Branching on real-world decisions

[Bruce Kellett]

I have been reading Sean Carroll's book "Something Deeply Hidden". It is
more reasonable than some of the commentary had led me to believe. The
issue at the moment is whether or not all things happen in the quantum
multiverse. I argued that just because I might turn left at some point,
it does not follow from Many-Worlds QM that in some other world I turn
right.

Carroll agrees with this, despite some reports to the contrary. On page
214 he says "No, you do not cause the wave function to branch by making
a decision.... Branching is the result of a microscopic process
amplified to macroscopic scales: a system in a quantum superposition
becomes entangled with the environment, leading to decoherence. A
decision, on the other hand, is a purely macroscopic phenomenon. There
are no decisions being made by the electrons and atoms inside your
brain; they're just obeying the laws of physics."

So there is not a coy of me in some other branch that is typing a
completely different email at this moment.....

Carroll also says sensible things about quantum suicide and other moral
issues.

I was, as Brent also reported, a little surprised by his argument that
it didn't really matter whether you thought of the splitting of the wave
function/universe on a decohered quantum event as spreading at light
speed, or as instantaneous throughout the entire universe. (pp.
170-171). I think this reflects the fact that Carroll does not seem to
be as opposed to the idea of non-locality as are other advocates of many
worlds. However, he does seem to think that the fact that outcomes of
experiments are not unique in many-worlds does deflect the impact of
Bell's theorem in that theory. "That doesn't mean that Bell's theorem is
wrong in Many-Worlds; mathematical theorems are unambiguously right. It
just means that the theorem doesn't apply. Bell's result does not imply
that we have to include spooky action at a distance in Everettian
quantum mechanics, as it does  for boring old single-world theories. The
correlations don't come about because of any kind of influence being
transmitted faster than light, but because of branching of the wave
function into different worlds, in which correlated things happen." (p. 105)

I think this is wrong, of course. The trouble with this argument is that
deflecting Bell's theorem does not automatically mean that your theory
is, in fact, local. And, as is usual for many-worlders, Carroll does not
go on the actually spell out how the magic of world branching actually
gives rise to the observed correlations. (He can't, of course, and that
is why the issue is glossed over.) Maudlin, on the other hand, is so
pissed off with people thinking that they can subvert Bell's theorem,
that he simply states baldly that the quantum mechanical wave function
is intrinsically non-local (Philosophy of Quantum Theory, 2019).

Bruce

[Philip Thrift]

Fundamentally, one can have a Many Worlds (a branching universe theory) if reality is information, which has been a trend among physicists for some time, e.g. Wheeler's "it from bit", now "it from qubit", but many others that talk about the universe being - at the fundamental level - information, or quantum information. (Related to the concept that reality is information is, perhaps more radically,  that reality is "mathematics".)

Under this view, 

   Many Words might be a completely coherent "formulation" of reality. 

But I think it is ultimately completely at odds with a strictly material (vs. informational) view of reality: the  "real" materialism of Galen Strawson (the common concept of matter is wrong) for example, or "radical" materialism of David Chalmers.

So the mathematics won't tell you one way (Many Worlds) or the other (One World), but metaphysics will.

@philipthrift

[Bruno Marchal]

> On 22 Nov 2019, at 08:35, Bruce Kellett <bhke...@optusnet.com.au> wrote:
>
> I have been reading Sean Carroll's book "Something Deeply Hidden". It is more reasonable than some of the commentary had led me to believe. The issue at the moment is whether or not all things happen in the quantum multiverse. I argued that just because I might turn left at some point, it does not follow from Many-Worlds QM that in some other world I turn right.

Absolutely. That follows directly from the Schroedinger equation. That is why we take life instead of jumping out of the window! On the contrary the linearity and decoherence assures us that when we take a decision, we acts similarly in all universe, unless the decision use a quantum coin of course.



>
> Carroll agrees with this, despite some reports to the contrary. On page 214 he says "No, you do not cause the wave function to branch by making a decision.... Branching is the result of a microscopic process amplified to macroscopic scales: a system in a quantum superposition becomes entangled with the environment, leading to decoherence. A decision, on the other hand, is a purely macroscopic phenomenon. There are no decisions being made by the electrons and atoms inside your brain; they're just obeying the laws of physics.”



OK. Of course, we can branch if we desire to do so, like deciding to take the holiday in the North or in the south by untangling that decision with a quantum coin.

>
> So there is not a coy of me in some other branch that is typing a completely different email at this moment.....
>
> Carroll also says sensible things about quantum suicide and other moral issues.
>
> I was, as Brent also reported, a little surprised by his argument that it didn't really matter whether you thought of the splitting of the wave function/universe on a decohered quantum event as spreading at light speed, or as instantaneous throughout the entire universe. (pp. 170-171). I think this reflects the fact that Carroll does not seem to be as opposed to the idea of non-locality as are other advocates of many worlds. However, he does seem to think that the fact that outcomes of experiments are not unique in many-worlds does deflect the impact of Bell's theorem in that theory. "That doesn't mean that Bell's theorem is wrong in Many-Worlds; mathematical theorems are unambiguously right. It just means that the theorem doesn't apply. Bell's result does not imply that we have to include spooky action at a distance in Everettian quantum mechanics, as it does for boring old single-world theories. The correlations don't come about because of any kind of influence being transmitted faster than light, but because of branching of the wave function into different worlds, in which correlated things happen." (p. 105)

I agree with Carroll. I guess you don’t ...

>
> I think this is wrong, of course.

… as you say.

> The trouble with this argument is that deflecting Bell's theorem does not automatically mean that your theory is, in fact, local.

I agree on this. But why would it be non local?

> And, as is usual for many-worlders, Carroll does not go on the actually spell out how the magic of world branching actually gives rise to the observed correlations. (He can't, of course, and that is why the issue is glossed over.) Maudlin, on the other hand, is so pissed off with people thinking that they can subvert Bell's theorem, that he simply states baldly that the quantum mechanical wave function is intrinsically non-local (Philosophy of Quantum Theory, 2019).

I will wait for a proof of this statement.

