Hi!
I have a process with multiple feynman diagrams where gluon propagators occur. When I use an axial gauge for the gluon propagator, do I have to use the same n-vector for every propagator? Following this I wonder whether I can use the same n-vector for every polarization sum in axial gauge...
Homework Statement
Given the probability/energyprobability current of the dirac equation
j^\mu=\Psi^{+}\gamma^{0}\gamma^{\mu}\Psi with continuity equation \partial_\mu j^\mu = 0
I need to find the current when there is an additional vector potential, introduced via minimal substitution...