English

Counterexample to the conjectured coarse grid theorem

Combinatorics 2026-02-25 v2 Metric Geometry

Abstract

We show that for every M,A,nNM,A,n \in \mathbb{N} there exists a graph GG that does not contain the (154×154)(154\times 154)-grid as a 33-fat minor and is not (M,A)(M,A)-quasi-isometric to a graph with no KnK_n minor. This refutes the conjectured coarse grid theorem by Georgakopoulos and Papasoglu and the weak fat minor conjecture of Davies, Hickingbotham, Illingworth, and McCarty. Our construction is a slight modification of the recent counterexample to the weak coarse Menger conjecture from Nguyen, Scott and Seymour. We further modify the construction to show that there are planar graphs that do not have the coarse Erd\H{o}s-P\'{o}sa property.

Keywords

Cite

@article{arxiv.2508.15342,
  title  = {Counterexample to the conjectured coarse grid theorem},
  author = {Sandra Albrechtsen and James Davies},
  journal= {arXiv preprint arXiv:2508.15342},
  year   = {2026}
}

Comments

Added a counterexample showing that not every planar graph has the coarse Erd\H{o}s-P\'{o}sa property

R2 v1 2026-07-01T04:59:39.623Z