If I have [tex]H=p^2/2m+V(x)[/tex], [tex]|a'>[/tex] are energy eigenkets with eigenvalue [tex]E_{a'}[/tex], isn't the expectation value of [tex][H,x][/tex] wrt [tex]|a'>[/tex] not always 0? Don't I have that(adsbygoogle = window.adsbygoogle || []).push({});

[tex]<a'|[H,x]|a'> = <a'|(Hx-xH)|a'> = <a'|Hx|a'> - <a'|xH|a'> = 0 [/tex]?

But if I calculate the commutator, I get:

[tex]<a'|[H,x]|a'> = <a'|-i p \hbar / m|a'> \neq 0 [/tex]

I suddenly can't see where I did wrong...

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# Is the expectation value of this commutator zero?

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