R: Re: R: Re: R: Re: Non-locality and MWI (literature)

Tue, 10 May 2016 10:06:54 -0700 




----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) must 
violate the Locality Condition. I do not have references at hand, right now. 
I'll write down something as soon as possible.



 
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