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Fourier transform of a functional derivative

A more direct way to derive the result is with the aid of the chain rule. So, consider a function $E[f]$, where $f(x)$ is a function of the one dimensional variable $x$. It is related to a spectrum ...
flippiefanus's user avatar
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Taking functional derivatives of generating functional

Be careful. Your first line is correct, but the statement in the second line is not. You can only use it inside the integration to get rid of the delta function. As I will show you how to compute the ...
Everlin Martins's user avatar
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Taking functional derivatives of generating functional

My main confusion is about how to take derivatives of function like $J(y_1)$ wrt to $J(x)$. For example what is the value of $$\frac{\delta J(y_1)}{\delta J(x)}$$. Is that equal some kind of delta ...
hft's user avatar
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