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SUMMARY:Behaviour of Hilbert compression for groups\, under group construc
 tions - Valette\, A (Neuchtel)
DTSTART:20110111T163000Z
DTEND:20110111T173000Z
UID:TALK28811@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:If $(X\,d)$ is a metric space\, the Hilbert compression of $X$
  is the supremum of all $lpha$'s for which there exists a Lipschitz embed
 ding $f$ from X to a Hilbert space\, such that $C.d(x\,y)^lpha leq |f(x)-
 f(y)|$ for every $x\,yin X$. When $G$ is a finitely generated group\, Hilb
 ert compression is a quasi-isometry invariant which has been related to co
 ncepts such as exactness\, amenability\, Haagerup property. In this survey
  talk\, we will review the known results about the range of this invariant
 \, then we will move on to some recent results (due to Naor-Peres\, Li\, D
 reesen) on the behaviour of Hilbert compression under various group constr
 uctions (wreath products\, free and amalgamated products\, HNN-extensions\
 , etc...).\n
LOCATION:Seminar Room 1\, Newton Institute
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