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Sunday, January 06, 2008

QUANTUM ELECTRODYNAMICS

Permanent Magnets and Photons

Question
Do permanent magnets "exchange" photons? What would the wavelength of such a continuous wave photon be? All forces are mediated by certain "carriers" of the force in question.
Photons carry the electromagnetic force, other particles carry the strong and weak atomic forces. Gravity may eventually be shown to be "carried" by a Graviton, and Dark Matter may have an inverse analog to the Graviton. What particle carries the force that is observed between to permanent magnets?
If photons are responsible for this force, wouldn't they have a very long (infinite) wavelength? For example light consists of photons of a particular wavelength depending upon the color of the light. As we descend into the radio frequencies, the wavelength gets longer and longer. What happens between two continuous permanent magnets, essentially a DC (direct current).
The force between two permanent magnets is caused by the electronic properties of the material, so photons must be involved with the magnetic attraction between the two masses? Maybe I am confusing electromagnetic with magnetic?
Some answers
"Permanent" magnets are made of materials with several electrons in the outer shells which are un-paired with other electrons.
Electrons carry "spin", either "up" or "down", which refers to their behaviour.
These unpaired spins exhibit a magnetic moment, its like a small current loop inside the material.
They must attract others in similar materials, I would think via photons.

Photon is the quantisation of an electromagnetic field. Is it affected by other photons ?? Not much, hardly at all.
Magnetic fields actually consist of a flux of virtual photons, as far as i know.

Photons can only interact with charged particles, so a photon can only interact with a magnetic field (really, more photons) via virtual charged particle loops.
That is, the photon must induce a virtual charged particle-antiparticle pair to come out of the vacuum, the pair interacts with the background field and then something comes out or the photons scatter or something. These sorts of interactions are possible, but are highly suppressed.

Wait ... but a magnetic field is composed of virtual photons, not of a ray of real ones.
Hence the virtual needs to become real to be able to form a virtual particle-antiparticle pair out of vacuum ?

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