no. 1-2
Combinatorics
A lower bound on the total outer-independent domination number of a tree
[Une borne inférieure pour le cardinal des sous-ensembles totalement dominants et extérieurement-indépendants d'un arbre]

Présenté par : the Editorial Board

Krzywkowski, Marcin1
1 Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland
Comptes Rendus. Mathématique, Tome 349 (2011) no. 1-2, pp. 7-9.

Un sous-ensemble totalement dominant et extérieurement indépendant d'un graphe est un sous-ensemble D des sommets de G tel que chaque sommet de G ait un voisin dans D et l'ensemble V(G)∖D soit indépendant. Le plus petit cardinal d'un tel sous-ensemble est noté γtoi(G). Nous démontrons que pour tout arbre T non trivial, d'ordre n avec l feuilles, nous avons γtoi(T)⩾(2n−2l+2)/3. De plus, nous caractérisons les arbres réalisant cette borne inférieure.

A total outer-independent dominating set of a graph G is a set D of vertices of G such that every vertex of G has a neighbour in D, and the set V(G)∖D is independent. The total outer-independent domination number of a graph G, denoted by γtoi(G), is the minimum cardinality of the total outer-independent dominating set of G. We prove that for every nontrivial tree T of order n with l leaves we have γtoi(T)⩾(2n−2l+2)/3, and we characterize the trees attaining this lower bound.

Reçu le :
Accepté le :
Publié le :
DOI : 10.1016/j.crma.2010.11.021
Krzywkowski, Marcin 1

1 Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland 
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Krzywkowski, Marcin. A lower bound on the total outer-independent domination number of a tree. Comptes Rendus. Mathématique, Tome 349 (2011) no. 1-2, pp. 7-9. doi : 10.1016/j.crma.2010.11.021. http://www.numdam.org/articles/10.1016/j.crma.2010.11.021/

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[3] Haynes, T.; Hedetniemi, S.; Slater, P. Fundamentals of Domination in Graphs, Marcel Dekker, New York, 1998

[4] Domination in Graphs: Advanced Topics (Haynes, T.; Hedetniemi, S.; Slater, P., eds.), Marcel Dekker, New York, 1998

[5] M. Krzywkowski, Total outer-independent domination in graphs, submitted for publication.

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