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Scalar spectral measures associated with an operator-fractal
Journal article   Peer reviewed

Scalar spectral measures associated with an operator-fractal

Palle E.T Jorgensen, Keri A Kornelson and Karen L Shuman
Journal of mathematical physics, Vol.55(2), p.22103
2014
DOI: 10.1063/1.4863897
url
https://arxiv.org/pdf/1204.5116View
Open Access

Abstract

We study a spectral-theoretic model on a Hilbert space L 2(μ) where μ is a fixed Cantor measure. In addition to μ, we also consider an independent scaling operator U acting in L 2(μ). To make our model concrete, we focus on explicit formulas: We take μ to be the Bernoulli infinite-convolution measure corresponding to scale number 1 4 . We then define the unitary operator U in L 2(μ) from a scale-by-5 operation. The spectral-theoretic and geometric properties we have previously established for U are as follows: (i) U acts as an ergodic operator; (ii) the action of U is not spatial; and finally, (iii) U is fractal in the sense that it is unitarily equivalent to a countable infinite direct sum of (twisted) copies of itself. In this paper, we prove new results about the projection-valued measures and scalar spectral measures associated to U and its constituent parts. Our techniques make use of the representations of the Cuntz algebra O 2 on L 2(μ).

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