subject:"Non\-locality and MWI"

Re: Non-locality and MWI

2016-05-12 Thread smitra


On 11-05-2016 22:31, John Mikes wrote:

BruceK and Smitra,
my apologies for being obsolete and uninformed, I learned math & phsx
in the very early 40s (19- that is) and did not need to refresh in my
1/2 c. of a successful R activity in specialty polymers. Since then
(1987), however, I became an agnostic.
What reverberates now is that Everett called MWI a bunch of IDENTICAL
universes. In my agnostic view "MY" MWI consists of possibly no two
identical universes, ours being one pretty simpleminded system - we
know it only from the inside. We have no access to the others.


I actually believe that the MWI is only an effective theory, an 
approximation to a multiverse of algorithms.It could be Bruno's theory 
or something else.


Saibal

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Re: Non-locality and MWI (literature)

2016-05-12 Thread smitra


On 12-05-2016 08:14, Bruce Kellett wrote:

The proof of non-locality, even in a many worlds model, is immediate.
Since the sequence under consideration comes from a series of quantum
events it must violate the Bell inequalities. And Bell has shown that
these inequalities must hold for any local theory. Hence quantum
mechanics, even in the many worlds interpretation, is non-local.


Bell showed that any local hidden variable explanation that would do 
away with  the randomness in quantum mechanics is ruled out. This has no 
bearing on the MWI, or just plain QM, as the randomness remains.


In the MWI the branches that effectively appear due to decoherence do 
not contain well defined hidden variables. Suppose e.g. that I measure 
the z-component if a spin that was initially polarized in the 
y-direction. The two branches where I find the two different outcomes 
can be evolved back in time, so you can write some state before I did 
the measurement as a superposition of these two states. But these states 
are not effective branches where I would get localized in before the 
measurement.


So, Bells's theorem rules out that you can use inverse time evolution, 
and project out the definite future outcomes and construct a local 
hidden variable theory this way.


Saibal

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Re: R: Re: Non-locality and MWI

2016-05-12 Thread Stathis Papaioannou

On 10 May 2016 at 02:50, Brent Meeker  wrote:

>
>
> On 5/9/2016 12:52 AM, 'scerir' via Everything List wrote:
>
> Saibal Mitra:
>
>
> And this is the core of the disagreement, you say that the results are
> already there, but in the MWI this is false. In the MWI the cat is not
> either dead or alive before you open the box, the superposition has
> become entangled with the environment, but both branches are relevant
> until you get to know the result.
>
> It seems (to me) interesting this quote from Nicolas Gisin "Against Many-
> Worlds",
> ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time?
> Nonlocality, free will and "no many-worlds" '
> http://arxiv.org/pdf/1011.3440.pdf
>
> "On the contrary, I do not see any explanatory power in the many worlds: it
> seems
> to be made just to prevent one from asking (possibly provocative) questions.
> Moreover, it has built in it the impossibility of any test: all its
> predictions are identical
> to those of quantum theory. For me, it looks like "cushion for laziness"
> (un coussin de paresse in French).
>
>
> It avoids the otherwise puzzling question of, "When does the wave function
> collapse?  Why is a measurement different from other physical
> interactions?"  QBism provides one answer, but at the cost of losing a kind
> of absolute objectivity.  Other solutions, like Bohm and GRW, postulate
> truly different physics that produce collapse.
>
> And there is a second, decisive, reason to
> reject
> the many-worlds view: it leaves no space for free will."
>
>
> That's a silly reason.  Daniel Dennett, in his book *Elbow Room*,
> explains that even Laplacian determinism leaves us all the free will worth
> having.
>

Moreover, even if MWI did somehow destroy free will, causing some people
consternation as a result, that would have no bearing on its truth.



-- 
Stathis Papaioannou

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R: Re: Non-locality and MWI

2016-05-12 Thread 'scerir' via Everything List



BruceK and Smitra,my apologies for being obsolete and uninformed, I learned 
math  phsx in the very early 40s (19- that is) and did not need to refresh 
in my 1/2 c. of a successful RD activity in specialty polymers. Since then 
(1987), however, I became an agnostic. What reverberates now is that Everett 
called MWI a bunch of IDENTICAL universes. In my agnostic view "MY" MWI 
consists of possibly no two identical universes, ours being one pretty 
simpleminded system - we know it only from the inside. We have no access to the 
others. 
John Mikes Ph.D. (chem-phys-math 1948)
-
'The ‘many world interpretation seems to me an extravagant, andabove all an 
extravagantly vague, hypothesis. I could almostdismiss it as silly. And yet... 
It may have something distinctiveto say in connection to ‘Einstein Podolsky 
Rosen puzzle’, and itwould be worthwhile, I think, to formulate some precise 
versionof it to see if it really so. And the existence of all possibleworlds 
may make us more comfortable about existence of ourown world... which seems to 
be in some ways a highly improbableone." (John Bell, 1986)



