Perfect divisions in ($P_2 \cup P_4$, bull)-free graphs
Combinatorics
2025-08-12 v2
Abstract
A graph has a perfect division if its vertex set can be partitioned into two sets , such that is perfect and . We call perfectly divisible if every induced subgraph of admits a perfect division. We prove that every (, bull)-free graph with has a perfect division if contains no homogeneous set. The clique-number condition is tight: a counterexample exists for . Additionally, we present a short proof of the perfect divisibility of (, bull)-free graphs, originally established by Chudnovsky and Sivaraman [J. Graph Theory 90 (2019), 54-60.].
Keywords
Cite
@article{arxiv.2507.18506,
title = {Perfect divisions in ($P_2 \cup P_4$, bull)-free graphs},
author = {Lizhong Chen and Hongyang Wang},
journal= {arXiv preprint arXiv:2507.18506},
year = {2025}
}