Re: Double Slit & Aharonov Bohm Effect



David wrote: 
RP wrote:

David wrote:

In volume II page 15-11 and 12 of Feynman Lectures of
Physics. Iron whiskers are mentioned as in:

"Precisely this experiment has recently been done. It is a very,
very difficult experiment. Because the wavelength of the
electrons is so small, the apparatus must be on a tiny scale
to observe the interference. The slits must be very close
together, and that means that one needs an exceedingly
small solenoid. It turns out that in certain circumstances,
iron crystals will grow in the form of very long,
microscopically thin filaments called whiskers. When
these iron whiskers are magnetized they are like a
tiny solenoid, and there is no field outside except
near the ends. The electron interference experiment
was done with such a whisker between two slits,
and the predicted displacement in the pattern of
electrons were observed".

Guys. Isn't it the official Aharonov Bohm experiment was
conducted in 1985. How could Feynman be mentioning
it in his 1964 book unless he was referring to another
experiment?. I thought 1985 was when it was first
experimentally confirmed. Can anyone all clarify this?


It's impossible to produce a contained alternating field.  Let me
explain the alternating part: Any passing electron will induce a
polarization of any material whatsoever, especially that located


within

the system, i.e. nearer the trajectory.  Look up "magnetron". The
presence and and subsequent absence of any body at all from the


system

constitutes a change in the system geometry, and a subsequent 

alteration

to the interference pattern.  The effect may be too small to measure
given some instances, but large enough to measure given others. The
presence of a polarized macroscopic field should certainly produce an



observable effect.

Recall that, in the thread to which the OP refers, I posited that 

the

em waves pass through everything, never being absorbed, but simply 

being

superposed over destructively by secondary radiation of the 

intercepted

charges, i.e. that radiation produced by their recoil. All of these
waves are spherical per Einstein's 1905 paper. Thus, though a field


may

be nulled by some means external to the coil, it is not nulled within


it, and the waves that I refer to pass through it, i.e. into the 

region

in which the field isn't nulled. Thus secondary radiation will  be
emitted by the particles within the coil as well, and one would
understandably expect this secondary radiation to influenced by the
internal field. IOW, the radiation due to the recoil of the charges
within the coil will by torqued in a manner similar to the torque
provided by a calcite filter.  Though the result of this influence


may

be difficult to account for in a quantitative fashion, it is
nevertheless an obvious general prediction of my model.

Richard Perry 



Are you saying the electron wave pass thru anything? If it does,
then there should be no interference since the slits don't
exist in the path of the wave.

I've addressed this previously, and we must speak in terms of the waves that are interfering, rather than the electrons. We'll add the electrons after. In effect we'll be deferring to the *light* version of the double slit experiment in order to make the argument.

The entire target area is in the path of the source wave, it is also in the path of every secondary wave, all of these waves being spherical. There is however a *lack* of secondary radiation from the slits, that is, since there is nothing there to emit waves. Supposing no slits at all in the plate, there will be a perfect shadow cast on the target. This is, according to the model that I've already related to you, due to the secondary radiation nulling the incident radiation. Since there is no secondary radiation emitted from the slits the result is that at any point on the target that was expecting radiation from these plate positions, there is none, and thus the incident wave that was expecting it is not completely nulled in certain regions (the bright fringes). Here's a simple diagram:


Target bf df bf df bf
. . . ...... . . . . . . ....... . . . . . . ........ . . .
\ /\ /
\ / \ /
\ / \ / negative rays
\ / \ /
\ / \ /
\ / \ /
\/ \/
-------------------------- ------------------- ------------------------------
Source side of plate

(b)right (f)ringes due to lack of nulling secondary field (shading) in these locations.

As you can see, it's identical to the classical (and incorrect) wave model, in appearance. The difference is that in my model there are secondary waves emanating from every point on the plate that interfere destructively with the source wave (this interference is the source of the ordinary shadow, e.g. your shadow on the sidewalk on a sunny day), but there is no nulling field emanating from the slits. In the classical flawed approach this scheme is in a sense reversed. The classical approach requires a medium in order to provide for the necessary secondary wavelets, that is, in order to go-around-the-corners<sic>, while my model does not require a medium, nor would my model be consistent with a medium.

The particles at the source interact directly with those at the target, and all of these not only with the plate, but directly with every other particle event along their light cones, irrespective of distance. That is, all sources interact at the target in the form of superposition of spherical waves. It is for this reason that the effect is sensitive to both the near and distant geometry. Of course the inverse square law renders the most distant effects insignificant. The very near surrounding geometry is certainly a big factor, in both the light and electron versions. The zpf at the target is superposed over the source wave, in a probabilistic sense when mere points on the target are taken into consideration. There is feedback generated as the waves volley back and forth, and thus standing wave patterns, beats, the whole gauntlet of interference effects. The de Broglie wavelength is produced by the apparatus, and is not an intrinsic property of the fermion.

The electron thus acquires a phase wave and its motion through the ambient standing wave pattern will cause it to veer in its course depending upon the relative balance between the opposing components of force that act on it on average over its path. The electron will have a higher probability of landing in a bright fringe because wrt to it that region is positively charged.

Richard Perry

But it does. If you put only one
slit, there is no interference pattern, putting a second one
gives the pattern. This means the wave doesn't just pass thru
the wall of the slit and into the inside of the solenoid and
got altered on its way to the detector. Anyway. Try to illustrate
your idea by some kind of drawing or diagram of how the wave
can regroup into a single particle. You know what. A wave function
concept as depicted by QM where the particle rides in it without
location and materializing upon hitting the detector with
the rule set by probability is more elegant and nice and is in
the tradition of entanglement, non-locality and all those Harry
Potter stuff :) 

Dz


.

Relevant Pages

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  • Re: double slit experiment [please explain]["This experiment should be included in every textbook on
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    (sci.physics)