منابع مشابه
Homomorphism bounded classes of graphs
A class C of graphs is said to be H-bounded if each graph in the class C admits a homomorphism to H. We give a general necessary and sufficient condition for the existence of bounds with special local properties. This gives a new proof of Häggkvist-Hell theorem [5] and implies several cases of the existence of triangle free bounds for planar graphs.
متن کاملHomomorphism-homogeneous graphs
We answer two open questions posed by Cameron and Nesetril concerning homomorphismhomogeneous graphs. In particular we show, by giving a characterization of these graphs, that extendability to monomorphism or to homomorphism leads to the same class of graphs when defining homomorphism-homogeneity. Further we show that there are homomorphism-homogeneous graphs that do not contain the Rado graph ...
متن کاملClasses of graphs with small rank decompositions are X-bounded
A class of graphs G is χ-bounded if the chromatic number of graphs in G is bounded by a function of the clique number. We show that if a class G is χ-bounded, then every class of graphs admitting a decomposition along cuts of small rank to graphs from G is χ-bounded. As a corollary, we obtain that every class of graphs with bounded rank-width (or equivalently, clique-width) is χ-bounded.
متن کاملLocally identifying coloring in bounded expansion classes of graphs
A proper vertex coloring of a graph is said to be locally identifying if the sets of colors in the closed neighborhood of any two adjacent non-twin vertices are distinct. The lid-chromatic number of a graph is the minimum number of colors used by a locally identifying vertex-coloring. In this paper, we prove that for any graph class of bounded expansion, the lid-chromatic number is bounded. Cla...
متن کاملGrad and classes with bounded expansion III. Restricted graph homomorphism dualities
We study restricted homomorphism dualities in the context of classes with bounded expansion. This presents a generalization of restricted dualities obtained earlier for bounded degree graphs and also for proper minor closed classes. This is related to distance coloring of graphs and to the “approximative version” of Hadwiger conjecture.
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ژورنال
عنوان ژورنال: European Journal of Combinatorics
سال: 2006
ISSN: 0195-6698
DOI: 10.1016/j.ejc.2004.07.014