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I found (Wikipedia page on Helmotz's decomposition theorem) the follwoing equality, which puzzles me:

$$\delta(x-y) = - (4 \pi)^{-1} \nabla^{2} \frac{1}{\vert x - y \vert}$$

I am not sure I understand, the r.h.s seems to me a proper function. The page mentions this a sa position, not an approximation, can maybe anuvboy help?

Many thanks

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# Dirac Delta substitution

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