On 11/17/2017 5:04 AM, Bruno Marchal wrote:

On 15 Nov 2017, at 22:10, Brent Meeker wrote:



On 11/15/2017 7:04 AM, Bruno Marchal wrote:

On 14 Nov 2017, at 21:15, Brent Meeker wrote:



On 11/14/2017 6:18 AM, Bruno Marchal wrote:

On 13 Nov 2017, at 22:40, Bruce Kellett wrote:

On 14/11/2017 2:07 am, Bruno Marchal wrote:
On 12 Nov 2017, at 23:05, Bruce Kellett wrote:

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state.

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

I have no clue what you mean. The singlet state guaranties the conservation of angular momentum in all worlds. The singlet state describes an infinity of "worlds",  and in each of them there is conservation of angular momentum, and it has a local common cause origin, the same in all worlds.

But it's not a sufficient 'hidden' variable to explain the space-like correlation of measurements.

If the the explanation is based on hidden variable, per branch, then there will be non-locality. But the many universe are not really hidden variable in the sense of EPR-Bell's, which assumes Alice and Bob have the same identity and keep it, when they do the space-like measurement, but it seems to me that this is a wrong interpretation of the singlet state when we suppress any possible collapse. If Alice and Bob are space-like separated, they will later only access to the Bob and Alice they will locally be able to interact with, and those are "new" people, not the original couple.

But that's the point of Bruce's version in which the measurements are time-like.  Alice and Bob will have continuity of identity and, as he argues, the explanation for the correlation of results being stronger than classical must be the same.

But there are the same. The singlet state explains this too. The mystery is in the apparent space-like separation, where it looks like a physical action at a distance plays some role,

Exactly, and since the explanation must be the same, it can't be the common cause of conservation of angular momentum.  That explanation doesn't account for the correlation function in the space-like case.

except that this has not been proved in the MW theory.

In another post, you say that decoherence is statistical. may be that is where we disagree. decoherence is only entanglement with the local environment (spreading/differentiating at the speed of light).

But it differs from coherence only in that the large number and spreading degrees of freedom make it statistically irreversible.

Brent


Bruno


Brent

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