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Mathematics of Computation
Mathematics of Computation
ISSN 1088-6842(online) ISSN 0025-5718(print)



Algebraic Fourier reconstruction of piecewise smooth functions

Authors: Dmitry Batenkov and Yosef Yomdin
Journal: Math. Comp. 81 (2012), 277-318
MSC (2010): Primary 42A16; Secondary 65T40, 41A25
Published electronically: August 30, 2011
MathSciNet review: 2833496
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Abstract: Accurate reconstruction of piecewise smooth functions from a finite number of Fourier coefficients is an important problem in various applications. This problem exhibits an inherent inaccuracy, in particular, the Gibbs phenomenon, and it has been intensively investigated during the last few decades. Several nonlinear reconstruction methods have been proposed in the literature, and it is by now well-established that the ``classical'' convergence order can be completely restored up to the discontinuities. Still, the maximal accuracy of determining the positions of these discontinuities remains an open question.

In this paper we prove that the locations of the jumps (and subsequently the pointwise values of the function) can be reconstructed with at least ``half the classical accuracy''. In particular, we develop a constructive approximation procedure which, given the first $ k$ Fourier coefficients of a piecewise $ C^{2d+1}$ function, recovers the locations of the jumps with accuracy $ \sim k^{-\left(d+2\right)}$, and the values of the function between the jumps with accuracy $ \sim k^{-\left(d+1\right)}$ (similar estimates are obtained for the associated jump magnitudes). A key ingredient of the algorithm is to start with the case of a single discontinuity, where a modified version of one of the existing algebraic methods (due to K. Eckhoff) may be applied. It turns out that the additional orders of smoothness produce highly correlated error terms in the Fourier coefficients, which eventually cancel out in the corresponding algebraic equations. To handle more than one jump, we apply a localization procedure via a convolution in the Fourier domain, which eventually preserves the accuracy estimates obtained for the single jump. We provide some numerical results which support the theoretical predictions.

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Additional Information

Dmitry Batenkov
Affiliation: Department of Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel

Yosef Yomdin
Affiliation: Department of Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel

Keywords: Fourier inversion, nonlinear approximation, piecewise smooth functions
Received by editor(s): May 13, 2010
Received by editor(s) in revised form: October 25, 2010
Published electronically: August 30, 2011
Additional Notes: We would like to thank Ch. Fefferman, E. Tadmor and N. Zobin for useful discussions.
This research was supported by ISF grant 264/09 and the Minerva Foundation.
Article copyright: © Copyright 2011 American Mathematical Society
The copyright for this article reverts to public domain 28 years after publication.

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