On 05 Jun 2017, at 19:09, David Nyman wrote:
On 5 June 2017 at 17:38, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 05 Jun 2017, at 15:48, David Nyman wrote:
On 5 June 2017 at 14:22, Bruno Marchal <marc...@ulb.ac.be> wrote:
On 04 Jun 2017, at 14:48, David Nyman wrote:
On 4 Jun 2017 1:05 p.m., "Bruno Marchal" <marc...@ulb.ac.be> wrote:
On 02 Jun 2017, at 03:01, Bruce Kellett wrote:
On 1/06/2017 10:19 pm, Bruno Marchal wrote:
On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:
On 31 May 2017, at 04:01, Bruce Kellett wrote:
On 30/05/2017 9:35 pm, Bruno Marchal wrote:
On 30 May 2017, at 11:28, Telmo Menezes wrote:
snip
Your claim appears to be that Bell's theorem is not valid in MWI.
Bell's theorem is valid. His inequality does not even assume QM,
but just locality. It is violate when we do the experience, like
Aspect, and this shows non-locality in our branch, but when
looking at the big picture, we see that this non-locality has a
local origin. It would need an action at a distance to destroy the
alternante branches alwailable to Bob, but without collapse, non-
locality is a local, branch-owned, phenomenon. I take Bells
theorem + Aspect as a quasi definite proof that if there is one
universe, then there are many universes.
This is nonsense. Bell's theorem is a theorem of quantum
mechanics, and it is therefore valid in all interpretations of
that theory.
Yes, in all interpretation of quantum mechanics, the relevant
branches violate the inequality, but they do that without
involving an action at a distance when we look at the entire wave.
It is phenomenological.
Suppose one were to enquire what makes those branches "relevant".
One answer is that other pairings would be in conflict both with
the predictions of QM and with observation, but that is circular.
What then? Perhaps one might speculate that other pairings would
somehow be fundamentally inconsistent with any physics that would
permit its own coherent (or for that matter decoherent) observation.
The branches are just the superposed states, and with singlet or
with simple qubit, the other branches are just the other term of
the superposition which describes ourselves. To get rid of such
superposition, we need to get rid of quantum mechanics, *and* of
mechanism.
I'm not sure I made myself clear. What I meant by "other
pairings" was the ones we never expect to witness - e.g. the ones
that presumably might not violate Bell's inequalities.
OK. You mean this in the context of assuming quantum mechanics. If
we say that we don't see them because QM disallows them, or because
things just aren't that way, that is circular.
I am not sure I understand this. If we assume QM, it is standard.
Unlike Mechanism, somehow QM solves the measure problem.
So is the idea then that all possible 'measurements that Alice and
Bob could possibly make are already 'paired', in terms of
superpositions, in the MWI view?
Yes. The MW view of the singlet state (up down + down up) is a multi-
relative states, or multiverse, where Alice is in front of any well
defined up' and Bob has the well paired corresponding down'. As there
is a continuum of angular values for up, it describes 2^aleph_0 pairs
of Alice and Bob, with maxiamlly correlated spin.
And then the question of which branch either of them is situated in,
and consequently which pairing they will be associated with, is
determined by the measurement subsequently performed (apparently
individually) by each of them?
Yes.
The amazing thing, eventually due to the trigonometric pythagorean
identity, that sin^2(theta) + cos^2(theta) = 1, + Born rules, makes
each branch violates the Bell's inequality, but there is no non local
influence that I can see, it is apparent because we abstract from all
Alice and Bob, and possible third parties involved.
Here I found a not too bad paper on this subtle subject:
https://arxiv.org/pdf/0902.3827.pdf
He do the calculus that different people have done sometimes. I mainly
agree with it, but read it quickly.
ISTM that saying it's "just the other term of the superposition
which describes ourselves" is equally circular. What about
superpositions that don't "describe ourselves"?
With Copenhagen, all superposition don't describe the observers, and
we get standard QM with collapse. Then with Everett, we have an
explanation why, even without collapse, the average observer, when
doing a measurement, entangled itself and correlate his brain with
the outcome, and the proba are justify by the FPI. may be I still
miss something?
(here, by superposition which describes ourself, I meant only
something like (me -- cat alive + me -- cat dead).
So my question was about whether there is a non-circular answer to
the question of why we don't expect observations by Alice and Bob
to lead to the correlation of such 'malformed' pairs. Perhaps
because such correlation might entail a 'physics' that precluded
the act of observation itself.
I am not sure what you are asking. If we suppose QM, the reason why
the "malformed pair" are not seen is that QM disallow them, or makes
them very rare.
If we don't suppose QM, like when assuming mechanism, we have to
derive QM, or the correct theory in case QM is incorrect, to answer
this.
But the context here was the question "does the abandon of the
collapse prevents influence at a distance". Bruce claims it does
not, and me (but here there are many others, even on this list)
claims it does, or at the least, that we cannot use the Bell
violation to claim MWI is not local. In that thread we fully assume
QM (without collapse).
