On coloring digraphs with forbidden induced subgraphs

Abstract

We prove a conjecture by Aboulker, Charbit and Naserasr by showing that every oriented graph in which the out-neighborhood of every vertex induces a transitive tournament can be partitioned into two acyclic induced subdigraphs. We prove multiple extensions of this result to larger classes of digraphs defined by a finite list of forbidden induced subdigraphs. We thereby resolve several special cases of an extension of the famous Gy\'{a}rf\'{a}s-Sumner conjecture to directed graphs by Aboulker et al.