Recent content by nikol

I found most helpful the Quantum Mechanics by Claude Cohen-Tannoudji

Sometimes I am getting confused about this too and then this is my line of reasoning that clears my mind: we would like to probe very small distances e.g. is the electron at position x or at position (x+ 10^{-9})m or in other words our \Delta x is of the order of nm. But how do we do that - in...

I was thinking this way - you have your electron A that got accelerated for the time interval \Delta t. If you imagine this interval to be very small \Delta t->0 so you can say that in words of QFT it emitted a photon, the photon carried away the change in the momentum \Delta p and then at some...

What I wanted to say is(but was not very clear) - for me your description is equivalent to the situation electron A emits a photon and electron B absorbs it. But QFT treats the 2 processes as one, you do not care if A emits and B absorbs or the opposite (B emits and A absorbs), only that they...

Yes, that what will happen. The momentum conservation is valid at every vertex(vertex is the point where the interaction happens). So in your case the moving electron A with a momentum p_{A} emits a photon with momentum let's say q and continues propagating now with momentum (p_{A}-q). The...

If I can add something to the discussion, you can thing this way: in order to see interference pattern you need a lot of photons(e.g. a beam) with the same wavelength (e.g.energy since for light E=\frac{hc}{\lambda} to go trough the slits, so this is making the experiment impossible, since the...

Thank you for the clarification

Hi, can someone confirm those or did I not get the meaning of the 4-vectors indices: \partial^{\mu}x_{\mu}=4;\partial^{\mu}x^{\mu}=2;\partial^{\mu}x_{\nu}= \delta ^{\mu}_{\nu};\partial^{\mu}x^{\nu}=g^{\mu\nu}

As I understand it the name 2,3,4... correlation function is coming from how many particles you have (or they call them external point in the Feynman diagrams). In the 2-point function you have 2 external fields at let's say space points x1 and x2. You can connect them by a line and that is it...

Thank you I think I almost understand. Another thing I am noticing is that while integrating over the high degrees of freedom \hat{\phi} the dependence of the large cutoff \Lambda goes into the coefficients (see for example the expression of \mu in formula 12.11 or for \lambda^{'} in 12.29)...

When I am reading about the Wilson approach to renormalization in Chapter12.1 of Peskin & Shroeder I am wondering why are you allowed only to contract the \hat{\phi} field (this is the field that carries the high-momentums degrees of freedom)as they show in equation 12.10, I thought that we...

I would like to ask if anyone can give me a hand with the understanding of the counterterms. I am reading by myself Chapter 10 of Peskin & Shroeder and got stuck in the middle of their example of how to renormalize \phi^{4} theory. What is puzzling me is how to obtain from the new Lagrangian...