- #1
dsr39
- 14
- 0
When working with Fourier transforms in Quantum mechanics you get the result that
[tex]\int_{-\infty}^{\infty}e^{-ikx}e^{ik'x} = \delta(k-k')[/tex]
I understand conceptually why this must be true, since you are taking the Fourier transform of a plane wave with a single frequency element.
I have also seen it sort of derived by looking at the formula for the Fourier series and tracking its components in the limit that it becomes a continuous Fourier transorm (letting the period go to infinity and [tex]\Delta\omega[/tex] go to 0)
But I really want to come up with some explicit expression, from doing the integral that behaves like a delta function. I have tried messing around with it, by sticking it inside of another integral and multiplying it by a test function etc. Is there a way to do this?
[tex]\int_{-\infty}^{\infty}e^{-ikx}e^{ik'x} = \delta(k-k')[/tex]
I understand conceptually why this must be true, since you are taking the Fourier transform of a plane wave with a single frequency element.
I have also seen it sort of derived by looking at the formula for the Fourier series and tracking its components in the limit that it becomes a continuous Fourier transorm (letting the period go to infinity and [tex]\Delta\omega[/tex] go to 0)
But I really want to come up with some explicit expression, from doing the integral that behaves like a delta function. I have tried messing around with it, by sticking it inside of another integral and multiplying it by a test function etc. Is there a way to do this?