- #1

BWV

- 1,172

- 1,269

-(∂

^{2}+m

^{2})D(x-y)=δ(x-y)

he then gets, by taking the Fourier transform of the Dirac delta and dividing through:

D(x-y) = [itex]\int\frac{d^4k}{2π^4} \frac{e^{ik(x-y)}}{k^2-m^2+iε}[/itex]

I get the FT and adding iε to avoid a pole, but not how you take

D(x-y)= -(∂

^{2}+m

^{2})

^{-1}[itex]\int\frac{d^4k}{2π^4} e^{ik(x-y)}[/itex]

and change the differential operator outside the integral to [itex]1/ (k^2-m^2) [/itex] inside it