Powered by OpenAIRE graph
Found an issue? Give us feedback
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao zbMATH Openarrow_drop_down
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
zbMATH Open
Article
Data sources: zbMATH Open
Transactions of the American Mathematical Society
Article . 1983 . Peer-reviewed
Data sources: Crossref
versions View all 2 versions
addClaim

Interpolating Sequences for QA B

Interpolating sequences for \(QA_ n\)
Authors: Sundberg, Carl; Wolff, Thomas H.;

Interpolating Sequences for QA B

Abstract

Let B be any intermediate closed algebra between \(H^{\infty}\) and \(L^{\infty}({\mathbb{T}})\), i.e. B is a Douglas algebra. The algebra \(Q_ B=\bar B\cap B\) is closely related to B and admits a description in terms of vanishing mean oscillation. One can consider the algebra \(QA_ B=H^{\infty}\cap \bar B\) which consists of the functions in \(Q_ B\) which can be extended analytically to \({\mathbb{D}}\). If \(B=L^{\infty}\) then clearly \(QA_ B=H^{\infty}.\) Therefore it looks quite natural to investigate \(QA_ B\) along the same line as it has been made in case of \(H^{\infty}.\) The paper deals with the interpolation problem for \(QA_ B\). Let \({\mathfrak M}(B)\) be the maximal ideal space of B. We say that \(\{z_ n\}\subseteq {\mathbb{D}}\) is thin near \({\mathfrak M}(B)\) if \(\inf_{n}\prod_{m\neq n}| \frac{z_ m-z_ n}{1-\bar z_ mz_ n}|>0,\) i.e. \(\{z_ n\}\) is an interpolating sequence for \(H^{\infty}\), and \(\prod_{m\neq n}| \frac{z_ n-z_ m}{1-\bar z_ mz_ n}| \to 1\) as \(z_ n\) approximates \({\mathfrak M}(B)\). Theorem. The following conditions are equivalent for a sequence \(\{z_ n\}\subseteq {\mathbb{D}}:\) (1) for any bounded sequence of complex numbers \(\{\lambda_ n\}\) there exists \(f\in QA_ B\) such that \(f(z_ n)=\lambda_ n\) for all n; (2) for any bounded sequence of complex numbers \(\{\lambda_ n\}\) there exists \(f\in VMO_ B\) such that \(f(z_ n)=\lambda_ n\) for all n; (3) \(\{z_ n\}\) is thin near \({\mathfrak M}(B)\). Moreover if (3) holds, then there exists P. Beurling functions yielding (1). That is, there are functions \(\phi_ n\in QA_ B\) such that \(\phi_ n(z_ k)=\delta_{nk}\) and for any bounded sequences \(\{\lambda_ n\}\), \(\sum_{n}\lambda_ n\phi_ n\in QA_ B.\)

Keywords

Douglas algebra, Banach algebras of differentiable or analytic functions, \(H^p\)-spaces, vanishing mean oscillation, Blaschke products, etc., \(H^p\)-classes, maximal ideal space, interpolating sequence

  • BIP!
    Impact byBIP!
    selected citations
    These citations are derived from selected sources.
    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    5
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    Top 10%
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Average
Powered by OpenAIRE graph
Found an issue? Give us feedback
selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
5
Average
Top 10%
Average
Upload OA version
Are you the author of this publication? Upload your Open Access version to Zenodo!
It’s fast and easy, just two clicks!