A Counterexample to Kaplansky's Direct-Finiteness Conjecture in Odd Characteristic

OpenAI

For a finite field K of odd characteristic and a finitely generated group G with torsion, the construction gives a linear cellular automaton on all K^G configurations that is injective but not surjective.

Sources for this record

What was already known

Surjunctivity is known for sofic groups, but the universal finite-alphabet conjecture remained open. A companion characteristic-two direct-finiteness construction has a related automaton consequence from a different witness.

AI involvement AI-led

OpenAI credits an internal model with the odd-characteristic manuscript and Lean proof, building on its companion algebra-to-automaton argument.

The OpenAI release attributes the odd-characteristic construction and proof artifact to its internal model.

Importance Major

The claimed automaton refutes Gottschalk’s universal surjunctivity conjecture.

Limitations

The Lean theorem covers the specified odd-characteristic witness. Its proof is source-reported and has no documented completed human check.

Technical verification Formal (Lean 4 with Mathlib and Comparator)

The source-reported Lean main theorem asserts both the prescribed odd-characteristic scalar defect and injectivity without surjectivity of the associated cellular automaton on all configurations. It matches this finite-alphabet surjunctivity counterexample, but was not rebuilt here.

Formal checking

Proof of OAI.OddKaplansky.main_theorem matched to the OddKaplansky Comparator MainClaim

Checker
Lean 4 kernel, as reported by the OpenAI math release
Scope
An injective nonsurjective cellular automaton on K^G for the specified odd-characteristic finite field and finitely generated group
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

No named human account of the odd-characteristic witness's construction is documented; Few is the evidence default.

Correction and publication history