Publication at Faculty of Mathematics and Physics |
2007
Abstract
Let K be a class of finite graphs and F1,...,Fm be a set of finite graphs. Then, K is said to have finite-duality if there exists a graph U in K such that for any graph G in K, G is homomorphic to U if and only if Fi is not homomorphic to G, for all i=1,2,,m.
In this note, we answer this positively a problem of the first author by showing minor closed subclasses containing arbitrary long anti-chains and yet having the finite-duality property.