On 30 Oct 2015, at 01:17, Bruce Kellett wrote:
On 30/10/2015 3:47 am, Bruno Marchal wrote:
On 27 Oct 2015, at 06:54, Bruce Kellett wrote:
On 27/10/2015 9:37 am, Russell Standish wrote:
The only clarification I would make is that (with
computationalism) the system is formal, but the observer
(individual in your terminology) and environment (universe with
its physics in your terminology) are a non formal partition of
the system.
How is that partition into observer and universe made? If it is
purely formal then it doesn't do the necessary work. But then, how
does a purely formal system generate a non-formal division? I
think your division builds in semantic content from the outside by
fiat -- not in a principled way.
This is similar to my objection to the many worlds interpretation
of QM. You have to distinguish between the different worlds in
some way -- unitary evolution cannot do this. Decoherence always
leaves residual correlations, and although these may be small,
there are a very large number of them, so the original
superposition is, in fact, still intact. Everett wants to make the
world relative to the particular observer (hence 'relative state'
interpretation). But to make sense of this mathematically you have
to get rid of the unwanted correlations.
I don't see why. We can fuse again by amnesia, and exploit the
unwanted correlation. They disappears only relatively, nothing is
lost, evolution is time symmetric.
No, amnesia does not reconnect the separate worlds -- it merely
indicates a confused individual. The world is not defined by what
one person sees or thinks. Inter-subjective agreement is essential
to understanding what is going on. You confuse the 1p and 3p, yet
again.
?
Most do this by fiat -- the worlds are orthogonal FAPP. But that
is not principled either. Mathematically, we take a partial trace.
But we take the trace, it is not in Schroedinger's equation.
It is in the relative choice made by our histories (long
computations), relatively to us. Zurek explains this rather well in
my opinion, I mean why our type of brain needs orthogonal
positioning, why position is favored by brain-like structures, for
consciousness to stabilize enough to make prediction in our deep
environment(universal computations).
Zurek does not explain the point that I am making. Zurek's
einselection is designed to explain the preferred basis problem. But
he misses the mark by quite a wide margin. He explains why the
position operator is often relevant, but that merely selects a
Hilbert space, it does not select a basis in that space.
?
The basis has to be robust against environmental interactions, not
just the operator itself. Einselection, like decoherence, is part of
the solution, but it is not the full solution.
But even if you have actually solved the basis problem, you still
have not solved the problem of quantum measurement. In order to get
just one result for an experiment with only probabilistic results,
you have to project a subspace out of the full Hilbert space.
You get it by the indexical FPI, so you can define it in arithmetic,
and in QM, with the usual machine's self-reference (à-la Gödel).
The full space might well still be 'there' (in whatever sense you
like), but the fact that the observer is conscious of only part of
that space involves a projection operator. And projection operators
are not time symmetric or unitary. This is the partial trace
problem, and it remains unsolved.
It is exactly what Everett solved, assuming mechanism, by taking into
account the personal point of view of the isolated system with respect
to what it is isolated and not isolated. Everett shows this does not
depend on the bases. It corresponds with the eigen value of the
frequency operator, justifying the "squaring" of the amplitude
(something seen by Paulette Février-Destouches, a student of De
Broglie, and by Finkelstein).
It is not solve for a computationalist as we have to justify the ortho-
structure, but we get one (well, 3) at the propositional level already.
Bruno
Bruce
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