- #1

- 675

- 4

real scalar:

[tex]\Delta_F(x-x')\propto\langle 0| T\phi(x)\phi(x')|0\rangle[/tex]

4-spinor

[tex]S_F(x-x')]\propto\langle 0| T\psi(x)\bar{\psi}(x')|0\rangle[/tex]

where T is the time-ordering operation and the proportionality depends on the choice of normalization.

I can prove these by direct calculation against other means of deriving the Green's functions but what is the explanation as to why it holds? I don't find one in my QFT texts.

Extra credit: what the does "F" subscript denote? Seems to be a standard notation.