From: *Bruno Marchal* <[email protected] <mailto:[email protected]>>
On 23 Apr 2018, at 05:43, Brent Meeker <[email protected]
<mailto:[email protected]>> wrote:
On 4/22/2018 6:50 PM, Bruce Kellett wrote:
From: *Brent Meeker* <[email protected]
<mailto:[email protected]>>
On 4/22/2018 9:19 AM, Bruno Marchal wrote:
It follows from both QM and Comp. If Alice and Bob are
space-separated, I cannot even makes sense of how you can
measure correlations, given that once they are separated,
whatever result they got, will be shared with different Alice
and Bob in different branch. I am not even sure we can define
what could be an action at a distance in the quantum formalism.
The notion does not even makes sense when we assume special
relativity. The only reason to believe this is the habit to
think that there is only one bob and one Alice, which makes no
sense once separated, unless they are correlated with a third
observer, but then, again by looking at the wave without
collapse, there will be no action at a distance. The no
locality is only an appearance due to the fact that we belong
to infinities of histories, and cannot known which one we are in.
It depends on what you mean by "action at a distance". The theory
you are depending on for these pronouncements entails that, on a MW
picture, some of the possible worlds have probabilities that go to
zero as a result of an interaction at Alice or at Bob. So an
interaction at one of them changes the probabilities at the other.
For Bruno, it seems that "non-locality" means "action at a
distance", where he interprets that to mean that there is some
superluminal transfer of information,
I prefer to distinguish non-locality (inseparability), action at a
distance, and transfer of information at a distance. Even in a
mono-universe theory, the action at a distance exists (by EPR-BELL)
but cannot be used to transfer information. But in the multiverse, we
have the inseparability, but we don’t have any action-at-a-distance.
At least that is what I am arguing for.
That is what you are arguing for. But you have not as yet put forward
any clear and convincing argument that you can succeed in your search
for such a theory. You have to take the accepted formalism for the
singlet state and develop a unitary theory that avoids non-locality. I
have recently reproduced the argument given by several MWI advocates,
and have shown that it does not avoid the non-locality intrinsic to the
non-separability of the singlet state wave function. Your challenge is
to start from the same state and apply unitary evolution to reach a
different conclusion.
by tachyons or some such. And he is quite right to say that there is
no such interaction or dynamics in quantum theory. Because if
"non-locality" meant some superluminal transfer of information, by
particles or something else, then that would be giving a *local*
explanation of non-locality, which is a contradiction. So
non-locality can never mean "action at a distance", it can only mean
that the theory is such that the state is not separable, and
changing one end automatically changes the other, just as pushing
one side of a billiard ball moves the other side as well. (Ignoring
the problems of a relativistic explanation of extended physical
objects. This is not a particularly good analogy, but it is the best
I can think of at short notice!) In quantum mechanics, there can be
no "mechanical" explanation of the non-locality inherent in the
non-separable state. That is why we call it "non-locality" rather
than "action at a distance".
I acknowledge that there are linguistic problems here, but that is
just the nature of quantum mechanics, and we have to live with it.
Trying to "explain" this fact further is bound to fail, because
there is no deeper explanation.
Of course, I do believe that there is a deeper and simpler
explanation. QM seems very plausibly be only how the numbers can
structured arithmetic from their indexical internal points of view. It
is the canonical logic, imposed by incompleteness, on what is
observable ([]p & <>t (& p)) for them.
Your own versions of mechanism and/or "comp" do not work here, because
you have claimed that MWI itself, within the standard formulae of
quantum theory, obviates non-locality. You have to reconcile the
acknowledged non-separability with a local explanation. This, I contend,
is impossible. Prove me wrong.........
I think one way to look at it is, if a hidden variable explanation
requires that the hidden variable be FTL, then the phenomenon is
non-local.
If find it hard to see how Bruno can say whether or not his theory is
non-local since he has not derived any concept of space, time, and a
Lorentz metric. I would think that would be a minimum before you
could claim a theory had not FTL signaling.
I was not reasoning in any theory. I was just saying that EPR-BELL
entails non-locality only in hidden variable theories in a
mono-universe theory, but that deriving action-at-a-distance, from
EPR-BELL in one branch of the multiverse is not valid (without
assuming Mechanism). It is pure applied logic.
That makes no sense.
Of course, all physical theories which assumes any number of universe
different from zero are wrong, so even Everett is wrong, but that is
another chapter of metaphysics, and I am not there in this discussion
in physics (not to confuse with metaphysics unless we put the
Aristotelian metaphysics in the hypothesis, which many do that implicitly.
Make your argument in the terms of standard physics, MWI or many-minds
,or whatever. Because that is where your claim resides, and it is
currently unproved. Metaphysics plays no role in what you are required
to do to make good on your frequent boasts.
Bruce
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