Multiresolution representation of operators with boundary conditions on simple domains

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• 作者：Gregory Beylkin^a ; ¹ ; ^{beylkin@colorado.edu} ; George Fann^b ; ² ; Robert J. Harrison^b ; ² ; Christopher Kurcz^a ; ¹ ; Lucas Monzó ; n^a ; ¹
• 关键词：Multiresolution ; Non-standard form ; Projector on divergence free functions ; Poisson Green始s function ; Non-oscillatory Helmholtz Green始s function ; Hilbert transform ; Periodic boundary conditions ; Separated representations
• 刊名：Applied and Computational Harmonic Analysis
• 出版年：2012
• 期刊代码：119_10635203
• 类别：cp
• 出版时间：July, 2012
• 卷：33
• 期：1
• 页码：109-139
• 文件大小：392 K

摘要

We develop a multiresolution representation of a class of integral operators satisfying boundary conditions on simple domains in order to construct fast algorithms for their application. We also elucidate some delicate theoretical issues related to the construction of periodic Green始s functions for Poisson始s equation.

By applying the method of images to the non-standard form of the free space operator, we obtain lattice sums that converge absolutely on all scales, except possibly on the coarsest scale. On the coarsest scale the lattice sums may be only conditionally convergent and, thus, allow for some freedom in their definition. We use the limit of square partial sums as a definition of the limit and obtain a systematic, simple approach to the construction (in any dimension) of periodized operators with sparse non-standard forms.

We illustrate the results on several examples in dimensions one and three: the Hilbert transform, the projector on divergence free functions, the non-oscillatory Helmholtz Green始s function and the Poisson operator. Remarkably, the limit of square partial sums yields a periodic Poisson Green始s function which is not a convolution.

Using a short sum of decaying Gaussians to approximate periodic Green始s functions, we arrive at fast algorithms for their application. We further show that the results obtained for operators with periodic boundary conditions extend to operators with Dirichlet, Neumann, or mixed boundary conditions.