Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.
Updated
Claim. Draw the edges of a graph on labeled vertices independently with probability , where . The probability that the graph contains a Hamiltonian cycle tends to if , to if , and to if . This is Theorem 1 of J. Komlós and E. Szemerédi, Limit distribution for the existence of Hamiltonian cycles in a random graph, Discrete Math. 43 (1983), no. 1, 55--63 (received 13 October 1977, revised 1 December 1980; the issue carries the year only, so this page's name uses the first day of it). The paper states on p. 56 that the independent-edge model is equivalent, in this setting, to the uniform choice among all graphs with vertices and edges, the problem's model, and its Reformulation 1 (p. 57) gives the uniform-model form. The corpus records the paper on its card, which holds no file of it, and pages the theorem at Theorem 1; Theorem 2 (p. 57), the Hamiltonian-path law, is paged at Theorem 2.
For Problem 746: the edge count is with , so the third case gives that the random graph with edges is almost surely Hamiltonian, and Hamiltonicity is preserved by adding edges, which is the site's "". The threshold itself had been announced and proved by Korshunov, on his claim page; the paper's abstract credits him with the case , and Korshunov's 1985 comment calls this paper an independent solution.
Acceptance. Refereed: Discrete Mathematics 43 (1983), no. 1, per the publisher's Crossref record. Reviewed: Erdős cites the paper, then "to appear", as settling the conjecture in his 1981 Combinatorica paper (Part VIII) and his 1982 Singapore paper (§ 1); the site's curator, Thomas Bloom, labels the problem proved and records the limit law in the problem's commentary; Frieze's 2021 bibliography records it. Theorems 1 and 2 are taken as printed and the proof (§§ 1--2) for structure only; the equivalence of the two random-graph models is asserted on p. 56 without argument. This corpus supplies no independent proof review.
Formalization. The file src/latest/ErdosProblems/Erdos746.lean of
Boris Alexeev's plby/lean-proofs repository, linked above at a pinned
commit, declares itself a Lean formalization of a solution to Erdős Problem
746 and names János Komlós and Endre Szemerédi as informal authors and Codex
and GPT-5.6 Sol as formal authors; the note ErdosProblems/Erdos746.md calls
it a formalized proof of the problem for Mathlib v4.33.0, and the file was
added to the repository on 20 August 2026. Its theorem erdos_746 states
that for every and every edge-count sequence eventually
at least and at most , the
probability that the uniform random graph with vertices and
edges is Hamiltonian tends to , which is the site's statement; the proof
goes through an expansion estimate and a sprinkling argument, by the file's
own summary, and the file ends with a #print axioms command whose output
is not recorded. Because the file names this paper's authors as the
informal authors, it is a link on this page and not its own claim; this
corpus has not built, audited or kernel-checked it, so it is no formalized
evidence.