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A Characterization of Trees for a New Lower Bound on the K-Independence Number

100%
Meddah N., Blidia M.
Discussiones Mathematicae Graph Theory
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2013
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tom 33
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nr 2
395-410
EN
Let k be a positive integer and G = (V,E) a graph of order n. A subset S of V is a k-independent set of G if the maximum degree of the subgraph induced by the vertices of S is less or equal to k − 1. The maximum cardinality of a k-independent set of G is the k-independence number βk(G). In this paper, we show that for every graph [xxx], where χ(G), s(G) and Lv are the chromatic number, the number of supports vertices and the number of leaves neighbors of v, in the graph G, respectively. Moreover, we characterize extremal trees attaining these bounds.
2
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A characterization of locating-total domination edge critical graphs

100%
Blidia M., Dali W.
Discussiones Mathematicae Graph Theory
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2011
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tom 31
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nr 1
197-202
EN
For a graph G = (V,E) without isolated vertices, a subset D of vertices of V is a total dominating set (TDS) of G if every vertex in V is adjacent to a vertex in D. The total domination number γₜ(G) is the minimum cardinality of a TDS of G. A subset D of V which is a total dominating set, is a locating-total dominating set, or just a LTDS of G, if for any two distinct vertices u and v of V(G)∖D, $N_G(u) ∩ D ≠ N_G(v) ∩ D$. The locating-total domination number $γ_L^t(G)$ is the minimum cardinality of a locating-total dominating set of G. A graph G is said to be a locating-total domination edge removal critical graph, or just a $γ_L^{t+}$-ER-critical graph, if $γ_L^t(G-e) > γ_L^t(G)$ for all e non-pendant edge of E. The purpose of this paper is to characterize the class of $γ_L^{t+}$-ER-critical graphs.
3
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Maximal k-independent sets in graphs

81%
Blidia M., Chellali M., Favaron O., Meddah N.
Discussiones Mathematicae Graph Theory
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2008
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tom 28
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nr 1
151-163
EN
A subset of vertices of a graph G is k-independent if it induces in G a subgraph of maximum degree less than k. The minimum and maximum cardinalities of a maximal k-independent set are respectively denoted iₖ(G) and βₖ(G). We give some relations between βₖ(G) and $β_j(G)$ and between iₖ(G) and $i_j(G)$ for j ≠ k. We study two families of extremal graphs for the inequality i₂(G) ≤ i(G) + β(G). Finally we give an upper bound on i₂(G) and a lower bound when G is a cactus.
4
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On the p-domination number of cactus graphs

81%
Blidia M., Chellali M., Volkmann L.
Discussiones Mathematicae Graph Theory
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2005
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tom 25
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nr 3
355-361
EN
Let p be a positive integer and G = (V,E) a graph. A subset S of V is a p-dominating set if every vertex of V-S is dominated at least p times. The minimum cardinality of a p-dominating set a of G is the p-domination number γₚ(G). It is proved for a cactus graph G that γₚ(G) ⩽ (|V| + |Lₚ(G)| + c(G))/2, for every positive integer p ⩾ 2, where Lₚ(G) is the set of vertices of G of degree at most p-1 and c(G) is the number of odd cycles in G.
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