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Wyświetlanie 1-11 z 11
Tytuł:
On Total Domination in the Cartesian Product of Graphs
Autorzy:
Brešar, Boštjan
Hartinger, Tatiana Romina
Kos, Tim
Milanič, Martin
Powiązania:
https://bibliotekanauki.pl/articles/31342240.pdf
Data publikacji:
2018-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total domination
Cartesian product
total domination quotient
Opis:
Ho proved in [A note on the total domination number, Util. Math. 77 (2008) 97–100] that the total domination number of the Cartesian product of any two graphs without isolated vertices is at least one half of the product of their total domination numbers. We extend a result of Lu and Hou from [Total domination in the Cartesian product of a graph and $ K_2 $ or $ C_n $, Util. Math. 83 (2010) 313–322] by characterizing the pairs of graphs $G$ and $H$ for which $ \gamma_t (G \square H)=1/2 \gamma_t (G) \gamma_t (H) $, whenever $ \gamma_t (H) = 2 $. In addition, we present an infinite family of graphs $ G_n $ with $ \gamma_t (G_n) = 2n $, which asymptotically approximate equality in $ \gamma_t (G_n \square H_n ) \ge 1/2 \gamma_t (G_n)^2 $.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 4; 963-976
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paired domination in prisms of graphs
Autorzy:
Mynhardt, Christina
Schurch, Mark
Powiązania:
https://bibliotekanauki.pl/articles/744116.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
paired domination
prism of a graph
Cartesian product
Opis:
The paired domination number $γ_{pr}(G)$ of a graph G is the smallest cardinality of a dominating set S of G such that ⟨S⟩ has a perfect matching. The generalized prisms πG of G are the graphs obtained by joining the vertices of two disjoint copies of G by |V(G)| independent edges. We provide characterizations of the following three classes of graphs: $γ_{pr}(πG) = 2γ_{pr}(G)$ for all πG; $γ_{pr}(K₂☐ G) = 2γ_{pr}(G)$; $γ_{pr}(K₂☐ G) = γ_{pr}(G)$.
Źródło:
Discussiones Mathematicae Graph Theory; 2011, 31, 1; 5-23
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graphs with convex domination number close to their order
Autorzy:
Cyman, Joanna
Lemańska, Magdalena
Raczek, Joanna
Powiązania:
https://bibliotekanauki.pl/articles/743979.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
convex domination
Cartesian product
Opis:
For a connected graph G = (V,E), a set D ⊆ V(G) is a dominating set of G if every vertex in V(G)-D has at least one neighbour in D. The distance $d_G(u,v)$ between two vertices u and v is the length of a shortest (u-v) path in G. An (u-v) path of length $d_G(u,v)$ is called an (u-v)-geodesic. A set X ⊆ V(G) is convex in G if vertices from all (a-b)-geodesics belong to X for any two vertices a,b ∈ X. A set X is a convex dominating set if it is convex and dominating. The convex domination number $γ_{con}(G)$ of a graph G is the minimum cardinality of a convex dominating set in G. Graphs with the convex domination number close to their order are studied. The convex domination number of a Cartesian product of graphs is also considered.
Źródło:
Discussiones Mathematicae Graph Theory; 2006, 26, 2; 307-316
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Vizings conjecture
Autorzy:
Bresar, Bostjan
Powiązania:
https://bibliotekanauki.pl/articles/743820.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph
Cartesian product
domination number
Opis:
A dominating set D for a graph G is a subset of V(G) such that any vertex in V(G)-D has a neighbor in D, and a domination number γ(G) is the size of a minimum dominating set for G. For the Cartesian product G ⃞ H Vizing's conjecture [10] states that γ(G ⃞ H) ≥ γ(G)γ(H) for every pair of graphs G,H. In this paper we introduce a new concept which extends the ordinary domination of graphs, and prove that the conjecture holds when γ(G) = γ(H) = 3.
Źródło:
Discussiones Mathematicae Graph Theory; 2001, 21, 1; 5-11
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The domination number of $K_n^3$
Autorzy:
Georges, John
Lin, Jianwei
Mauro, David
Powiązania:
https://bibliotekanauki.pl/articles/30148694.pdf
Data publikacji:
2014-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Cartesian product
dominating set
domination number
Opis:
Let $K_n^3$ denote the Cartesian product $K_n□K_n□K_n$, where $K_n$ is the complete graph on $n$ vertices. We show that the domination number of $K_n^3$ is $⌈\frac{n^2}{2}⌉$.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 3; 629-632
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vizings conjecture and the one-half argument
Autorzy:
Hartnell, Bert
Rall, Douglas
Powiązania:
https://bibliotekanauki.pl/articles/972044.pdf
Data publikacji:
1995
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination number
Cartesian product
Vizing's conjecture
clique
Opis:
The domination number of a graph G is the smallest order, γ(G), of a dominating set for G. A conjecture of V. G. Vizing [5] states that for every pair of graphs G and H, γ(G☐H) ≥ γ(G)γ(H), where G☐H denotes the Cartesian product of G and H. We show that if the vertex set of G can be partitioned in a certain way then the above inequality holds for every graph H. The class of graphs G which have this type of partitioning includes those whose 2-packing number is no smaller than γ(G)-1 as well as the collection of graphs considered by Barcalkin and German in [1]. A crucial part of the proof depends on the well-known fact that the domination number of any connected graph of order at least two is no more than half its order.
