Fourier transform. Impulse representation.

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SUMMARY

The discussion centers on the Fourier transform in quantum mechanics, specifically the impulse representation of wave functions. The equation for the Fourier transform includes the reduced Planck constant, ##\hbar##, which is essential for maintaining normalization across the transformation. The identity ##\int^{\infty}_{-\infty}|\varphi(p)|^2dp=\int^{\infty}_{-\infty}|\psi(x)|^2dx=1## holds true due to the inclusion of ##\hbar##, ensuring that the state in impulse space is normalized. This clarification addresses the concerns regarding the normalization of wave functions in momentum space.

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LagrangeEuler
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##\varphi(p)=\frac{1}{\sqrt{2\pi\hbar}}\int^{\infty}_{-\infty}dx\psi(x)e^{-\frac{ipx}{\hbar}}##. This ##\hbar## looks strange here for me. Does it holds identity
##\int^{\infty}_{-\infty}|\varphi(p)|^2dp=\int^{\infty}_{-\infty}|\psi(x)|^2dx=1##?
I'm don't think so because this ##\hbar##. So state in impulse space is not normalized.
 
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LagrangeEuler said:
Does it holds identity
##\int^{\infty}_{-\infty}|\varphi(p)|^2dp=\int^{\infty}_{-\infty}|\psi(x)|^2dx=1##?

Yes, it does. The ##\hbar## in the transform is required in order to make this true. You may be thinking of the standard Fourier transform:
$$A(k) = \frac{1}{\sqrt{2\pi}}\int_{-\infty}^{+\infty}{\psi(x)e^{-ikx}dx}$$
Changing variables from k to ##p = \hbar k## introduces the extra ##\hbar## in the constant factor.
 

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