Bruno


>
> Bruce
>
> --
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[Bruce Kellett]

On Tue, Nov 26, 2019 at 1:31 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

> On 22 Nov 2019, at 08:35, Bruce Kellett <bhke...@optusnet.com.au> wrote:
>
> I have been reading Sean Carroll's book "Something Deeply Hidden". It is more reasonable than some of the commentary had led me to believe. The issue at the moment is whether or not all things happen in the quantum multiverse. I argued that just because I might turn left at some point, it does not follow from Many-Worlds QM that in some other world I turn right.

Absolutely. That follows directly from the Schroedinger equation. That is why we take life instead of jumping out of the window! On the contrary the linearity and decoherence assures us that when we take a decision, we acts similarly in all universe, unless the decision use a quantum coin of course.


> Carroll agrees with this, despite some reports to the contrary. On page 214 he says "No, you do not cause the wave function to branch by making a decision.... Branching is the result of a microscopic process amplified to macroscopic scales: a system in a quantum superposition becomes entangled with the environment, leading to decoherence. A decision, on the other hand, is a purely macroscopic phenomenon. There are no decisions being made by the electrons and atoms inside your brain; they're just obeying the laws of physics.”

OK.  Of course, we can branch if we desire to do so, like deciding to take the holiday in the North or in the south by untangling that decision with a quantum coin.

>
> So there is not a coy of me in some other branch that is typing a completely different email at this moment.....
>
> Carroll also says sensible things about quantum suicide and other moral issues.
>
> I was, as Brent also reported, a little surprised by his argument that it didn't really matter whether you thought of the splitting of the wave function/universe on a decohered quantum event as spreading at light speed, or as instantaneous throughout the entire universe. (pp. 170-171). I think this reflects the fact that Carroll does not seem to be as opposed to the idea of non-locality as are other advocates of many worlds. However, he does seem to think that the fact that outcomes of experiments are not unique in many-worlds does deflect the impact of Bell's theorem in that theory. "That doesn't mean that Bell's theorem is wrong in Many-Worlds; mathematical theorems are unambiguously right. It just means that the theorem doesn't apply. Bell's result does not imply that we have to include spooky action at a distance in Everettian quantum mechanics, as it does  for boring old single-world theories. The correlations don't come about because of any kind of influence being transmitted faster than light, but because of branching of the wave function into different worlds, in which correlated things happen." (p. 105)

I agree with Carroll. I guess you don’t ...

No, as I say. One problem is that his stance on decoherence spreading instantaneously is at variance with his rejection of Bell non-locality.  Actually, Carroll's ambivalence towards non-locality is even more evident in the latter part of his book, where he attempts to find space-time emerging from entanglement. He has to acknowledge that entanglement is intrinsically non-local, in that it mixes the wave function at one point with that at another. And the points that are entangled act as a unit, even though widely separated -- with no intervening physical processes.

On page 233, he distinguishes between two senses of "locality": what we might call 'measurement locality' and 'dynamical locality'. The EPR thought experiment shows that there is something that seems non-local about quantum measurement. ... Whether many-worlds is non-local in this sense depends on how we choose to define our branches of the wave function: we're allowed to make either local or non-local choices, where branching happens only nearby or immediately throughout space.

  Dynamical locality, on the other hand, refers to the smooth evolution of the quantum state when no measurement or branching is happening....This kind of locality is enforced by the rule in special relativity that nothing can travel faster than light. And it's this dynamical locality that we're concerned with at the moment as we study the nature and emergence of space itself." (p. 233)

I think this whole section is rather confused and this is little more than sophistry. Sean is trying to cover up what is really a glaring inconsistency in his approach. Maybe more work will enable one to make a bit more sense of this......

>
> I think this is wrong, of course.

… as you say.



> The trouble with this argument is that deflecting Bell's theorem does not automatically mean that your theory is, in fact, local.

I agree on this. But why would it be non local?

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

> And, as is usual for many-worlders, Carroll does not go on the actually spell out how the magic of world branching actually gives rise to the observed correlations. (He can't, of course, and that is why the issue is glossed over.) Maudlin, on the other hand, is so pissed off with people thinking that they can subvert Bell's theorem, that he simply states baldly that the quantum mechanical wave function is intrinsically non-local (Philosophy of Quantum Theory, 2019).

I will wait for a proof of this statement.

I suggest you read Maudlin's new book, or even the second edition (2011) of his earlier book on Quantum Non-Locality and Relativity. As I have often said, the singlet state of two entangled spin-half particles is intrinsically non-local because it is a single quantum state that refers to two distinct spatial locations. This is true for any entangled state -- it refers to two or more spatial locations simultaneously, which is the definition of non-local.

Bruce

[Lawrence Crowell]

On Friday, November 22, 2019 at 1:36:05 AM UTC-6, Bruce wrote:

Whether there is a splitting of the observer with the various possible outcomes of a quantum state observed depends upon whether QM is ultimately all there is. This is really an open question. Physics has quantum mechanics that is an L^2 system, with norm determined by the square of amplitudes that determine probabilities. Non-quantum mechanical stochastic systems are L^1 systems. Here I am thinking of macroscopic systems that have pure stochastic  measures. For convex systems or hull with an L^p measure there is a dual L^q system such that 1/p + 1/q = 1. For quantum physics there is a dual system, it is general relativity with its pseudo-Euclidean distance. For my purely stochastic system the dual system is an L^∞ system, which is a deterministic physics such as classical mechanics of Newton, Lagrange and Hamilton. There is a fair amount of mathematics behind this, which I will avoid now, but think of the L^∞ system where there are no distributions fundamental to the theory. Classical physics and any deterministic system, say a Turing machine, is not about some distribution over a system state. The classical stochastic system is just a sum of probabilities, so there is no trouble with seeing that as L^1. The duality between quantum physics and spacetime physics is very suggestive of some deep physics.. 

In this perspective a quantum measurement is then where there is a shifting of the system from p = ½ to p = 1, thinking of a classical-like probability system after decoherence, or with the einselection this flips to  an L^∞ system as a state selection closest to the classical or greatest expectation value. I read last May on how experiments were performed to detect how a system was starting to quantum tunnel. This might be some signature of how this flipping starts. It is still not clear how this flipping can be made into a dynamical principle.

