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Mar15-12, 05:56 PM
P: 30
Quote Quote by jambaugh View Post
This is absolutely,without qualifications, not true!!! Firstly there is a perfectly good classical theory of electromagnetism with a perfectly good classical mechanical model. See e.g. Maxwell's Mechanical model. Prior to SR one can "explain" magnetism as "vorticity" in the "aether".

The business about the Fermion statistics, PEP, and tunneling is utter nonsense! Magnetism is part of electromagnetism and is explained wholly within the gauge theory of their bosonic mediator the photon. Its effects on other systems may involve e.g. charges, and their statistics, et al but that is secondary. That's the quantum mechanical part.
The photon field has a perfectly well behaved classical limit in the electromagnetic field described by a classical gauge theory. But the gauge business is not necessary to understand and apply the physical theory.
Perhaps, to clarify a bit more, the words "Quantum Magnetism" do not refer to the quantum field theory of the electromagnetic field but to: Condensed matter field theory, quantum many-body theory, exchange interactions, domain formation, spintronics, superconductivity, quantum phase transitions, etc.

EDIT: In fact if you type Quantum Magnetism into wikpedia it apparently redirects you straight to "Spin Models" (i.e. Heisenberg model, Hubbard model, etc.)