Wyniki wyszukiwania

1

Signed Total Roman Edge Domination In Graphs

100%

Asgharsharghi L., Sheikholeslami S. M.

Discussiones Mathematicae Graph Theory

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2017

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tom 37

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nr 4

1039-1053

EN

Let G = (V,E) be a simple graph with vertex set V and edge set E. A signed total Roman edge dominating function of G is a function f : Ʃ → {−1, 1, 2} satisfying the conditions that (i) Ʃe′∈N(e) f(e′) ≥ 1 for each e ∈ E, where N(e) is the open neighborhood of e, and (ii) every edge e for which f(e) = −1 is adjacent to at least one edge e′ for which f(e′) = 2. The weight of a signed total Roman edge dominating function f is !(f) = Ʃe∈E f(e). The signed total Roman edge domination number y′stR(G) of G is the minimum weight of a signed total Roman edge dominating function of G. In this paper, we first prove that for every tree T of order n ≥ 4, y′stR(T) ≥ 17−2n/5 and we characterize all extreme trees, and then we present some sharp bounds for the signed total Roman edge domination number. We also determine this parameter for some classes of graphs.

2

Signed Roman Edgek-Domination in Graphs

81%

Asgharsharghi L., Sheikholeslami S. M., Volkmann L.

Discussiones Mathematicae Graph Theory

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2017

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tom 37

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nr 1

39-53

EN

Let k ≥ 1 be an integer, and G = (V, E) be a finite and simple graph. The closed neighborhood NG[e] of an edge e in a graph G is the set consisting of e and all edges having a common end-vertex with e. A signed Roman edge k-dominating function (SREkDF) on a graph G is a function f : E → {−1, 1, 2} satisfying the conditions that (i) for every edge e of G, ∑x∈NG[e] f(x) ≥ k and (ii) every edge e for which f(e) = −1 is adjacent to at least one edge e′ for which f(e′) = 2. The minimum of the values ∑e∈E f(e), taken over all signed Roman edge k-dominating functions f of G is called the signed Roman edge k-domination number of G, and is denoted by γ′sRk(G). In this paper we initiate the study of the signed Roman edge k-domination in graphs and present some (sharp) bounds for this parameter.

3

The Distance Roman Domination Numbers of Graphs

81%

Aram H., Norouzian S., Sheikholeslami S. M.

Discussiones Mathematicae Graph Theory

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2013

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tom 33

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nr 4

717-730

EN

Let k be a positive integer, and let G be a simple graph with vertex set V (G). A k-distance Roman dominating function on G is a labeling f : V (G) → {0, 1, 2} such that for every vertex with label 0, there is a vertex with label 2 at distance at most k from each other. The weight of a k-distance Roman dominating function f is the value w(f) =∑v∈V f(v). The k-distance Roman domination number of a graph G, denoted by γkR (D), equals the minimum weight of a k-distance Roman dominating function on G. Note that the 1-distance Roman domination number γ1R (G) is the usual Roman domination number γR(G). In this paper, we investigate properties of the k-distance Roman domination number. In particular, we prove that for any connected graph G of order n ≥ k +2, γkR (G) ≤ 4n/(2k +3) and we characterize all graphs that achieve this bound. Some of our results extend these ones given by Cockayne et al. in 2004 and Chambers et al. in 2009 for the Roman domination number.

4

The k-Rainbow Bondage Number of a Digraph

81%

Amjadi J., Mohammadi N., Sheikholeslami S. M., Volkmann L.

Discussiones Mathematicae Graph Theory

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2015

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tom 35

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nr 2

261-270

EN

Let D = (V,A) be a finite and simple digraph. A k-rainbow dominating function (kRDF) of a digraph D is a function f from the vertex set V to the set of all subsets of the set {1, 2, . . . , k} such that for any vertex v ∈ V with f(v) = Ø the condition ∪u∈N−(v) f(u) = {1, 2, . . . , k} is fulfilled, where N−(v) is the set of in-neighbors of v. The weight of a kRDF f is the value w(f) = ∑v∈V |f(v)|. The k-rainbow domination number of a digraph D, denoted by γrk(D), is the minimum weight of a kRDF of D. The k-rainbow bondage number brk(D) of a digraph D with maximum in-degree at least two, is the minimum cardinality of all sets A′ ⊆ A for which γrk(D−A′) > γrk(D). In this paper, we establish some bounds for the k-rainbow bondage number and determine the k-rainbow bondage number of several classes of digraphs.

Ograniczanie wyników

4 Discussiones Mathematicae Graph Theory

4 Sheikholeslami S. M.

2 Asgharsharghi L.

2 Volkmann L.

1 Amjadi J.

1 Aram H.

1 Mohammadi N.

1 Norouzian S.

2 2017

1 2015

1 2013

Signed Total Roman Edge Domination In Graphs

Signed Roman Edgek-Domination in Graphs

The Distance Roman Domination Numbers of Graphs

The k-Rainbow Bondage Number of a Digraph