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Inner amenability for groups and central sequences in factors

Published online by Cambridge University Press:  12 December 2014

IONUT CHIFAN
Affiliation:
Department of Mathematics, University of Iowa, 14 MacLean Hall, IA 52242, USA IMAR, Bucharest, Romania email ionut-chifan@uiowa.edu
THOMAS SINCLAIR
Affiliation:
Department of Mathematics, University of California, Los Angeles, Box 951555, Los Angeles, CA 90095-1555, USA email thomas.sinclair@math.ucla.edu
BOGDAN UDREA
Affiliation:
IMAR, Bucharest, Romania email ionut-chifan@uiowa.edu Department of Mathematics, University of Illinois, Urbana Champaign, IL 61801, USA email budrea@illinois.edu

Abstract

We show that a large class of i.c.c., countable, discrete groups satisfying a weak negative curvature condition are not inner amenable. By recent work of Hull and Osin [Groups with hyperbolically embedded subgroups. Algebr. Geom. Topol.13 (2013), 2635–2665], our result recovers that mapping class groups and $\text{Out}(\mathbb{F}_{n})$ are not inner amenable. We also show that the group-measure space constructions associated to free, strongly ergodic p.m.p. actions of such groups do not have property Gamma of Murray and von Neumann [On rings of operators IV. Ann. of Math. (2) 44 (1943), 716–808].

Type
Research Article
Copyright
© Cambridge University Press, 2014 

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