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I encountered this problem while solving a problem related to characterization of delta function upto constant multiple.

$\phi \in D(R)$, Space of compactly supported infinitely differentiable functions. If $\phi(0)=0$, Then there exist a $\psi \in D(R)$ such that $\phi = x\psi$

Original question is as follow:

If $xT=0$, where T is a distribution. Then, $T = c\delta$

If above proposition could be proved, then this characterization would follow.

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2 Answers

up vote 1 down vote accepted

You are looking for Hadamard's lemma. http://en.wikipedia.org/wiki/Hadamard%27s_lemma

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What a manipulation! :D –  Rahul Gupta Apr 27 '11 at 15:02
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For the original question, you could use the fact that the support of $T$ can only be at the origin. Then a theorem (I forgot the name, it is in the distribution book of Kolk and Duistermaat) states that we can write

$T=\sum_{i=0}^{n}c_i\delta^{(i)}$

for some $n$. It easily follows that $c_i=0$ for $i>0$.

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