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Relative generation and the generator problem for finite factors
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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
- George A. Elliott, Chun Guang Li, Zhuang Niu, On the generators of separable unital C*-algebras (arXiv:2610.17411, 2026-10-12). Applies "Theorem SG", cited as Theorem 1.2 of a recent preprint (every separable-predual II$_1$ factor is generated by two self-adjoint elements), to II$_1$ factors and their corners to prove two-generator and single-generator results for separable unital C*-algebras whose extreme tracial boundary is compact and zero-dimensional, including single generation of $C^*_r(\mathbb F_n)$; the arXiv comments say the work was carried out using ChatGPT.
- Ben Bouwen, Jorge Castillejos and Jakub Curda, The generator problem for C-algebras with comparison* (arXiv:2610.13792v1, 9 October 2026). The introduction cites the OpenAI manuscript as the announced solution of the finite-factor generator problem while developing generation results for C*-algebras with comparison, including simple separable tracially AF algebras.
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.leanandRelativeGeneration.lean; the reduction of general von Neumann algebras to the II$_1$ factor case is not part of it. [family-level]
Related prior literature mentioned by others
- 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)
- G. K. Eleftherakis, V. I. Paulsen, Hyperreflexivity of von Neumann algebras and similarity of finitely generated C*-algebras (arXiv:2505.08720, v3 2025-11-19). Its Corollary 4.7 assumes that every von Neumann algebra on a separable Hilbert space is singly generated, which is the statement the paper derives from Theorem 1.2 together with Willig's reduction in its final section.
- Kenley Jung, Strongly 1-bounded von Neumann algebras (arXiv:math/0510576, 2005). Shows that if one generating set is strongly 1-bounded, then every finite generating set has microstates free entropy dimension at most 1, a partial generator-independence result relevant to the paper's corollary that $\delta$ and $\delta_0$ depend on the generating tuple.
- George A. Elliott, Chun Guang Li, Zhuang Niu, On generators of $C^*_r(\mathbb F_2)$ (arXiv:2609.32058, 2026-09-25). Gives an explicit single generator of $C^*_r(\mathbb F_2)$ and computes its topological free entropy dimension as 2, a C*-algebra analogue of the paper's free-entropy corollary for a self-adjoint generating pair of $L(\mathbb F_n)$; the arXiv comments say the generator and the computation were obtained by ChatGPT.
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
- VibeMathed: Problem record
- Emergent Mind: family 296
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.