imbAF

and partially understand that we need to consider the quark propagator for Z_2 (I don't fully understand how we come to this conclusion), I have no idea why the first term underlined, implies gluon propagator ?

And while I can kind of understand why Z_1 is found by considering the quark-quark-gluon vertix (something one can read in the counterterm lagrangian)

Above, I highlighted the terms where Z_1, Z_2 and Z_3 appear.

?

What I don't understand is how does the lecturer come to the conclusion that in order to find Z_3 he has to consider the gluon propagator

The one-loop corrections relevant for QCD are

Now, for reasons that are not important I need to find Z_1 Z_2 and Z_3

We considered the lagrange density of QCD, and we split it in the bare, renormalized and counterterm lagrangian. I will just post down the resulting expressions

In our class we were discussing QCD, and how to show the energy scale dependency of the strong coupling constant as we include higher order corrections

Yes, I am writing down the question

Could you help me with one additional thing, that I cannot figure out why is the case

I see

wouldn't that be an infinite expression ?

if you would include all the terms

But how would that be the case when you are given a certain expression for the counterterm lagrangian and is finite

Is there any way to tell the loop correction order considered, by just looking at the counterterm lagrangian of some theory?

can there be an s-channel between a photon and a quark ?

I am not sure what the process described is here

contain a quark, photon, gluon interaction?

would a process, like the one described here

but I don't get the 1/g term in the end

I am trying to plug in the transformation considered

Can someone help me with the derivation of what is in the red box?

Is there an argumentative way to prove that the diagrams with odd nr. of vertices in their fermion loops, cancel pairwise ?

for odd n>3

Is it possible to show proof of Furry's theorem without the use of the C- operator?

Why Trace appears when calculating loop integral of a tadpole ?

Would it be accurate to say that tadpole diagrams that emerge when we consider higher order feynman diagrams for a particular process, are always part of a larger diagram, connected with?

is the self-energy correction to a propagator, a 2 point 1PI diagram ?

Is there any procedure one can perform to show if an arbitrary feynman diagram vanishes? And what does vanishing mean ?

Are $G_\mu^k$ coef. of some sort?

How does cause a further 2n-1 reduction ?

If I use it every n^2 term left gets multiplied by something like $e^{i\theta}$

@Feynmate use it where exactly? On the field operators of the quarks, which are entries in te CKM matrix?

Could someone explain to me the underlined part? what exactly does the redefinition of the fermionic field has to do with the complex phase, assuming that the entries are written in the form $e^{i\theta}$, and how it reduces the nr. of parameters by 2n-1?

I tried to bring my expression to the suggested one, but that is not possible ofc since I have x^2 and x present

I am having an integral of the form $Im\int_{x_}^x^{+}log(m^2-x(1-x)s)dx$. The interval of integration is such that the argument of log is negative, while the x values are positive. I am suggested that I can do the following: $Imlog(-y \pm i\epsilon)=\pm \pi$ for y>0

I forgot

I don't understand how are are eliminating the term l(1-x)lnx ?

Could someone help me understand the solution to this thread

Hello Guys