POWER GROUPS OF FREE ABELIAN GROUPS OF FINITE RANK
Geoff C. Smith, Gunnar Traustason · Communications in Algebra · 2002
The power set of a group G has an induced semigroup structure, some subsets of which will form groups in their own right. We are especially interested in such subsets that are maximal. We demonstrate that even when G is a free abelian group of finite rank, the groups which arise in this way can be diverse profinite abelian groups.