12 June 2013

16:00

Benno Kuckuck

Abstract

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<div> To any splitting of a group G as an HNN extension we can associate a
map from G to Z. Conversely, a group that allows a non-trivial
homomorphism to Z may be written as an HNN extension in an obvious way.
In this talk we will consider the question when
such a homomorphism G->Z is associated to a non-obvious HNN splitting
of G. We will then see how this information can be collected into an
invariant of the group which may be described by a simple connectivity
condition on Cayley graphs.<span><span style="color: black; font-family: Calibri; font-size: small;"><span style="font-size: 12pt;">
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