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An Operator-Fractal
Journal article   Peer reviewed

An Operator-Fractal

Palle E. T Jorgensen, Keri A Kornelson and Karen L Shuman
Numerical Functional Analysis and Optimization: Operator Algebras and Representation Theory: Frames, Wavelets, and Fractals, Vol.33(7-9), pp.1070-1094
07/01/2012
DOI: 10.1080/01630563.2012.682127

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Abstract

Certain Bernoulli convolution measures μ are known to be spectral. Recently, much work has concentrated on determining conditions under which orthonormal Fourier bases (i.e. spectral bases) exist. For a fixed measure known to be spectral, the ONB need not be unique; indeed, there are often families of such spectral bases. Let for a natural number n and consider the Bernoulli measure with scale factor λ. It is known that L 2 (μ λ ) has a Fourier basis. We first show that there are Cuntz operators acting on this Hilbert space which create an orthogonal decomposition, thereby offering powerful algorithms for computations for Fourier expansions. When L 2 (μ λ ) has more than one Fourier basis, there are natural unitary operators U, indexed by a subset of odd scaling factors p; each U is defined by mapping one ONB to another. We show that the unitary operator U can also be orthogonally decomposed according to the Cuntz relations. Moreover, this operator-fractal U exhibits its own self-similarity.
Cuntz relations Multiresolution C-algebras Unitary operators Fractals Fourier basis Spectrum

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