Ubiquity of locally finite graphs with extensive tree-decompositions
Abstract
A graph \(G\) is said to be ubiquitous, if every graph \(\Gamma\) that contains arbitrarily many disjoint \(G\)-minors automatically contains infinitely many disjoint \(G\)-minors. The well-known Ubiquity conjecture of Andreae says that every locally finite graph is ubiquitous. In this paper we show that locally finite graphs admitting a certain type of tree-decomposition, which we call an extensive tree-decomposition, are ubiquitous. In particular this includes all locally finite graphs of finite tree-width, and also all locally finite graphs with finitely many ends, all of which have finite degree. It remains an open question whether every locally finite graph admits an extensive tree-decomposition.
Mathematics Subject Classifications: 05C83, 05C63
Keywords: Graph minors, infinite graphs, ubiquity