Hi,
I am reading the BRST Symmetry section of Peskin and Schroeder but I can't find anywhere
why the BRST transformation for the gauge vector,
\delta A_\mu^a = \varepsilon \partial_\mu c^a
implies that only forward polarized states can create ghosts by applying Q, Q being define by...
Hi,
In Mandl&Shaw, when we calculate the covaiant commutation relations for a scalar field we obtain :
[\phi(x),\phi(y)]= i\Delta(x-y)=0
and the last equality stands if x-y is a space-like interval. But I don't understand why. We know that it is zero if the time component is zero and we...
Thank you!
But now I wonder if I can also wick rotate q so that after the change of variable k' = k+ qx I will get no linear term in k in the denominator.
Hi,
I am trying to calculate the first order photon self-energy.
At a point, I must calculte the following integral :
\int d^4k \frac{(k+q)^\mu k^\nu+(k+q)^\nu k^\mu - g^{\mu \nu}(k \cdot(k+q) - m^2}{k^2 + 2x(q\cdot k) + xq^2 -m^2}
I know that I must wick rotate and that k^2 will...