Ten Advances in Mathematics and Theoretical Computer Science

OpenAI

A finite family of connected bipartite graphs, each containing a cycle, has joint extremal number O(n^(4/3−1/48)), while every member has extremal number Ω(n^(4/3)). This refutes the substantive cyclic version of the Erdős–Simonovits compactness claim.

Sources for this record

What was already known

An elementary two-forest example already defeated the unrestricted wording. The cycle-containing bipartite case remained open.

AI involvement AI-led

OpenAI credits Astra with the Chapter 10 family and proof. Humans selected the problem and prepared the manuscript; Xu supplied the later statement bridge.

OpenAI is credited as author and attributes Chapter 10 results to its internal model; the later bridge/formalization is not assigned to that model.

Importance Major

Gives a polynomial separation for the corrected compactness question.

Limitations

The elementary forest example is prior work. Linmiao Xu later formalized a bridge to the related Erdős #575 formulation; that bridge is Xu’s work. One Chapter 10 optimization remains compressed in the exposition.

Technical verification Formal (Lean 4.35.0-rc2 with Mathlib; Comparator, Lean and NanoDa kernels + human)

The cited Xu project reports complete Lean and NanoDa checks of the cyclic family and #575 bridge. Chapter 10 human reviewers also checked the family’s construction and bound structure, but did not report a complete independent proof reconstruction.

Independent checking

chapter-specific mathematical review of the published argument, with the limited coverage summarized in the audit. Table 1; Chapter 10 discussion

Checker
Chapter 10 human reviewers in the Sienicki et al. review corpus
Scope
quantitative compactness counterexample and related Chapter 10 steps
Basis
Reported by the linked checker
Evidence source

Formal checking

complete formal proof, Comparator and axiom audit. status, main_results and review

Checker
Lean and NanoDa kernels via Xu’s pinned project
Scope
quantitative connected all-bipartite cyclic family and its #575 bridge
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

Chapter 10 explains the quotient-template family, path-count upper bound and generalized-quadrangle witnesses; Xu explains the #180-to-#575 bridge.

Correction and publication history