On 10 May 2016, at 19:06, 'scerir' via Everything List wrote:
----Messaggio originale----
Da: Bruno Marchal <[email protected]>
Data: 10/05/2016 18.31
A: <[email protected]>
Ogg: Re: R: Re: R: Re: Non-locality and MWI (literature)
On 10 May 2016, at 15:37, 'scerir' via Everything List wrote:
Thanks Scerir, but yet again, this paper get the same conclusion as
mine (and most people here). With the MWI, non-locality does not
imply action-at-a distance. (d'Espagnat would call it non-
separability).
What I look for would be a paper which would show that in the MWI
there are action-at-a-distance, like Bruce and John C claim.
I might comment later, as I am late in my scheduling, but will just
notice that Gisin's paper (mentionned by Brent) use the non-
compatibilist theory of free-will, which makes no-sense to a
mechanist. I think Brent concluded similarly.
Bruno
If A and B are two wings of a typical Bell apparatus, i the
observable to be measured in A
and x its possible value, j is the observable to be measured in B
and y its possible value,
and if Lambda are hidden variables, we could write
Locality Condition
p_A,Lambda (x|i,j) = p_A,Lambda (x|i)
p_B,Lambda (y|i,j) = p_B,Lambda (y|j)
Separability Condition
p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j)
p_B,Lambda (y|i,j,x) = P_B,Lambda (y|i,j)
There is (was) some agreement that a (phantomatic) deterministic
theory (i.e. one in which
the range of any probability distribution of outcomes is the set: 0
or 1)
?
The question is: are the probabilities, or the indeterminacies, and
the non locality, phenomenological (1p) or factual (ontological,
real, 3p)?
QM+collapse admit factual indeterminacies (God plays dice, and
there are action at a distance, even if they cannot be used to
transmit signal quicker than light).
QM-without-collapse is purely deterministic at the 3p level, and
admits indeterminacies at the phenomenological level.
I think everyone agree on this.
The debate is on the following question: does QM-without-collapse
admit factual non-locality (real physical action at a distance, like
QM-with-collapse), or do the non-locality becomes, like the
indeterminacy, phenomenological?
(I think yes, as Jesse, Saibal and others, but it seems Bruce and
John C. differ on this).
#### Frankly it is not easy for me to say anything about that, at
least something consistent. Mainly because "Many-worlds with its
multiplicity of results in different worlds violates CFD, of course,
and thus can be local. Thus many-worlds is the only local quantum
theory in accord with the standard predictions of QM and, so far,
with experiment.".
reproducing all the predictions of QM, can not violate the
Separability Condition, (the specification of Lambda, i, j, in
principle determines
completely the outcomes x, y, then any additional conditioning on
x or y is superfluous, having x and y just one value allowed, so they
cannot affect the probability, which - in a deterministic theory -
can
just take the values 0 or 1) and must violate the Locality
Condition.
Following the above reasoning MWI (if it is a truly deterministic
theory)
should violate the locality condition.
I doubt this, but if you find a proof, in the literature (or not), I
am interested. As I explained, and also give references, it seems to
me that the MWI restores both 3p determinacy and 3p locality, making
both the indeterminacy and non-locality only first person plural
phenomenological happening. That is also Everett's position, and I
would say the position of most Everettian (I still don't find any
Everettian claiming that the MWI remains non-local, except the
beginners who often think at first that the entire universe split
instantaneously, but this does not deserve to be commented as nobody
believes in this anymore).
Bruno
#### Jarrett, but also Shimony, and also Ghirardi, gave the proof
that a *deterministic* QM (I should say a *deterministic and single-
valued* QM)
Yes, that is important to add. It was notoriously implicit in EPR and
Bell 1964, even after.
must violate the Locality Condition.
EPR and Bell shows this, and the usual papers (Clauser and Horne,
Clauser Horne Shimony, Holt, Aspect, ...).
I do not have references at hand, right now. I'll write down
something as soon as possible.
I think we all agree that QM-with-collapse entails a violation of
Locality. The debate was for the case of the non-single value QM, that
is QM-without-collapse, where all branches of the wave are kept "alive".
Bruno
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