On 18/11/2017 12:04 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, except that this has
not been proved in the MW theory.
Again you appeal to the 'apparent space-like separation'. As Brent said,
the point of my time-like example was that there is no space-like
separation at any time, so that escape is not available to you.
And exactly what is it that you claim has not been proved in MW theory?
Bell's theorem applies there too: it has never been proved that it does
not. Bell was no fool: he did not like MWI, but if that provided an
escape from his theorem, he would have addressed the issue. The fact
that he did not suggests strongly that you do not have a case.
Bruce
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).
Bruno
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