[extropy-chat] Planck life and `thought bubbles'

scerir scerir at libero.it
Wed Dec 3 20:38:06 UTC 2003


"The problem any such analysis has to face is that of explaining how it is
that, if such a mechanism for ESP or other paranormal processes exists,
these processes manifest themselves only in very specific ways, and in ways
that are not readily controllable."
- Brian D. Josephson (therein)

W. Pauli and N. Bohr were both, and independently, very close to elaborate
concepts like those by Josephson (see "N. Bohr - Collected Works", vol. 10,
Bohr - Pauli correspondence, circa 1955) and maybe something more
'polished'. Not to mention here Wigner, London and Bauer, etc.

For something much more orthodox see the quotation below, very
technical, and very clean too.

"In an experiment the [quantum] state reflects not what is actually
known about the system, but rather what is knowable, in principle,
with the help of auxiliary measurements that do not disturb
the original experiment. By focusing on what is knowable in
principle, and treating what is known as largely irrelevant,
one completely avoids the anthropomorphism and any reference
to consciousness that some physicists have tried to inject
into quantum mechanics."
- Leonard Mandel (Rev. Mod. Phys., 1999, p. S-274)

But going back to that Josephson's quotation, he speaks of
"processes [which] manifest themselves only in very specific ways,
and in ways that are not readily controllable." This is, perhaps,
the point. But, look, it is a 'standard' point in quantum physics.

Behind the curtain, W. Pauli wrote:
"Quite independently of Einstein, it appears
to me that, in providing a systematic foundation
for quantum mechanics, one should start more from
the composition and separation of systems than
has until now (with Dirac, e.g.) been the case.
- This is indeed - as Einstein has correctly felt -
a very fundamental point in quantum mechanics,
which has, moreover, a direct connection with
your reflections about the cut and the possibility
of its being shifted to an arbitrary place."
(W. Pauli, in a letter to W. Heisenberg, just after
the EPR paper has been published).

Composition and separation of systems, hmmm. Conceptual issue 
indeed. This has something to do with Von Neumann who, speaking
of quantum mechanical problems, wrote: "I WOULD LIKE
TO MAKE A CONFESSION WHICH MAY SEEM IMMORAL: I DO NOT
BELIEVE IN HILBERT SPACE ANYMORE." in G.D. Birkhoff, Proceedings
of Symposia in Pure Mathematics, Vol. 2, p. 158, (Ed. R.P. Dilworth),
American Mathematical Society, Rhode Island, 1961.

But, also, i.e., there is another simple, old, and famous problem.
The Young's interference effect, the double slit. Wheeler
(with his delayed choice gedanken exp.) and Zurek & Wootters 
tried many times to break the wall here. The question
is: is there an "uncontrollable" retrocausation?

We know that the two-slit (also the single slit) is just an 
apparatus capable of measuring the positions of photons passing 
through it. Thus it is an apparatus capable of (Heisenberg's
principle here) scattering those photons (which means:
spreading momentum of photons) in a forward directions,
and producing the well known interference pattern on the
screen. The interference is produced by the the probability
function |<p|psi>|^2, where p is momentum of each photon.

We also know (Copenhagen Interpretation, chapter:
Complementasrity Principle; Feynman's discussion; etc.) 
that the interference pattern disappears when the path of each 
photon (say through slit one, or trough slit two) becomes 
distinguishable.

As Anton Zeilinger writes (Rev. Mod. Phys., 1999, page S-288)
"The superposition of amplitudes is only valid if there
is no way to know, even in principle, which path the particle
took. It is important to realize that this does not imply
that an observer actually takes note of what happens.
It is sufficient to destroy the interference pattern,
if the path information is accessible in principle from
the experiment or even if it is dispersed in the environment
and beyond any technical possibility to be recovered, but
in principle "still out there".
 
Now, imagine we have a Damien's screen, which 'feels' the path 
of each photon (say through slit one, or through slit two).
Impossible? Well, not so impossible. But let us skip this 
'material' point, for the moment.

So, if we substitute, in the two-slit apparatus, 
that Damien's screen for the usual screen, after those
photons have already passed through the slit(s), the 
interference pattern must vanish. (If the above principle
by Bohr, Feynman, Zeilinger, etc. is ok).

Now, what does it mean? What does it mean in terms of 
the quantum theoretical description? Interference 
means a certain kind of scattering, specifically
it means that the interference is produced by the the
probability function |<p|psi>|^2, where p is momentum
of each photon. No interference means a different kind 
of scattering, specifically it means that the interference 
is produced by a probability function |<p|psi>|^2 which  
lost the interference term.

Ok? Ok. Let us go on. If we set the usual screen we get
interference (pattern). If we set the Damien's screen
we get no interference (pattern). But how the
interference was created? By the scattering. Thus
by the position measurement performed at the
two-slit level. Thus: at the two-slit.

If we substitute the Damien's screen for the usual
screen (after the photons passed the two-slit) we change 
the scattering, which happened at the two-slit, that
is to say: in a different place, and at an earlier time.

Retrocausation? Who knows? Anyway not much different from
those para-psycho-effects, and from those bubble-models.








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