Primitive sets and von Mangoldt chains: Erdős Problem #1196 and beyond

Boris Alexeev, Kevin Barreto, Yanyang Li, Jared Duker Lichtman, Liam Price, Jibran Iqbal Shah, Quanyu Tang, Terence Tao

If A has positive upper doubly logarithmic density Δ, then A contains an infinite strictly increasing divisibility chain whose upper count through x, divided by log log x, is at least Δ.

Sources for this record

What was already known

Erdős, Sárközy and Szemerédi conjectured a chain under the stronger condition of positive lower logarithmic density. Davenport–Erdős had proved a chain for positive lower natural density.

AI involvement AI-autonomous

The authors credit a separate autonomous GPT-5.4 Pro run with the theorem. Eight human authors rewrote, explained and reviewed the final proof.

Section 11 explicitly describes a similar autonomous run establishing Theorem 1.6; the final exposition is human.

Importance Notable

Resolves the divisibility-chain conjecture under a weaker density assumption and gives a quantitative chain bound.

Limitations

The autonomous run transcript is unavailable, so its exact steps cannot be compared with the human final proof. No Lean formalization of this theorem is claimed.

Technical verification Formal (human)

The authors report reviewing the final proof of Theorem 1.6; no Lean formalization of this theorem is claimed.

Formal checking

Generation and review of the final proof

Checker
Eight human authors of the primitive-sets paper
Scope
Theorem 1.6 quantitative infinite divisibility-chain conclusion
Basis
Reported by the linked checker
Evidence source

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

Human understanding Full

Section 9 explains the invariant weight and Markov-chain construction; Remark 9.1 explains why finite chains alone cannot be glued into the asserted infinite chain.

Correction and publication history

2026-10-18 · publication

Resolves the divisibility-chain conjecture under a weaker density assumption and gives a quantitative chain bound.

Read this published revision