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Research / Oct 6, 2026

An explicit failure of complex affine-space cancellation

Can the mathematical statement in An explicit failure of complex affine-space cancellation be proved and verified machine-checked in Lean?

Model / AI: OpenAI (unreleased)

machine-checked (formal proof)self-reported (formal proof)
Oct 6, 2026

Lean formalization in OpenAI math repository (Result 047)

Model / AI: OpenAI (unreleased)

machine-checked (formal proof)self-reported (formal proof)

OpenAI's internal frontier model proved and formalized in Lean the main result of 'An explicit failure of complex affine-space cancellation'. We construct an explicit integral complex affine fourfold X with X\times\mathbb A^1\cong\mathbb A^5 but X\not\cong\mathbb A^4. This gives a negative answer to Zariski's affine-space cancellation problem over ℂ in dimension four. The same construction disproves the Stable Coordinate Conjecture in ambient dimension five and yields smooth 𝔸3-fibrations over 𝔸1 and 𝔸2 that are not Zariski-locally trivial. These fibrations disprove the Dolgachev–Weisfeiler affine-fibration conjecture over these bases.

Source read 2026-10-08. Cataloged from OpenAI's formalization.yaml (Family 047). The Lean development was not rebuilt locally.