Sparse colour-critical hypergraphs
A hypergraph H is called an n-hypergraph if the order of each of its edges equals n. It is called s-critical with respect to colouring if its chromatic number is r and the removal of any edge results in a graph which has chromatic number r-1. A hypergraph is called linear if the intersection of two arbitrary edges is at most 1 vertex. The main question treated in this paper is how few edges on (m,n,r)-graph or linear (m,n,r)-graph may possess. Estimates for the least numbers of that kind are given.
scientific article; zbMATH DE number 4210165
scientific article