The strong coarse Menger conjecture

Let GG be a finite or infinite graph, and let X,YV(G)X,Y\subseteq V(G). An XX-YY path is a path with at least one end in XX and at least one end in YY. For sets S,TV(G)S,T\subseteq V(G), let distG(S,T)\operatorname{dist}_G(S,T) be the infimum of the distances between their vertices. For SV(G)S\subseteq V(G) and rRr\in\mathbb R, let

NGr[S]={vV(G):distG(v,S)r}.N_G^{\leq r}[S]=\{v\in V(G):\operatorname{dist}_G(v,S)\leq r\}.

A set ZV(G)Z\subseteq V(G) is (k,r)(k,r)-centered if ZNGr[W]Z\subseteq N_G^{\leq r}[W] for some WV(G)W\subseteq V(G) with Wk|W|\leq k. The strong coarse Menger conjecture. There exists a real number c>0c>0 such that for any graph GG, subsets X,YX,Y of V(G)V(G) and positive integers k,rk,r, either GG contains kk XX-YY paths pairwise at distance at least rr, or there exists a set (k1,cr)(k-1,cr)-centered in GG intersecting all XX-YY paths. This is a large-scale analogue of Menger's theorem. The cases k=2k=2 and arbitrary rr were proved, but Nguyen, Scott and Seymour disproved the case k=r=3k=r=3, even for graphs of maximum degree at most 33; consequently the conjecture is refuted.

Sources & referencesView supporting material

Primary source

Chun-Hung Liu, “Coarse Menger property of quasi-minor excluded graphs and length spaces”, arXiv:2605.10068 (2026).

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