An explicit noncoordinate polynomial with affine three-space zero fibre

OpenAI

An explicit polynomial F in four complex variables has zero-fibre coordinate ring isomorphic to C[3], while its gradient vanishes at a point, so F is not a coordinate. Adding variables extends this counterexample to every ambient dimension at least four.

Sources for this record

What was already known

The conjecture asks whether an affine-space zero fibre must be a coordinate hyperplane. Dimension two and restricted higher-dimensional cases were known, while the general ambient-four case remained open.

AI involvement AI-led

OpenAI credits its internal model with the September construction. The later stable-coordinate example is a separate model-produced result.

OpenAI authorship and the release's internal-model provenance support model-led mathematical construction, without proving individual-session autonomy.

Importance Notable

The example disproves the embedding conjecture in its first unresolved ambient dimension.

Limitations

The available Lean target file states the theorem without a completed proof. The later one-stable-coordinate example uses a different polynomial.

Technical verification Reported

The September paper gives an explicit quotient isomorphism and a vanishing-gradient obstruction. The visible Abhyankar–Sathaye and stable-coordinate ComparatorChallenges end in sorry; they are target statements, not checked proofs. No completed human or machine check of the September theorem is documented, so Reported is the evidence default.

Human understanding Few

No named human explanation of the cusp-based coordinate-ring isomorphism and noncoordinate obstruction is documented. Few is the evidence default.

Correction and publication history

2026-10-18 · publication

If correct, the example disproves the embedding conjecture in its first unresolved ambient dimension.

Read this published revision