An integral transform \(\tilde{f}(x)\) of a function f(x)$\ can be regarded as a result of applying an operator $F$ to the function such that
\((F f)(x) \equiv \tilde{f}(x)=\int_{-\infty}^{\infty} d y e^{-i x y} f(y)\)
If I is the identity operator, then the operator F4 is given by
1
(2π)4I
2
(2π)I
3
I
4
(2π)2I