sci.physics.electromag

On Mar 13, 2:05 am, Timo Nieminen wrote:

> Which brings us to another part of the discussion: is the electromagnetic
> potential "real" in a physical sense? (I intended "field" in the thread
> title in the more general sense of field, including the potential(s), not
> just E,D,H,B.)
>
> Aharonov-Bohm would suggest that, yes, the potential is real. Lorenz's
> potential would be an ideal candidate for the "real" potential. I've just
> read one of Carpenter's papers on electrodynamics taught in terms of
> potentials rather than the conventional EM fields. Using the potential
> gives a very different picture of where the energy is (again, this is the
> ambiguity that results from the Lagrangian+Noether conservation laws only
> telling us _total_ quantities, not densities). Alas, the paper only dealt
> with static/DC current cases.

This rather gets down to it, doesn't it? We take a solenoid (or
toroid) and we probe around the outside of it and there seem to be no
magnetic fields. This pretty much implies that outside the solenoid
there is nothing but plain old ordinary "free space". But in fact
nothing could be further from the truth. And that would be because
there is plenty of "A" outside these devices. And even more
interesting A-B demonstrates that A actually has measurable action.
So asserting that "A" is real may be going just a bit too far, but
clearly SOMETHING is going on in "free space" that is able to cause
actions in field-free regions! I strongly suspect there is something
fundamental here that has heretofore been overlooked! Feynman has
noted that all attempts to generate universal quantum expressions
using fields have more or less failed while the magnetic vector
potential seems to be the "fundamental" quantity. Does that make it
"real"? Don't know. But it sure gives it a good head start in that
direction!