An Artin group with no geometric CAT(0) action

OpenAI

An Artin group on 116 generators, with off-diagonal labels only 2, 3 or infinity, has no proper cocompact isometric action on any nonempty proper CAT(0) metric space, in any dimension.

Sources for this record

What was already known

The finite-rank geometric CAT(0) conjecture remained open. Earlier examples required higher-dimensional actions but did not rule out all geometric CAT(0) actions.

AI involvement AI-led

OpenAI attributes the manuscript and proof artifacts to an internal model. It does not document the individual session well enough to establish autonomous origin.

The mathematical construction is in OpenAI's internal-model manuscript collection; no individual autonomous run is documented.

Importance Major

Gives a counterexample to the finite-rank geometric CAT(0) conjecture.

Limitations

The release maps the explicit construction to a Lean theorem and comparator. No named human proof check or explanation is documented.

Technical verification Formal (Lean 4)

The formalization catalogue maps the CAT(0) comparator to OAI.ArtinCAT0.main. The released Lean theorem proves the explicit matrix properties and excludes geometric actions on nonempty proper CAT(0) spaces. This is a source-reported machine proof.

Formal checking

The formalization catalogue maps the CAT(0) comparator to OAI.ArtinCAT0.main. The released Lean theorem proves the explicit matrix properties and excludes geometric actions on nonempty proper CAT(0) spaces. This is a source-reported machine proof.

Checker
Lean 4 kernel, as reported by the OpenAI math release
Scope
The explicit 116-generator Artin group has no geometric action on any nonempty proper CAT(0) 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

The manuscript explains the stable-length and six-sector obstruction, but no named human explanation is documented. Few is the evidence default.

Correction and publication history