Session 37. Wild algebraic and geometric topology

Generalized presentations of groups, in particular of \({\rm Aut}(F_{\omega})\)

Oleg Bogopolski, Universität Düsseldorf, Germany
The talk is based on joint work with Wilhelm Singhof.
We introduce generalized presentations of groups. Roughly speaking, a generalized presentation of a group \(G\) consists of a generalized free group \(\mathcal{F}\) (which is a certain subgroup of a big free group \({\rm BF(\Lambda)}\)) and of a subset \(R\) of \(\mathcal{F}\) such that \(G\) is isomorphic to \(\mathcal{F}/\overline{\langle\langle R\rangle\rangle}\), where \(\overline{\langle\langle R\rangle\rangle}\) is the closure of \(\langle\langle R\rangle\rangle\) with respect to an appropriate topology on \(\mathcal{F}\).

We give a generalized presentation of \({\rm Aut}(F_{\omega})\), the automorphism group of the free group of infinite countable rank. This generalized presentation is countable, although the group itself is uncountable.

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