Finite Groups whose Powers have no Countably Infinite Factor Groups

Abstract

Let P be the class of all finite groups G whose powers GI have no countably infinite factor groups. Neumann and Yamamuro (1) proved that if G is a finite non-Abelian simple group, then G ∈ P. We generalize this result by proving the following theorem.THEOREM. A finite group G ∈ P if and only if G is perfect2. Inheritance properties ofP.P1. If G ∈ P and N is normal in G, then G/N ∈ P.Proof. Since (G/N)I is isomorphic to GI/NI it is clear that factor groups of (G/N)I are isomorphic to factor groups of GI, and hence finite or uncountable.P2. If G = HK, where H ∈ P and K ∈ P, then G ∈ P.Proof. We show that homomorphic images of GI are either finite or uncountable. Let ϕ be a homomorphism of GI. Then GIϕ = (HK)Iϕ = (HI/KI)ϕ = (HIϕ) (KIϕ). Since HIϕ and KIϕ must be finite or uncountable, the conclusion follows.