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arXiv · 2508.15342

Counterexample to the conjectured coarse grid theorem

Sandra Albrechtsen·James Davies
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Abstract

We show that for every $M,A,n \in \mathbb{N}$ there exists a graph $G$ that does not contain the $(154\times 154)$-grid as a $3$-fat minor and is not $(M,A)$-quasi-isometric to a graph with no $K_n$ 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.

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Sandra Albrechtsen, James Davies. 2025-08-21. Counterexample to the conjectured coarse grid theorem. https://arxiv.org/abs/2508.15342

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