Consistency of Postulates of QM

[agrays...@gmail.com]

If the measurement problem were solved in the sense being able to predict exact outcomes, thus making QM a deterministic theory, would that imply an INCONSISTENCY in the postulates of QM? TIA.

[Brent Meeker]

It would make it possible to use EPR like experiments to send signals faster than light...which is to say backward in time.  That would pretty much screw up all known physics...and common sense.

Brent

On 11/9/2017 7:43 AM, agrays...@gmail.com wrote:

If the measurement problem were solved in the sense being able to predict exact outcomes, thus making QM a deterministic theory, would that imply an INCONSISTENCY in the postulates of QM? TIA.

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[agrays...@gmail.com]

If what you state is correct, then there's no solution to the measurement problem (if that means discovering a deterministic outcome for individual trials). Why then is the "measurement problem" still considered a problem to be solved? What you've presented is more or less proof that no such solution exists. 

[Brent Meeker]

The "measurement problem" isn't necessarily finding a deterministic subquantum dynamics.  If you could show that the density matrix becomes strictly diagonal in some non-arbitrary way (i.e. described by dynamics) and the eigenvalues obey the Born rule (which I think would follow from Gleason's theorem) then I think that would be a satisfactory solution.  And in fact I think Zurek has provided most of that except for the details of the dynamic description.  He relies on decoherence which produces multiple copies of the measurement result in the environment and he argues that the density matrix must be strictly diagonal in order that repeating a measurement yields a repeat of the result.  Given that much then you can either suppose this defines the splitting into multiple worlds OR, following Omnes, you can say the theory predicts probabilities and one of them is realized...which is all you can expect of a probabilistic theory.

Brent

[Alan Grayson]

How would you define "the measurement problem" to conclude that strictly diagonalizing the density matrix would be a solution? TIA

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[Brent Meeker]

Already, people like Omnes regard it as a non-problem because decoherence diagonalizes the density matrix FAPP and so it can be interpreted as being the same as a mixed state, which is how classical probability is represented in QM.  But others say FAPP isn't good enough because (1) in principle it's reversible and (2) it doesn't answer the problem of the Heisenberg cut.  I think everyone agrees that if, within QM, it can be shown that the density matrix is strictly diagonalized by known dynamics - then that solves the measurement problem.

Brent

[Bruno Marchal]

On 09 Nov 2017, at 16:43, agrays...@gmail.com wrote:

If the measurement problem were solved in the sense being able to predict exact outcomes,

?

Quantum Mechanics would be refuted (with or without wave packet reduction). 

thus making QM a deterministic theory,

You mean QM+collapse. With QM-without-collapse: QM is determinist in the third person picture, and non determinist from the perspective of the most observers.

would that imply an INCONSISTENCY in the postulates of QM? TIA.

Yes. If QM with collapse becomes deterministic, I think this would be close to adding local hidden variable, which are refuted by EPR/Bell.

Ah, I see Brent wrote

It would make it possible to use EPR like experiments to send signals faster than light...which is to say backward in time.  That would pretty much screw up all known physics...and common sense.

Yes, I agree. QM+collapse+SP would be close to nonsense.

I agree with all what brent say, so I don't need to add anything. The measurement problem is quasi conceptually solved by decoherence in QM without collapse, although not entirely when we take into account Mechanism !

But the measurement problem is a "physical problem" if you assume the wave packet reduction, and the problem consists in making sense of it, in a way having testable consequence, and an as clear as possible interpretation of the wave(s) or the (density) matrix. It is not a problem for the applications. Measurement is indeed a powerful gate in quantum computing. The measurement problem is mainly the interpretation problem of the wave/matrix, to make sense of a notion of "physical reality".

It is also a good introduction of the mind body problem. Digital Mechanism generalizes it to arithmetic, and where the wave/matrix itself has to be justified from the reality about the numbers semi-computable relations verified in Arithmetic. 

Bruno

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

[John Clark]

On Thu, Nov 9, 2017 at 10:43 AM, <agrays...@gmail.com> wrote:

​> ​

If the measurement problem were solved in the sense being able to predict exact outcomes,

​That's not the measurement problem, its determining if how and why observation effects things. ​

​> ​

thus making QM a deterministic theory, would that imply an INCONSISTENCY in the postulates of QM?

