algebra / Combinatorial Group Theory

Commutator Relators Do Not Force Hopficity, Residual Finiteness or Automaticity

Baumslag asked whether a one-relator group $G=F/\langle\langle r\rangle\rangle$ with $r$ a commutator is Hopfian, residually finite or automatic. The paper constructs a family $G_m=\langle a,t \mid [t,a[a,t]^{-m}]\rangle$ answering all three negatively.

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algebraJul 23, 2026Significance 20/100Registry: unreviewed

Commutator Relators Do Not Force Hopficity, Residual Finiteness or Automaticity

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Baumslag asked whether a one-relator group $G=F/\langle\langle r\rangle\rangle$ with $r$ a commutator is Hopfian, residually finite or automatic. The paper constructs a family $G_m=\langle a,t \mid [t,a[a,t]^{-m}]\rangle$ answering all three negatively.

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Baumslag asked whether a one-relator group $G=F/\langle\langle r\rangle\rangle$ with $r$ a commutator is Hopfian, residually finite or automatic. The paper constructs a family $G_m=\langle a,t \mid [t,a[a,t]^{-m}]\rangle$ answering all three negatively.

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