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Polynomial approximation and Carleson measures on a general domain and equivalence classes of subnormal operators

This thesis consists of eight chapters. Chapter 1 contains the preliminaries: the background, notation and results needed for this work.

In Chapter 2 we study the problem of when P, the set of analytic polynomials, is dense in the Hardy space H<sup>t</sup>(G) or the Bergman space L<sup>t</sup><sub>n</sub>G, where G is a bounded domain and t ∈ [1,∞). Characterizations of special domains are also given.

In Chapter 3 we generalize the definition of a Carleson measure to an arbitrary simply connected domain. Let G be a bounded simply connected domain with harmonic measure ω. We say a positive measure τ on G is a Carleson measure if there exists a positive constant c such that for each t ∈ [1, ∞) and each polynomial p we have

⎮⎮p⎮⎮<sub>L¹(τ)</sub>≤ c ⎮⎮p⎮⎮ <sub>Lᵗ(ω)</sub>,

We characterize all Carleson measures on a normal domain-definition: a domain G where P is dense in H¹(G). It turns out that P is dense in Hᵗ(G) for all t when G is normal.

In Chapter 4 we describe some special simply connected domains and describe how they are related to each other via various types of polynomial approximation.

In Chapter 5 we study the various equivalence classes of subnormal operators under the relations of unitary equivalence, similarity and quasi similarity under the assumption that G is a normal domain.

In Chapter 6 we characterize the Carleson measures on a finitely connected domain. We are able to push our techniques in the latter setting to characterize those subnormal operators similar to the shift on the closure of R(K) in L²(σ) when R(K) is a hypo dirichlet algebra.

In Chapter 7 we illustrate our results by looking at their implications when G' is a crescent. Several interesting function theory problems are studied.

In Chapter 8 we study arc length and harmonic measures. Let G be a Dirichlet domain with a countable number of boundary components. Let ω be the harmonic measure of G. We show that if J is a rectifiable curve and E ⊂ ∂G ∩ J is a subset with ω(E) > 0, then E has positive length. / Ph. D.

Identiferoai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/38499
Date06 June 2008
CreatorsQiu, James Zhijan
ContributorsMathematics, Olin, Robert F., Thomson, James E., Holub, James R., McCoy, Robert A., Linnell, Peter A.
PublisherVirginia Tech
Source SetsVirginia Tech Theses and Dissertation
LanguageEnglish
Detected LanguageEnglish
TypeDissertation, Text
Formatvii, 118 leaves, BTD, application/pdf, application/pdf
RightsIn Copyright, http://rightsstatements.org/vocab/InC/1.0/
RelationOCLC# 29985306, LD5655.V856_1993.Q58.pdf

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