Commutator relators of one-relator groups do not force Hopficity, residual finiteness, or automaticity

Ke Wang, Qiang Zhang

For G_m=⟨a,t | [t,a[a,t]^(−m)]⟩, a Baumslag–Solitar group BS(m,m+1) is a retract. In particular, G_2 is non-Hopfian and non-residually finite, while G_1 is non-automatic. Literal commutator relators therefore do not force any of these properties.

Sources for this record

What was already known

Baumslag asked whether one-relator groups with commutator relators have these properties. Olshanskii had already given negative residual-finiteness and automaticity examples for the broader condition that the relator lies in [F,F].

AI involvement AI-centered

Wang and Zhang credit ChatGPT with assisting in construction of the example family. They supplied the retract, epimorphism and Dehn-function arguments, checked all proofs and edited the paper.

ChatGPT is credited with constructing the example family on which the negative answers depend; the human authors supplied the proofs.

Importance Notable

Answers the three questions for the narrower literal-commutator case with one explicit family.

Limitations

The authors checked the proofs, but the precise model prompts and its share in selecting the parameterized relator are undisclosed.

Technical verification Formal (human)

Both authors explicitly report checking all arguments in the final paper; this is source-reported human verification.

Independent checking

Checking all arguments and editing the paper

Checker
Ke Wang and Qiang Zhang, authors
Scope
Theorem 1.3 for G_m and its three consequences
Basis
Reported by the linked checker
Evidence source

Human understanding Full

The authors explain the Baumslag–Solitar retract, noninjective epimorphism and non-quadratic Dehn-function obstruction.

Correction and publication history

2026-10-18 · publication

Answers the three questions for the narrower literal-commutator case with one explicit family.

Read this published revision