Źródło:
Discussiones Mathematicae Graph Theory; 1995, 15, 2; 205-216
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Total domination of Cartesian products of graphs
Autorzy:
Hou, Xinmin
Powiązania:
https://bibliotekanauki.pl/articles/743735.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
total domination number
Cartesian product
Vizing's conjecture
Opis:
Let γₜ(G) and $γ_{pr}(G)$ denote the total domination and the paired domination numbers of graph G, respectively, and let G □ H denote the Cartesian product of graphs G and H. In this paper, we show that γₜ(G)γₜ(H) ≤ 5γₜ(G □ H), which improves the known result γₜ(G)γₜ(H) ≤ 6γₜ(G □ H) given by Henning and Rall.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 1; 175-178
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Domination of Cartesian Product of Directed Cycles: Results for Certain Equivalence Classes of Lengths
Autorzy:
Mollard, Michel
Powiązania:
https://bibliotekanauki.pl/articles/30146581.pdf
Data publikacji:
2013-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
directed graph
Cartesian product
domination number
directed cycle
Opis:
Let \( \gamma ( \overrightarrow{C_m} \square \overrightarrow{C_n} ) \) be the domination number of the Cartesian product of directed cycles \( \overrightarrow{C_m} \) and \( \overrightarrow{C_n} \) for $m, n \ge 2 $. Shaheen [13] and Liu et al. ([11], [12]) determined the value of \( \gamma ( \overrightarrow{C_m} \square \overrightarrow{C_n} ) \) when $ m \le 6 $ and [12] when both $m$ and $ n \equiv 0 (\mod 3) $. In this article we give, in general, the value of \( \gamma ( \overrightarrow{C_m} \square \overrightarrow{C_n} ) \) when $ m \equiv 2(\mod 3) $ and improve the known lower bounds for most of the remaining cases. We also disprove the conjectured formula for the case $ m \equiv 0 ( \mod 3) $ appearing in [12].
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 2; 387-394
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improving some bounds for dominating Cartesian products
Autorzy:
Hartnell, Bert
Rall, Douglas
Powiązania:
https://bibliotekanauki.pl/articles/743158.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination number
Cartesian product
Vizing's conjecture
2-packing
Opis:
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 for dominating the Cartesian product of any two graphs. We show how it is possible to improve some of these bounds by imposing conditions on both graphs. For example, we establish a new lower bound for the domination number of T T, when T is a tree, and we improve an upper bound of Vizing in the case when one of the graphs has k > 1 dominating sets which cover the vertex set and the other has a dominating set which partitions in a certain way.
Źródło:
Discussiones Mathematicae Graph Theory; 2003, 23, 2; 261-272
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A New Framework to Approach Vizing’s Conjecture
Autorzy:
Brešar, Boštjan
Hartnell, Bert L.
Henning, Michael A.
Kuenzel, Kirsti
Rall, Douglas F.
Powiązania:
https://bibliotekanauki.pl/articles/32222699.pdf
Data publikacji:
2021-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Cartesian product
total domination
Vizing’s conjecture
Clark and Suen bound
Opis:
We introduce a new setting for dealing with the problem of the domination number of the Cartesian product of graphs related to Vizing’s conjecture. The new framework unifies two different approaches to the conjecture. The most common approach restricts one of the factors of the product to some class of graphs and proves the inequality of the conjecture then holds when the other factor is any graph. The other approach utilizes the so-called Clark-Suen partition for proving a weaker inequality that holds for all pairs of graphs. We demonstrate the strength of our framework by improving the bound of Clark and Suen as follows: $ \gamma (X \square Y) \ge \max \{\frac{1}{2} \gamma (X) \gamma_t (Y), \frac{1}{2} \gamma_t (X) \gamma (Y) \} $, where $ \gamma $ stands for the domination number, $ \gamma_t $ is the total domination number, and $ X \square Y $ is the Cartesian product of graphs $X$ and $Y$.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 3; 749-762
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterizing Cartesian fixers and multipliers
Autorzy:
Benecke, Stephen
Mynhardt, Christina
Powiązania:
https://bibliotekanauki.pl/articles/743719.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Cartesian product
prism fixer
Cartesian fixer
prism doubler
Cartesian multiplier
domination number
Opis:
Let G ☐ H denote the Cartesian product of the graphs G and H. In 2004, Hartnell and Rall [On dominating the Cartesian product of a graph and K₂, Discuss. Math. Graph Theory 24(3) (2004), 389-402] characterized prism fixers, i.e., graphs G for which γ(G ☐ K₂) = γ(G), and noted that γ(G ☐ Kₙ) ≥ min{|V(G)|, γ(G)+n-2}. We call a graph G a consistent fixer if γ(G ☐ Kₙ) = γ(G)+n-2 for each n such that 2 ≤ n < |V(G)|- γ(G)+2, and characterize this class of graphs.
Also in 2004, Burger, Mynhardt and Weakley [On the domination number of prisms of graphs, Dicuss. Math. Graph Theory 24(2) (2004), 303-318] characterized prism doublers, i.e., graphs G for which γ(G ☐ K₂) = 2γ(G). In general γ(G ☐ Kₙ) ≤ nγ(G) for any n ≥ 2. We call a graph attaining equality in this bound a Cartesian n-multiplier and also characterize this class of graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 1; 161-175
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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