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Mapping tori of free group automorphisms are coherent

Mark Feighn·Michael Handel
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Abstract

The mapping torus of an endomorphism Φof a group G is the HNN-extension G*_G with bonding maps the identity and Φ. We show that a mapping torus of an injective free group endomorphism has the property that its finitely generated subgroups are finitely presented and, moreover, these subgroups are of finite type.

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Mark Feighn, Michael Handel. 1999-05-01. Mapping tori of free group automorphisms are coherent. https://arxiv.org/abs/math/9905209

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