On 5/23/2018 11:48 PM, [email protected] wrote:
On Thursday, May 24, 2018 at 6:02:30 AM UTC, Brent wrote:
On 5/23/2018 10:37 PM, [email protected] <javascript:> wrote:
On Thursday, May 24, 2018 at 4:53:29 AM UTC, Brent wrote:
On 5/23/2018 9:43 PM, [email protected] wrote:
On Thursday, May 24, 2018 at 4:28:58 AM UTC, Brent wrote:
On 5/23/2018 9:17 PM, [email protected] wrote:
In the MWI interpretation there is no reason to
preference one over the other with the honorific of
"exists". They are just projective subspaces that
are essentially (FAPP) orthogonal to one another.
I can buy that, although tentatively, with difficulty,
until I see the mathematics which demonstrates it. AG
Each one includes copies of the system, the
environment, and the observer(s) which is necessary
so that it constitute a classical "world" in which
everyone agrees on the result.
This I absolutely CANNOT buy, as I have explained
numerous times. Cannot decoherence and the MWI have
descriptive value without all of this COPYING being
assumed, which I find outlandish? Would it be fatal to
any of these concepts to affirm that the entanglements
which occur in these subspaces are equivalent to
measurements in these subspaces? AG
It's fine if you just assume the other subspaces vanish
as far as doing physics. Metaphysically it's problematic
because you've used a certain theory up to that point
which predicts that all the subspaces are equally real
(and may be more probable than the one you experience)
and there are copies of you and your lab etc which are
equally real and now you're going to stop using that
theory which was so amazingly successful...why?
Brent
The other subspaces don't vanish. They continue to exist and
all possible measurements are in fact measured according to
my proposal. But the subspace in which the observer exists
seems apriori different and more significant in terms of
physical reality; it's the environment in which all
entanglements of all subspaces come into being.
The entanglements coming into being is what makes the
subspaces become orthogonal and become separate "worlds".
The entanglements are different (in detail) in each different
subspace reflecting the fact that they are correlated with a
different result.
Yes, I am imagining a different result in each subspace. AG
It seems metaphysically problematic to give all subspaces
the same existential status, when only one provides the
environment for all entanglements for all subspaces. AG
I don't know what entanglements you're talking about. The
system measured has different entanglements with the
different environments and observers in the different
"worlds". There is no privileged world which provides a
privileged environment and observer.
I am imagining a superposition of states, and when the
measurement occurs, each component of the superposition becomes
entangled with the environment in this world, the world in which
the measuring device exists. Then, somehow, the subspaces become
orthogonal FAPP. AG
No, it's the interaction, the entangling of different results with
the environment, that makes the subspaces orthogonal.
That's what I assumed; that the entanglement for each subspace causes
the orthogonality (though I can't imagine how that would come about).
If you look at the mathematics of the total
(system+environment+observer) density matrix, the off-diagonal terms
have products of wf terms from the system and environment. The
environment wf are of course unknown, so one averages over them by
taking the trace over them. This makes the cross terms for the reduce
density matrix (that of the system) go to zero, so now it is /formally/
the same as the probability matrix for a set of classical states. As
Bruce points out this "taking the trace" is a non-unitary operation that
is equivalent to applying a projection operator, as in the Copenhagen
interpretation. Which is why I say decoherence only gets you part way
to solving the measurement problem. It has a mechanism and a
statistical rationale, but it still takes a little jump to get to the
classical definite result.
Isn't "the environment" the this-world environment, the measuring
device in this world? Isn't it this entanglement that destroys the
interference FAPP with the other components of the superposition in
this world, which might be what the Bucky Ball experiment establishes?
What are you objecting to? AG
That there is a unique "this world". I use use "world" (with the scare
quotes) to indicate a coherent, quasi-classical world where observers
don't see superpositions of alive and dead cats. The measuring device
and the environment is in all the "worlds", one for each measurement result.
I happened across a very good book that discusses these questions well
without mathematics, "Mind, Brain, and the Quantum" by Michael
Lockwood. It's a philosophy book about epistemology and consciousness
and discusses a lot more about the brain and it's function. But is has a
couple of chapters on the quantum measurement problem. It says the same
thing Bruce and I have been saying except Lockwood looks at what I've
been calling "worlds" (per the usual MWI terminology) as macroscopic
states which exist in superposition in one world (which is usually
called the universe or multi-verse), the superpositions just happen to
be orthogonal (FAPP) and so don't interfere.
Brent
The result is in effect encoded all through the subspace, that's
why different people in that "world" can agree on what happened;
that's what makes it a (quasi) classical world where people don't
see superpositions of measurement results.
Brent
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