New answers tagged feynman-diagrams
1
vote
One-loop diagrams for the Yukawa pseudo-scalar interaction
OP's Lagrangian (1) should include a $\phi^4$ interaction term to be generic.
Then there are 6 counterterms (2 wave function renormaliztions + 2 mass terms + 2 coupling constants).
All other relevant &...
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Pole at Infinity of a 1-loop scalar bubble diagram
You have to think about it as having to deform your integration contour to avoid the roots $\alpha_\pm$. When you move along the real $s$ axis, the roots move as follows (the arrows indicate ...
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Accepted
How are $t$ and $u$ channel processses different?
Well, you are right in that the two diagrams you show for the Compton scattering are indeed equivalent. However, these are neither t- nor u-channel diagrams; the diagrams you show are s-channel ...
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How are $t$ and $u$ channel processses different?
The dependence of the processes on the moemnta are entirely different, being roughly
$$
\frac{1}{(p_2-p_4)^2 -m^2}
$$
for the first and
$$
\frac{1}{(p_2-p_3)^2 -m^2}
$$
for the second.
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1
vote
Accepted
Virtual soft photons Weinberg volume I chapter 13.2
The soft virtual photons inside the diagram do not contribute to the $\frac{1}{q^0}$ pole. The reason is that the pole comes by considering a new contribution that looks like (using the $-+++$ ...
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