Displaying similar documents to “Some results on total domination in direct products of graphs”

Improving some bounds for dominating Cartesian products

Bert L. Hartnell, Douglas F. Rall (2003)

Discussiones Mathematicae Graph Theory

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The study of domination in Cartesian products has received its main motivation from attempts to settle a conjecture made by V.G. Vizing in 1968. He conjectured that γ(G)γ(H) is a lower bound for the domination number of the Cartesian product of any two graphs G and H. Most of the progress on settling this conjecture has been limited to verifying the conjectured lower bound if one of the graphs has a certain structural property. In addition, a number of authors have established bounds...

New Bounds on the Signed Total Domination Number of Graphs

Seyyed Mehdi Hosseini Moghaddam, Doost Ali Mojdeh, Babak Samadi, Lutz Volkmann (2016)

Discussiones Mathematicae Graph Theory

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In this paper, we study the signed total domination number in graphs and present new sharp lower and upper bounds for this parameter. For example by making use of the classic theorem of Turán [8], we present a sharp lower bound on Kr+1-free graphs for r ≥ 2. Applying the concept of total limited packing we bound the signed total domination number of G with δ(G) ≥ 3 from above by [...] . Also, we prove that γst(T) ≤ n − 2(s − s′) for any tree T of order n, with s support vertices and...

On dominating the Cartesian product of a graph and K₂

Bert L. Hartnell, Douglas F. Rall (2004)

Discussiones Mathematicae Graph Theory

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In this paper we consider the Cartesian product of an arbitrary graph and a complete graph of order two. Although an upper and lower bound for the domination number of this product follow easily from known results, we are interested in the graphs that actually attain these bounds. In each case, we provide an infinite class of graphs to show that the bound is sharp. The graphs that achieve the lower bound are of particular interest given the special nature of their dominating sets and...

A Note on the Locating-Total Domination in Graphs

Mirka Miller, R. Sundara Rajan, R. Jayagopal, Indra Rajasingh, Paul Manuel (2017)

Discussiones Mathematicae Graph Theory

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In this paper we obtain a sharp (improved) lower bound on the locating-total domination number of a graph, and show that the decision problem for the locating-total domination is NP-complete.

On the Complexity of Reinforcement in Graphs

Nader Jafari Rad (2016)

Discussiones Mathematicae Graph Theory

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We show that the decision problem for p-reinforcement, p-total rein- forcement, total restrained reinforcement, and k-rainbow reinforcement are NP-hard for bipartite graphs.

Domination, independence and irredundance in graphs

Jerzy Topp

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CONTENTS1. Introduction........................................................................................................ 5 1.1. Purpose and scope................................................................................. 5 1.2. Basic graphtheoretical terms................................................................ 62. Domination, independence and irredundance in graphs................................ 9 2.1. Introduction and preliminaries.................................................................

Placing bipartite graphs of small size II

Beata Orchel (1996)

Discussiones Mathematicae Graph Theory

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In this paper we give all pairs of non mutually placeable (p,q)-bipartite graphs G and H such that 2 ≤ p ≤ q, e(H) ≤ p and e(G)+e(H) ≤ 2p+q-1.

Relating 2-Rainbow Domination To Roman Domination

José D. Alvarado, Simone Dantas, Dieter Rautenbach (2017)

Discussiones Mathematicae Graph Theory

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For a graph G, let R(G) and yr2(G) denote the Roman domination number of G and the 2-rainbow domination number of G, respectively. It is known that yr2(G) ≤ R(G) ≤ 3/2yr2(G). Fujita and Furuya [Difference between 2-rainbow domination and Roman domination in graphs, Discrete Appl. Math. 161 (2013) 806-812] present some kind of characterization of the graphs G for which R(G) − yr2(G) = k for some integer k. Unfortunately, their result does not lead to an algorithm that allows to recognize...

Generalized domination, independence and irredudance in graphs

Mieczysław Borowiecki, Danuta Michalak, Elżbieta Sidorowicz (1997)

Discussiones Mathematicae Graph Theory

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The purpose of this paper is to present some basic properties of 𝓟-dominating, 𝓟-independent, and 𝓟-irredundant sets in graphs which generalize well-known properties of dominating, independent and irredundant sets, respectively.

Some recent results on domination in graphs

Michael D. Plummer (2006)

Discussiones Mathematicae Graph Theory

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In this paper, we survey some new results in four areas of domination in graphs, namely: (1) the toughness and matching structure of graphs having domination number 3 and which are "critical" in the sense that if one adds any missing edge, the domination number falls to 2; (2) the matching structure of graphs having domination number 3 and which are "critical" in the sense that if one deletes any vertex, the domination number falls to 2; ...