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Re: Non-locality and MWI (literature)

2016-05-12 Thread Bruce Kellett


On 11/05/2016 11:37 pm, Bruno Marchal wrote:

On 10 May 2016, at 02:10, Bruce Kellett wrote:

Bell's original argument didn't mention collapse, and the argument 
that his theorem fails because he assumed definite outcomes from 
measurements is actually without substance: no such assumption is 
required by Bell.


Bell does not mention collapse, nor EPR, because it is the assumption 
by default.


Bell didn't mention collapse because his argument is valid whether or 
not you make this assumption (or the equivalent assumption of 
countertfactual determinism). Let me try and explain it in a different way.


We have Alice with her measurement apparatus where she can make a 
measurement x, say, and get result a. Similarly Bob can make a 
measurement y and get result b. The Bell of CHSH inequalities apply to 
the outcomes of experiments, so we calculate probabilities (expectation 
values) for a sequence of joint outcomes for Alice and Bob. Since we are 
dealing with correlations between outcomes, the data we are working with 
come only after Alice and Bob have met and exchanged information. Let us 
call the joint result of such a meeting in one world as (ab|xy) for 
results a and b given settings x and y, respectively.


If there are two possible outcomes for a and b, there are four such 
combinations in the superposition representing any run of the 
experiment. If, in order to estimate correlations, we do N runs of the 
experiment, there will be 4^N possible sequences of results for Alice 
and Bob, represented by:


  (ab|xy)_1, (ab|xy)_2, (ab|xy)_3,(ab|xy)_N,

where the subscripts indicating run number actually apply to all of 
a,b,x, and y; and a,b can each be + or -, giving the 4^N distinct 
sequences.  In the many worlds approach, all such sequences are realized 
in one world or another.


All we have to do now is choose a typical world, any world, and look at 
that particular sequence. The sequence consists of actual measurement 
results, pointer setting, or whatever. And they occur after Alice and 
Bob have met after each trial. So this is now just a sequence of results 
that could have been obtained in a run of N trials in the collapse 
model. There is absolutely no difference in the data sequences obtained 
from either model.


The Bell inequalities are obtained by calculating the expectation values 
for just such sequences:  where the sequence came from -- a collapse 
model or selection of one world from the universal wave function -- is 
irrelevant for Bell's calculation. So Bell did not make explicit an 
collapse assumption because no such assumption is needed for his derivation.


The proof of non-locality, even in a many worlds model, is immediate. 
Since the sequence under consideration comes from a series of quantum 
events it must violate the Bell inequalities. And Bell has shown that 
these inequalities must hold for any local theory. Hence quantum 
mechanics, even in the many worlds interpretation, is non-local.


Bruce

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Re: Non-locality and MWI

2016-05-11 Thread John Mikes

BruceK and Smitra,
my apologies for being obsolete and uninformed, I learned math & phsx in
the very early 40s (19- that is) and did not need to refresh in my 1/2 c.
of a successful R activity in specialty polymers. Since then (1987),
however, I became an agnostic.
What reverberates now is that Everett called MWI a bunch of IDENTICAL
universes. In my agnostic view "MY" MWI consists of possibly no two
identical universes, ours being one pretty simpleminded system - we know it
only from the inside. We have no access to the others.

