Hickingbotham's conjecture on low-connectivity ghost-edges

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Let k∈Nk\in\mathbb{N}, let GG be a connected graph with tw(G)≤ktw(G)\leq k, and let xy∈E(Gc)xy\in E(G^c). A kk-ghost-edge is a nonedge xyxy such that every tree decomposition (T,B)(T,\mathcal{B}) of GG with width at most kk has a bag containing both xx and yy. Hickingbotham's conjecture. If there are at most kk internally vertex-disjoint (x,y)(x,y)-paths in GG, then xyxy is not a kk-ghost-edge of GG. The paper's abstract states that this conjecture is wrong, so the claim is refuted.

References

Primary source

Rong Chen, “A counterexample to Hickingbotham's conjecture about k-ghost-edges”, arXiv:2602.03016 (2026).

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