sci.physics.electromag

On Mar 12, 11:54=A0pm, Benj wrote:
> On Mar 13, 2:05 am, Timo Nieminen wrote:
>
> > Which brings us to another part of the discussion: is the electromagneti=
c
> > potential "real" in a physical sense? (I intended "field" in the thread
> > title in the more general sense of field, including the potential(s), no=
t
> > 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 jus=
t
> > 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 th=
e
> > ambiguity that results from the Lagrangian+Noether conservation laws onl=
y
> > telling us _total_ quantities, not densities). Alas, the paper only deal=
t
> > 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. =A0 This pretty much implies that outside the solenoid
> there is nothing but plain old ordinary "free space". =A0But in fact
> nothing could be further from the truth. =A0And 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! =A0Feynman 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. =A0Does that make it
> "real"? Don't know. But it sure gives it a good head start in that
> direction!
Most textbook authors don't seem to realize that Maxwell first gave
primacy to his 'magnetic vector potential' in his 1865 paper before he
'forgot' when he wrote it all up in his 1873 Treatise. This IS where
the interaction is happening!