GPT-assisted bound settles Erdős #953 exponent

For the largest measure M(R) of a measurable subset of a radius-R planar disk with no positive integer distance between distinct points, M(R)≤C√R. Together with Sárközy’s earlier lower construction, this yields M(R)=R^(1/2+o(1)).

Sources for this record

What was already known

The prior upper control was O(R), while Sárközy had a lower construction of order R^(1/2−o(1)).

AI involvement AI-led

Chojecki's first-person problem post says he obtained the upper-bound proof with GPT-5.5 Pro and credits the model's weighting in the positive-definiteness argument. The record does not resolve exactly which prompts or derivations came from Chojecki, so AI-led is supported by their joint proof account, without an autonomy claim.

Chojecki's original first-person post attributes the central new upper-bound proof to work with GPT-5.5 Pro; the division of steps is not detailed enough for AI-autonomous.

Importance Notable

Matches the known lower exponent for the measurable planar problem.

Limitations

The new contribution is the Poisson–Bessel/Delsarte upper bound; Sárközy’s lower construction is independent earlier work. Kovač reports checking the proof, and Hart formalized the upper bound in Lean.

Technical verification Formal (Lean 4 + human)

Kovač explicitly says the original proof is correct after examining it, and Hart's Lean Main.lean states the exact upper bound with the Poisson formula discharged in the repository. The machine artifact was inspected for axioms/sorries in its project files but not rebuilt; the prior lower bound is separate.

Formal checking

Human examination, explanation and correctness judgment of the argument

Checker
Vjeko Kovač
Scope
Chojecki–GPT proof of the O(sqrt(R)) upper bound
Basis
Reported by the linked checker
Evidence source

Formal checking

Lean proof erdos953_upper in Erdos953Formalization/Main.lean, including a discharged Poisson circle-average formula

Checker
Lean 4 formalization by Allen Hart
Scope
There exists C>0 such that M(R)<=C sqrt(R) for R>=1
Basis
Reported by the linked checker
Evidence source

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

Human understanding Full

Kovač identifies the positive-definiteness/Delsarte mechanism, and the later streamlined exposition spells out the direct continuous argument.

Correction and publication history