With coherent states there may be some bridge. Coherent states have a remarkable property of having a representation in both momentum and position. Think of a state as determined by each coordinate point on the stretched horizon as a coherent state with 

ψ(x;q, p) = (x|q, p) = e^{-ipq/2 + ipx - (x - q)^2/2}} 

for x the Gaussian center of the q coordinate. The overlap of this state is then

(q', p'\q, p) = e^{i(qp - q'p')/2} e^{(q - q')^2 + (p - p')^2}

where the first term is the value of a symplectic form and the second is a Riemannian distance. So we could see the states on a stretched horizon as in a coherent condensate, which is a form of entanglement. These quantum states are in effect are nonabelian anyonic states. The nonabelian group is SU(1,1), which is a reduced Lorentz group. Then classical reality is then a sort of condensate effect. This is what interests me with quantum gravity and how the classical theory of gravitation can have nonlinearities, which are not permitted in QM. 

Whether this implies MWI or not, at least MWI as “quantum all the way” so worlds entirely split is not clear. There is a struggle here I think between locality and nonlocality, where with the Bohr or CI there is more of a clear localization of a quantum state in a measurement, but at a cost to QM. With MWI there is a nonlocality to how a wave function splits, or an observer is “frame dragged” along one path in the Fubini-Study metric, but an ambiguity to what is meant by probability at a time of measurement, for there is no real locality of such. 

LC

 

[Philip Thrift]

Yhis is why stochastic spacetime (with stochastic quantum mechanics) seems like the right mixture.

https://groups.google.com/d/msg/everything-list/pyP_Qbcvhyc/T1dKT203BwAJ

https://groups.google.com/d/msg/everything-list/QtkPAqMpIL0/9xQNmvDhBgAJ

@philipthrift

[Bruno Marchal]

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

On Tue, Nov 26, 2019 at 1:31 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

> On 22 Nov 2019, at 08:35, Bruce Kellett <bhke...@optusnet.com.au> wrote:
>
> I have been reading Sean Carroll's book "Something Deeply Hidden". It is more reasonable than some of the commentary had led me to believe. The issue at the moment is whether or not all things happen in the quantum multiverse. I argued that just because I might turn left at some point, it does not follow from Many-Worlds QM that in some other world I turn right.

Absolutely. That follows directly from the Schroedinger equation. That is why we take life instead of jumping out of the window! On the contrary the linearity and decoherence assures us that when we take a decision, we acts similarly in all universe, unless the decision use a quantum coin of course.


> Carroll agrees with this, despite some reports to the contrary. On page 214 he says "No, you do not cause the wave function to branch by making a decision.... Branching is the result of a microscopic process amplified to macroscopic scales: a system in a quantum superposition becomes entangled with the environment, leading to decoherence. A decision, on the other hand, is a purely macroscopic phenomenon. There are no decisions being made by the electrons and atoms inside your brain; they're just obeying the laws of physics.”

OK.  Of course, we can branch if we desire to do so, like deciding to take the holiday in the North or in the south by untangling that decision with a quantum coin.

>
> So there is not a coy of me in some other branch that is typing a completely different email at this moment.....
>
> Carroll also says sensible things about quantum suicide and other moral issues.
>
> I was, as Brent also reported, a little surprised by his argument that it didn't really matter whether you thought of the splitting of the wave function/universe on a decohered quantum event as spreading at light speed, or as instantaneous throughout the entire universe. (pp. 170-171). I think this reflects the fact that Carroll does not seem to be as opposed to the idea of non-locality as are other advocates of many worlds. However, he does seem to think that the fact that outcomes of experiments are not unique in many-worlds does deflect the impact of Bell's theorem in that theory. "That doesn't mean that Bell's theorem is wrong in Many-Worlds; mathematical theorems are unambiguously right. It just means that the theorem doesn't apply. Bell's result does not imply that we have to include spooky action at a distance in Everettian quantum mechanics, as it does  for boring old single-world theories. The correlations don't come about because of any kind of influence being transmitted faster than light, but because of branching of the wave function into different worlds, in which correlated things happen." (p. 105)

I agree with Carroll. I guess you don’t ...

No, as I say. One problem is that his stance on decoherence spreading instantaneously is at variance with his rejection of Bell non-locality. 

Yes, that is weird.

Actually, Carroll's ambivalence towards non-locality is even more evident in the latter part of his book, where he attempts to find space-time emerging from entanglement. He has to acknowledge that entanglement is intrinsically non-local, in that it mixes the wave function at one point with that at another. And the points that are entangled act as a unit, even though widely separated -- with no intervening physical processes.

On page 233, he distinguishes between two senses of "locality": what we might call 'measurement locality' and 'dynamical locality'. The EPR thought experiment shows that there is something that seems non-local about quantum measurement. ... Whether many-worlds is non-local in this sense depends on how we choose to define our branches of the wave function: we're allowed to make either local or non-local choices, where branching happens only nearby or immediately throughout space.

  Dynamical locality, on the other hand, refers to the smooth evolution of the quantum state when no measurement or branching is happening....This kind of locality is enforced by the rule in special relativity that nothing can travel faster than light. And it's this dynamical locality that we're concerned with at the moment as we study the nature and emergence of space itself." (p. 233)

I think this whole section is rather confused and this is little more than sophistry. Sean is trying to cover up what is really a glaring inconsistency in his approach. Maybe more work will enable one to make a bit more sense of this……

Let us hope. I still don’t see any FTL influence in the MWI, as I conceive it, but I know we do differ on how to interpret the wave. More on this later perhaps. 

>
> I think this is wrong, of course.

… as you say.



> The trouble with this argument is that deflecting Bell's theorem does not automatically mean that your theory is, in fact, local.

I agree on this. But why would it be non local?

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”. In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality. 

> And, as is usual for many-worlders, Carroll does not go on the actually spell out how the magic of world branching actually gives rise to the observed correlations. (He can't, of course, and that is why the issue is glossed over.) Maudlin, on the other hand, is so pissed off with people thinking that they can subvert Bell's theorem, that he simply states baldly that the quantum mechanical wave function is intrinsically non-local (Philosophy of Quantum Theory, 2019).

I will wait for a proof of this statement.

