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I'm working through Griffiths' Introduction to QM, In the derivation for the expectation value of momentum, he uses that

[tex]\left( x \left. \left( \Psi^* \frac{\partial\Psi}{\partial x} - \frac{\partial \Psi^*}{\partial x}\Psi \right) \right) \right|_{-\infty}^{+\infty} = 0[/tex]

Why is this so? It's easy to see that this is zero if the x weren't there, but I can't figure out why the limits are zero with the x in.

Thanks,

A_B

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# Homework Help: Derivation of momentum expectancy

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