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The one-sided ergodic Hilbert transform in Banach spaces

Guy Cohen, Christophe Cuny, Michael Lin (2010)

Studia Mathematica

Let T be a power-bounded operator on a (real or complex) Banach space. We study the convergence of the one-sided ergodic Hilbert transform l i m n k = 1 n ( T k x ) / k . We prove that weak and strong convergence are equivalent, and in a reflexive space also s u p n | | k = 1 n ( T k x ) / k | | < is equivalent to the convergence. We also show that - k = 1 ( T k ) / k (which converges on (I-T)X) is precisely the infinitesimal generator of the semigroup ( I - T ) | ( I - T ) X ¯ r .

The Stein-Weiss theorem for the ergodic Hilbert transform

Lasha Ephremidze (2004)

Studia Mathematica

The Stein-Weiss theorem that the distribution function of the Hilbert transform of the characteristic function of E depends only on the measure of E is generalized for the ergodic Hilbert transform in the case of a one-parameter flow of measure-preserving transformations on a σ-finite measure space.

The topological centralizers of Toeplitz flows and their Z2-extensions.

Wojciech Bulatek, Jan Kwiatkowski (1990)

Publicacions Matemàtiques

The topological centralizers of Toeplitz flows satisfying a condition (Sh) and their Z2-extensions are described. Such Toeplitz flows are topologically coalescent. If {q0, q1, ...} is a set of all except at least one prime numbers and I0, I1, ... are positive integers then the direct sum ⊕i=0∞ Zqi|i ⊕ Z can be the topological centralizer of a Toeplitz flow.

The σ-ideal of closed smooth sets does not have the covering property

Carlos Uzcátegui (1996)

Fundamenta Mathematicae

We prove that the σ-ideal I(E) (of closed smooth sets with respect to a non-smooth Borel equivalence relation E) does not have the covering property. In fact, the same holds for any σ-ideal containing the closed transversals with respect to an equivalence relation generated by a countable group of homeomorphisms. As a consequence we show that I(E) does not have a Borel basis.

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