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Displaying similar documents to “Discontinuity of the Fuglede-Kadison determinant on a group von Neumann algebra”

On approximation of functions by certain operators preserving x 2

Lucyna Rempulska, Karolina Tomczak (2008)

Commentationes Mathematicae Universitatis Carolinae

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In this paper we extend the Duman-King idea of approximation of functions by positive linear operators preserving e k ( x ) = x k , k = 0 , 2 . Using a modification of certain operators L n preserving e 0 and e 1 , we introduce operators L n * which preserve e 0 and e 2 and next we define operators L n ; r * for r -times differentiable functions. We show that L n * and L n ; r * have better approximation properties than L n and L n ; r .

Subadditive measures on projectors of a von Neumann algebra

Leszek J. Ciach

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CONTENTSIntroduction...............................................................................................................................................5§0. Fundamental definitions and notations...............................................................................................7§1. Subadditive measure on projectors of a von Neumann algebra.........................................................8§2. m-measurable operators. Convergence in measure.........................................................................10§3....

Dual algebras generated by von Neumann n-tuples over strictly pseudoconvex sets

Michael Didas

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Let D ⋐ X denote a relatively compact strictly pseudoconvex open subset of a Stein submanifold X ⊂ ℂⁿ and let H be a separable complex Hilbert space. By a von Neumann n-tuple of class over D we mean a commuting n-tuple of operators T ∈ L(H)ⁿ possessing an isometric and weak* continuous H ( D ) -functional calculus as well as a ∂D-unitary dilation. The aim of this paper is to present an introduction to the structure theory of von Neumann n-tuples of class over D including the necessary function-...

The order topology for a von Neumann algebra

Emmanuel Chetcuti, Jan Hamhalter, Hans Weber (2015)

Studia Mathematica

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The order topology τ o ( P ) (resp. the sequential order topology τ o s ( P ) ) on a poset P is the topology that has as its closed sets those that contain the order limits of all their order convergent nets (resp. sequences). For a von Neumann algebra M we consider the following three posets: the self-adjoint part M s a , the self-adjoint part of the unit ball M ¹ s a , and the projection lattice P(M). We study the order topology (and the corresponding sequential variant) on these posets, compare the order topology...

Spectral subspaces and non-commutative Hilbert transforms

Narcisse Randrianantoanina (2002)

Colloquium Mathematicae

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Let G be a locally compact abelian group and ℳ be a semifinite von Neumann algebra with a faithful semifinite normal trace τ. We study Hilbert transforms associated with G-flows on ℳ and closed semigroups Σ of Ĝ satisfying the condition Σ ∪ (-Σ) = Ĝ. We prove that Hilbert transforms on such closed semigroups satisfy a weak-type estimate and can be extended as linear maps from L¹(ℳ,τ) into L 1 , ( , τ ) . As an application, we obtain a Matsaev-type result for p = 1: if x is a quasi-nilpotent compact...

Smooth operators in the commutant of a contraction

Pascale Vitse (2003)

Studia Mathematica

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For a completely non-unitary contraction T, some necessary (and, in certain cases, sufficient) conditions are found for the range of the H calculus, H ( T ) , and the commutant, T’, to contain non-zero compact operators, and for the finite rank operators of T’ to be dense in the set of compact operators of T’. A sufficient condition is given for T’ to contain non-zero operators from the Schatten-von Neumann classes S p .

On the Neumann-Poincaré operator

Josef Král, Dagmar Medková (1998)

Czechoslovak Mathematical Journal

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Let Γ be a rectifiable Jordan curve in the finite complex plane which is regular in the sense of Ahlfors and David. Denote by L C 2 ( Γ ) the space of all complex-valued functions on Γ which are square integrable w.r. to the arc-length on Γ . Let L 2 ( Γ ) stand for the space of all real-valued functions in L C 2 ( Γ ) and put L 0 2 ( Γ ) = { h L 2 ( Γ ) Γ h ( ζ ) | d ζ | = 0 } . Since the Cauchy singular operator is bounded on L C 2 ( Γ ) , the Neumann-Poincaré operator C 1 Γ sending each h L 2 ( Γ ) into C 1 Γ h ( ζ 0 ) : = ( π i ) - 1 P . V . Γ h ( ζ ) ζ - ζ 0 d ζ , ζ 0 Γ , is bounded on L 2 ( Γ ) . We show that the inclusion C 1 Γ ( L 0 2 ( Γ ) ) L 0 2 ( Γ ) characterizes the circle in the...

On completely bounded bimodule maps over W*-algebras

Bojan Magajna (2003)

Studia Mathematica

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It is proved that for a von Neumann algebra A ⊆ B(ℋ ) the subspace of normal maps is dense in the space of all completely bounded A-bimodule homomorphisms of B(ℋ ) in the point norm topology if and only if the same holds for the corresponding unit balls, which is the case if and only if A is atomic with no central summands of type I , . Then a duality result for normal operator modules is presented and applied to the following problem. Given an operator space X and a von Neumann algebra...