Hyperbolicity Cones Without Semidefinite Lifts

OpenAI

An OpenAI manuscript claims a real homogeneous hyperbolic polynomial whose closed cone has no exact finite affine semidefinite lift, even with arbitrary real coefficients and any finite number of auxiliary variables.

Sources for this record

What was already known

The generalized Lax question asked for a direct matrix representation of every hyperbolicity cone. Smooth cones were known to admit semidefinite lifts, but a cone lacking a direct representation can still have such a lift.

AI involvement AI-led

OpenAI credits its internal model with the manuscript family and is named as author. The release does not detail this proof’s human prompting or editing.

The repository credits internal-model production and institutional OpenAI authorship; item-specific independence is undocumented.

Importance Major

The existence theorem refutes the projected Lax conjecture and excludes a universal finite semidefinite-lift representation.

Limitations

This is an existence result, not a lift-size bound for a named cone. An exact finite-field calculation checks a seed-matrix lemma; no completed check of the analytic obstruction or full nonliftability argument is documented. A Lean proof of a different nonspectrahedral cone does not cover this claim.

Technical verification Partial

Appendix A reports a finite-field certificate for the seed-matrix rank lemma and says an accompanying exact-arithmetic script reproduces its displayed minors and ranks. That check covers a finite subcalculation only; the high-dimensional existence, analytic obstruction and no-lift conclusion have no documented complete rigorous check. The separate Lean formalization covers only the weaker nonspectrahedral cone.

Formal checking

Exact integer arithmetic modulo seven reproducing the finite certificate; Appendix A, Reproducible calculation; see §1.2 for its limited role

Checker
verify_certificate.py accompanying the October 5 OpenAI manuscript
Scope
Appendix A seed-matrix specialization, tangent, displayed minors and weight-six-through-nine ranks
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

No named human explanation of the central nonliftability mechanism is documented in the cited release; Few is the evidence default.

Correction and publication history

2026-10-18 · publication

If correct, the existence theorem refutes the projected Lax conjecture and excludes a universal finite semidefinite-lift representation.

Read this published revision