- #1
Niles
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Homework Statement
Hi guys
As we have discussed earlier, we can represent some operator in an arbitrary basis by the use of the 1-operator:
[tex]
T = \hat{1} T \hat{1} = \sum\limits_{\sigma_a,\sigma_b } {\left| {\psi _{\sigma_a} \left( {r_i } \right)} \right\rangle T_{\sigma_a\sigma_b \right\rangle \left\langle {\psi_{\sigma_b} \left( {r_i } \right)} \right|}
[/tex]
However, in my book they represent the kinetic energy operator in momentum space by the following (disregarding spin)
[tex]
\left\langle {{\bf{k}}'} \right|T\left| {\bf{k}} \right\rangle \propto k^2 \delta _{{\bf{k}},{\bf{k}}'}.
[/tex]
I cannot seem to connect these two methods of representing operators in some basis. How can one realize that the book's way of transforming is the same as ours with 1-operators?Niles.
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