Divergence of the mock and scrambled Fourier series on fractal measures

Dutkay, Dorin; Han, Deguang; Sun, Qiyu

doi:10.1090/S0002-9947-2013-06021-7

Divergence of the mock and scrambled Fourier series on fractal measures
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by Dorin Ervin Dutkay, Deguang Han and Qiyu Sun PDF

Trans. Amer. Math. Soc. 366 (2014), 2191-2208 Request permission

Abstract:

We study divergence properties of the Fourier series on Cantor-type fractal measures, also called the mock Fourier series. We show that in some cases the $L^1$-norm of the corresponding Dirichlet kernel grows exponentially fast, and therefore the Fourier series are not even pointwise convergent. We apply these results to the Lebesgue measure to show that a certain rearrangement of the exponential functions, with affine structure, which we call a scrambled Fourier series, have a corresponding Dirichlet kernel whose $L^1$-norm grows exponentially fast, which is much worse than the known logarithmic bound. The divergence properties are related to the Mahler measure of certain polynomials and to spectral properties of Ruelle operators.

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