OpenAI reports CH counterexamples to the separable quotient property

Assuming the continuum hypothesis, there are infinite-dimensional real and complex Banach spaces with no bounded linear surjection onto any infinite-dimensional separable Banach space.

Sources for this record

What was already known

The separable quotient problem remained open for arbitrary Banach spaces. Positive cases included separable spaces and many dual spaces, while earlier set-theoretic results did not provide this CH counterexample in both scalar fields.

AI involvement AI-led

OpenAI credits itself as manuscript author and states that its internal frontier model produced the results in this release. Individual human input is not detailed enough to establish task-only autonomy.

OpenAI is named as author on the manuscript, and its release attributes the results to an internal frontier model. The individual human input is not detailed enough to establish autonomy.

Importance Major

Establishes failure of the separable quotient assertion under the continuum hypothesis.

Limitations

This is the negative direction under CH. The linked Lean note does not check the manuscript’s positive consistency direction or full relative-independence conclusion.

Technical verification Formal (Lean 4)

OpenAI reports a Lean proof matching the selected claim.

Formal checking

The pinned Lean note proves CH-conditional counterexamples for real and complex Banach spaces.

Checker
OpenAI-reported Lean 4 / Comparator
Scope
Assuming the continuum hypothesis, there are infinite-dimensional real and complex Banach spaces with no bounded linear surjection onto any infinite-dimensional separable Banach space.
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

Few is the default when evidence for a higher level is insufficient. No named person is documented as explaining the central argument for this assessed contribution.

Correction and publication history

2026-10-18 · publication

Primary manuscript, attribution, prior-work, and scoped checking review for non-notifying local inclusion.

Read this published revision