Temat: trees - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: On the global offensive alliance number of a tree
Autorzy:: Bouzefrane, M.
Chellali, M.
Powiązania:: https://bibliotekanauki.pl/articles/255263.pdf
Data publikacji:: 2009
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: global offensive alliance number
domination number
trees
Opis:: For a graph G = (V, E), a set S ⊆ V is a dominating set if every vertex in V - S has at least a neighbor in S. A dominating set S is a global offensive alliance if for every vertex v in V - S, at least half of the vertices in its closed neighborhood are in S. The domination number ϒ(G) is the minimum cardinality of a dominating set of G and the global offensive alliance number ϒo(G) is the minimum cardinality of a global offensive alliance of G. We first show that every tree of order at least three with l leaves and s support vertices satisfies ϒo(T) ≥ (n - l + s + 1)/3 and we characterize extremal trees attaining this lower bound. Then we give a constructive characterization of trees with equal domination and global offensive alliance numbers.
Źródło:: Opuscula Mathematica; 2009, 29, 3; 223-228
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 2.

Tytuł:: Global offensive k-alliance in bipartite graphs
Autorzy:: Chellali, M.
Volkmann, L.
Powiązania:: https://bibliotekanauki.pl/articles/255370.pdf
Data publikacji:: 2012
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: global offensive k-alliance number
bipartite graphs
trees
Opis:: Let k ≥ 0 be an integer. A set S of vertices of a graph G = (V (G), E(G)) is called a global offensive k-alliance if /N(v) ∩ S/ ≥ /N(v) - S/ + k for every v ∈ V (G) - S, where 0 ≤ k Δ and Δ is the maximum degree of G. The global offensive k-alliance number [formula] is the minimum cardinality of a global offensive k-alliance in G. We show that for every bipartite graph G and every integer k ≥ 2, [formula], where Lk(G) is the set of vertices of degree at most k - 1. Moreover, extremal trees attaining this upper bound are characterized.
Źródło:: Opuscula Mathematica; 2012, 32, 1; 83-89
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 3.

Tytuł:: A note on global alliances in trees
Autorzy:: Bouzefrane, M.
Chellali, M.
Powiązania:: https://bibliotekanauki.pl/articles/254977.pdf
Data publikacji:: 2011
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: global defensive alliance
global offensive alliance
domination
trees
Opis:: For a graph G = (V,E), a set S ⊆ V is a dominating set if every vertex in V - S has at least a neighbor in S. A dominating set S is a global offensive (respectively, defensive) alliance if for each vertex in V - S (respectively, in S) at least half the vertices from the closed neighborhood of v are in S. The domination number γ (G) is the minimum cardinality of a dominating set of G, and the global offensive alliance number γo(G) (respectively, global defensive alliance number γa(G)) is the minimum cardinality of a global offensive alliance (respectively, global deffensive alliance) of G. We show that if T is a tree of order n, then γo(T) ≤ 2γ (T) - 1 and if n ≥ 3, then γo(T) ≤ 3/2?a(T) ? 1. Moreover, all extremal trees attaining the first bound are characterized.
Źródło:: Opuscula Mathematica; 2011, 31, 2; 153-159
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 4.

Tytuł:: Trees with equal global offensive k-alliance and k-domination numbers
Autorzy:: Chellali, M.
Powiązania:: https://bibliotekanauki.pl/articles/255451.pdf
Data publikacji:: 2010
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: global offensive k-alliance number
k-domination number
trees
Opis:: Let k ≥ 1 be an integer. A set S of vertices of a graph G = (V (G), E(G)) is called a global offensive k-alliance if |N(v) ∩ S| ≥ |N(v) - S| + k for every v ∈ V (G) - S, where N(v) is the neighborhood of v. The subset S is a k-dominating set of G if every vertex in V (G) - S has at least k neighbors in S. The global offensive k-alliance number [formula] is the minimum cardinality of a global offensive k-alliance in G and the k-domination number ϒ k(G) is the minimum cardinality of a k-dominating set of G. For every integer k ≥ 1 every graph G satisfies [formula]. In this paper we provide for k ≥ 2 a characterization of trees T with equal [formula] and ϒ k(T).
Źródło:: Opuscula Mathematica; 2010, 30, 3; 249-254
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 5.

Tytuł:: Bounds on the 2-domination number in cactus graphs
Autorzy:: Chellali, M.
Powiązania:: https://bibliotekanauki.pl/articles/254915.pdf
Data publikacji:: 2006
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: 2-domination number
total domination number
independence number
cactus graphs
trees
Opis:: A 2-dominating set of a graph G is a set D of vertices of G such that every vertex not in S is dominated at least twice. The minimum cardinality of a 2-dominating set of G is the 2-domination number γ2(G). We show that if G is a nontrivial connected cactus graph with k(G) even cycles (k(G) ≥ 0), then γ2(G) ≥ γt(G) - k(G), and if G is a graph of order n with at most one cycle, then γ2(G) ≥ (n + l - s)/2 improving Fink and Jacobson's lower bound for trees with l > s, where γt(G), l and s are the total domination number, the number of leaves and support vertices of G, respectively. We also show that if T is a tree of order n ≥ 3, then γ2(T) ≤ β(T) + s - 1, where β(T) is the independence number of T.
Źródło:: Opuscula Mathematica; 2006, 26, 1; 5-12
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

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