On kernel engineering via Paley---Wiener

  • Authors:
  • B. J. Baxter

  • Affiliations:
  • Department of Economics, Mathematics and Statistics, Birkbeck College, University of London, London, UK

  • Venue:
  • Calcolo: a quarterly on numerical analysis and theory of computation
  • Year:
  • 2011

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Abstract

A radial basis function approximation takes the form $$s(x)=\sum_{k=1}^na_k\phi(x-b_k),\quad x\in {\mathbb{R}}^d,$$ where the coefficients a 1,驴,a n are real numbers, the centres b 1,驴,b n are distinct points in 驴 d , and the function 驴:驴 d 驴驴 is radially symmetric. Such functions are highly useful in practice and enjoy many beautiful theoretical properties. In particular, much work has been devoted to the polyharmonic radial basis functions, for which 驴 is the fundamental solution of some iterate of the Laplacian. In this note, we consider the construction of a rotation-invariant signed (Borel) measure μ for which the convolution 驴=μ 驴 is a function of compact support, and when 驴 is polyharmonic. The novelty of this construction is its use of the Paley---Wiener theorem to identify compact support via analysis of the Fourier transform of the new kernel 驴, so providing a new form of kernel engineering.