​It's not just Quantum Mechanics, Bell proved that any theory that is deterministic must ​be nonlocal or non realistic or both, otherwise it would be inconsistent with experimental results. 

 John K Clark 

 

[Alan Grayson]

On Fri, Nov 10, 2017 at 12:46 PM, John Clark <johnk...@gmail.com> wrote:

On Thu, Nov 9, 2017 at 10:43 AM, <agrays...@gmail.com> wrote:

​> ​

If the measurement problem were solved in the sense being able to predict exact outcomes,

​That's not the measurement problem, its determining if how and why observation effects things. ​

Not to split hairs, but why we get what we get in quantum measurements, and how measurement outcomes come to be what they are, are the same problem IMO.  

​> ​

thus making QM a deterministic theory, would that imply an INCONSISTENCY in the postulates of QM?

​It's not just Quantum Mechanics, Bell proved that any theory that is deterministic must ​be nonlocal or non realistic or both, otherwise it would be inconsistent with experimental results. 

 John K Clark 

 

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[John Clark]

On Fri, Nov 10, 2017 at 7:08 PM, Alan Grayson <agrays...@gmail.com> wrote:

​

​>> ​

That's not the measurement problem, its determining if how and why observation effects things. ​

​> ​

Not to split hairs, but why we get what we get in quantum measurements, and how measurement outcomes come to be what they are, are the same problem IMO.  

The measurement problem is not the ability or inability to predict exact outcomes,

​ ​

the measurement problem is defining what is

​ ​

and

​ ​

what

​ ​

is not a measurement and

​ ​

finding the

​ ​

minimum properties a system

​ ​

must

​ ​

have to be an observer. Nondeterminism is not a problem and there is no inconsistency at all regardless of what turns out to be true

​;​

if some effects have no cause and true randomness exists then that's just the way things are are

​ ​

and

​ ​t

here is no resulting paradox and no question that needs answering.

​

The title of this thread is about the consistency of Quantum Mechanics, but far more important than QM is the ability of ANY theory to be compatible with experimental results, and one of those experiments shows the violation of Bell's Inequality. And that violation tells us that for ANY theory to be successful at explaining how the world works AT LEAST one of the following properties of that theory must be untrue:

1) Determinism

2) Locality   

3) Realism    

Is Many Worlds deterministic? Yes in the sense that it just follows the wave function and that is deterministic, it's only the collapse of the wave function that is nondeterministic and that never happens in Manny Worlds.

Is Many Worlds Local? Some say yes but I would say no because those other worlds are about as non-local as you can get, you can't get there even with infinite time on your side. But even if I'm wrong about locality Many Worlds would still be in the running for a successful theory because it is certainly not realistic.  

John K Clark 

[agrays...@gmail.com]

Why not just assume the wf collapses by an as-yet unknown process? Then, unlike MWI, you have a theory within the realm of testable physics and no need to explain where the energy comes from to create those other worlds -- uncountable in a simply slit experiment -- or what part of another world needs to be created to do these other worldly measurements? Is collapse so repugnant  (how so?) that one has to grasp at a cure that ostensibly is hugely worse than the alleged disease? Inquiring minds want to know. AG

[Bruce Kellett]

I would agree with you that the many worlds account is non-local. The problem that MW faces is that the separate worlds split off when measurements are made at either end of the EPR experiment must somehow be made to match up appropriately when the two experimenters communicate. This requires coordination of separate worlds, which, as you say, is about as non-local as you can get.

The problem becomes particularly apparent if you consider an EPR experiment with time-like separation. Let Alice prepare an EPR pair in her laboratory, then measure the spin of one of the pair in some defined direction. She then takes the other member of the EPR pair down the corridor to her partner, Bob, and gets him to measure the spin projection in the same direction. If the two particles are independent, then both measurements give 50/50 chances for up/down. After Alice measures her particle, she splits into Alice_up and Alice _down according to her result. Both copies then go to Bob's laboratory, which by then has also split according to Alice's result. So Alice_up meets Bob, but when he measures his particle, he still has 50/50 chances of either result. Unfortunately, the only result that is consistent with spin conservation is that if Alice got 'up', he must get 'down', and vice verse (remember that the measurements are aligned by design).

Since Alice_up can't meet a Bob_up, there must be a non-local influence that determines Bob's result according to which Alice he meets. This is not removed be assuming no collapse and many worlds.