I think I follow. Wallace, in The Emergent Multiverse which I am
slowly reading, claims that MWI implies non-locality but not action
at a distance.
It is slightly ambiguous What does he means by non locality. In this
discussion, Bruce and me do agree that even in a mono-universe, the
non-locality cannot be used to transmit information at distance.
The question is about a possible real unibranche physical influence at
a distance remaining in the MWI.
I claim that with the MW, this vanishes completely, and that it is
almost trivial because there is no collapse ever, and you see that the
measurement results just get contagious, in the respective proportion
allowed statistically by the "Born rule". I think we agree (you and
me) agree on this, palusibly that is what Wallace thinks.
It is tricky, because sometimes non-locality means influence at a
distance, and sometimes means only violation of Bell's inequality. MWI
predict the violation of Bell's inequality (indeed it is often
criticzed for making the same prediction than the collpase theory) but
in doing so it avoids any physical influence at a distance. But Bruce
and John Clark seems to differ on this.
The non-local information encoding entanglement, in this view, is
part of the overall state discoverable upon 'measurement' but is
never propagated at more than light speed.
Yes. I think so.
This might ultimately be related to the speculation that the
appearance of spacetime itself may emerge as a consequence of
entanglement.
Possibly, although you might elaborate a little bit.
Well, my (admittedly vague) speculation was that the
'entanglements' we never expect to observe might be 'malformed'
in some way that precluded the emergence of a spacetime within
which such observation could occur.
It is a bit vague indeed. I think our allusion between space and
entanglement is related to some approach trying to derive the space-
time-gravity structure of the physical universe from the quantum
entanglement. I am far away to be familiar with this. It would be
nice, notably to simplify the future (very future) extraction of
General Relativity from the "material hypostases".
A summary is given in this paper:
http://www.nature.com/news/the-quantum-source-of-space-time-1.18797
Thanks.
Good evening,
Bruno
David
Bruno
I certainly like the idea that space emerge from entanglement.
There are some relation between "entanglement" in knot theory, and
the quantum entanglement, notably suggested by some work by Louis
Kauffman, but that too needs some elaboration. I expect that the
emergence of space in Mechanism will comes from a more primitive
notion of entanglement, but for this we need to derive the tensor
product, and that is not easy at all, and requires solution of open
problems related to the semantics of the "material hypostases".
Bruno
David
If it is not valid in MWI, then Many-Worlds is a different theory,
and not just an interpretation of standard QM.
It is valid in the MWI, but interpreted differently than in a mono-
universe interpretation which requires non local action at a
distance to get the same non-locality.
(with or without hidden variables).
As on the previous occasion we discussed this, you were unable to
demonstrate where the notion of 'collapse' is used in Bell's
theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as
in any other interpretation.
We did eventually agree. May be reread those post. Bell's supposed
that when the two measurement are done, Alice and Bob get a
precise answer, which makes no sense without-collapse.
That is what making a measurement means. It is what happens in all
interpretations. It makes no sense to deny counterfactual
definiteness -- that is not QM.
It is QM without collapse, and using the simple mechanist FPI.
Alice and Bob get *all* (always correlated) answers, but when
light-separated, it make no sense to compare them. They can only
make comparison with the person accessible in their light cone,
where the contagious superposition spread out.
I presume you mean "space-like separated". Alice and Bob do their
measurements;
The infinities of Alices and Bobs do their measurements.
they get their results and write them in their lab books. They
meet years later and compare lab books. Are you trying to suggest
that they do not have definite answers in their lab books before
then?
The infinities of Alices and Bobs get their infinities of definite
results.
In MWI (with two-outcome experiments), there is a copy of Alice
that writes '+' in her lab book, and a copy who writes '-' (for a
given orientation theta). Similarly for Bob. There are, therefore,
only four possibilities when they meet: '++', '+-', '--', and '-
+'. The non-locality is necessary to set the probabilities for
each of these four possible combinations of results. If you want
to eliminate the non-locality, you have to give a non-magical way
of establishing the necessary probabilities. You have never been
able to do this.
QM does that, and without collapse, I don't see how any influence
leaking at the speed of light need to be introduced.
Remember that in a sequence of such experiments, the probabilities
for '+' and '-' are 50/50 for both Alice and Bob.
OK.
The joint probabilities, or correlations, depend on the relative
orientations of their polarizers.
Right.
It is information about this relative orientation that must be
conveyed non-locally for the correlations to come out correctly
when they meet.
Why? That would be the case if you think that it is the same Bob
and Alice all along the experiences, but that cannot be the case.
It is not sufficient for them simply to exchange this information
later, because their results at particular orientations are
already fixed when they meet.
I don't see this. If the angle is some theta different from 0° or
90° they will both split/differentiate, and whoever they will meet
later will be the correspond partner with the correct correlation,
obtained by the decoherence local to their respective branch. In
this case, it is clear that it does not make sense to attribute to
"Alice and Bob" the same identity than the initial one.
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com
.
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com
.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
--
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com
.
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-
l...@googlegroups.com.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
--
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-
l...@googlegroups.com.
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
--
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
