Finite presentations of metabelian groups: effective enumeration via Laurent relations

Abstract

For an ordinary finite presentation $P=\langle x_1,\ldots,x_n\mid R\rangle$, put $G(P)=F_n/\langle\langle R\rangle\rangle$. We construct a primitive-recursive predicate $V$ with $G(P)''=1 \Longleftrightarrow \exists c\in\mathbb{N}: V(P,c)=1$. Thus finite presentations of metabelian groups are recursively enumerable, answering Kourovka Problem 17.124. An effective form of the Bieri-Strebel covering construction, using signed Laurent relations and rational separation, gives a family of finitely presented metabelian groups cofinal under epimorphisms. Products of conjugates of defining relators witness these epimorphisms. The construction and enumeration theorem are formalized in Lean 4.