Das and Fox prove Murty-Simon conjecture with AI-found proof, Lean-verified

kevrussell · x · 2026-11-01

Sanjana Das and Jacob Fox posted an arXiv proof of the Murty-Simon conjecture (Erdős #742): diameter-2-critical graphs have at most ⌊n²/4⌋ edges, with equality only for the balanced complete bipartite graph. The ⌊n²/4⌋ bound was originally found by AI; they simplified it and extended the ideas to cover all n, where Füredi's regularity approach only handled astronomically large n. Not yet refereed, but checked by an AI-written Lean proof from J.P. Traverso Gianini.

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