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Relative generation and the generator problem for finite factors

OpenAI · September 23, 2026

Lean

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Abstract

We prove that every type II1 factor with separable predual is generated by one operator, equivalently by two self-adjoint operators. Combined with the established direct-integral reduction to this case, this gives an affirmative solution of the generator problem for von Neumann algebras with separable predual.

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work in progress

Collected automatically by AI tools (Claude Opus 5.5 and GPT-6 Astra, 2026-10-21) and not checked by a person. May be wrong or incomplete. Report an error.

Follow-up works

Formalization

  • OpenAI math release, Lean scope note for family 296, The generator problem for finite factors (lean/docs/296.md, 6 October 2026). States that the formalization covers single generation of separable-predual II$_1$ factors (Theorem 1.2) and the dense $G_\delta$ relative-generation result for irreducible inclusions in the trace two-norm topology (Theorem 1.1), with comparator statements FactorGeneration.lean and RelativeGeneration.lean; the reduction of general von Neumann algebras to the II$_1$ factor case is not part of it. [family-level]
  • Ben Hayes, On Generators for W-bundles* (arXiv:2609.16428, 14 September 2026; revised 16 September 2026). Linked as background by the AI Proved What? exposition, this paper constructs a W*-bundle with separable-predual II₁ fibers for which no finite family of continuous sections generates every fiber, addressing continuous choices of generators rather than the manuscript's individual-factor assertion.

Possibly relevant literature (found by the agent, not checked)

Digests and expositions

  • AI Proved What?, One operator for all? Kadison’s generator problem (Episode 296, October 2026). This AI-assisted video and transcript outline the relative-generation argument, its reduction to two self-adjoint generators and its free-entropy consequence, while distinguishing a source scan of the Lean files from a rebuild. [AI-generated per source]

Elsewhere

Independent sites; their content is not reviewed here.

Cite

@misc{OAI:Relative-generation-and-the-generator-problem-for-finite-factors-September-23-2026,
  author = {{OpenAI}},
  title = {{Relative generation and the generator problem for finite factors}},
  howpublished = {OpenAI Math Release preprint
                  \href{https://github.com/openai/math/blob/main/preprints/Relative-generation-and-the-generator-problem-for-finite-factors-September-23-2026/paper.pdf}{OAI:Relative-generation-and-the-generator-problem-for-finite-factors-September-23-2026}},
  year = {2026}
}

Lean formalization

OpenAI provides Lean files for this family: lean/docs/296.md. The Lean statements have not been checked by people against the paper's claims.

Family 296: The generator problem for finite factors

Proves that every type II1 factor with separable predual is generated by a single operator, equivalently by two self-adjoint operators, resolving the generator problem. More strongly, for every irreducible inclusion $P\subset M$ of such factors, the unitaries u with $M=W^*(P,u)$ form a dense Gδ subset in the trace 2-norm topology.

This is the only paper in this family.