Of course, with time-like separation, the results can be explained by a local hidden variable, but no such explanation is available for space-like separated measurements, and the same explanation must be available for both cases. Since non-locality is still present for time-like separations, it must be present in all cases. So many worlds do not eliminate non-locality in Bell-pair measurements.

Bruce

[John Clark]

On Sat, Nov 11, 2017 at 3:31 PM, <agrays...@gmail.com> wrote:

​> ​

Why not just assume the wf collapses by an as-yet unknown process?

​You can do that if you want, but Bell proved that if his inequality is violated, and we now know from experiment that it is, and if that unknown process is deterministic then the world is non-local or non-realistic or both.   ​

 

 

​> ​

Then, unlike MWI, you have a theory within the realm of testable physics and no need to explain where the energy comes from to create those other worlds

​That is not unique to the MWI. In a accelerating  ​Einsteinian universe such as ours energy is not conserved at the cosmological level.

 

​> ​

Is collapse so repugnant  (how so?)

​It's repugnant because the mathematics say nothing about a collapse, the C

openhagen

​ people just wave there arms and say that it does when a observation is made, and they can't even say what is observation is. ​Can only a person make a observation or can a cockroach collapse the wave function too? And what observed the universe at the Big Bang?  If it's God what is observing God? The MWI is actually very conservative, it just assumes the mathematics means what it says and it doesn't stick on a bunch of other stuff as Copenhagen does. 

 

​> ​

that one has to grasp at a cure that ostensibly is hugely worse than the alleged disease

​ ​

 Inquiring minds want to know.

​Whatever the truth turns out to be one thing is certain, it will be weird.

John K Clark ​

 

[Brent Meeker]

But Bruno's model assumes infinitely many worlds; some in which Alice sees up and Bob sees down and others in which Alice sees down and Bob sees up..."influence" doesn't really appear in the model because it's kind of block multiverse and there's some rule (conservation of angular momentum) that means up-up and down-down don't appear.  I think this is also true of t'Hooft's super-deterministic model because in that model there's nothing special about the event of Alice's measurement that needs to be communicated.  The idea of influence propagating from an event derives from the idea that Alice had "free-will" and so her choice had to be communicated from the measurement event. 

Brent

Of course, with time-like separation, the results can be explained by a local hidden variable, but no such explanation is available for space-like separated measurements, and the same explanation must be available for both cases. Since non-locality is still present for time-like separations, it must be present in all cases. So many worlds do not eliminate non-locality in Bell-pair measurements.

Bruce

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[Bruce Kellett]

That does not address the scenario I have outlined. In the time-like case, Alice_up meets Bob with a spin state that can result in either up or down; similarly Alice_down meets Bob with a spin state on which Bob's measurement can result in either up or down with 50% of each. There are only two worlds involved at that stage. The question is, how does Bob with Alice_up not get an up result, contradicting conservation of angular momentum. Similarly, how does Bob with Alice_down not get a down result. Since the measurement axes are explicitly aligned in this case, the 'up-up' and 'down-down' observations are forbidden. Appealing to an infinity of worlds is not going to help.

't Hooft's superdeterministic model simply says that in this case the particles are originally produced with spins in the previously agreed measurement direction. In other words, the 'previously agreed' direction was determined from the time of the big bang. Maudlin in his Facebook discussion with 't Hooft makes it clear that he thinks this is not a well-formulated position. It is not a matter of freedom of the will in choosing setups and orientations, because these can be chosen according to the digits of pi after the 10,000,000th. Or anything else, and the initial conditions at the big bang could not have covered all possibilities - at least not in any believable way.

If many worlders are to explain the time-like case I have outlined, they are going to have to work quite hard to avoid the notion of some influence at a distance.

Bruce

[agrays...@gmail.com]

On Saturday, November 11, 2017 at 9:37:28 PM UTC-7, John Clark wrote:

On Sat, Nov 11, 2017 at 3:31 PM, <agrays...@gmail.com> wrote:

​> ​

Why not just assume the wf collapses by an as-yet unknown process?

​You can do that if you want, but Bell proved that if his inequality is violated, and we now know from experiment that it is, and if that unknown process is deterministic then the world is non-local or non-realistic or both.  

Bell showed, and experiments confirm, that our universe is non-local. I think that's the case whether or not the proposed collapse process is deterministic. But if it is deterministic, it messes up physics as Brent earlier indicated. So I suppose it can't be deterministic. And if not deterministic, I think we're back to collapse, and there doesn't seem to be any way to resolve the randomness, the resolution of which I had in mind. 