I suggest you read Maudlin's new book, or even the second edition (2011) of his earlier book on Quantum Non-Locality and Relativity. As I have often said, the singlet state of two entangled spin-half particles is intrinsically non-local because it is a single quantum state that refers to two distinct spatial locations. This is true for any entangled state -- it refers to two or more spatial locations simultaneously, which is the definition of non-local.

Then we might agree, if you agree that this does not entail any FTL actions.

Bruno

Bruce

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[Bruce Kellett]

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place. Some attempt has been made to replace the term "non-local" with the term "non-seperable". I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle. I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

Bruce

[Bruno Marchal]

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place.

Then even Newton Universe is non local. 

Some attempt has been made to replace the term "non-local" with the term "non-seperable”.

Yes, notably d’Espagnat. It avoids the confusion with the Eisnsteinian non-locality, which requires FTL (cf the “spooky action at a distance”), which must exist in QM + the assumption of a unique universe.

I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle.

Yes, we agree on this.

I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

I invite you, and Alice, and I give you an envelop to each of you. You are told that one contain a piece of paper with O inscribed on it, and the other with one. Then you go in different galaxies, say, and open it. Once you see 0 (res. 1) you know that Alice will see 1 (res. 0). This seems non local in your sense, where most would agree that in this case, there is no “non-locality” issue. What I claim is that in the Everett theory, all non-locality are of that type.

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

That is right. But the violation of Bell’s inequality entails FTL only when one world is assumed, with well defined outcome for all measurement, or put in another way, assuming a unique reality, with one Bob and one Alice, but Bell’s reasoning does not prove FTL influence in The many-worlds, where all outcomes are obtained, and propagate between diverse Alice and Bob locally, leading to the apparent violation of Bell’s inequality, but without FTL.

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

Bruno

Bruce

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[Bruce Kellett]

On Fri, Nov 29, 2019 at 1:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place.

Then even Newton Universe is non local. 

Yes Newton was aware of this.

 

Some attempt has been made to replace the term "non-local" with the term "non-seperable”.

Yes, notably d’Espagnat. It avoids the confusion with the Eisnsteinian non-locality, which requires FTL (cf the “spooky action at a distance”), which must exist in QM + the assumption of a unique universe.

I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle.

Yes, we agree on this.

I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

I invite you, and Alice, and I give you an envelop to each of you. You are told that one contain a piece of paper with O inscribed on it, and the other with one. Then you go in different galaxies, say, and open it. Once you see 0 (res. 1) you know that Alice will see 1 (res. 0). This seems non local in your sense, where most would agree that in this case, there is no “non-locality” issue. What I claim is that in the Everett theory, all non-locality are of that type.

That non-loclality has a common cause explanation. Like Bertlmann's socks, there is no mystery here. The problem is with entangled systems, where non-separability means non-locality that has no common cause explanation, even in many-worlds theory.

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

That is right. But the violation of Bell’s inequality entails FTL only when one world is assumed, with well defined outcome for all measurement, or put in another way, assuming a unique reality, with one Bob and one Alice, but Bell’s reasoning does not prove FTL influence in The many-worlds, where all outcomes are obtained, and propagate between diverse Alice and Bob locally, leading to the apparent violation of Bell’s inequality, but without FTL.

Bell did not assume a collapse. His is a mathematical result, where the only assumption is locality. As usual, if you think there is a local explanation of the EPR correlations in many-worlds, then produce it.

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

No, there is no need of FTL. For example, in the third (2011) edition of his book 'Quantum Non-Locality and Relativity', Maudlin shows that Flash GRW theory, as developed by Temulka, gives a perfectly relativistic account of the EPR correlations without any FTL action.

Bruce

[Philip Thrift]

The GRW flash theory: a relativistic quantum ontology of matter in space-time?

https://arxiv.org/pdf/1310.5308.pdf

whenever there is a spontaneous localization of the wave-function in configuration space, that development of the wave-function in configuration space represents an event occurring in physical space, namely there being a flash centred around a space-time point. The flashes are all there is in space-time. That is to say, apart from when it spontaneously localizes, the  temporal development of the wave-function in configuration space does not represent the distribution of matter in physical space. It represents the objective probabilities for the occurrence of further flashes, given an initial configuration of flashes. As in BM, there hence are no superpositions of anything existing in physical space. However, by contrast to BM, GRWf does not admit a continuous distribution of matter: there are only flashes being

sparsely distributed in space-time, but no trajectories or worldlines of anything

Over and above the flashes being the primitive stuff in physical space, the initial configuration of flashes instantiates a dispositional property – more precisely a propensity – that fixes probabilities for the occurrence of further flashes. The occurrence of such further flashes is the manifestation of that propensity. The propensity of any given configuration of flashes to manifest itself in the occurrence of further flashes is represented by the wave-function. The GRW law supervenes on that propensity in the sense that whenever such a propensity is instantiated in a possible world, the GRW law holds in that world. By contrast to what is admitted by Humeanism, that disposition or propensity hence is a modal property.

...

In conclusion, one may go for an event ontology instead of a particle ontology. But the

flash ontology is too sparse an ontology: since it does not provide for anything like

continuous sequences of events, it does not have the means at its disposal to account for

interactions that are supposed to trigger the occurrence of further flashes (such as e.g.

measurements). In the end, therefore, it seems that the flash ontology hardly is a convincing

answer to the question of what quantum mechanics tells us about what there is in space-time.

@philipthrift 

[Philip Thrift]

On Thursday, November 28, 2019 at 8:27:28 AM UTC-6, Bruno Marchal wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

Bruno

(Some physicists and philosophers point out that "nonlocal" is ambiguous: nonlocal in space? or nonlocal in time?)

In programming (theoretic) there is a notion of nonlocality in programs in the logic programming paradigms, specifically in (for modeling physics)

     https://en.wikipedia.org/wiki/Concurrent_logic_programming

It's the logical variable.

When theoretical physicists begin using logical variables in their theory, then there might be a God after all.

