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.
Brent
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