sci.physics.particle

Thanks Jim,

The equation of the propagator is as follows:
Its in Euclidean space.

Int(d^4k * exp(i*k*x)/ (k^4 +m^2 +i*epsilon).

I have Peskin and Zee but cannot find the justification of adding i-epsilon
except that its added to make it integrable.

I would like to keep the poles on real axis and avoid the poles by excluding
them through
closing the countor without them therefore avoiding the i-epsilon.