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Transactions of the American Mathematical Society

ISSN 1088-6850(online) ISSN 0002-9947(print)



On relative property (T) and Haagerup's property

Authors: Ionut Chifan and Adrian Ioana
Journal: Trans. Amer. Math. Soc. 363 (2011), 6407-6420
MSC (2010): Primary 20F69; Secondary 46L10
Published electronically: July 14, 2011
MathSciNet review: 2833560
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Abstract: We consider the following three properties for countable discrete groups $ \Gamma $: (1) $ \Gamma $ has an infinite subgroup with relative property (T), (2) the group von Neumann algebra $ L\Gamma $ has a diffuse von Neumann subalgebra with relative property (T) and (3) $ \Gamma $ does not have Haagerup's property. It is clear that (1) $ \Longrightarrow $ (2) $ \Longrightarrow $ (3). We prove that both of the converses are false.

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Additional Information

Ionut Chifan
Affiliation: Department of Mathematics, 1326 Stevenson Center, Vanderbilt University, Nash- ville, Tennessee 37240 – and – Institute of Mathematics of the Romanian Academy, Bucharest, Romania

Adrian Ioana
Affiliation: Department of Mathematics, University of California, Los Angeles, Los Angeles, California 90095-155505 – and – Institute of Mathematics of the Romanian Academy, Bucharest, Romania

Received by editor(s): July 14, 2009
Received by editor(s) in revised form: November 23, 2009
Published electronically: July 14, 2011
Additional Notes: The second author was supported by a Clay Research Fellowship
Article copyright: © Copyright 2011 American Mathematical Society
The copyright for this article reverts to public domain 28 years after publication.

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