What is your definition of non-realistic? TIA.

​

 

 

​> ​

Then, unlike MWI, you have a theory within the realm of testable physics and no need to explain where the energy comes from to create those other worlds

​That is not unique to the MWI. In a accelerating  ​Einsteinian universe such as ours energy is not conserved at the cosmological level.

There was some unique condition that gave rise to our universe. MWI has it happening wily-nily when someone performs a slit experiment in a lab (and uncountably many times). Hardly a conservative interpretation IMO.  

 

​> ​

Is collapse so repugnant  (how so?)

​It's repugnant because the mathematics say nothing about a collapse, the C

openhagen

​ people just wave there arms and say that it does when a observation is made, and they can't even say what is observation is. ​

I can. They can. In a SG experiment, e.g., an observation occurs when the electron's spin state is aligned, or anti-aligned to the magnetic field. 

 

Can only a person make a observation or can a cockroach collapse the wave function too?

Feynman is conclusive on this point. No person or cockroach needed; just an instrument to record the result.

 

And what observed the universe at the Big Bang?  If it's God what is observing God? The MWI is actually very conservative, it just assumes the mathematics means what it says and it doesn't stick on a bunch of other stuff as Copenhagen does. 

Does every event require an observer or instrument to witness it? I think not. 

[Brent Meeker]

No, that's the point.  There are infinitely many "worlds" involved from the beginning.  There's no splitting.  It's all predetermined.

The question is, how does Bob with Alice_up not get an up result, contradicting conservation of angular momentum.

Because each world obeys conservation of angular momentum.

Similarly, how does Bob with Alice_down not get a down result. Since the measurement axes are explicitly aligned in this case, the 'up-up' and 'down-down' observations are forbidden. Appealing to an infinity of worlds is not going to help.

They don't really need to be infinite, just very numerous so that when we repeat some experiment for which the Born rule predicts 1/pi or other irrational number, we won't get results in our finite number of tests that are inconsistent with it.

't Hooft's superdeterministic model simply says that in this case the particles are originally produced with spins in the previously agreed measurement direction. In other words, the 'previously agreed' direction was determined from the time of the big bang. Maudlin in his Facebook discussion with 't Hooft makes it clear that he thinks this is not a well-formulated position. It is not a matter of freedom of the will in choosing setups and orientations, because these can be chosen according to the digits of pi after the 10,000,000th.

They can only be chosen that way by physically computing and choosing that number; events determined since the Big Bang.

Or anything else, and the initial conditions at the big bang could not have covered all possibilities - at least not in any believable way.

But we can't test all possibilities.  Alice and Bob can only do the experiments determined by the past state of the universe, i.e. those determined by the Big Bang.  I don't know what's "unbelievable" about that - it's what Laplace et al once believed about the world.

If many worlders are to explain the time-like case I have outlined, they are going to have to work quite hard to avoid the notion of some influence at a distance.

In Bruno's model the "influence at a distance" is determing which world you're in.

Brent

[Bruce Kellett]

That is simply not true. There are, by construction, only two worlds in this scenario before Bob makes his measurment, and that splits him (along with the Alice beside him) into two more.

The question is, how does Bob with Alice_up not get an up result, contradicting conservation of angular momentum.

Because each world obeys conservation of angular momentum.

The world in which Alice and Bob both get an 'up' result does not obey conservation of angular momentum. How do you exclude that world?

Similarly, how does Bob with Alice_down not get a down result. Since the measurement axes are explicitly aligned in this case, the 'up-up' and 'down-down' observations are forbidden. Appealing to an infinity of worlds is not going to help.

They don't really need to be infinite, just very numerous so that when we repeat some experiment for which the Born rule predicts 1/pi or other irrational number, we won't get results in our finite number of tests that are inconsistent with it.

You are not getting it, Brent! There is only one EPR pair made in this scenario. Alice and Bob each measure their separate particles, and get either up or down, with 50% each way. Once Alice has measured and takes her 'up' result to Bob, he has to make a separate measurement. According to AM conservation he can't get 'up' also (in this world) since Alice has presented him with an 'up' result. What prevents him getting 'up'? That is still a 50% chance, after all, according to the wave function. The point of this scenario is that the only possibility for Bob after Alice brings him an 'up' result is 'down'. What stops the 'up' possibility for his measurement?

