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Displaying 161 – 180 of 207

Unicellularity of the multiplication operator on Banach spaces of formal power series

B. Yousefi (2001)

Studia Mathematica

Let ${β (n)}_{n = 0}^{\infty}$ be a sequence of positive numbers and 1 ≤ p < ∞. We consider the space $ℓ^{p} (β)$ of all power series $f (z) = \sum_{n = 0}^{\infty} f ̂ (n) z ⁿ$ such that $\sum_{n = 0}^{\infty} {| f ̂ (n) |}^{p} {| β (n) |}^{p} < \infty$ . We give some sufficient conditions for the multiplication operator, $M_{z}$ , to be unicellular on the Banach space $ℓ^{p} (β)$ . This generalizes the main results obtained by Lu Fang [1].

Unitary asymptotes of Hilbert space operators

László Kérchy (1994)

Banach Center Publications

In this survey article we are going to present the effectiveness of the use of unitary asymptotes in the study of Hilbert space operators.

Variations on a theme of Beurling.

Douglas, Ronald G. (2011)

The New York Journal of Mathematics [electronic only]

Von Neumann operators are reflexive.

John B. Conway, James J. Dudziak (1990)

Journal für die reine und angewandte Mathematik

Wandering subspaces and quasi-wandering subspaces in the Bergman space.

Izuchi, Kou Hei (2011)

The New York Journal of Mathematics [electronic only]

Wandering subspaces and the Beurling type theorem. II.

Izuchi, Kei Ji, Izuchi, Kou Hei, Izuchi, Yuko (2010)

The New York Journal of Mathematics [electronic only]

Weighted shift operators on lp spaces.

Lucas Jódar (1986)

Stochastica

The analytic-spectral structure of the commutant of a weighted shift operator defined on a lp space (1 ≤ p < ∞) is studied. The cases unilateral, bilateral and quasinilpotent are treated. We apply the results to study certain questions related to unicellularity, strictly cyclicity and the existence of hyperinvariant subspaces.

Wold-type extension for N-tuples of commuting contractions

Marek Kosiek, Alfredo Octavio (1999)

Studia Mathematica

Let (T1,…,TN) be an N-tuple of commuting contractions on a separable, complex, infinite-dimensional Hilbert space ℋ. We obtain the existence of a commuting N-tuple (V1,…,VN) of contractions on a superspace K of ℋ such that each $V_{j}$ extends $T_{j}$ , j=1,…,N, and the N-tuple (V1,…,VN) has a decomposition similar to the Wold-von Neumann decomposition for coisometries (although the $V_{j}$ need not be coisometries). As an application, we obtain a new proof of a result of Słociński (see [9])