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arXiv · 1303.7279

On a conjecture of Karrass and Solitar

Benjamin Steinberg
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Abstract

We settle an old conjecture of Karrass and Solitar by proving that a finitely generated subgroup of a non-trivial free product $G = A\ast B$ has finite index if and only if it intersects non-trivially each non-trivial normal subgroup of $G$. This holds, more generally, for subgroups of finite Kurosh rank.

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Benjamin Steinberg. 2013-03-29. On a conjecture of Karrass and Solitar. https://arxiv.org/abs/1303.7279

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