On 10 Sep 2015, at 01:20, Bruce Kellett wrote:
On 10/09/2015 7:42 am, Brent Meeker wrote:
On 9/9/2015 10:27 AM, Bruno Marchal wrote:
On 09 Sep 2015, at 07:55, Quentin Anciaux wrote:
As for Bruce, could you then be honest, and simply say you don't
believe in the many world interpretation and don't want to
explore it... yes we're talking mostly metaphysics on this list,
if you dislike it, I wonder what you're doing here.
Indeed the point is notably that we can reason about this, that is
doing science, so that we never disagree except about the choice
of the assumptions.
Now, I disagree with Bruce, and I guess many philosophers and
scientists, except Deutsch (on this), but I do think that QM
(without collapse) is a theory of many worlds (in a perhaps
admittedly more abstract than usual notion of world).
If we define a physical world by a set of events close for
interaction,
But can computationalism give a coherent account of this? Doesn't
the UD imply at every set of events will have many (countably
many?) causal histories and infinitely many causal futures.
then the "many-world" is a consequence of the linearity of the
wave evolution together with the linearity of the tensor product.
But they are only "many" FAPP. Decoherence suppresses cross terms
in the density matrix, but it doesn't make them zero - and I don't
think it's even provable that there is a unique basis in which it
diagonalized FAPP. And of course we have no theory of quantum
spacetime. QM assumes a continuous spacetime, so QM is not the
last word and if computationalism only reproduces QM it will fail
when QM fails.
I think it is clear that Bruno does not understand either QM or the
MWI. MWI is not a consequence of the linearity of the wave function.
It is when you define a world by the maximal consistent extension
close for the local observable interactions.
Superposition is the consequence of linearity,
OK. And if the computations done can interfere, they have an
equivalent physical reality, and determined alternate accessible
realities, but if entangling oneself with them, we loss or make very
hard the ability to see the interference.
and superposition implies interactions between outcomes.
?
I would say interference between the outcomes.
Many-worlds requires decoherence in a preferred basis,
I would say that classical macroscopic brain or universal machine
requires a classical-enough base, which benefits of that decoherence,
although with quantum computing we can exploit the ignorance by
changing the base (which is still rather mysterious from the comp pov).
with actual zeroing of the off-diagonal terms in the density matrix.
Indeed, this latter step is just the standard "collapse" postulate
in a different guise. So, far from eliminating "collapse", MWI
relies on it as much as any other interpretation of QM.
Not at all. There is no physical collapse, just an epistemological
differentiation when one get entangled in the other's business.
The real difference between interpretations is whether this
"collapse" is a physical process or merely an epistemological one.
In the MWI, actually in Everett theory, there is only the SWE. Sating
"there is no collapse", means, for a logician, that we don't add the
collapse postulate (unlike many textbook). So the collapse is
necessarily an epistemological, even indexical, and relative, notion.
In MWI, which reifies the wave function
Which is indeed an error, at least with the mind-body problem in mind,
but physicists do this very often.
and the elements of the superposition, the collapse is definitely
physical.
?
So it is, after all, no different in this respect from the von
Neumann Copenhagen interpretation.
I have a problem. In Everett theory there is no postulation of
collapse. The collapse is explained by the postluation of universal
machine, or at least good approximation of universal machine.
Copenhague:
- SWE
- Collapse
- Dualist theory of mind and matter
Everett:
- SWE
- COMP
And what I try to explain is that COMP ->. [](COMP -> SWE) & (COMP
-> SWE), so "my" theory is just
- COMP
Formally it is just any theory which is Turing universal, and
observation is defined by the logic of self-reference (of rcher
entities living there) and the intensional variants.
This is not supposed to compete with physics, but to supply the
qualia, and the range of non communicable, but true, realities.
Bruno
Bruce
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