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Wyszukujesz frazę "oriented coloring" wg kryterium: Temat


Wyświetlanie 1-5 z 5
Tytuł:
Oriented Chromatic Number of Cartesian Products and Strong Products of Paths
Autorzy:
Dybizbański, Janusz
Nenca, Anna
Powiązania:
https://bibliotekanauki.pl/articles/31343580.pdf
Data publikacji:
2019-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph
oriented coloring
grid
Opis:
An oriented coloring of an oriented graph G is a homomorphism from G to H such that H is without selfloops and arcs in opposite directions. We shall say that H is a coloring graph. In this paper, we focus on oriented col- orings of Cartesian products of two paths, called grids, and strong products of two paths, called strong-grids. We show that there exists a coloring graph with nine vertices that can be used to color every orientation of grids with five columns. We also show that there exists a strong-grid with two columns and its orientation which requires 11 colors for oriented coloring. Moreover, we show that every orientation of every strong-grid with three columns can be colored by 19 colors and that every orientation of every strong-grid with four columns can be colored by 43 colors. The above statements were proved with the help of computer programs.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 1; 211-223
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oriented Chromatic Number of Cartesian Products $ P_m \square P_n $ and $ C_m \square P_n $
Autorzy:
Nenca, Anna
Powiązania:
https://bibliotekanauki.pl/articles/32304155.pdf
Data publikacji:
2022-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graphs
oriented coloring
oriented chromatic number
Opis:
We consider oriented chromatic number of Cartesian products of two paths $ P_m \square P_n $ and of Cartesian products of paths and cycles, $ C_m \square P_n $. We say that the oriented graph \( \overrightarrow{G} \) is colored by an oriented graph \( \overrightarrow{H} \) if there is a homomorphism from \( \overrightarrow{G} \) to \( \overrightarrow{H} \). In this paper we show that there exists an oriented tournament \( \overrightarrow{H}_{10} \) with ten vertices which colors every orientation of $ P_8 \square P_n $ and every orientation of $ C_m \square P_n $, for $m = 3, 4, 5, 6, 7$ and $n \ge 1 $. We also show that there exists an oriented graph \( \overrightarrow{T}_{16} \) with sixteen vertices which colors every orientation of $ C_m \square P_n $.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 3; 799-810
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analogues of cliques for oriented coloring
Autorzy:
Klostermeyer, William
MacGillivray, Gary
Powiązania:
https://bibliotekanauki.pl/articles/744524.pdf
Data publikacji:
2004
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph coloring
oriented coloring
clique
planar graph
Opis:
We examine subgraphs of oriented graphs in the context of oriented coloring that are analogous to cliques in traditional vertex coloring. Bounds on the sizes of these subgraphs are given for planar, outerplanar, and series-parallel graphs. In particular, the main result of the paper is that a planar graph cannot contain an induced subgraph D with more than 36 vertices such that each pair of vertices in D are joined by a directed path of length at most two.
Źródło:
Discussiones Mathematicae Graph Theory; 2004, 24, 3; 373-387
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Upper oriented chromatic number of undirected graphs and oriented colorings of product graphs
Autorzy:
Sopena, Éric
Powiązania:
https://bibliotekanauki.pl/articles/743250.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
product graph
oriented coloring
oriented chromatic number
Opis:
The oriented chromatic number of an oriented graph $^→G$ is the minimum order of an oriented graph $^→H$ such that $^→G$ admits a homomorphism to $^→H$. The oriented chromatic number of an undirected graph G is then the greatest oriented chromatic number of its orientations.
In this paper, we introduce the new notion of the upper oriented chromatic number of an undirected graph G, defined as the minimum order of an oriented graph $^→U$ such that every orientation $^→G$ of G admits a homomorphism to $^→U$. We give some properties of this parameter, derive some general upper bounds on the ordinary and upper oriented chromatic numbers of lexicographic, strong, Cartesian and direct products of graphs, and consider the particular case of products of paths.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 3; 517-533
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hamiltonian-colored powers of strong digraphs
Autorzy:
Johns, Garry
Jones, Ryan
Kolasinski, Kyle
Zhang, Ping
Powiązania:
https://bibliotekanauki.pl/articles/743288.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
powers of a strong oriented graph
distance-colored digraphs
Hamiltonian-colored digraphs
Hamiltonian coloring exponents
Opis:
For a strong oriented graph D of order n and diameter d and an integer k with 1 ≤ k ≤ d, the kth power $D^k$ of D is that digraph having vertex set V(D) with the property that (u, v) is an arc of $D^k$ if the directed distance $^{→}d_D(u,v)$ from u to v in D is at most k. For every strong digraph D of order n ≥ 2 and every integer k ≥ ⌈n/2⌉, the digraph $D^k$ is Hamiltonian and the lower bound ⌈n/2⌉ is sharp. The digraph $D^k$ is distance-colored if each arc (u, v) of $D^k$ is assigned the color i where $i = ^{→}d_D(u,v)$. The digraph $D^k$ is Hamiltonian-colored if $D^k$ contains a properly arc-colored Hamiltonian cycle. The smallest positive integer k for which $D^k$ is Hamiltonian-colored is the Hamiltonian coloring exponent hce(D) of D. For each integer n ≥ 3, the Hamiltonian coloring exponent of the directed cycle $^{→}Cₙ$ of order n is determined whenever this number exists. It is shown for each integer k ≥ 2 that there exists a strong oriented graph Dₖ such that hce(Dₖ) = k with the added property that every properly colored Hamiltonian cycle in the kth power of Dₖ must use all k colors. It is shown for every positive integer p there exists a a connected graph G with two different strong orientations D and D' such that hce(D) - hce(D') ≥ p.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 4; 705-724
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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