Le 08-juil.-08, à 21:00, Brent Meeker a écrit :
Bruno Marchal wrote:
On 08 Jul 2008, at 18:38, Brent Meeker wrote:
Bruno Marchal wrote:
If I look to a particle in the state (UP + DOWN), the state I
cross (UP + DOWN)
evolves (by SWE) to:
I-seeing-UP cross UP + I-seeing-DOWN cross DOWN,
I don't see how to avoid this without abandoning QM.
If we can't show that a quasi-classical world emerges from QM we will
abandon it -
We have already shown (Everett ... Zurek) how quasi-classical worlds
emerge in the memory of classical machines through QM.
QM justifies the *appearance* of classicality.
I don't think this problem is solved. Dowker and Kent's paper was
written
primarily as an investigation of the consistent histories
interpretation,
but it's conclusions also seem to apply to Everett+decoherence; namely
that
in general there are no quasi-classical continuations of a state.
I have read it some times ago. I am ok with the idea that they are
remaing questions 'course. And I do agree that in general there are no
quasi-classical continuations of state. but this does not prevent
quasi-classical continuations of some state to exist. In particular I
don't see how Dowker and Kent's anaylis can be used to make
disappearing on of the terms in Me-seeing-up CROSS up + Me-seeing-down
CROSS down.
Also, remind that with assuming comp, then there is already
Many-Interfering-histories with just (N, +, *). If someone really comes
up with a one-universe interpretation of QM, I will most probably
conclude that QM is most probably wrong, given that I tend to believe
more in comp than in QM. Up to now, I take QM as confirming comp,
because interfering dreams appears where comp predict it has to appear.
(By QM I mean QM without collapse of course).
at least as fundamental. Perhaps the long sought quantum
theory of gravity will come to the rescue.
All approaches now keep intact QM. Everett is the one who realize the
more clearly that only the collapse axioms was incoherent with
relativity. Even Bohr admitted that the collapse could not be
physical.
Once you abandon the collapse, QM and (special) relativity fit very
well together. That is why all current approaches in quantum gravity
prefer to keep intact QM (and thus the MW) and correct only a bit GR,
in some (different) ways.
By quantifying gravity, i.e. introducing many spaces-times, you put a
(quantum) topological structure on the multidreams.
And why do you want a rescue? You betray you are wishing ONE universe,
and certainly I wish ONE reality, but current physics implies Many
alternate histories, and the current theory of mind (computer science,
universal machine introspection) implies it too.
Scientists are (or should be) agnostic if there is 0, 1, 2, 3,
aleph_zero, ... universes. But today evidences are in between: 0,
aleph_zero, 2^aleph_0.
I don't care how many there are - I'm just concerned with the
evidence. I
was referring to rescuing Everett+decoherence from the problem Dowker
and
Kent point to. It seems to be the white rabbit problem within QM.
I have never pretend the contrary, especially about the first person
white rabbits.
The only problem of QM is that it does not yet take comp seriously
enough imo.
The collapse can
be explained
*phenomenologically* (first person plural) through MW +
decoherence.
And if I make a decision based on what state I measure on the
particle, the divergence will
propagate.
And Weinberg has given a convincing argument that once SWE is made
slightly non
linear, then, not only we keep the Many Worlds/Dreams, but
interaction
is made
possible between them (falsifying then thermodynamics though: that
is
why I don't
take that the delinearisation of the SWE idea very seriously).
That's
speculation.
Do you have a reference for Weinberg? I'd like to read his paper.
I'm afraid I will not find quickly my copy which I have not read for
many years, but I found a (physicist's, without title) reference:
S. Weinberg, Ann. Phys. (N.Y.) 194, 336 (1989)
Perhaps more helpful is this:
http://prola.aps.org/abstract/PRL/v66/i4/p397_1
Thanks.
(at the time I thought I could easily proof that Plaga + Polchinsky +
Weinberg implies the existence of absolute elasticity, and thus on
some continuous matter/energy/space-time/information, but of course it
appears harder than I thought and I abandoned the project: that would
NOT have contradicted Mechanism, on the contrary).
I wonder how it would apply to the idea that there is a smallest
unit of
probability amplitude.
Except perhaps for some interpretation of Loop Gravity, but I don't
see why they would be a smallest unit of probability amplitude.
From the UDA it is rather clear that this could not exist, unless you
introduce some ad hoc non computable criteria of equivalence.
I would think that something like it would follow from the UDA.
Aren't all
