Hi everyone.(adsbygoogle = window.adsbygoogle || []).push({});

I am now learning the perturbation theory in QM.

and I have encountered something that puzzles me.

from

http://en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics [Broken])

says,

"...Since the overall phase is not determined in quantum mechanics, without loss of generality, we may assume <n(0)|n> is purely real. Therefore, <n(0)|n(1)>=-<n(1)|n(0)>, and we deduce..."

What do you mean by "the overall phase is not determined in quantum mechanics" ?

I especially emphasize "in quantum mechanics". Does this mean that we cannot find a specific value for the phase by quantum calculation?

I appreciate your help!

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# Phase in quantum mechanics

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