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Artículo
Quasi-similarity of contractions having 2 x 2 a singular characteristic function
(Elsevier, 2008)
LetT1:H1→H1be a completely non-unitary contraction having a 2×2 singular characteristic function Θ1; thatis, Θ1=[θi,j]i, j=1,2withθij∈H∞and det(Θ1)=0. Asit is well known, Θ1is a singular matrix if and only ifΘ1can be written ...
Artículo
Volterra operators and semigroups in weighted Banach spaces of analytic functions
(Springer Open Choice, 2014)
We characterize the boundedness, compactness and weak compactness of Volterra operators Vg( f )(z) := z 0 f (ζ )g (ζ ) dζ acting between different weighted spaces of type H∞ v in terms of the symbol function g, ...
Artículo
On Pták's generalization of Hankel operators
(Springer, 2001)
In 1997 Pták defined generalized Hankel operators as follows: Given two contractions T1 ∈ B(H1) and T2 ∈ B(H2), an operator X: H1 → H2 is said to be a generalized Hankel operator if T2X = XT ∗ 1 and X satisfies a ...
Artículo
Lifting the solutions of a Toeplitz type equation; the semigroup case X = TsXT*s
(Universita del Salento, 1995)
A Toeplitz operator with respect to a contractive representation {Ts} of an abelian semigroup Σ in a Hilbert space H is an operator X ∈ B(H) such that X = TsXT ∗ s for all s ∈ Σ. We show that if {Ts} has a minimal ...