Kasteleyn's Bunkbed Conjecture for Bernoulli bond percolation
Kasteleyn's Bunkbed Conjecture for Bernoulli bond percolation
Let be an undirected graph, and let and be two copies of . For each , write and for its copies, and form the bunkbed graph by adding bidirected vertical edges between and for every . Under -Bernoulli bond percolation, let denote the event that the percolated bunkbed graph contains a path connecting and . Kasteleyn's Bunkbed Conjecture. For every undirected graph and every ,
The conjecture asserts that the two vertices on the same floor should be at least as likely to be connected as vertices on opposite floors. It was disproved by Gladkov, Pak and Zimin, whose counterexample was based on a graph found by Hollom.
Sources & referencesView supporting material
Primary source
Tomasz Przybyłowski, “The acyclic directed bunkbed conjecture is false”, arXiv:2506.22284 (2025).
Additional references
2 papers in this index state this conjecture (2022–2025). The statement above is taken from the most recent of them; the others are arXiv:2205.07318.
Source: https://arxiv.org/abs/2506.22284 Kasteleyn (1985), cited in Berg, Kahn and collaborators (2001) Gladkov, Pak and Zimin (2024), counterexample to the Bunkbed Conjecture Hollom (2024), counterexample to the Hypergraph Bunkbed Conjecture
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