Magnetic moment from neutral particles in QFT

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Discussion Overview

The discussion revolves around the concept of how quantum fluctuations or quantum corrections can lead to a magnetic moment in neutral elementary particles, particularly in the context of quantum field theory (QFT). Participants are exploring the physical mechanisms behind this phenomenon and questioning the classical analogs of such effects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant seeks an explanation of how quantum fluctuations can give rise to a magnetic moment in neutral particles, expressing interest in the physical mechanism rather than just the theoretical framework.
  • Another participant references an older thread about the neutrino's magnetic moment, suggesting that the discussion may have parallels with previous explorations of this topic.
  • Some participants express skepticism about the sufficiency of existing explanations, questioning whether the only justification is that it arises from quantum effects without a deeper physical rationale.
  • It is noted that there is no classical analog to the magnetic moment of neutral particles, which raises questions about the nature of these quantum effects.
  • Concerns are raised regarding the distinction between quantum effects in neutral particles and those in charged particles, with emphasis on the anomalous nature of the magnetic moment in the absence of charge.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the explanations for the magnetic moment of neutral particles, with multiple competing views and uncertainties remaining about the underlying mechanisms.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about quantum effects and their relationship to classical electromagnetism, as well as the lack of a clear resolution on the nature of the magnetic moment in neutral particles.

TrickyDicky
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Could somebody take a stab at explaining how can quantum fluctuations give neutral elementary particles a magnetic moment?
(in the usual explanation given by QFT textbooks, I think there are people around here denying the existence of quantum fluctuations, insert the more neutral expression "quantum corrections" if it suits you but I'm interested in the physical mechanism)
 
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Avodyne said:
Here is an older thread about the neutrino magnetic moment:

https://www.physicsforums.com/threads/why-does-the-neutrino-have-a-magnetic-moment.587646/
Thanks, I suppose geoduck's reply in post #3 is my starting point, the rest of the thread concentrates on neutrino mass.
Is there really no answer beyond that it comes from quantum effects? No physical justification of how that quantum influence make us ignore that magnetic effects used to be related to charges in motion?
 
TrickyDicky said:
Is there really no answer beyond that it comes from quantum effects?
I don't think so. There is no classical analog to this effect.
 
mfb said:
I don't think so. There is no classical analog to this effect.
There is no relativistic QM analogue either, unlike in the electrón case, where the anomalous moment is a correction to a RQM prediction due to a quantum effect, spin, with no classical counterpart. In the absence of charge the whole thing is anomalous rather than a renormalization correction and it seems to decouple the electric and magnetic sides of electromagnetism.
 

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