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Browsing by Author "Rodríguez Piazza, Luis"
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A criterion of weak compactness for operators on subspaces of Orlicz spaces [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Hindawi, 2008)We give a criterion of weak compactness for the operators on the MorseTransue space MΨ , the subspace of the Orlicz space LΨ generated by L∞.

A spectral radius type formula for approximation numbers of composition operators [Article]
Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Elsevier, 20141215)For approximation numbers an(Cφ) of composition operators Cφ on weighted analytic Hilbert spaces, including the Hardy, Bergman and Dirichlet cases, with symbol φ of uniform norm <1, we prove that limn→∞[an(Cφ)]1/n=e−1 ...

Absolutely summing Carleson embeddings on Hardy spaces [Presentation]
Rodríguez Piazza, Luis (2013) 
Approximation numbers of composition operators on Hp [Article]
Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (De Gruyter Open, 201501)We give estimates for the approximation numbers of composition operators on the Hp spaces, 1 ≤ p < ∞.

Approximation numbers of composition operators on the Dirichlet space [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Springer, 201504)We study the decay of approximation numbers of compact composition operators on the Dirichlet space. We give upper and lower bounds for these numbers. In particular, we improve on a result of O. ElFallah, K. Kellay, M. ...

Approximation numbers of composition operators on the Hardy space of the infinite polydisk [Article]
Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Springer, 201712)We study the composition operators of the Hardy space on D∞ ∩ℓ1, the ℓ1 part of the infinite polydisk, and the behavior of their approximation numbers.

Approximation numbers of weighted composition operators [Article]
Lechner, Gandalf; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Elsevier, 2018)We study the approximation numbers of weighted composition operators f 7→ w · (f ◦ ϕ) on the Hardy space H2 on the unit disc. For general classes of such operators, upper and lower bounds on their approximation numbers ...

Compact composition operators on HardyOrlicz and BergmanOrlicz spaces [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Springer, 201109)We construct an analytic selfmap ϕ of the unit disk and an Orlicz function Ψ for which the composition operator of symbol ϕ is compact on the HardyOrlicz space HΨ, but not on the BergmanOrlicz space BΨ. For that, we first ...

Compact composition operators on the Dirichlet space and capacity of sets of contact points [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Elsevier, 20130215)We prove several results about composition operators on the Dirichlet space D⁎. For every compact set K⊆∂D of logarithmic capacity , there exists a Schur function φ both in the disk algebra A(D) and in D⁎ such that the ...

Composition operators on HardyOrlicz spaces [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (American Mathematical Society, 2010)We investigate composition operators on HardyOrlicz spaces when the Orlicz function Ψ grows rapidly: compactness, weak compactness, to be psumming, order bounded,..., and show how these notions behave according to the ...

Conjuntos evitables, capacidad analítica y medidas de Hausdorff [Final Degree Work]
Rosales Tristancho, Abel (201606)The main problem we consider in this work is the characterization of removable sets. A compact set E in the complex plane is removable if there exists an open set Ω containing E such that every bounded and analytic function ...

La desigualdad de Von Neumann y la teoría de dilatación [Master's Thesis]
Constantino Oitavén, Carlos (201809)A famous inequality by von Neumann states that if T is a contraction on a Hilbert space and p is a polynomial, then kp(T)k ≤ sup{p(z) : z ∈ C, z ≤ 1}. As time went on, this inequality has given rise to a large variety ...

Estimates for approximation numbers of some classes of composition operators on the Hardy space [Article]
Rodríguez Piazza, Luis; Li, Daniel; Queffélec, Hervé (2013) 
Function algebras with a strongly precompact unit ball [Article]
Lacruz Martín, Miguel Benito; Rodríguez Piazza, Luis (Elsevier, 20131001)Let µ be a finite positive Borel measure with compact support K ⊆ C, and regard L∞(µ) as an algebra of multiplication operators on the Hilbert space L2(µ). Then consider the subalgebra A(K) of all continuous functions on ...

Infinitesimal Carleson property for weighted measures induced by analytic selfmaps of the unit disk [Article]
Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Springer, 201308)We prove that, for every α>−1, the pullback measure φ(Aα) of the measure dAα(z)=(α+1)(1−z2)αdA(z), where A is the normalized area measure on the unit disk D, by every analytic selfmap φ:D→D is not only an (α+2)Carleson ...

Invariant means and thin sets in harmonic analysis with applications to prime numbers [Article]
Lefèvre, Pascal; Rodríguez Piazza, Luis (Wiley, 200908)We first prove a localization principle characterising LustPiquard sets. We obtain that the union of two LustPiquard sets is a LustPiquard set, provided that one of these two sets is closed for the Bohr topology. We ...

Lpvalued measures without finite Xsemivariation for 2 < p < ∞ [Article]
Jefferies, Brian; Okada, Susumu; Rodríguez Piazza, Luis (Taylor & Francis, 2007)We show that for 1 ≤ p < ∞, the property that every Lpvalued vector measure has finite Xsemivariation in Lp(μ, X) is equivalent to the property that every continuous linear map from 1 to X is psumming. For 2 < p < ...

Medidas cónicas y rangos de medidas vectoriales [PhD Thesis]
Romero Moreno, María del Carmen (1996) 
Nevanlinna counting function and Carleson function of analytic maps [Article]
Lefèvre, Pascal; Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Springer, 201110)We show that the maximal Nevanlinna counting function and the Carleson function of analytic selfmaps of the unit disk are equivalent, up to constants.

On approximation numbers of composition operators [Article]
Li, Daniel; Queffélec, Hervé; Rodríguez Piazza, Luis (Elsevier, 201204)We show that the approximation numbers of a compact composition operator on the weighted Bergman spaces Bα of the unit disk can tend to 0 arbitrarily slowly, but that they never tend quickly to 0: they grow at ...