# Magnetic moment from neutral particles in QFT

## Main Question or Discussion Point

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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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?

mfb
Mentor
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.

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.