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Finite Groups whose Powers have no Countably Infinite Factor Groups
Published online by Cambridge University Press: 20 November 2018
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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 perfect
2. 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.
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