English

Dominating Hadwiger's Conjecture for graphs $G$ with $\alpha(G)=2$

Combinatorics 2025-11-18 v2

Abstract

Hadwiger's Conjecture from 1943 states that every graph with chromatic number tt contains a KtK_t minor. Illingworth and Wood [arXiv:2405.14299] introduced the concept of a ``dominating KtK_t minor'' and asked whether every graph with chromatic number tt contains a dominating KtK_t minor. This question is a substantial strengthening of Hadwiger's Conjecture. Norin referred to it as the ``Dominating Hadwiger's Conjecture'' and believes it is likely false. In this paper we first observe that a tt-chromatic GG on nn vertices with independence number α(G)2\alpha(G)\le2 contains a dominating KtK_t minor if and only if GG contains a dominating Kn/2K_{\lceil n/2\rceil} minor. Building on this and using a deep result of Chudnovsky and Seymour on packing seagulls, we prove that every graph GG on nn vertices with α(G)2\alpha(G)\le 2 and 2ω(G)n/2+12\omega(G)\ge \lceil n/2\rceil+1 satisfies the Dominating Hadwiger's Conjecture, where ω(G)\omega(G) denotes the clique number of GG. We further prove that every HH-free graph GG with α(G)2\alpha(G)\le 2 satisfies the Dominating Hadwiger's Conjecture, where H{2K1+P4,K2+2K2,K2+(K1K3),K1+(K1K5),W5<,W5,W5,K7<,K7,K7}H\in\{2K_1+P_4, K_2+2K_2, K_2+(K_1\cup K_3), K_1+(K_1\cup K_5), W_5^<, W_5^-, W_5, K_7^<, K_7^-, K_7\}, or HK2K3H\ne K_2\cup K_3 is any graph on at most five vertices such that α(H)2\alpha(H)\le2.

Keywords

Cite

@article{arxiv.2510.12564,
  title  = {Dominating Hadwiger's Conjecture for graphs $G$ with $\alpha(G)=2$},
  author = {Michael Scully and Zi-Xia Song},
  journal= {arXiv preprint arXiv:2510.12564},
  year   = {2025}
}

Comments

Fixed typos and added credit to Illingworth and Wood regarding their question on dominating clique minors in graphs with independence number two

R2 v1 2026-07-01T06:36:43.235Z