When $t$-intersecting hypergraphs admit bounded $c$-strong colourings

Abstract

The $c$-strong chromatic number of a hypergraph is the smallest number of colours needed to colour its vertices so that every edge sees at least $c$ colours or is rainbow. We show that every $t$-intersecting hypergraph has bounded $(t+1)$-strong chromatic number, resolving a problem of Blais, Weinstein and Yoshida. In fact, we characterise when a $t$-intersecting hypergraph has large $c$-strong chromatic number for $c\ge t+2$. Our characterisation also applies to hypergraphs which exclude sunflowers with specified parameters.

13 pages