On 10-05-2016 01:35, Bruce Kellett wrote:
On 10/05/2016 2:42 am, smitra wrote:
On 09-05-2016 07:43, Bruce Kellett wrote:
On 9/05/2016 3:17 pm, smitra wrote:
On 09-05-2016 03:40, Bruce Kellett wrote:
The idea that Alice splits further into different branches
according
to Bob's results only after their respective light cones overlap is
an
interpretive gloss on the theory (which, as already pointed out,
you
do not apply consistently) -- it is not there in the mathematics.
Alice and Bob are in the same world even at spacelike separations.
This must be the case, or else my feet would be in a different
world
from my head at every single instant of time. So Bob and Alice
separate in the same world. When they perform their measurements
there
is a Bob in each world created by Alice's results, and an Alice in
every world created by Bob's results. The fact that neither Alice
nor
Bob do not know the other's result does not mean that there are no
such results. Are there separate worlds in which these results are
combined? It doesn't really matter, because anything that can be
seen
when information is exchanged is already set: the exchange of
information is like opening the box -- the cat is already either
alive
or dead, opening the box does not change that. So Alice and Bob
talking to each other does not change anything either. The results
are
already present in the universal wave function -- talk of splitting
into worlds is irrelevant to the universal wave function and the
unitary dynamics. So the fact that A does not know B's results at
some
time is irrelevant -- the results are already there. The question
of
who knows what is not a relevant question for the universal wave
function. And the universal wave function takes account of the
unity
of the singlet state and the reality of non-local effects.
And this is the core of the disagreement, you say that the results
are already there, but in the MWI this is false.
What? Are you claiming the the universal wave function -- which
contains all possible branches corresponding to all possible outcomes
-- does not contain the results? I think what you mean is that you do
not know the result (which branch you are on) until you open the box.
But that does not mean that you are not on one branch or the other.
The death of the cat (if it be so) can be in your past light cone, so
the splitting of worlds occasioned by that death has already split
you. Your knowledge of this is strictly irrelevant. You can be in a
particular world without being aware of it. In Bruno's famous person
duplication experiments, you are in either Washington or Moscow
before
you are necessarily ever aware of which city it is. You make personal
knowledge of outcomes far too prominent in your theory; things can
actually happen without your being aware of them!
While your body does split up, if you don't have the "which branch"
information then you are in both branches until that time that you do
have this information.
Nah. That places far too much emphasis on the conscious mind --
making "what you know" the determiner of physical reality. I think
Brent might refer to this as QBism (Quantum Bayesianism). A person is
more than just what they happen to be thinking at the moment. If the
body participates in the split, the brain also so participates.
Instantaneous conscious (or computational) states are transient, and
will be influenced by many external influences. Your suggestion, if
taken literally, would have us fluctuating uncontrollably between one
world or many. Not a good idea. I think we have to gives some
significance to the objective state of the wave function. That is what
is determined by unitary evolution; what we think about it is
irreducibly secondary.
One has to be more rigorous about including the observer here. In the
MWI there is no excuse to not do this as it's a complete theory and in
this discussion we're assuming that the MWI is correct, which supposedly
leads to a problem with non-locality just as in collapse
interpretations.
So, the computational state you are in at some moment may contain noise.
Even if that noise is perfectly correlated with the state of the cat,
this would then mean that you end up in a branch where the fate of the
cat is determined due to the addition of the noise in your brain. There
is then no difference between the noiseless case as far as the necessity
for a local interaction is concerned (we're replacing explicit
communication of the facts with implicit information transfer via
noise).
If we consider ourselves as programs run by our brains and consider
some well defined computational state, look at all the branches
where that particular computational state is implemented, then
you'll find that it's present in both situations where the
information about the cat is different.
Hmm. I think there may be a typo here. If the information about the
cat is different, it would suggest that the computational state of the
brain is different -- information is reflected in the computational
state, after all. If it is not, it is just noise, not information. By
relying so completely on what we know, or our conscious state, I think
you push computationalism beyond its reasonable limits.
I think it's important to include the state of the observer in the
description. We can only do that in a formal way, but we need to include
at least the things that are relevant here. If the cat has 50% chance of
dying, then it's one bit of information that we need to keep track of.
We can't just pretend that this bit of information can just appear
somewhere by magic, it's going to make it into the observer via the
dynamics of the system.
If we then consider the observer splitting up in the two MWI branches
and want to consider if there is anything non-local about that, we do
need to consider how this one bit of information ends up interacting
with the observer.
Saibal
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