- #36
kexue
- 196
- 2
It doesn't seem to me that such a sticky would stop a lot of these posts, which boil down to arguing, not asking a question.
I ask a painfully clear question: how do you explain Coulomb force between two charged quantum particles without virtual particles? No one answered.
That is what Zee is saying, yes.
Zee dislikes virtual particles so much that he only mentions them about 10 times in the book, apparently each time as a shorthand for an internal line or similar concept.
He most certainly is not referring to real particles as transmitting forces. Are you trying to tell me that in a Coulomb force you can measure individual photons?
Have you read page 19 of the book where he writes about vacuum? Let me quote:"Incidentally, the vacuum in quantum field theory is a stormy sea of quantum fluctuations", it goes on on the next page "watching a boiling sea of quantum fluctuations. We would like to disturb the vacuum..."
You picked here the wrong text to argue against the idea of virtual particles, tiny-tim. And P&S can be found in every library or at amazon.
I follow you peoples argumentation here and see your point, but saying quantum field theory is just computing S-matrices and everything else just tricks and tools and fictious does not convince.
But what the heck, I was even childish enough to write Prof. Zee an email to come clean about this virtual business. I also wrote Edward Witten and Frank Wilczek an email. Zee did not answer yet, Witten and Wilczek did! Obviously must be very kind people.(If you don't believe me, I can redirect you the emails.)
My question to them was:
Hi,
I'm a physics student with a quick question.
Are virtual/ off mass particles really out there, do they really exist or are they just mathematical artifacts of pertubation theory and thus fictious?
I would be very grateful for any answer.
Witten answered rather shortly
This is a not such a simple
question, because the meaning of ``real'' is a little subtle in quantum mechanics.
A precise statement, but one that may not satisfy you, is that virtual particles do not
exist as asymptotic states.
Wilczek wrote
Hi,
It comes down to what you mean by "really there". When we use a concept with great success and precision to describe empirical observations, I'm inclined to include that concept in my inventory of reality. Buy that standard, virtual particles qualify. On the other hand, the very meaning of "virtual" is that they (i.e., virtual particles) don't appear *directly* in experimental apparatus. Of course, they do appear when you allow yourself a very little boldness in interpreting observations. It comes down to a matter of taste how you express the objective situation in ordinary language, since ordinary language was not designed to deal with the surprising discoveries of modern physics.
All the best,
Frank W.