't Hooft's superdeterministic model simply says that in this case the particles are originally produced with spins in the previously agreed measurement direction. In other words, the 'previously agreed' direction was determined from the time of the big bang. Maudlin in his Facebook discussion with 't Hooft makes it clear that he thinks this is not a well-formulated position. It is not a matter of freedom of the will in choosing setups and orientations, because these can be chosen according to the digits of pi after the 10,000,000th.

They can only be chosen that way by physically computing and choosing that number; events determined since the Big Bang.

Or anything else, and the initial conditions at the big bang could not have covered all possibilities - at least not in any believable way.

But we can't test all possibilities.  Alice and Bob can only do the experiments determined by the past state of the universe, i.e. those determined by the Big Bang.  I don't know what's "unbelievable" about that - it's what Laplace et al once believed about the world.

Superdeterminism is a red herring here. 't Hooft explicitly rejects many words, so his arguments do not apply to the case I am presenting, which is developed in an explicit no-collapse, many worlds context.

If many worlders are to explain the time-like case I have outlined, they are going to have to work quite hard to avoid the notion of some influence at a distance.

In Bruno's model the "influence at a distance" is determing which world you're in.

If that means anything at all, it is still non-local because Bruno has to rule out the worlds in which angular momentum is not conserved;  he has not shown how he can do this. If it is simply that you cannot find yourself in a world in which AM is not conserved, then that is just an unabashed appeal to magic, since such worlds have not been shown not to exist.

Bruce

[smitra]

> _only_ possibility for Bob after Alice brings him an 'up' result is

There are two correlated copies of Alice and Bob induced by the
correlated spins, there is nothing nonlocal about that in the MWI. There
is only a non- locality problem here if you assume a collapse
interpretation of QM. In the MWI the correlation arises via an
originally local common cause.

Saibal

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[Bruce Kellett]

There is no collapse assumption in anything that I have written about
this scenario. What is the local common cause in MWI? Is that a local
hidden variable? Such would work in the time-like case, but not in
general -- that is Bell's result.

But you have still not answered the fundamental question as to what
causes Bob to necessarily measure spin down when Alice joins him with a
spin-up result? What turns Bob's particle from an unpolarized to a
polarized state so that the probabilities change from 50/50 to 100% for
spin down?

Bruce

[Brent Meeker]

True?  This is a hypothetical model.  In Bruno's model there are infinitely many worlds "by construction".

The question is, how does Bob with Alice_up not get an up result, contradicting conservation of angular momentum.

Because each world obeys conservation of angular momentum.

The world in which Alice and Bob both get an 'up' result does not obey conservation of angular momentum. How do you exclude that world?

Exactly the problem with Bruno's model.  He says it recovers things like linearity and superposition - but beyond that it's not clear that it can recover QM.  He calls this "the white rabbit problem" as though it will be confined to a few peculiarities.

Similarly, how does Bob with Alice_down not get a down result. Since the measurement axes are explicitly aligned in this case, the 'up-up' and 'down-down' observations are forbidden. Appealing to an infinity of worlds is not going to help.

They don't really need to be infinite, just very numerous so that when we repeat some experiment for which the Born rule predicts 1/pi or other irrational number, we won't get results in our finite number of tests that are inconsistent with it.

You are not getting it, Brent! There is only one EPR pair made in this scenario.

No, Bruce, you're not getting. It your stuck in Everett/Dewitt version of many worlds in which there is branching from one to two to many.  Imagine an ensemble of worlds which "splits" into two ensembles when Alice makes her measurement.

Alice and Bob each measure their separate particles, and get either up or down, with 50% each way. Once Alice has measured and takes her 'up' result to Bob, he has to make a separate measurement. According to AM conservation he can't get 'up' also (in this world) since Alice has presented him with an 'up' result. What prevents him getting 'up'? That is still a 50% chance, after all, according to the wave function. The point of this scenario is that the only possibility for Bob after Alice brings him an 'up' result is 'down'. What stops the 'up' possibility for his measurement?

't Hooft's superdeterministic model simply says that in this case the particles are originally produced with spins in the previously agreed measurement direction. In other words, the 'previously agreed' direction was determined from the time of the big bang. Maudlin in his Facebook discussion with 't Hooft makes it clear that he thinks this is not a well-formulated position. It is not a matter of freedom of the will in choosing setups and orientations, because these can be chosen according to the digits of pi after the 10,000,000th.

