sci.physics.particle

Hello,

Can anyone explain to me that why is "ioata-epsilon" added to the euclidean
propagator in
k or p space?
Without it, the Euclidean porpagator has poles on real axis and it can be
integrated
with countour integration as I see it by deforming the countour. Then why
are the poles shifted from real axis
by adding "ioata-epsilon" ?? OR is it postulated for reasons not obvious
until the one
goes from Euclidean to Minkowski
and t in introduced?

Is "ioata-epsilon" always added or it may also be subtracted?

The course I am following is Introduction to QFT.

Thanks.

PS: I forgot the I can't post the symbols thats why this is duplicate with
correction to symbols!