@philipthrift

[Philip Thrift]

The semantics of concurrent logic programming is tricky. Some based on lineal logic or metric spaces.

https://en.wikipedia.org/wiki/Linear_logic

linear logic have been influential in fields such as programming languages, game semantics, and quantum physics (because linear logic can be seen as the logic of quantum information theory), as well as linguistics, particularly because of its emphasis on resource-boundedness, duality, and interaction

https://link.springer.com/chapter/10.1007/BFb0035860

https://www.researchgate.net/publication/221255421_Linear_Logic_Semantics_for_Concurrent_Prolog

https://www.sciencedirect.com/science/article/pii/030439759090060U

@philipthrift

 

[Bruce Kellett]

On Fri, Nov 29, 2019 at 7:15 PM Philip Thrift <cloud...@gmail.com> wrote:

On Thursday, November 28, 2019 at 5:50:18 PM UTC-6, Bruce wrote:

On Fri, Nov 29, 2019 at 1:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

No, there is no need of FTL. For example, in the third (2011) edition of his book 'Quantum Non-Locality and Relativity', Maudlin shows that Flash GRW theory, as developed by Tumulka, gives a perfectly relativistic account of the EPR correlations without any FTL action.

Bruce

The GRW flash theory: a relativistic quantum ontology of matter in space-time?

https://arxiv.org/pdf/1310.5308.pdf

whenever there is a spontaneous localization of the wave-function in configuration space, that development of the wave-function in configuration space represents an event occurring in physical space, namely there being a flash centred around a space-time point. The flashes are all there is in space-time. That is to say, apart from when it spontaneously localizes, the  temporal development of the wave-function in configuration space does not represent the distribution of matter in physical space. It represents the objective probabilities for the occurrence of further flashes, given an initial configuration of flashes. As in BM, there hence are no superpositions of anything existing in physical space. However, by contrast to BM, GRWf does not admit a continuous distribution of matter: there are only flashes being

sparsely distributed in space-time, but no trajectories or worldlines of anything

Over and above the flashes being the primitive stuff in physical space, the initial configuration of flashes instantiates a dispositional property – more precisely a propensity – that fixes probabilities for the occurrence of further flashes. The occurrence of such further flashes is the manifestation of that propensity. The propensity of any given configuration of flashes to manifest itself in the occurrence of further flashes is represented by the wave-function. The GRW law supervenes on that propensity in the sense that whenever such a propensity is instantiated in a possible world, the GRW law holds in that world. By contrast to what is admitted by Humeanism, that disposition or propensity hence is a modal property.

...

In conclusion, one may go for an event ontology instead of a particle ontology. But the

flash ontology is too sparse an ontology: since it does not provide for anything like

continuous sequences of events, it does not have the means at its disposal to account for

interactions that are supposed to trigger the occurrence of further flashes (such as e.g.

measurements). In the end, therefore, it seems that the flash ontology hardly is a convincing

answer to the question of what quantum mechanics tells us about what there is in space-time.

Which is not to say that there is anything clearly wrong with the GRW -flash idea: it is just that  Esfeld and Gisin do not like it much.

Bruce

[Bruno Marchal]

On 29 Nov 2019, at 00:50, Bruce Kellett <bhkel...@gmail.com> wrote:

On Fri, Nov 29, 2019 at 1:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place.

Then even Newton Universe is non local. 

Yes Newton was aware of this.

 

Some attempt has been made to replace the term "non-local" with the term "non-seperable”.

Yes, notably d’Espagnat. It avoids the confusion with the Eisnsteinian non-locality, which requires FTL (cf the “spooky action at a distance”), which must exist in QM + the assumption of a unique universe.

I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle.

Yes, we agree on this.

I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

I invite you, and Alice, and I give you an envelop to each of you. You are told that one contain a piece of paper with O inscribed on it, and the other with one. Then you go in different galaxies, say, and open it. Once you see 0 (res. 1) you know that Alice will see 1 (res. 0). This seems non local in your sense, where most would agree that in this case, there is no “non-locality” issue. What I claim is that in the Everett theory, all non-locality are of that type.

That non-loclality has a common cause explanation. Like Bertlmann's socks, there is no mystery here. The problem is with entangled systems, where non-separability means non-locality that has no common cause explanation, even in many-worlds theory.

I doubt this. The MWI reduces the non-separability of the probabilities into an equivalent with Bertlmann’s socks, still keeping the violation of Bell’s inequality justifying the appearance of non-locality. 

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

That is right. But the violation of Bell’s inequality entails FTL only when one world is assumed, with well defined outcome for all measurement, or put in another way, assuming a unique reality, with one Bob and one Alice, but Bell’s reasoning does not prove FTL influence in The many-worlds, where all outcomes are obtained, and propagate between diverse Alice and Bob locally, leading to the apparent violation of Bell’s inequality, but without FTL.

Bell did not assume a collapse. His is a mathematical result, where the only assumption is locality. As usual, if you think there is a local explanation of the EPR correlations in many-worlds, then produce it.

We differ only on the way we interpreted the wave and the worlds. The singlet state is … local! It does not entail any correlation between the Alices and the Bobs. It enforces only that the Alices and Bobs can meet only their corresponding correlated partners, among the infinitely many Alices and Bobs (most of them being not accessible from each others).

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

No, there is no need of FTL. For example, in the third (2011) edition of his book 'Quantum Non-Locality and Relativity', Maudlin shows that Flash GRW theory, as developed by Temulka, gives a perfectly relativistic account of the EPR correlations without any FTL action.

This astonishes me. If you have a link I could try to see if this makes sense, but, to be sure, I am not enthusiast at all on the GRW theory, which is new QM theory. If some measurement affects the rest of the Universe instantaneously, I think that imply FTL (without signals, but still with a physical influence). 

Bruno

Bruce

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[Bruce Kellett]

On Mon, Dec 2, 2019 at 8:08 PM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 29 Nov 2019, at 00:50, Bruce Kellett <bhkel...@gmail.com> wrote:

On Fri, Nov 29, 2019 at 1:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place.

Then even Newton Universe is non local. 

Yes Newton was aware of this.

 

Some attempt has been made to replace the term "non-local" with the term "non-seperable”.

Yes, notably d’Espagnat. It avoids the confusion with the Eisnsteinian non-locality, which requires FTL (cf the “spooky action at a distance”), which must exist in QM + the assumption of a unique universe.

I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle.

Yes, we agree on this.

I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

I invite you, and Alice, and I give you an envelop to each of you. You are told that one contain a piece of paper with O inscribed on it, and the other with one. Then you go in different galaxies, say, and open it. Once you see 0 (res. 1) you know that Alice will see 1 (res. 0). This seems non local in your sense, where most would agree that in this case, there is no “non-locality” issue. What I claim is that in the Everett theory, all non-locality are of that type.

