OpenAI reports a counterexample to unrestricted infinite matroid packing and covering

In ZFC, two self-dual partitional matroids on a countably infinite common ground set admit neither a packing/covering partition nor an intersection witness.

Sources for this record

What was already known

Bowler and Carmesin formulated the unrestricted packing/covering conjecture and its connection to infinite matroid intersection. Joó had positive results for two finitary matroids on countable ground sets.

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

Refutes the unrestricted packing/covering and intersection conjectures with only two matroids.

Limitations

The counterexample matroids are neither finitary nor cofinitary, so it does not contradict positive results under those restrictions.

Technical verification Formal (Lean 4)

OpenAI reports a Lean proof matching the selected claim.

Formal checking

The pinned OpenAI Lean scope note identifies this selected claim.

Checker
OpenAI-reported Lean 4 / Comparator
Scope
In ZFC, two self-dual partitional matroids on a countably infinite common ground set admit neither a packing/covering partition nor an intersection witness.
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