Weak commutativity and finiteness properties of groups

Abstract

We consider the group X(G) obtained from G*G by forcing each element g in the first free factor to commute with the copy of g in the second free factor. Deceptively complicated finitely presented groups arise from this construction: X(G) is finitely presented if and only if G is finitely presented, but if F is a non-abelian free group of finite rank then X(F) has a subgroup of finite index whose third homology is not finitely generated