John Mikes Ph.D. (chem-phys-math 1948)



On Tue, May 10, 2016 at 6:39 PM, Bruce Kellett 
wrote:

> On 11/05/2016 1:54 am, smitra wrote:
>
>> On 10-05-2016 06:04, Bruce Kellett wrote:
>>
>> Non-locality was not the issue with this example of the cat in the
>>> box. All I was seeking to establish was that the observer maybe on
>>> definite branches of the wave function (i.e., have been "split")
>>> without knowing about it. The wave function here is taken to be an
>>> objective description of the system, and the observer is part of the
>>> wave function. So the observer might well be on both the cat-dead and
>>> cat-alive branches, but be unaware of which. The cat is definitely
>>> dead on the cat-dead branch and alive on the cat-alive branch. So this
>>> is an objective fact of the evolved wave function, even thought the
>>> observer has no yet self-located. Opening the box then conveys
>>> information to the observer, but does not kill the cat, or cause the
>>> split in the wave function, or the observer. The duplicated persons
>>> may objectively be, one in Washington and one in Moscow, without being
>>> aware of which city (branch of the wave function) they are in. Opening
>>> the door and finding out conveys information, but does not transport
>>> the person to that city.
>>>
>>
>> Yes, but even in the case of the observer getting localized without he or
>> she consciously being aware of that, this localization effect will still be
>> due to local interaction with the branches in the region he/she is in. So
>> whether or not localization in a branch requires conscious awareness of the
>> differences between the two branches isn't relevant.
>>
>> This means that when Alice is on her way to meet with Bob, she won't be
>> localized inside Bob's branches corresponding to Bob having obtained
>> definite results with definite polarizer settings, at least until that time
>> she gets located inside the light cone emanating from the points at Bob's
>> location at the times when the relevant information about these facts were
>> created.
>>
>
> So what? The information is already present in the wave function-- nothing
> new is created when the light cones overlap.
>
> Bruce
>
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R: Re: R: Re: R: Re: Non-locality and MWI (literature)

2016-05-11 Thread 'scerir' via Everything List


Following the above reasoning MWI (if it is a truly deterministic theory) 
should violate the locality condition.
I doubt this, but if you find a proof, in the literature (or not), I am 
interested. As I explained, and also give references, it seems to me that the 
MWI restores both 3p determinacy and 3p locality, making both the indeterminacy 
and non-locality only first person plural phenomenological happening. That is 
also Everett's position, and I would say the position of most Everettian (I 
still don't find any Everettian claiming that the MWI remains non-local, except 
the beginners who often think at first that the entire universe split 
instantaneously, but this does not deserve to be commented as nobody believes 
in this anymore).
Bruno
 Jarrett, but also Shimony, and also Ghirardi, gave the proof that a 
*deterministic* QM (I should say a *deterministic and single-valued* QM) must 
violate the Locality Condition. I do not have references at hand, right now. 
I'll write down something as soon as possible.
 I did not re-read it, but a paper (about differences between 
non-separability, non-locality, determinism, etc.) could  be this one 
http://dropcanvas.com/#n9m72p90WEc54O (I hope the link works)



 


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R: Re: R: Re: R: Re: Non-locality and MWI (literature)

2016-05-11 Thread 'scerir' via Everything List

Bruce:

I came across the following brief statement by Goldstein et al:
Many-worlds and relational interpretations of quantum theory

[etc.]

# Adrian Kent writes: "Making scientific sense of Everett’s idea is difficult, 
as evidenced by the many and generally incompatible attempts to show how 
unitary quantum theory explains the appearance of
a quasiclassical world and the apparent validity of the Born rule and 
Copenhagen quantum theory, and evidenced also
by the problems with all of these attempts. There is still nothing close to a 
consensus on the
most promising way forward, even among many-worlds enthusiasts. This adds 
motivation for developing alternative
ways of formulating quantum theory that have the purported advantages of 
many-worlds ideas — realism,
and Lorentz invariance — but describe a single real world, so avoiding both the 
conceptual problems and the fantastic
nature of many-worlds ideas. Still, for many, the appeal of many-worlds ideas 
evidently persists."
in http://arxiv.org/abs/1408.1944 "Does it Make Sense to Speak of Self-Locating 
Uncertainty in the Universal Wave
Function?"

see also http://arxiv.org/abs/0905.0624

and http://arxiv.org/abs/gr-qc/9703089




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Re: Non-locality and MWI (literature)

2016-05-11 Thread Bruno Marchal

  
distance. But by defining a world by a structure closed for  
interaction, that becomes impossible, unless you abstract the  
"parallel terms" away.








But in the MWI, some work needs to be done (at least) to convince  
me. I don't even find a paper on the subject, only paper which  
shows that MWI is local (some more rigorous than other). Do you  
have a reference of a paper showing that Bell's inequality  
violation entails non locality in the MWI? I would like to take a  
look on it, if it exists.


