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From the ordinary courses in QM it is known that the momentum kets satisfy the completeness relation

[tex] \int d^3 p \mid p \rangle \langle p \mid = 1[/tex]

Knowing this, how can you calculate

[tex] \int d^3 p \mid p \rangle p \langle p \mid [/tex]

?

Thanks a lot!

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# Might be a basic question

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