English

Counterexamples to Clique Immersion Conjecture for Direct Products

Combinatorics 2026-05-29 v2

Abstract

Let GG and HH be graphs, and let G×HG\times H denote their direct product. For a graph GG, let im(G)\operatorname{im}(G) be the largest integer tt such that GG contains a KtK_t-immersion. Collins, Heenehan, and McDonald conjectured that if im(G)=t\operatorname{im}(G)=t and im(H)=r\operatorname{im}(H)=r, then im(G×H)(t1)(r1)+1.\operatorname{im}(G\times H)\ge (t-1)(r-1)+1. We disprove this conjecture by constructing an infinite family of connected bipartite counterexamples.

Cite

@article{arxiv.2605.28518,
  title  = {Counterexamples to Clique Immersion Conjecture for Direct Products},
  author = {Chuanshu Wu and Zijian Deng},
  journal= {arXiv preprint arXiv:2605.28518},
  year   = {2026}
}
R2 v1 2026-07-22T07:37:17.005Z