ABSTRACT
A group is called (PF)L if the subgroups generated by its elements having same order (finite or infinite) are polycyclic-by-finite. In the present paper we prove that a group is locally graded minimal non-((PF)Lβͺ(ππ)π) if, and only if, it is non-perfect minimal non-FC, where (ππ)π denotes the class of (polycyclic-by-finite)-by-abelian groups. We prove also that a group of infinite rank whose proper subgroups of infinite rank are in ((PF)Lβͺ(ππ)π) is itself in ((PF)Lβͺ(ππ)π) provided that it is locally (soluble-by-finite) without simple homomorphic images of infinite rank. Our last result concerns groups that satisfy the minimal condition on non-((PF)Lβͺ(ππ)π)-subgroups.
Acknowledgment
Both authors are grateful to the referee whose comments improved the presentation of our results.