On 20 Nov 2017, at 23:04, Bruce Kellett wrote:
On 21/11/2017 12:22 am, Bruno Marchal wrote:
On 17 Nov 2017, at 23:11, Bruce Kellett wrote:
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.
Without space-like separation, I don't see why invoke a physical
action at a distance at all.
No, as I pointed out in my original post, a local hidden variable
explanation for the time-like correlations is available.
I am not sure of this. A local theory can exist, but it will
contradict QM.
That would mean no more than that QM is incomplete.
It means QM is false, given that QM entails space-like correlation.
The problem is that this explanation is not available in the space-
like case, and you cannot use one explanation in one place when it
doesn't work elsewhere.
OK. We agree.
When the singlet particles are produced before separation, they
cannot know whether they are going to be measured at space-like or
time-like separations: any hidden variables that are going to
explain the correlations by some common cause mechanism have to be
set in place from the start. That is ruled out by simple logic given
the time-like violations of angular momentum conservation.
I think you "MW" interpretation of the singlet state is incorrect.
When Alice measure her particles, she just knows in which branch she
belongs, and she knows the result that Bob would get in that branch.
There is no action at a distance.
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.
EPR and Bell assumes unicity of outcomes, or the collapse. Without
this, the "spliting/differentiation" of consciousness/universe
becomes a local phenomenon, and the formalism ensure locality.
That is just false.
Proof?
Bell was no fool: he did not like MWI, but if that provided an
escape from his theorem, he would have addressed the issue.
He did not. He arguably made something worst: reinterpretating the
Many-world in term of a local hidden variable theory.
The fact that he did not suggests strongly that you do not have a
case.
That is not a convincing argument. I just do not see any non-
locality derivable from the SWE-without-collapse. Indeterminism
also go away in the MWI. The MWI replace all nonsensical weirdness
by one fact, which is trivial with mechanism: we are in may
"histories", and cannot decide which one.
You clearly have not grasped the implications of my argument. The
idea that "MWI replaces all nonsensical weirdness by one fact (many
histories)" does not work, and is not really an explanation at all
-- you are simply evading the issue.
Without collapse, the apparent correlations are explained by the
linear evolution, and the linear tensor products only. I have not yet
seen one proof that some action at a distance are at play in quantum
mechanics, although I agree that would be the case if the outcome
where unique, as EPER/BELL show convincingly.
Aspect experience was a shock for many, because they find action at a
distance astonishing, but are unaware of the many-worlds, or just want
to dismiss it directly as pure science fiction. But after Aspect, the
choice is really between deterministic and local QM + many worlds, or
one world and 3p indeterminacy and non locality. Like Maudlin said,
choose your poison.
Bruno
Bruce
--
You received this message because you are subscribed to the Google
Groups "Everything List" group.
To unsubscribe from this group and stop receiving emails from it,
send an email to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
http://iridia.ulb.ac.be/~marchal/
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