That non-loclality has a common cause explanation. Like Bertlmann's socks, there is no mystery here. The problem is with entangled systems, where non-separability means non-locality that has no common cause explanation, even in many-worlds theory.

I doubt this. The MWI reduces the non-separability of the probabilities into an equivalent with Bertlmann’s socks, still keeping the violation of Bell’s inequality justifying the appearance of non-locality. 

The devil is in the detail. And you have still not provided any detail.

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

That is right. But the violation of Bell’s inequality entails FTL only when one world is assumed, with well defined outcome for all measurement, or put in another way, assuming a unique reality, with one Bob and one Alice, but Bell’s reasoning does not prove FTL influence in The many-worlds, where all outcomes are obtained, and propagate between diverse Alice and Bob locally, leading to the apparent violation of Bell’s inequality, but without FTL.

Bell did not assume a collapse. His is a mathematical result, where the only assumption is locality. As usual, if you think there is a local explanation of the EPR correlations in many-worlds, then produce it.

We differ only on the way we interpreted the wave and the worlds. The singlet state is … local! It does not entail any correlation between the Alices and the Bobs. It enforces only that the Alices and Bobs can meet only their corresponding correlated partners, among the infinitely many Alices and Bobs (most of them being not accessible from each others).

The singlet state is non-separable, and hence non-local when Alice and Bob are separated. The rest of you comment here is without meaning. You have to flesh it out, and your reluctance to do so convinces me that you cannot. You are just hoping for a miracle.

 

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

No, there is no need of FTL. For example, in the third (2011) edition of his book 'Quantum Non-Locality and Relativity', Maudlin shows that Flash GRW theory, as developed by Temulka, gives a perfectly relativistic account of the EPR correlations without any FTL action.

This astonishes me. If you have a link I could try to see if this makes sense, but, to be sure, I am not enthusiast at all on the GRW theory, which is new QM theory. If some measurement affects the rest of the Universe instantaneously, I think that imply FTL (without signals, but still with a physical influence). 

I only know this from Maudlin's books. There is a detailed account in his recent book, "Philosophy of Physics: Quantum Theory" (Princeton, 2019). The paper that Phil referenced: Esfeld and Gisin (arXiv:1310.5308) contains a summary and discussion, even though those authors are not convinced by the theory.

I must admit that Flash GRW is not an approach that I find convincing either. The ontology of this theory is the flashes themselves, the wave-function is not part of the ontology, so the collapse is entirely epistemic, and just like the "collapse" in classical probability theory. It works, but may not be convincing to everyone, since the ontology is remarkable thin!

The real problem is, as ever, that despite many promises, many-worlds theory does even less well in that it offers nothing in the way of an explanation. Maudlin's recent book discusses many worlds, but he concentrates on the problems with this idea, and essentially is not convinced that many-worlds makes sufficient sense in its own terms to provide an explanation for anything. Sean Carroll, in his recent book "Something Deeply Hidden", also evades the question. His discussion is on pages 104-105. He states that Bell assumed "that measurements have definite outcomes". Essentially, this is the assumption of counterfactual definiteness that has often been proposed. Carroll then says that since many-worlds does not assume that experiments have single outcomes, Bell's theorem doesn't apply. His unspoken assumption here is that if many-worlds evades Bell's result, then it can give a local account of the EPR correlations -- they happen "because of branching of the wave function into different worlds, in which correlated things happen." (p. 105) This is similar to your claim above, but it is not an explanation. And even if Bell's theorem doesn't apply, it does not follow that the theory can provide a local account of the correlations.You still have to provide that account.

The other major source I can refer to is the book "The Emergent Multiverse" by David Wallace (Oxford, 2012). This book is the most comprehensive account of Everettian ideas currently available. Wallace also ducks the issue. In sections 8.5-8.7 (pages 302-312) he gives a detailed account of the branching structure that arises if Alice and Bob do independent spin measurements at space-like separations. Then on page 310 he gives a general entangled wave-function and points out that Alice's and Bob's measurements again lead to splitting. But he then says: "In this case, the amplitudes of the four sets of branches into which C [a central, neutral observer] eventually branches are not determined simply by the separate weights of the branchings at A and B. Nor is this to be expected: as I stressed previously, in Everettian quantum mechanics interactions are local but states are nonlocal. The entanglement between the particle at A and the particle at B is a nonlocal property of the forward light cone of A and that of B. Only in their intersection can it have locally determinable effects---and it does, giving rise to the branch weights which, in turn, give rise to the sorts of statistical results recorded in Aspect's experiments."

This might sound good, but again, there is no detail. What exactly is supposed to happen at the intersection of the forward light cones from A and B? There is no interaction there -- any information that is made locally present there was already present in the only relevant interactions, which are the original measurements made by A and B; any branch weights that are around are set there, exactly as in the case of non-entangled particles. Wallace started out well, but ducked out at the last minute, and he failed to give any comprehensible account that does not rely on simple magic.

So the best authorities available fail to give a local account of the EPR correlations in a many-worlds setting -- they all simply duck the issue when the rubber hits the road. Just as you routinely do.

Bruce

[Brent Meeker]

I think that measurements have definite outcomes is just definiteness; and denying it is just indefiniteness.  Counterfactual definiteness is that unmeasured variables have definite values...something QM denies.

Carroll then says that since many-worlds does not assume that experiments have single outcomes, Bell's theorem doesn't apply. His unspoken assumption here is that if many-worlds evades Bell's result, then it can give a local account of the EPR correlations -- they happen "because of branching of the wave function into different worlds, in which correlated things happen." (p. 105) This is similar to your claim above, but it is not an explanation. And even if Bell's theorem doesn't apply, it does not follow that the theory can provide a local account of the correlations.You still have to provide that account.

In Carroll's "disappearing worlds" picture the problem is to explain why the worlds in which Alice and Bob can meet with the wrong value pairs are the ones that disappear.