They can only be chosen that way by physically computing and choosing that number; events determined since the Big Bang.

Or anything else, and the initial conditions at the big bang could not have covered all possibilities - at least not in any believable way.

But we can't test all possibilities.  Alice and Bob can only do the experiments determined by the past state of the universe, i.e. those determined by the Big Bang.  I don't know what's "unbelievable" about that - it's what Laplace et al once believed about the world.

Superdeterminism is a red herring here. 't Hooft explicitly rejects many words, so his arguments do not apply to the case I am presenting, which is developed in an explicit no-collapse, many worlds context.

I understand that.  I just noted it as another no-collapse model.

If many worlders are to explain the time-like case I have outlined, they are going to have to work quite hard to avoid the notion of some influence at a distance.

In Bruno's model the "influence at a distance" is determing which world you're in.

If that means anything at all, it is still non-local because Bruno has to rule out the worlds in which angular momentum is not conserved;  he has not shown how he can do this. If it is simply that you cannot find yourself in a world in which AM is not conserved, then that is just an unabashed appeal to magic, since such worlds have not been shown not to exist.

Right.   They haven't been shown not to exist, or even be rare, in the plenum of Bruno's Everything Computable.  It has been shown empirically that we never experience one.

Brent

[Brent Meeker]

Bell's theorem shows there is no way to communicate which spin direction
is the correlated one for all choices of measurement direction.  You
seem to taking "correlated" as the value of a variable, instead of two
spin values.  That's OK, but then "correlated" is a global (non-local)
variable; it's just "angular momentum is conserved".

Brent

[Bruno Marchal]

OK, but without action at a distance. If you take into account the local propagation of the observers (treating them quantum mechanically), and the same for their "future" counterparts. The coordination is just kept locally by the observers. There is a strong "local" first person sharable non locality, but yet no physical action at a distance, nor problem with physical realism (albeit multiversal). 

The problem becomes particularly apparent if you consider an EPR experiment with time-like separation. Let Alice prepare an EPR pair in her laboratory, then measure the spin of one of the pair in some defined direction. She then takes the other member of the EPR pair down the corridor to her partner, Bob, and gets him to measure the spin projection in the same direction. If the two particles are independent,

then both measurements give 50/50 chances for up/down.

OK. But they are not independent. After her measurement she is in a class of worlds with some definite result for both particle, with respect to the base up/down.

After Alice measures her particle, she splits into Alice_up and Alice _down according to her result. Both copies then go to Bob's laboratory, which by then has also split according to Alice's result.

OK.

So Alice_up meets Bob, but when he measures his particle, he still has 50/50 chances of either result.

I don't think so. Only if he got the time to do it before Alice splits has not rich him. But he would propagate a possibly "violating Bell" result to a different Alice, just by tyhe lienarity of the tensor products and evolution.

Unfortunately, the only result that is consistent with spin conservation is that if Alice got 'up', he must get 'down', and vice verse (remember that the measurements are aligned by design).

Yes.

Since Alice_up can't meet a Bob_up, there must be a non-local influence that determines Bob's result according to which Alice he meets. This is not removed be assuming no collapse and many worlds.

Of course, with time-like separation, the results can be explained by a local hidden variable, but no such explanation is available for space-like separated measurements, and the same explanation must be available for both cases.

But it is. Because the Alice and Bob moves locally, causally and lives always in the partition dictated by the result of ùeasurement, which propagate locally. In a pure space-like separation, you cannot even defined the identity of the observers with respect to their counterparts.

Since non-locality is still present for time-like separations, it must be present in all cases. So many worlds do not eliminate non-locality in Bell-pair measurements.

It does not eliminate the apparent non-locality, or Bell's results, but it eliminate the "physical action at a distance".

Bruno

Bruce

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[John Clark]

On Sun, Nov 12, 2017 at 1:01 AM, <agrays...@gmail.com> wrote:

​> ​

What is your definition of non-realistic? 

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​ A photon ​hits a horizontally polarizing filter and the universe splits in two if Many Worlds is right, in one the photon makes it through the filter and the inhabitants of that world conclude it is 100% horizontally polarized , in the other world it doesn't get through the filter and they conclude it must have been 100% vertically polarized, but in the world before the split, before it hit the filter, the inhabitants of that world would conclude (if they believed in Many Worlds) that the photon did not have any one definite polarized state at all.     

