Recent content by Icosahedron

No problemo, robousy. A little overreacting on my behalf, I guess. Here Zee gives lectures based on the book: http://www.asti.ac.za/lectures.php

Position of a photon? But you know that a photon has no rest frame... Right. I think every QFT text starts with this observation. What is wrong with it?

http://www2.physics.utoronto.ca/~luke/PHY2403/References_files/lecturenotes.pdf Otherwise, Srednicki writes in his book on page 10, that keeping X and promoting t to an operator can also be done to get a relativistic particle theory. Which leaves me puzzled.

No. If you had some better manners and had showed at least some appreciation for my posts, I would explain some more.

What other websites do you frequently visit? What can you recommend?

There is no position operator and no states in position space in QFT! Read the first 7 pages of these https://www.physicsforums.com/newreply.php?do=newreply&noquote=1&p=1784740" .

Wait! Last paragraph is not quite right. You have Z=\langle {0}|{0}\rangle_{J}, which is one. So despite sources and sinks everywhere, and disturbances propagating everywhere, you start in the vacuum state and you end in the vacuum state with probability of one. Your vacuum is a boiling sea of...

The Z(J) here is a functional of the field J, it gives the amplitude of the field \phigoing from ground state to ground state ( or vacuum state). D(x-y) is the propagation amplitude of one disturbance going from some x to some y. In the path integral Z(J), we integrate over all x and y, over...

Well, because in post 15 you said this is wrong. Further I like reminding you that also in QFT we can switch between Schrödinger and Heisenberg picture, read P&S, section 2.4 for example. Also, while you are at it, in chapter two of the same book, they discuss propagating of state vectors...

Really? Why then do mass and energy have different units?

Frederick, please open any QFT text of your choice and read that quantum fields are operator-valued functions of space-time. Also, a wave function made collapsed by a non-localized quantum mechanical operator is a clear violation of special relativity.

Collapse of wave function= measurement. Construct operators from quantum fields?? Quantum fields are operators, operator-valued function of spacetime.

Here is a real inconsistency of quantum mechanics and SR, which makes it necessary to bring quantum fields in. Measurements of quantum observables, the collapse of the state vector happens instantaneous, faster than light, clear violation of SR. So when you naively add SR to QM faster than...

As far as your OP Observers in relative motion to each other in SR disagree duration of time between two events, the length of objects and the simultanity of two events. One event, in your case a measurement, does not lead to disagreement.

Thanks Ibris so far. Not yet totally clear. I will now reread chapter 4 of P&S, then come back. Further comments in this thread are very welcome!