Exact Homomorphism Thresholds Beyond Cliques
Combinatorics
2026-07-30 v1
Abstract
The chromatic threshold, originating in a question of Erd\H{o}s 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.
Cite
@article{arxiv.2607.28241,
title = {Exact Homomorphism Thresholds Beyond Cliques},
author = {Xinqi Huang and Mingyuan Rong and Chong Shangguan},
journal= {arXiv preprint arXiv:2607.28241},
year = {2026}
}
Comments
19 pages, no figures