Exact Homomorphism Thresholds Beyond Cliques
arXiv:2607.28241
The paper determines the exact homomorphism thresholds for a broad family of non‑complete forbidden graphs, extending previous results that were limited to cliques.
Abstract
The chromatic threshold, originating in a question of ErdÅs and Simonovits, asks when a linear minimum-degree condition forces bounded chromatic number in H-free graphs. Motivated by a question of Thomassen, the homomorphism threshold asks for the stronger conclusion that every such graph admits a homomorphism to an H-free graph of bounded order. Since the work of Goddard and Lyle determined the clique case, exact homomorphism thresholds for individual non-complete forbidden graphs have remained unknown. In this paper, we extend the clique case to a larger family of forbidden graphs, determining the homomorphism threshold exactly for every graph in this family.
19 pages, no figures