Aspects topologiques de la séperation dans les graphes infinis. II.
A class C of graphs is said to be dually compact closed if, for every infinite G ∈ C, each finite subgraph of G is contained in a finite induced subgraph of G which belongs to C. The class of trees and more generally the one of chordal graphs are dually compact closed. One of the main part of this paper is to settle a question of Hahn, Sands, Sauer and Woodrow by showing that the class of bridged graphs is dually compact closed. To prove this result we use the concept of constructible graph. A (finite...
We prove that a countable connected graph has an end-faithful spanning tree that contains a prescribed set of rays whenever this set is countable, and we show that this solution is, in a certain sense, the best possible. This improves a result of Hahn and Širáň Theorem 1.
For an end and a tree of a graph we denote respectively by and the maximum numbers of pairwise disjoint rays of and belonging to , and we define . In this paper we give partial answers—affirmative and negative ones—to the general problem of determining if, for a function mapping every end of to a cardinal such that , there exists a spanning tree of such that for every end of .
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