Finite quotients of one-relator groups
DefinitionFinite soluble groups as images of one-relator groups (Kourovka 18.75)#✓fully proved
The statement, posed by A. Yu. Olshanskii, that every finite soluble group \(G\) has a natural number \(d\) such that for every element \(w\) of the free group on \(x_1, \dots, x_d\) there is a surjective homomorphism from the one-relator group \(\langle x_1, \dots, x_d \mid w \rangle\) onto \(G\).
def solubleGroupImageOfOneRelatorGroups : Prop :=
∀ (G : Type) [Group G] [Finite G], Group.IsSolvable G →
∃ d : ℕ, ∀ w : FreeGroup (Fin d),
∃ f : PresentedGroup ({w} : Set (FreeGroup (Fin d))) →* G, Function.Surjective f
Used by 1
TheoremFinite soluble groups are images of one-relator groups#●ready to prove
Every finite soluble group \(G\) has a natural number \(d\) such that for every element \(w\) of the free group on \(x_1, \dots, x_d\) there is a surjective homomorphism from the one-relator group \(\langle x_1, \dots, x_d \mid w \rangle\) onto \(G\). That is, Kourovka Problem 18.75 has a positive answer.
Resolved true: the Kourovka Archive answers 18.75 "Yes, it does" (N. Nikolov and D. Segal, 2007).
public theorem_wanted solubleGroupImageOfOneRelatorGroups_holds :
solubleGroupImageOfOneRelatorGroups
def solubleGroupImageOfOneRelatorGroups : Prop :=
∀ (G : Type) [Group G] [Finite G], Group.IsSolvable G →
∃ d : ℕ, ∀ w : FreeGroup (Fin d),
∃ f : PresentedGroup ({w} : Set (FreeGroup (Fin d))) →* G, Function.Surjective f
WantedExt/GroupTheory/SolubleOneRelatorQuotientKourovka18Problem75Wanted.lean:38
Sources
- E. I. Khukhro and V. D. Mazurov (eds.), Unsolved Problems in Group Theory: The Kourovka Notebook, 21st issue, arXiv:1401.0300v49 (2026), Archive of Solved Problems, Problem 18.75 (A. Yu. Olshanskii); resolution: N. Nikolov and D. Segal, Bull. London Math. Soc. 39 (2007), no. 2, 209-213, Kourovka Archive, Problem 18.75: Yes, it does, https://arxiv.org/abs/1401.0300v49.
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