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Valette, Alain
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Valette, Alain
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Professeur ordinaire
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alain.valette@unine.ch
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Voici les éléments 1 - 10 sur 15
- PublicationMétadonnées seulementAmenability and margulis super-rigidity(: Springer-Verlag Berlin, 2008)
; ;Cowling, Michael ;Kashiwara, Masaki ;Vogan, David A ;Frenkel, Edward; Wallach, Nolan R - PublicationMétadonnées seulementNon-Properness of Amenable Actions on Graphs with Infinitely Many Ends(: World Scientific Pub Co Inc, 2006)
;Moon, Soyoung; ;Hawkes, TrevorLongobardi, Patrizia - PublicationAccès libreWreath products with the integers, proper actions and Hilbert space compressionWe prove that the properties of acting metrically properly on some space with walls or some CAT(0) cube complex are closed by taking the wreath product with Z. We also give a lower bound for the (equivariant) Hilbert space compression of H Z in terms of the (equivariant) Hilbert space compression of H.
- PublicationMétadonnées seulementRestricting cohomological representations of SO(n, 1) and SU(n, 1)Let G denote either SO0(n, 1) or SU(n, 1). We study restrictions of cohomological representations of G to subgroups H isomorphic to SO0(m, 1) or SU(m, 1). We prove that such a restriction contains, as a subrepresentation, some cohomological representation of H. When G = SU(n, 1), we extend a result of Delorme by showing that cohomological representations are non-spherical in a strong sense: if H is isomorphic to SU(m, 1) (with 1
- PublicationMétadonnées seulementProper affine isometric actions of amenable groups(1995)
;Bekka, Bachir ;Cherix, Pierre-Alain - PublicationMétadonnées seulementAn application of Ramanujan graphs to C*-algebra tensor productsIn a remarkable recent paper, Junge and Pisier (1995) prove that there are several distinct C*-norms on the tensor product B(H) x B(H), where B(H) is the C*-algebra of bounded linear operators on the usual Hilbert space H. To give a quantitative version of this result, they introduce the function lambda(n) = sup{\\u\\(max)/\\u\\(min): u a tensor with rank at most n in B(H) x B(H)}, and prove cn(1/8) less than or equal to lambda(n) less than or equal to n(1/2) for n > 2. In this note, we use Ramanujan graphs to get 1/2n(1/2) < lambda(n) for any n = q + 1, q a prime power. From this we deduce lim inf/pi-->infinity lambda(n)/root n greater than or equal to 1/2 root 3.
- PublicationMétadonnées seulementLattices in semi-simple Lie groups and multipliers of group C*-algebras(1995)
;Bekka, BachirLet Gamma be a lattice in a non-compact simple Lie group G. We prove that the canonical map from the full C*-algebra C*(Gamma) to the multiplier algebra M(C*(G)) is not injective in general (it is never injective if G has Kazhdan's property (T), and not injective for many lattices either in SO(n, 1) or SU(n, 1)). For a locally compact group G, Fell introduced a property (WF3), stating that for any closed subgroup H of G, the canonical map from C*(H) to M(C*(G)) is injective. We prove that, for an almost connected G, property (WF3) is equivalent to amenability. - PublicationMétadonnées seulementOn the spectrum of the sum of generators of a finitely generated group II(1993)
;De La Harpe, Pierre ;Robertson, Guyan