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The prof says: "for 1Dimensional bound states with a real potential, the wave function is real, up to a phase". The proof goes like this:

1D bound states are never degenerated. So $\Psi_{real}$ and $\Psi_{imaginary}$ are linearly dependent. So $\Psi \equiv \Psi_{real} +i\Psi_{imaginary}=\Psi_{real} (1+ic)=(1+c^2)e^{iArg(1+ic)}\Psi_{real}$

Whatever the proof, I don't understand the statement since any complex number (the wavefunction is one complex number) is in some way real up to a phase. So I don't really understand what this theorem is trying to teach us.

PS: I cannot ask directly the professor because I study from a video recorded 6 years ago

Qmechanic
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niobium
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  • Possible duplicates: https://physics.stackexchange.com/q/77894/2451 , https://physics.stackexchange.com/q/44003/2451 and links therein. – Qmechanic May 16 '22 at 19:59
  • From the second post, xebtl wrote all the bound states can simultaneously be made real ... Does that mean that the $c$ constant (from my proof) can be cancelled out? – niobium May 17 '22 at 08:35

1 Answers1

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No, the wavefunction $\psi(\vec{r})$ is not just 1 complex number: it is infinitely many complex numbers, 1 for each value of position $\vec{r}$. In contrast, the professor is making the non-trivial statement that there exists a global (i.e. $\vec{r}$-independent) complex constant $c$.

For more details, see also this & this related Phys.SE posts.

Qmechanic
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