The other major source I can refer to is the book "The Emergent Multiverse" by David Wallace (Oxford, 2012). This book is the most comprehensive account of Everettian ideas currently available. Wallace also ducks the issue. In sections 8.5-8.7 (pages 302-312) he gives a detailed account of the branching structure that arises if Alice and Bob do independent spin measurements at space-like separations. Then on page 310 he gives a general entangled wave-function and points out that Alice's and Bob's measurements again lead to splitting. But he then says: "In this case, the amplitudes of the four sets of branches into which C [a central, neutral observer] eventually branches are not determined simply by the separate weights of the branchings at A and B. Nor is this to be expected: as I stressed previously, in Everettian quantum mechanics interactions are local but states are nonlocal. The entanglement between the particle at A and the particle at B is a nonlocal property of the forward light cone of A and that of B. Only in their intersection can it have locally determinable effects---and it does, giving rise to the branch weights which, in turn, give rise to the sorts of statistical results recorded in Aspect's experiments."

This might sound good, but again, there is no detail. What exactly is supposed to happen at the intersection of the forward light cones from A and B?

Whatever it is, it must depend on the decoherence and Zurek's envariance implicit in the measurement.  This is what makes the off-diagonal terms of the reduced density matrix go to zero and, in a sense, make Carroll's disappearing worlds, disappear. 

Brent

There is no interaction there -- any information that is made locally present there was already present in the only relevant interactions, which are the original measurements made by A and B; any branch weights that are around are set there, exactly as in the case of non-entangled particles. Wallace started out well, but ducked out at the last minute, and he failed to give any comprehensible account that does not rely on simple magic.

So the best authorities available fail to give a local account of the EPR correlations in a many-worlds setting -- they all simply duck the issue when the rubber hits the road. Just as you routinely do.

Bruce

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[Philip Thrift]

On Monday, December 2, 2019 at 1:21:26 PM UTC-6, Brent wrote:

Counterfactual definiteness is that unmeasured variables have definite values...something QM denies.

Brent

 

What do you make of this regarding indefiniteness?

https://groups.google.com/d/msg/everything-list/xhE7ICd_HDs/LQslm0YFAQAJ

@philipthrift 

[Brent Meeker]

Thirty one years ago, Dick Feynman told me about his 'sum over
histories' version of quantum mechanics.  "The electron does anything it
likes', he said.  "It goes in any direction at any speed, forward or
backward in time, however it likes, and then you add up all the
amplitudes and it gives you the wave-function."
I said to him, "You're crazy."  But he wasn't.
      --- Freeman J. Dyson, 'Some Strangeness in the Proportion' 1980

Brent

[Bruce Kellett]

Again, this lacks detail. In what way can decoherence after the measurement affect what happens at the intersection of the forward light cones. Decoherence is over in 10^{-20} sec, the light cones may not intersect until thousands of years later?  Decoherence, envariance, and the diagonalization of the density matrix are all associated with physical interactions occurring with the basic measurement interaction. Turning this into "disappearing worlds" at some later time is just fantasy stuff. Even if you could work such magic, it would still be non-local. The weights of the four branches at the intersection of the light cones (at C's position, to use Wallace's notation) are given exactly by the cos^2(theta/2) and sin^2(theta/2) terms that come from the form of the singlet wave function at the point of measurement by A and B. Nothing ever happens to change these original weights. Wallace's account of the branching and weights associated with independent measurements at A and B is exactly right. And exactly the same analysis applies to the case of entangled particles.

Prove me wrong by giving a coherent account that is different.

Bruce

[Bruno Marchal]

On 2 Dec 2019, at 12:06, Bruce Kellett <bhkel...@gmail.com> wrote:

On Mon, Dec 2, 2019 at 8:08 PM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 29 Nov 2019, at 00:50, Bruce Kellett <bhkel...@gmail.com> wrote:

On Fri, Nov 29, 2019 at 1:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 26 Nov 2019, at 22:39, Bruce Kellett <bhkel...@gmail.com> wrote:

On Wed, Nov 27, 2019 at 12:27 AM Bruno Marchal <mar...@ulb.ac.be> wrote:

On 25 Nov 2019, at 22:53, Bruce Kellett <bhkel...@gmail.com> wrote:

Because, the wave-function itself is non-local -- it contains entangled particles that are widely separated in space. That is the definition of non-locality!

I am not sure. I use “non-locality” for “FTL physical influence”.

That is just an abuse of language. Non-local means "not local", i.e., not all in one place.

Then even Newton Universe is non local. 

Yes Newton was aware of this.

 

Some attempt has been made to replace the term "non-local" with the term "non-seperable”.

Yes, notably d’Espagnat. It avoids the confusion with the Eisnsteinian non-locality, which requires FTL (cf the “spooky action at a distance”), which must exist in QM + the assumption of a unique universe.

I think we can all agree that the singlet wave function is non-separable -- it cannot be written as a simple product of two terms, one referring to each particle.

Yes, we agree on this.

I maintain that it is also non-local, in that the two particles are at different locations (locales). Non-local can have no other meaning in ordinary linguistic usage.

I invite you, and Alice, and I give you an envelop to each of you. You are told that one contain a piece of paper with O inscribed on it, and the other with one. Then you go in different galaxies, say, and open it. Once you see 0 (res. 1) you know that Alice will see 1 (res. 0). This seems non local in your sense, where most would agree that in this case, there is no “non-locality” issue. What I claim is that in the Everett theory, all non-locality are of that type.

That non-loclality has a common cause explanation. Like Bertlmann's socks, there is no mystery here. The problem is with entangled systems, where non-separability means non-locality that has no common cause explanation, even in many-worlds theory.

I doubt this. The MWI reduces the non-separability of the probabilities into an equivalent with Bertlmann’s socks, still keeping the violation of Bell’s inequality justifying the appearance of non-locality. 

The devil is in the detail. And you have still not provided any detail.

You are the one who seem to believe in some FTL physical action (not just the quantum inseparability), and that indeed follows clearly from the “one-world” assumption. Then with mechanism, we get 0 universes, but infinitely many relative histories, structured by self-reference. 

In the MWI, some particles can be entangled but without implying any possible FTL when we do measurement on them, except from the local point of view, due to our ignorance of all terms of the wave. It means simply that Alice and Bob belongs to the same branch of history/reality.

