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Wyszukujesz frazę "Vizing's Conjecture" wg kryterium: Temat


Wyświetlanie 1-6 z 6
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:
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:
Edge-choosability and total-choosability of planar graphs with no adjacent 3-cycles
Autorzy:
Cranston, Daniel
Powiązania:
https://bibliotekanauki.pl/articles/743133.pdf
Data publikacji:
2009
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
list coloring
edge coloring
total coloring
Vizing's Conjecture
Opis:
Let G be a planar graph with no two 3-cycles sharing an edge. We show that if Δ(G) ≥ 9, then χ'ₗ(G) = Δ(G) and χ''ₗ(G) = Δ(G)+1. We also show that if Δ(G) ≥ 6, then χ'ₗ(G) ≤ Δ(G)+1 and if Δ(G) ≥ 7, then χ''ₗ(G) ≤ Δ(G)+2. All of these results extend to graphs in the projective plane and when Δ(G) ≥ 7 the results also extend to graphs in the torus and Klein bottle. This second edge-choosability result improves on work of Wang and Lih and of Zhang and Wu. All of our results use the discharging method to prove structural lemmas about the existence of subgraphs with small degree-sum. For example, we prove that if G is a planar graph with no two 3-cycles sharing an edge and with Δ(G) ≥ 7, then G has an edge uv with d(u) ≤ 4 and d(u)+d(v) ≤ Δ(G)+2. All of our proofs yield linear-time algorithms that produce the desired colorings.
Źródło:
Discussiones Mathematicae Graph Theory; 2009, 29, 1; 163-178
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:
3-Tuple Total Domination Number of Rook’s Graphs
Autorzy:
Pahlavsay, Behnaz
Palezzato, Elisa
Torielli, Michele
Powiązania:
https://bibliotekanauki.pl/articles/32361755.pdf
Data publikacji:
2022-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
k -tuple total domination
Cartesian product of graphs
rook’s graph
Vizing’s conjecture
Opis:
A k-tuple total dominating set (kTDS) of a graph G is a set S of vertices in which every vertex in G is adjacent to at least k vertices in S. The minimum size of a kTDS is called the k-tuple total dominating number and it is denoted by γ×k,t(G). We give a constructive proof of a general formula for γ×3,t(Kn□Km).
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 1; 15-37
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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