November 1st, 2024

Math's 'Bunkbed Conjecture' Has Been Debunked

The Bunkbed Conjecture, proposed in the 1980s, has been disproven by mathematicians, revealing that navigating upper graphs is often easier than lower ones, challenging established assumptions in probability theory.

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Math's 'Bunkbed Conjecture' Has Been Debunked

The "Bunkbed Conjecture," a hypothesis in probability theory regarding the navigation of graphs stacked like bunk beds, has been disproven by a team of mathematicians. Initially proposed by Pieter Kasteleyn in the 1980s, the conjecture suggested that the probability of finding a path in the lower graph was always greater than or equal to that in the upper graph. Despite its intuitive appeal, the conjecture was challenged by Igor Pak and his colleagues, who initially attempted to find a counterexample through computational methods. After a year of unsuccessful attempts, they shifted focus to theoretical arguments. A breakthrough came when Lawrence Hollom provided a counterexample in a related context involving hypergraphs. This inspired Pak, Nikita Gladkov, and Aleksandr Zimin to adapt Hollom's findings into a graph format, ultimately proving that the probability of finding a path in the upper graph was significantly higher than in the lower graph. This result emphasizes the need for mathematicians to question established assumptions and consider alternative approaches, particularly as computational methods gain traction in mathematical research.

- The Bunkbed Conjecture has been disproven, challenging long-held beliefs in probability theory.

- The conjecture suggested that navigating a lower graph was always easier than jumping to an upper graph.

- A breakthrough came from adapting a counterexample from hypergraphs to traditional graphs.

- The result highlights the importance of questioning intuitive assumptions in mathematics.

- The debate continues on the role of computational methods in mathematical proofs.

Link Icon 4 comments
By @pvg - 6 months
By @Jeff_Brown - 6 months
Funny how "barely false" the conjecture is: "in this graph, finding an upper path was 1/10^6500 percent more likely than finding a lower one — an unimaginably small but nonzero number. The bunkbed conjecture was wrong."

I'm a little disappointed that the brute force search didn't work -- it it had, I would have come away feeling like I could have done it myself.

By @OisinMoran - 6 months
Interesting read! I assume the hunt is now on for both the smallest graph where this is the case, and the largest discrepancy. It would be great if there was a graph small enough to make some nice art out of, or even just to fit in your head.