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arXiv math-ph/0408044math-phmath.APmath.MPphysics.optics
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波动方程的特征小波

Eigenwavelets of the Wave equation

Gerald Kaiser

摘要:

我们研究了一类波动方程的局部化解,称之为特征小波,通过将其基本解在超函数的意义下扩展到复时空而得到。虚时空变量y构成一个类时向量,作为尺度参数,将小波的尺度变量推广到一维。它们决定了时空中小波的形状,使它们成为脉冲光束,通过让y接近光锥,它们可以尽可能紧密地聚焦在一条光线周围。此外,没有任何旁瓣使得它们对于使用声波的通信、遥感和其他应用特别有吸引力。(麦克斯韦方程组也有类似的“电磁本征小波”。我回顾了闵可夫斯基空间的基本思想,然后计算其实现应使辐射和吸收这样的小波的来源。这激发了惠更斯原理的扩展,允许等效源被表示在壳上而不是围绕有界源的表面上。

英文摘要:

We study a class of localized solutions of the wave equation, called eigenwavelets, obtained by extending its fundamental solutions to complex spacetime in the sense of hyperfunctions. The imaginary spacetime variables y, which form a timelike vector, act as scale parameters generalizing the scale variable of wavelets in one dimension. They determine the shape of the wavelets in spacetime, making them pulsed beams that can be focused as tightly as desired around a single ray by letting y approach the light cone. Furthermore, the absence of any sidelobes makes them especially attractive for communications, remote sensing and other applications using acoustic waves. (A similar set of "electromagnetic eigenwavelets" exists for Maxwell's equations.) I review the basic ideas in Minkowski space, then compute sources whose realization should make it possible to radiate and absorb such wavelets. This motivates an extension of Huygens' principle allowing equivalent sources to be represented on shells instead of surfaces surrounding a bounded source.

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