I have not seen anything published along these lines. That does not  
mean that no such papers exist -- I have not really been keeping up  
with all the literature in recent years. But I do know that many  
remain unconvinced by the many worlds argument, and it is clear that  
Bell's theorem does not ultimately depend on any assumption of  
collapse, despite claims to the contrary.


May be write a paper yourself. If you are right, you are on something.  
I might reread Bell to show you the precise place where the collapse  
is used implicitly. Not to much time right now.






Many physicists just never think about the many-worlds, and use QM  
as an instrument prediction only, and get shwoekd by Bell's result,  
without ever pondering about the fact that all outcomes are  
realized. That is why many believes in locality, they have just  
never study Everett.


Many physicists are instrumentalists at heart -- and who is to say  
that they are wrong?


Certainly not me, unless they forget instrumentalism at the pause- 
café, and make metaphysical statement which do not follow the theory.



They are interested in results, after all:  reality can look after  
itself!


Sure, but our conversation is not on practical thing, but on the  
nature of reality.


Bruno





Bruce

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http://iridia.ulb.ac.be/~marchal/



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Re: R: Re: R: Re: Non-locality and MWI (literature)

2016-05-11 Thread Bruce Kellett

On 11/05/2016 2:31 am, Bruno Marchal wrote:

On 10 May 2016, at 15:37, 'scerir' via Everything List wrote:

Following the above reasoning MWI (if it is a truly deterministic
theory)

should violate the locality condition.

I doubt this, but if you find a proof, in the literature (or not), I
am interested. As I explained, and also give references, it seems to
me that the MWI restores both 3p determinacy and 3p locality, making
both the indeterminacy and non-locality only first person plural
phenomenological happening. That is also Everett's position, and I
would say the position of most Everettian (I still don't find any
Everettian claiming that the MWI remains non-local, except the
beginners who often think at first that the entire universe split
instantaneously, but this does not deserve to be commented as nobody
believes in this anymore).

I came across the following brief statement by Goldstein et al:

*Many-worlds and relational interpretations of quantum theory**
*
Strictly speaking, there is yet another assumption, besides locality and
the "no conspiracy" condition that is necessary for the proof of Bell's
theorem: one has to assume that, after the experiment on one given side
is performed, its ±1-valued outcome is a well-defined element of
physical reality. (Recall that in Section 6, in order to apply Bell's
definition of locality to the type of experiment considered in Section
5, we assumed that the outcomes A1 and A2 were functions of the local
beables in regions 1 and 2, respectively.) Now one might wonder how
anyone could deny that assumption. After all, the outcome of the
experiment is recorded by the configuration of a macroscopic object
(say, a pointer position, ink on a piece of paper, etc.) that can be
directly inspected by a human experimenter. However, there exists one
fairly popular interpretation of quantum theory that does deny that one
has (after the experiments are concluded) a well-defined physically real
±1-valued outcome on each side: the many-worlds interpretation90. More
precisely, according to the many-worlds interpretation, both outcomes
are equally real on each side, so that it doesn't make sense to talk
about "the one ±1-valued outcome that actually occurs". Certain
"relational" interpretations of quantum theory91 also deny that a
completed experiment has a well-defined physically real outcome. It is
possible that this type of strategy could succeed in evading the
consequences of Bell's theorem, allowing for the possibility of a
universe governed by a local theory such that conscious observers living
in that universe attest to the validity of the quantum predictions.
However, it is not clear how to actually do the trick. There are many
difficulties and the subject is rather subtle. To begin with, there are
controversies around the problem of finding an appropriate formulation
of a many-worlds (or relational) interpretation. Moreover, it is not
clear whether such an appropriate formulation can be made local, given
that the wave function — which seems to be all there is in standard
formulations of many-worlds theories — is not a localized object; in the
terminology of Bell, it is not a local beable. (Indeed, if a theory has
no local beables, it is certainly not meaningful to ask whether it is
local or not in the relevant sense.) A formulation of a version of the
many-worlds interpretation which includes, in addition to the wave
function, some local beables, was presented in a recent paper92, but it
was found by the authors to be non-local. The question of whether a
many-worlds (or relational) approach can be taken advantage of to create
a local (and empirically viable) theory thus remains open — as does the
question of how seriously one should take a theory of this type, should
it be successfully constructed.

http://www.scholarpedia.org/article/Bell%27s_theorem#Manyworlds_and_relational_interpretations_of_quantum_theory

This Scholarpedia article (*6*, 8378) is available on-line and has many
additional references.

Bruce

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