The trouble with this hope is that it no local account of the EPR correlations been realised in any coherent mathematics. Bell's theorem rules it out: no local hidden variable account of the EPR correlations is possible in any theory, whatsoever. It is a no-go theorem; it proves a negative -- something is impossible. Many-worlds does not subvert Bell's theorem.

That is right. But the violation of Bell’s inequality entails FTL only when one world is assumed, with well defined outcome for all measurement, or put in another way, assuming a unique reality, with one Bob and one Alice, but Bell’s reasoning does not prove FTL influence in The many-worlds, where all outcomes are obtained, and propagate between diverse Alice and Bob locally, leading to the apparent violation of Bell’s inequality, but without FTL.

Bell did not assume a collapse. His is a mathematical result, where the only assumption is locality. As usual, if you think there is a local explanation of the EPR correlations in many-worlds, then produce it.

We differ only on the way we interpreted the wave and the worlds. The singlet state is … local! It does not entail any correlation between the Alices and the Bobs. It enforces only that the Alices and Bobs can meet only their corresponding correlated partners, among the infinitely many Alices and Bobs (most of them being not accessible from each others).

The singlet state is non-separable, and hence non-local when Alice and Bob are separated.

I don’t know which difference you make between non-separable and non-local.

With "one world", both requires FTL actions, but not so with many histories, where a non separable state just means that we differentiate into multiples histories verifying some internal correlations. I agree with LC that eventually the entire notion of space will be explained by such (qubit) entanglements.

The rest of you comment here is without meaning.

Why?

You have to flesh it out, and your reluctance to do so convinces me that you cannot. You are just hoping for a miracle.

 

I think it is becoming generally accepted in the physics community that the entangled state is intrinsically non-local: acting on one part of it affects the rest, even across the entire universe.

That would mean some FTL actions, but I very much doubt this.

No, there is no need of FTL. For example, in the third (2011) edition of his book 'Quantum Non-Locality and Relativity', Maudlin shows that Flash GRW theory, as developed by Temulka, gives a perfectly relativistic account of the EPR correlations without any FTL action.

This astonishes me. If you have a link I could try to see if this makes sense, but, to be sure, I am not enthusiast at all on the GRW theory, which is new QM theory. If some measurement affects the rest of the Universe instantaneously, I think that imply FTL (without signals, but still with a physical influence). 

I only know this from Maudlin's books. There is a detailed account in his recent book, "Philosophy of Physics: Quantum Theory" (Princeton, 2019).

I will plausibly order that book.

The paper that Phil referenced: Esfeld and Gisin (arXiv:1310.5308) contains a summary and discussion, even though those authors are not convinced by the theory.

I must admit that Flash GRW is not an approach that I find convincing either. The ontology of this theory is the flashes themselves, the wave-function is not part of the ontology, so the collapse is entirely epistemic, and just like the "collapse" in classical probability theory. It works, but may not be convincing to everyone, since the ontology is remarkable thin!

The real problem is, as ever, that despite many promises, many-worlds theory does even less well in that it offers nothing in the way of an explanation.

The partial computable histories belongs already to elementary arithmetic, assumed by all scientists and philosophers. The problem is not in explaining the many “worlds/histories”, but the appearance of a stable and sharable “long dream”.

I worked on that problem well before even knowing that Everett type of QM existed already.

Maudlin's recent book discusses many worlds, but he concentrates on the problems with this idea, and essentially is not convinced that many-worlds makes sufficient sense in its own terms to provide an explanation for anything. Sean Carroll, in his recent book "Something Deeply Hidden", also evades the question. His discussion is on pages 104-105. He states that Bell assumed "that measurements have definite outcomes”.

That is what I think too.

Essentially, this is the assumption of counterfactual definiteness that has often been proposed. Carroll then says that since many-worlds does not assume that experiments have single outcomes, Bell's theorem doesn't apply. His unspoken assumption here is that if many-worlds evades Bell's result, then it can give a local account of the EPR correlations -- they happen "because of branching of the wave function into different worlds, in which correlated things happen." (p. 105) This is similar to your claim above, but it is not an explanation. And even if Bell's theorem doesn't apply, it does not follow that the theory can provide a local account of the correlations.You still have to provide that account.

But it is “trivial”, for the reason that the locality is in the unitary transformation. The local account is in the Hilbert space or in the von Neuman Algebra. My account is modest, because I have to derived it from self-reference to distinguish the qualia and the quanta. Keep in mind that my goal is to put some light in the mind-body problem frame. 

The other major source I can refer to is the book "The Emergent Multiverse" by David Wallace (Oxford, 2012). This book is the most comprehensive account of Everettian ideas currently available. Wallace also ducks the issue. In sections 8.5-8.7 (pages 302-312) he gives a detailed account of the branching structure that arises if Alice and Bob do independent spin measurements at space-like separations. Then on page 310 he gives a general entangled wave-function and points out that Alice's and Bob's measurements again lead to splitting. But he then says: "In this case, the amplitudes of the four sets of branches into which C [a central, neutral observer] eventually branches are not determined simply by the separate weights of the branchings at A and B. Nor is this to be expected: as I stressed previously, in Everettian quantum mechanics interactions are local but states are nonlocal. The entanglement between the particle at A and the particle at B is a nonlocal property of the forward light cone of A and that of B. Only in their intersection can it have locally determinable effects---and it does, giving rise to the branch weights which, in turn, give rise to the sorts of statistical results recorded in Aspect's experiments."

This might sound good, but again, there is no detail. What exactly is supposed to happen at the intersection of the forward light cones from A and B? There is no interaction there -- any information that is made locally present there was already present in the only relevant interactions, which are the original measurements made by A and B; any branch weights that are around are set there, exactly as in the case of non-entangled particles. Wallace started out well, but ducked out at the last minute, and he failed to give any comprehensible account that does not rely on simple magic.

I should read Wallace book. I am not sure I see that magic. There is an infinity of light cones, and in all intersection Alice and Bob have prepared entangled particles.  They are just both always unaware of their possible measurement results, and this makes them belonging to many of them, and that, normally, lift the QM predictions on each differentiated histories.

Bruno

So the best authorities available fail to give a local account of the EPR correlations in a many-worlds setting -- they all simply duck the issue when the rubber hits the road. Just as you routinely do.

Bruce

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