Uffe Haagerup

  1. Factorization and dilation problems for completely positive maps on von Neumann algebras.

    Authors: Uffe Haagerup, Magdalena Musat
    Subjects: Operator Algebras
    Abstract

    We study factorization and dilation properties of Markov maps between von
    Neumann algebras equipped with normal faithful states, i.e., completely
    positive unital maps which preserve the given states and also intertwine their
    automorphism groups. The starting point for our investigation has been the
    question of existence of non-factorizable Markov maps, as formulated by C.
    Anantharaman-Delaroche.

  2. Schur Multipliers and Spherical Functions on Homogeneous Trees.

    Authors: Uffe Haagerup, Troels Steenstrup, Ryszard Szwarc
    Subjects: Group Theory
    Abstract

    Let X be a homogeneous tree of degree q+1 (for q between 2 and infinity) and
    let f be a complex function on X times X for which f(x,y) only depend on the
    distance between x and y in X. Our main result gives a necessary and sufficient
    condition for such a function to be a Schur multiplier on X times X. Moreover,
    we find a closed expression for the Schur norm of f.

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