Latest

Algebra

When reversing an algebraic operation fails

OpenAI research collection · 4 manuscripts · Source checked 2026-10-19

The idea in plain language

In familiar finite square matrices, if AB equals the identity, BA does too. This family constructs more exotic group-algebra settings where that expectation fails and develops related counterexamples.

Why it matters

The claims concern specialised infinite algebraic structures. They do not contradict ordinary finite-dimensional matrix arithmetic.

Read the technical source claim

Constructs a finitely presented torsion-free nonsofic group whose group algebra over 𝔽_(2) is not directly finite, disproving Kaplansky's conjecture even without torsion. Companion examples give injective nonsurjective cellular automata on all configurations, refuting Gottschalk's surjunctivity conjecture. Another counterexample is an integral group-ring matrix, invertible over the rational group ring, with Fuglede–Kadison determinant strictly between zero and one, disproving the unrestricted Determinant Conjecture.

Read the manuscripts

Short excerpts below come from OpenAI's abstracts. The full abstract and original PDF preserve the paper's precise scope.

MANUSCRIPT 01

A Torsion-Free Group Algebra That Is Not Directly Finite

We construct a finitely presented torsion-free counterexample to Kaplansky's direct finiteness conjecture over the field of two elements. The group admits a finite two-dimensional classifying complex.

This exact PDF is not listed in the imported formalization catalogue. Family scope notes may contain further information.

MANUSCRIPT 02

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

We disprove Kaplansky's direct-finiteness conjecture by constructing a finite field K of characteristic two, a finitely presented group G, and finite sums a,b∈ K[G] with ab=1 but ba\ne1. The group G is nonsofic. The same elements define a cellular automaton on K^(G) that is injective but not surjective, disproving Gottschalk's…

Full source abstract

We disprove Kaplansky's direct-finiteness conjecture by constructing a finite field K of characteristic two, a finitely presented group G, and finite sums a,b∈ K[G] with ab=1 but ba\ne1. The group G is nonsofic. The same elements define a cellular automaton on K^(G) that is injective but not surjective, disproving Gottschalk's surjunctivity conjecture.

This PDF is listed in OpenAI's formalization catalogue. See the scope and dependencies before interpreting coverage.

MANUSCRIPT 03

A Counterexample to the Group-Ring Determinant Conjecture

We disprove the unrestricted group-ring Determinant Conjecture. We construct a finitely generated group G and a square matrix over \mathbb Z[G] that is invertible over \mathbb Q[G] and has Fuglede–Kadison determinant strictly between zero and one. The logarithmic integral defining the determinant is finite.

This PDF is listed in OpenAI's formalization catalogue. See the scope and dependencies before interpreting coverage.

MANUSCRIPT 04

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

We construct a counterexample to Kaplansky's direct-finiteness conjecture in odd characteristic. For one specified odd prime p, we obtain a field K of order p^(4), a finitely generated group G containing torsion, and finite sums a,b∈ K[G] with ab=1 but ba\ne1. The same elements define a cellular automaton on K^(G) that is…

Full source abstract

We construct a counterexample to Kaplansky's direct-finiteness conjecture in odd characteristic. For one specified odd prime p, we obtain a field K of order p^(4), a finitely generated group G containing torsion, and finite sums a,b∈ K[G] with ab=1 but ba\ne1. The same elements define a cellular automaton on K^(G) that is injective but not surjective.

This PDF is listed in OpenAI's formalization catalogue. See the scope and dependencies before interpreting coverage.

One signal in the wider AGI picture

New mathematical reasoning could help AI tackle harder scientific and computational problems. How reliably these skills transfer beyond mathematics will determine how much they contribute to general intelligence.

Explore the AGI Clock ↗