Problem Statement: In harmonic analysis, spectral synthesis concerns the ability to reconstruct functions from their spectral data. Let H = L²(T), where T is the unit circle, and let T be the multiplication operator by eig 1. Spectral Synthesis for T: Prove that spectral synthesis holds for T, meaning that every function in H can be approximated in the L²-norm by finite linear combinations of eigenfunctions of T. 2. Measure-Theoretic Thin Sets: Define what it means for a set to be spectral-synthetic and prove that certain measure-theoretic thin sets (e.g., sets of Lebesgue measure zero) fail to support spectral synthesis for T. 3. Extension to Singular Measures: Extend the concept of spectral synthesis to measures singular with respect to the Lebesgue measure on T and prove conditions under which spectral synthesis is possible or obstructed based on the spectral measure's support. Requirements: . Apply spectral synthesis concepts within the spectral theory of unitary operators. • Utilize measure-theoretic notions of thinness and singularity. • Explore the interplay between spectral properties and function approximation in L² spaces.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter3: Functions And Graphs
Section3.5: Graphs Of Functions
Problem 52E
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Problem Statement:
In harmonic analysis, spectral synthesis concerns the ability to reconstruct functions from their
spectral data. Let H = L²(T), where T is the unit circle, and let T be the multiplication operator by
eig
1. Spectral Synthesis for T: Prove that spectral synthesis holds for T, meaning that every function
in H can be approximated in the L²-norm by finite linear combinations of eigenfunctions of T.
2. Measure-Theoretic Thin Sets: Define what it means for a set to be spectral-synthetic and prove
that certain measure-theoretic thin sets (e.g., sets of Lebesgue measure zero) fail to support
spectral synthesis for T.
3. Extension to Singular Measures: Extend the concept of spectral synthesis to measures singular
with respect to the Lebesgue measure on T and prove conditions under which spectral
synthesis is possible or obstructed based on the spectral measure's support.
Requirements:
.
Apply spectral synthesis concepts within the spectral theory of unitary operators.
•
Utilize measure-theoretic notions of thinness and singularity.
•
Explore the interplay between spectral properties and function approximation in L²
spaces.
Transcribed Image Text:Problem Statement: In harmonic analysis, spectral synthesis concerns the ability to reconstruct functions from their spectral data. Let H = L²(T), where T is the unit circle, and let T be the multiplication operator by eig 1. Spectral Synthesis for T: Prove that spectral synthesis holds for T, meaning that every function in H can be approximated in the L²-norm by finite linear combinations of eigenfunctions of T. 2. Measure-Theoretic Thin Sets: Define what it means for a set to be spectral-synthetic and prove that certain measure-theoretic thin sets (e.g., sets of Lebesgue measure zero) fail to support spectral synthesis for T. 3. Extension to Singular Measures: Extend the concept of spectral synthesis to measures singular with respect to the Lebesgue measure on T and prove conditions under which spectral synthesis is possible or obstructed based on the spectral measure's support. Requirements: . Apply spectral synthesis concepts within the spectral theory of unitary operators. • Utilize measure-theoretic notions of thinness and singularity. • Explore the interplay between spectral properties and function approximation in L² spaces.
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