The coarse connectivity witness conjecture

From papers

Let K,n,m,rNK,n,m,r\in\mathbb{N}. A graph is (M,A)(M,A)-quasi-isometric to a graph of tree-width at most gg in the usual coarse sense, and connected sets are at least KK apart when every pair of vertices from distinct sets has distance at least KK. Then there exist some M,A,gNM,A,g\in\mathbb{N} such that every graph with no (M,A)(M,A)-quasi-isometry to a graph of tree-width at most gg contains connected sets U1,,UnU_1,\ldots,U_n that are pairwise at least KK apart and such that for every pair 1i<jn1\leqslant i<j\leqslant n, there exist no mm balls of radius at most rr hitting all paths between UiU_i and UjU_j. Coarse connectivity witness conjecture.

This proposes a coarse analogue of the connectivity-witness step in proofs of the classical grid theorem. The paper explains that the coarse Menger step fails, but leaves this alternative structural statement open.

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Sources & referencesView supporting material

Primary source

Sandra Albrechtsen and James Davies, “Counterexample to the conjectured coarse grid theorem”, arXiv:2508.15342 (2026).

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