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Functions of subnormal operators

If f is analytic in a neighborhood of ∂D = {z| |z|= 1} and if K = f(∂D), then C-K has only finitely many components; moreover, if U is a bounded simply connected region of the plane, then

∂U = U<sub>j=0</sub><sup>n</sup r<sub>j</sub>

where each r<sub>j</sub> is a rectifiable Jordan curve and r<sub>i</sub> ∩ r<sub>j</sub> is a finite set whenever i ≠ j.

Let μ be a positive regular Borel measure supported on ∂D and let m denote normalized Lebesgue measure on ∂D. If L is a compact set such that ∂L ⊂ K and R(L) is a Dirichlet algebra and if ν = μof⁻¹, then the Lebesgue decomposition of ν|<sub>∂V</sub> with respect to harmonic measure for L is

ν|<sub>∂V</sub> = μ<sub>a</sub>of⁻¹|<sub>∂V</sub> + μ<sub>s</sub>of⁻¹|<sub>∂V</sub>

where V = intL and μ = μ<sub>a</sub> + μ<sub>s</sub> is the Lebesgue decomposition of μ with respect to m.

Applying Sarason’s process, we obtain P<sup>∞</sup>(ν) ≠ L<sup>∞</sup>(ν) if, and only if there is a Jordan curve r contained in K such that mof⁻¹|<sub>Γ</sub> << μ<sub>a</sub>of⁻¹|<sub>Γ</sub>. If U is a unitary operator with scalar-valued spectral measure μ then f(U) is non-reductive if and only if there is a Jordan curve r ⊂ K such that mof⁻¹|<sub>Γ</sub> << μ<sub>a</sub>of⁻¹|<sub>Γ</sub>.

Let G be a bounded region of the plane and B(H) the algebra of bounded operators in the separable Hilbert space H. If π: H<sup>∞</sup>(G)→B(H) is a norm-continuous homomorphism such that π(1) = 1 and π(z) is pure subnormal then π is weak-star, weak-star continuous. Moreover, if S is a pure subnormal contraction, the S<sup>*n</sup>→0 sot. / Ph. D.

Identiferoai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/80999
Date January 1982
CreatorsMiller, Thomas L.
ContributorsMathematics, Olin, Robert F., Thomson, J.E., Fletcher, Peter, Farkas, Daniel R., Arnold, Jesse T.
PublisherVirginia Polytechnic Institute and State University
Source SetsVirginia Tech Theses and Dissertation
Languageen_US
Detected LanguageEnglish
TypeDissertation, Text
Formatiii, 76, [2] leaves, application/pdf, application/pdf
RightsIn Copyright, http://rightsstatements.org/vocab/InC/1.0/
RelationOCLC# 9185319

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