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Universal groups, binate groups and acyclicity. (English) Zbl 0663.20053
Group theory, Proc. Conf., Singapore 1987, 253-266 (1989).
[For the entire collection see Zbl 0652.00004.]
The author introduces the notion of a “binate group” $$(binate''=arranged$$ in pairs”). More precisely, the universal binate-filtered group with base H is the tower $$H=H_ 0\leq H_ 1\leq H_ 2\leq..$$. where $$H_{i+1}$$ is the HNN-extension $$(H_ i\times H_ i)*\psi$$ resulting from $$\psi$$ : [1]$$\times H_ i\to H_ i\times H_ i$$ given by $$\psi (l,h)=(h,h)$$. It is shown that any binate-filtered group is an infinitely generated, acyclic group.
The author examines the basic properties of binate-ness and uses them to prove acyclicity for a number of groups (e.g. Ph. Hall’s countable, universal locally finite group [J. Lond. Math. Soc. 34, 305-319 (1959; Zbl 0088.023)], groups of diffeomorphisms, mitotic groups, general linear groups of the cone on a ring etc.).
Reviewer: V.P.Snaith

##### MSC:
 20J05 Homological methods in group theory 20E06 Free products of groups, free products with amalgamation, Higman-Neumann-Neumann extensions, and generalizations 55R40 Homology of classifying spaces and characteristic classes in algebraic topology 20F05 Generators, relations, and presentations of groups