On the Signed (Total) K-Independence Number in Graphs

Abdollah Khodkar, Babak Samadi, Lutz Volkmann (2015)

Discussiones Mathematicae Graph Theory

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Let G be a graph. A function f : V (G) → {−1, 1} is a signed k- independence function if the sum of its function values over any closed neighborhood is at most k − 1, where k ≥ 2. The signed k-independence number of G is the maximum weight of a signed k-independence function of G. Similarly, the signed total k-independence number of G is the maximum weight of a signed total k-independence function of G. In this paper, we present new bounds on these two parameters which improve some existing...

Total domination in categorical products of graphs

Douglas F. Rall (2005)

Discussiones Mathematicae Graph Theory

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Several of the best known problems and conjectures in graph theory arise in studying the behavior of a graphical invariant on a graph product. Examples of this are Vizing's conjecture, Hedetniemi's conjecture and the calculation of the Shannon capacity of graphs, where the invariants are the domination number, the chromatic number and the independence number on the Cartesian, categorical and strong product, respectively. In this paper we begin an investigation of the total domination...

A note on (k,l)-kernels in B-products of graphs

Iwona Włoch (1996)

Discussiones Mathematicae Graph Theory

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B-products of graphs and their generalizations were introduced in [4]. We determined the parameters k, l of (k,l)-kernels in generalized B-products of graphs. These results are generalizations of theorems from [2].

On the total restrained domination number of direct products of graphs

Wai Chee Shiu, Hong-Yu Chen, Xue-Gang Chen, Pak Kiu Sun (2012)

Discussiones Mathematicae Graph Theory

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Let G = (V,E) be a graph. A total restrained dominating set is a set S ⊆ V where every vertex in V∖S is adjacent to a vertex in S as well as to another vertex in V∖S, and every vertex in S is adjacent to another vertex in S. The total restrained domination number of G, denoted by γ r t ( G ) , is the smallest cardinality of a total restrained dominating set of G. We determine lower and upper bounds on the total restrained domination number of the direct product of two graphs. Also, we show that...

On partitions of hereditary properties of graphs

Mieczysław Borowiecki, Anna Fiedorowicz (2006)

Discussiones Mathematicae Graph Theory

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In this paper a concept 𝓠-Ramsey Class of graphs is introduced, where 𝓠 is a class of bipartite graphs. It is a generalization of well-known concept of Ramsey Class of graphs. Some 𝓠-Ramsey Classes of graphs are presented (Theorem 1 and 2). We proved that 𝓣₂, the class of all outerplanar graphs, is not 𝓓₁-Ramsey Class (Theorem 3). This results leads us to the concept of acyclic reducible bounds for a hereditary property 𝓟 . For 𝓣₂ we found two bounds (Theorem 4). An improvement,...

Packing of graphs

Woźniak Mariusz

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PrefaceThere are two basic reference texts on packing theory: the last chapter of Bollobás's book [6] (1978) and the 4th chapter of Yap's book [85] (1986). They still remain the main references to packing problems. However, many papers related to these problems have recently been published and the reason for writing this survey is to gather in a systematic form results scattered throughout the literature.I wish I could name all who deserve my thanks. I am particularly grateful to A....

Labeled Embedding Of (n, n-2)-Graphs In Their Complements

M.-A. Tahraoui, E. Duchêne, H. Kheddouci (2017)

Discussiones Mathematicae Graph Theory

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Graph packing generally deals with unlabeled graphs. In [4], the authors have introduced a new variant of the graph packing problem, called the labeled packing of a graph. This problem has recently been studied on trees [M.A. Tahraoui, E. Duchêne and H. Kheddouci, Labeled 2-packings of trees, Discrete Math. 338 (2015) 816-824] and cycles [E. Duchˆene, H. Kheddouci, R.J. Nowakowski and M.A. Tahraoui, Labeled packing of graphs, Australas. J. Combin. 57 (2013) 109-126]. In this note, we...

A note on uniquely embeddable graphs

Mariusz Woźniak (1998)

Discussiones Mathematicae Graph Theory

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Let G be a simple graph of order n and size e(G). It is well known that if e(G) ≤ n-2, then there is an embedding G into its complement [G̅]. In this note, we consider a problem concerning the uniqueness of such an embedding.

Eternal Domination: Criticality and Reachability

William F. Klostermeyer, Gary MacGillivray (2017)

Discussiones Mathematicae Graph Theory

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We show that for every minimum eternal dominating set, D, of a graph G and every vertex v ∈ D, there is a sequence of attacks at the vertices of G which can be defended in such a way that an eternal dominating set not containing v is reached. The study of the stronger assertion that such a set can be reached after a single attack is defended leads to the study of graphs which are critical in the sense that deleting any vertex reduces the eternal domination number. Examples of these graphs...

On Generalized Sierpiński Graphs

Juan Alberto Rodríguez-Velázquez, Erick David Rodríguez-Bazan, Alejandro Estrada-Moreno (2017)

Discussiones Mathematicae Graph Theory

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In this paper we obtain closed formulae for several parameters of generalized Sierpiński graphs S(G, t) in terms of parameters of the base graph G. In particular, we focus on the chromatic, vertex cover, clique and domination numbers.