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Hi:
If we want to work out the expectation of:
<0|T(φ1φ2)|0>
ie. <0|<0|T(φ1φ2)|0>|0>
apparently it is acceptable to pull out the <0|T(φ1φ2)|0>:
So <0|<0|T(φ1φ2)|0>|0>=<0|T(φ1φ2)|0><0|I|0>
I do realize this is a really stupid question, but I want to be 100% sure. Is this simply because an expectation is always a constant, not an operator which acts on a state? Can you always pull out an expectation in this way?
Thanks.
If we want to work out the expectation of:
<0|T(φ1φ2)|0>
ie. <0|<0|T(φ1φ2)|0>|0>
apparently it is acceptable to pull out the <0|T(φ1φ2)|0>:
So <0|<0|T(φ1φ2)|0>|0>=<0|T(φ1φ2)|0><0|I|0>
I do realize this is a really stupid question, but I want to be 100% sure. Is this simply because an expectation is always a constant, not an operator which acts on a state? Can you always pull out an expectation in this way?
Thanks.