A question about Zee's book QFT in a nutshell

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Discussion Overview

The discussion revolves around the nature of potential in quantum field theory (QFT), specifically questioning the validity of deriving potentials between particles within the framework of QFT as presented in Zee's book "QFT in a Nutshell." Participants explore the distinctions between non-relativistic and relativistic QFT, and the implications of these distinctions on the concept of potential.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions why the derivation of the potential between two particles is not considered a true QFT, seeking clarification on what constitutes true QFT.
  • Another participant requests specific references to support the claim made about the potential in QFT.
  • A participant mentions the existence of potentials in non-relativistic QFT but notes the absence of potentials in relativistic QFT due to concerns about faster-than-light interactions.
  • There is uncertainty expressed regarding whether a formal proof exists that all potentials are inconsistent with the commutation of spacelike observables in relativistic QFT.
  • A later reply highlights a remark by Zee indicating that earlier discussions in the book pertain to non-interacting theories, suggesting that QFT should involve interactions.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as multiple competing views regarding the role of potentials in QFT are presented, and the discussion remains unresolved.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about potentials in different QFT frameworks, and the lack of formal proofs or references may affect the clarity of the arguments presented.

ftr
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I have read( even Peter Donis mentioned it) that the derivation of the potential between two particles is not a true QFT, why is that? if not, then what is it?

Thanks in advance.
 
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ftr said:
I have read( even Peter Donis mentioned it)

Please give specific references.
 
I will search for the post. I am sure of it but I don't have the time now. I think even Zee himself makes a passing remark.
 
In non-relativistic QFT, there can be a potential, eg. https://www.colorado.edu/physics/phys7450/phys7450_sp10/notes/2nd_quantization.pdf

However, there is usually not a potential in relativistic QFT. This is because even in classical relativistic field theory, a potential will cause faster than light interactions. However, I am not sure whether there is a formal proof that all potentials are inconsistent with commutation of spacelike observables in relativistic QFT.

Weinberg's first QFT volume https://www.amazon.com/dp/0521670535/?tag=pfamazon01-20 discusses when the external field approximation can be used (eg. section 13.6)
 
Last edited:
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I am still digging. But to add to the confusion, Zee at the beginning of Feynman Diagrams(page 41) says that so far we have been doing (in previuos chapters) non interacting theory! So I guess QFT should be interacting.
 

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