Magnetic moment from neutral particles in QFT

In summary, the thread discusses the question of why neutrinos have a magnetic moment and whether it is due to quantum fluctuations or corrections. While there is no definitive answer, it appears that quantum effects are the main contributor to this phenomenon, with no classical or relativistic quantum mechanics analogues. This magnetic moment is anomalous and decouples the electric and magnetic sides of electromagnetism in the absence of charge.
  • #1
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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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  • #3
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?
 
  • #4
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.
 
  • #5
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.
 

1. What is a magnetic moment in quantum field theory (QFT)?

In QFT, a magnetic moment is a measure of the strength of the interaction between a particle's magnetic dipole moment and an external magnetic field. It is a fundamental property of particles that describes how they respond to magnetic fields.

2. How is the magnetic moment of a particle calculated in QFT?

The magnetic moment of a particle in QFT is calculated using the Dirac equation, which relates the spin of a particle to its magnetic moment. This equation takes into account the effects of relativity and quantum mechanics.

3. What is the difference between a magnetic moment in classical physics and QFT?

In classical physics, a magnetic moment is a vector quantity that describes the strength and direction of a magnetic dipole. In QFT, it is a quantum mechanical property that describes the interaction between a particle's spin and an external magnetic field.

4. Can a particle have a magnetic moment if it has no charge?

Yes, a particle can have a magnetic moment even if it has no charge. This is because the magnetic moment is related to the particle's spin, which is a fundamental property of all particles, regardless of their charge.

5. How does the magnetic moment affect the behavior of particles in QFT?

The magnetic moment plays a crucial role in the behavior of particles in QFT, as it is a fundamental property that determines how they interact with magnetic fields. It also contributes to the overall spin of the particle, which affects its properties and behavior in various physical processes.

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