- #1
LAHLH
- 409
- 1
Hi,
In Birrel and Davies ch4 they write:
[tex] \langle \psi|:T_{ab}:|\psi \rangle =\langle \psi|T_{ab}|\psi \rangle -\langle 0|T_{ab}|0 \rangle [/tex]
this is for the usual Mink field modes and vac state. Why does normal ordering reduce to this expression, could anybody point me the way to deriving this?
In Birrel and Davies ch4 they write:
[tex] \langle \psi|:T_{ab}:|\psi \rangle =\langle \psi|T_{ab}|\psi \rangle -\langle 0|T_{ab}|0 \rangle [/tex]
this is for the usual Mink field modes and vac state. Why does normal ordering reduce to this expression, could anybody point me the way to deriving this?