Recent content by andrex904

Cosine of the angle betwen z axis and the 3momentum of fermion in the rest frame of Z.

Could yuo be more specific? Because i compute the polarized amplitude and there is a term proportional to cosine (that is clearly not parity invariant), but i don't know how to show that it's not C invariant.

Considering a Z boson decay into a fermion-antifermion pair. How can i say if the process respect parity and charge conjugation?Thanks

Look at euclidean gamma matrices https://en.m.wikipedia.org/wiki/Gamma_matrices

Above i use two fact : - ## \not p \not p = \gamma_\mu \gamma_\nu p^\mu p^\nu = \frac{1}{2} \{ \gamma_\mu ,\gamma_\nu \} p^\mu p^\nu = \frac{1}{2} (-2\delta_{\mu\nu}) p^\mu p^\nu = -p_E^2## - ## \not p_M = p_0\gamma^0 - p_i\gamma^i \rightarrow ip_0 i\gamma^0 - p_i\gamma^i=- \not p_E ##...

I don't take the negative of the Minkowskain tensor, when you change your coordinate over a manifold the metric tensor transform ( as a rank 2 tensor) and you get the negative of euclidean metric (----) or ##-\delta_{\mu\nu}## in this particular case

I find something about here http://physics.stackexchange.com/questions/106292/how-to-perform-wick-rotation-in-the-lagrangian-of-a-gauge-theory-like-qcd

i don't understand when you say " but its not just the negative of Minkowskian metric", because i got the negative of euclidean metric tensor

I don't have a ref for this... Anyway wick rotation is a change of coordinates, so you get a new metric tensor. So you have to take "euclidean" gamma matricies define as above

Wick rotation is a diffeomorphism so the metric of your space change ## \eta_{\mu\nu} \rightarrow -\delta_{\mu\nu} ##, so for the clifford algebra gamma matrices must satisfy ## \{\gamma_\mu,\gamma_\nu \}=-2\delta_{\mu\nu} ##

When you go to euclidean space ## (p_\mu \gamma^\mu)_M \rightarrow -(p_\mu \gamma^\mu)_E ## so the equation become \begin{eqnarray*} S(x-y)_{E} & = & \int d^{4}p_{E}\frac{(-(p_{\mu}\gamma^{\mu})_{E}+m))}{p_{E}^{2}+m^{2}} \\ & = & \int...

So if i start from ## \frac{i}{p_\mu \gamma^\mu - m} ## using euclidean clifford algebra i should find ## \frac{1}{p_\mu \gamma^\mu + m} ##? Because in many textbooks i find ## \frac{-i}{p_\mu \gamma^\mu + m} ##. Maybe they start from another definition of fermion propagator?

Hi, i have some trouble with feynman rules after wick's rotation. I don't understand how the propagators transform. In particular if i take the photon's propagator in minkowskian coordinates i don't understand where the factor "-i" goes after the transformation. ## \frac{-i\eta_{\mu\nu}}{p^2}...