On minimal arbitrarily partitionable graphs
Résumé
A graph G = (V , E) of order n is called arbitrarily partitionable, or AP for short, if given any sequence of positive integers n1 , . . . , nk summing up to n, we can always partition V into subsets V1,...,Vk of sizes n1,...,nk, resp., inducing connected subgraphs in G. If additionally G is minimal with respect to this property, i.e. it contains no AP spanning subgraph, we call it a minimal AP-graph. It has been conjectured that such graphs are sparse, i.e., there exists an absolute constant C such that |E| ≤ C.n for each of them. We construct a family of minimal AP-graphs which prove that C ≥ 1 + 1/30 (if such C exists).