Short proofs in combinatorics, probability and number theory II

Boris Alexeev, Moe Putterman, Mehtaab Sawhney, Mark Sellke, Gregory Valiant

A single real sequence has uniformly bounded partial exponential sums A_k= sup_N |Σ_{n<N} exp(2πikx_n)|=O(√(k log(2k))) for every positive integer k. This implies the weaker limsup Ã_k=o(k) sought in Erdős Problem 987.

Sources for this record

What was already known

Clunie proved Ã_k≫√k infinitely often for every sequence and constructed a dyadic sequence with A_k≤k.

AI involvement AI-led

An internal OpenAI model found the prefix-randomized binary van der Corput construction and its dyadic-block estimate. Boris Alexeev, Moe Putterman, Mehtaab Sawhney, Mark Sellke and Gregory Valiant report checking the proof and explain its mechanism.

The construction and proof are explicitly attributed to the model; detailed prompt independence is undisclosed.

Importance Notable

The bound answers the Erdős question and approaches Clunie’s lower bound up to a logarithmic factor.

Limitations

The result is an existence theorem for one sequence, with a uniform bound over all partial sums and positive k.

Technical verification Formal (human)

The coauthors explicitly report verifying this model solution. The probabilistic existence proof is not a machine certificate, but completed human checking qualifies under the policy.

Independent checking

human verification of the model proof

Checker
Alexeev, Putterman, Sawhney, Sellke and Valiant
Scope
Problem 987 simultaneous uniform exponential-sum bound
Basis
Reported by the linked checker
Evidence source

Human understanding Full

The paper's human-authored exposition explains the randomized dyadic mechanism and explicitly connects the uniform bound to Clunie's baseline.

Correction and publication history

2026-10-18 · publication

The bound answers the Erdős question and approaches Clunie’s lower bound up to a logarithmic factor.

Read this published revision