Tuza (1995)

Discussiones Mathematicae Graph Theory

For positive integers d and m, let P d , m ( G ) denote the property that between each pair of vertices of the graph G, there are m internally vertex disjoint paths of length at most d. For a positive integer t a graph G satisfies the minimum generalized degree condition δₜ(G) ≥ s if the cardinality of the union of the neighborhoods of each set of t vertices of G is at least s. Generalized degree conditions that ensure that P d , m ( G ) is satisfied have been investigated. In particular, it has been shown, for fixed positive...

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