## Klein-Gordon propagator

1. The problem statement, all variables and given/known data
2. Relevant equations
Show that the KG propagator
$$G_F (x) = \int \frac{d^4p}{(2\pi)^4} e^{-ip.x} \frac{1}{p^2-m^2+i\epsilon}$$
satsify
$$(\square + m^2) G_F (x) = -\delta(x)$$

3. The attempt at a solution
I get
$$(\square + m^2) G_F (x) = - \int \frac{d^4p}{(2\pi)^4} (p^2-m^2) e^{-ip.x} \frac{1}{p^2-m^2+i\epsilon}$$
but where do I go from there?
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 Cancel the numerate and denominator p^2-m^2. The i epsilon is just a direction how to take the contour, and is negligible here. The remaining integral is \delta^4.
 Blog Entries: 9 Recognitions: Homework Help Science Advisor how does (p^2-m^2)/(p^2-m^+i*epsilon) cancel? I would try to do the limit of epsilon -> 0+

## Klein-Gordon propagator

 Quote by malawi_glenn how does (p^2-m^2)/(p^2-m^+i*epsilon) cancel? I would try to do the limit of epsilon -> 0+
That's what
"The i epsilon is just a direction how to take the contour, and is negligible here."
means.