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Wyświetlanie 1-6 z 6
Tytuł:
Edge colorings and total colorings of integer distance graphs
Autorzy:
Kemnitz, Arnfried
Marangio, Massimiliano
Powiązania:
https://bibliotekanauki.pl/articles/743555.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
integer distance graph
chromatic number
choice number
chromatic index
choice index
total chromatic number
total choice number
Opis:
An integer distance graph is a graph G(D) with the set Z of integers as vertex set and two vertices u,v ∈ Z are adjacent if and only if |u-v| ∈ D where the distance set D is a subset of the positive integers N. In this note we determine the chromatic index, the choice index, the total chromatic number and the total choice number of all integer distance graphs, and the choice number of special integer distance graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 1; 149-158
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sum List Edge Colorings of Graphs
Autorzy:
Kemnitz, Arnfried
Marangio, Massimiliano
Voigt, Margit
Powiązania:
https://bibliotekanauki.pl/articles/31340809.pdf
Data publikacji:
2016-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
sum list edge coloring
sum choice index
sum list coloring
sum choice number
choice function
line graph
Opis:
Let $ G = (V,E) $ be a simple graph and for every edge $ \mathcal{e} \in E $ let $ L(e) $ be a set (list) of available colors. The graph $ G $ is called $L$-edge colorable if there is a proper edge coloring $ c $ of $ G $ with $ c(\mathcal{e} ) \in L( \mathcal{e} ) $ for all $ \mathcal{e} \in E $. A function $ f : E \rightarrow \mathbb{N} $ is called an edge choice function of $G$ and $G$ is said to be $f$-edge choosable if $G$ is $L$-edge colorable for every list assignment $L$ with $ |L( \mathcal{e} )| = f( \mathcal{e} ) $ for all $ \mathcal{e} \in E $. Set $ \text{size}(f) = \Sigma_{ \mathcal{e} \in E } f(e) $ and define the sum choice index $ \chi_{sc}^' (G) $ as the minimum of $ \text{size} (f) $ over all edge choice functions $f$ of $G$. There exists a greedy coloring of the edges of $G$ which leads to the upper bound $ \chi_{sc}^′ (G) \le 1/2 \Sigma_{ v \in V } d(v)^2 $. A graph is called sec-greedy if its sum choice index equals this upper bound. We present some general results on the sum choice index of graphs including a lower bound and we determine this index for several classes of graphs. Moreover, we present classes of sec-greedy graphs as well as all such graphs of order at most 5.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 3; 709-722
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
List coloring of complete multipartite graphs
Autorzy:
Vetrík, Tomáš
Powiązania:
https://bibliotekanauki.pl/articles/743641.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
list coloring
choice number
complete multipartite graph
Opis:
The choice number of a graph G is the smallest integer k such that for every assignment of a list L(v) of k colors to each vertex v of G, there is a proper coloring of G that assigns to each vertex v a color from L(v). We present upper and lower bounds on the choice number of complete multipartite graphs with partite classes of equal sizes and complete r-partite graphs with r-1 partite classes of order two.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 1; 31-37
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Choice-Perfect Graphs
Autorzy:
Tuza, Zsolt
Powiązania:
https://bibliotekanauki.pl/articles/30146654.pdf
Data publikacji:
2013-03-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph coloring
list coloring
choice-perfect graph
Opis:
Given a graph $ G = (V,E) $ and a set $ L_v $ of admissible colors for each vertex $ v \in V $ (termed the list at $v$), a list coloring of $G$ is a (proper) vertex coloring $ \phi : V \rightarrow \bigcup \text{}_{v \in V} L_v $ such that $ \phi (v) \in L_v $ for all $ v \in V $ and $ \phi(u) \ne \phi(v) $ for all $ uv \in E $. If such a $ \phi $ exists, $G$ is said to be list colorable. The choice number of $G$ is the smallest natural number $k$ for which $G$ is list colorable whenever each list contains at least $k$ colors. In this note we initiate the study of graphs in which the choice number equals the clique number or the chromatic number in every induced subgraph. We call them choice-ω-perfect and choice-χ-perfect graphs, respectively. The main result of the paper states that the square of every cycle is choice-χ-perfect.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 1; 231-242
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graph colorings with local constraints - a survey
Autorzy:
Tuza, Zsolt
Powiązania:
https://bibliotekanauki.pl/articles/972031.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph coloring
list coloring
choice number
precoloring extension
complexity of algorithms
chromatic number
Opis:
We survey the literature on those variants of the chromatic number problem where not only a proper coloring has to be found (i.e., adjacent vertices must not receive the same color) but some further local restrictions are imposed on the color assignment. Mostly, the list colorings and the precoloring extensions are considered.
In one of the most general formulations, a graph G = (V,E), sets L(v) of admissible colors, and natural numbers $c_v$ for the vertices v ∈ V are given, and the question is whether there can be chosen a subset C(v) ⊆ L(v) of cardinality $c_v$ for each vertex in such a way that the sets C(v),C(v') are disjoint for each pair v,v' of adjacent vertices. The particular case of constant |L(v)| with $c_v$ = 1 for all v ∈ V leads to the concept of choice number, a graph parameter showing unexpectedly different behavior compared to the chromatic number, despite these two invariants have nearly the same value for almost all graphs.
To illustrate typical techniques, some of the proofs are sketched.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 2; 161-228
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Generalized Sum List Colorings of Graphs
Autorzy:
Kemnitz, Arnfried
Marangio, Massimiliano
Voigt, Margit
Powiązania:
https://bibliotekanauki.pl/articles/31343297.pdf
Data publikacji:
2019-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
sum list coloring
sum choice number
generalized sum list coloring
additive hereditary graph property
Opis:
A (graph) property \( \mathcal{P} \) is a class of simple finite graphs closed under isomorphisms. In this paper we consider generalizations of sum list colorings of graphs with respect to properties \( \mathcal{P} \). If to each vertex $v$ of a graph $G$ a list $L(v)$ of colors is assigned, then in an \( (L, \mathcal{P} ) \)-coloring of $G$ every vertex obtains a color from its list and the subgraphs of $G$ induced by vertices of the same color are always in \( \mathcal{P} \). The \( \mathcal{P} \)-sum choice number \( X_{sc}^\mathcal{P} (G) \) of $G$ is the minimum of the sum of all list sizes such that, for any assignment $L$ of lists of colors with the given sizes, there is always an \( (L, \mathcal{P} ) \)-coloring of $G$. We state some basic results on monotonicity, give upper bounds on the \( \mathcal{P} \)-sum choice number of arbitrary graphs for several properties, and determine the \( \mathcal{P} \)-sum choice number of specific classes of graphs, namely, of all complete graphs, stars, paths, cycles, and all graphs of order at most 4.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 3; 689-703
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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