​

​>> ​

That is not unique to the MWI. In a accelerating  ​Einsteinian universe such as ours energy is not conserved at the cosmological level.

​> ​

There was some unique condition that gave rise to our universe.

​The multiverse may have always existed, if so then nothing, unique or otherwise, gave rise to it,​

 

 

​> ​

MWI has it happening wily-nily when someone performs a slit experiment in a lab (and uncountably many times). Hardly a conservative interpretation IMO.  

​Many Worlds is very conservative if the mathematics doesn't say ​

​anything about a wave collapse. And it doesn't.

​>> ​

they can't even say what is observation is. ​

​> ​

I can. They can. In a SG experiment, e.g., an observation occurs when the electron's spin state is aligned, or anti-aligned to the magnetic field. 

​Observation is the wrong word if no observer is involved, then its just a change and a change is the criteria Many Worlds uses. In MWI everything that can happen does happen, so when a photon approaches 2 slits the universe splits and one photon goes through the right slit and one goes through the left slit. If after that the photons hit a photographic plate (or a brick wall) then the photons no longer exist in either universe and so they merge back together into one universe and this merger causes the interference lines. If instead after passing the slits there is no photographic plate (or brick wall) and the photons are allowed to continue on into infinite space then the 2 universes remain different and remain separated forever.

The universe splits because there is a difference, in one the photon went through the left slit and in another it went through the right slit, and the wave function never collapses it just keeps on going. And there is nothing special about me, I split just like everything else in the universe, the fact that I am conscious is irrelevant.  That's another great advantage of Many Worlds, unlike Copenhagen it doesn't need to explain what consciousness is or how it works because consciousness has nothing to do with it.   

 

​>> ​

Can only a person make a observation or can a cockroach collapse the wave function too?

​> ​

Feynman is conclusive on this point. No person or cockroach needed; just an instrument to record the result.

​If an instrument is anything that can exist in at least 2 states then I would be fine with that, but that sounds much more like Many Worlds than Copenhagen. ​All that's needed is a change, any change, it need not be anything as dramatic as a change in something as complex as a brain.

​> ​

Does every event require an observer or instrument to witness it? I think not. 

​I think ever observation requires a observer to witness a change, and Copenhagen requires an observation to trigger the collapse of the wave function. Many Worlds just requires a simple change to trigger a split, a change in anything, and nothing triggers 

the collapse o

​f​

the wave function

​ because the mathematics doesn't even hint at such a thing happening, the Copenhagen people just tacked that on. Somebody said that Many Worlds is cheap on assumptions but expensive in universes and I think that's true, I'm a fan because universes are cheaper than assumptions. ​

  John K Clark

[Bruno Marchal]

I just assume quantum mechanics without collapse here. 

When I assume Mechanism, we are in a different field, and there at first sight we get total indeterminacy, super-non locality, etc., and the hard things is to explain the local appearance of determinism, locality, etc. With mechanism we have the quantum logic, the symmetries, but the Bell's theorem is already untractable. The interest reside in getting a unify picture of qualia and quanta, albeit in a platonic metaphysics, excluding the usual Aristotelian one.

Bruno 

Bruce

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[smitra]

Bob's particle never changed due to anything Alice did in the MWI. All
that happened was that Alice got entangled with her particle (and not
just Alice, her entire environment gets entangled with the state of her
particle), which in turn was entangled with Bob's particle. So, Bob has
the same probabilities for finding spin up or down, except that he can
now measure the state of his particle by performing a measurement on
Alice, by asking her what she found for her spin.

It's not true that before Bob knows what Alice has found that only one
of the two version's of Alice has arrived and that the information of
her spin state is then already present in Bob's sector. This is not true
in the MWI, decoherence simple means that you can't demonstrate the
existence of the two versions of Alice via an interference experiment.
But the inability to do so, doesn't by itself imply that only one
version really exists.

Saibal

[Bruce Kellett]

In other words, you have no idea how to explain the violations of Bell's inequality -- in many worlds or any other account of QM. It is a pity you continue to claim that many worlds eliminates the need for non-locality.

Bruce

[Bruce Kellett]

Right.

> All that happened was that Alice got entangled with her particle (and
> not just Alice, her entire environment gets entangled with the state
> of her particle), which in turn was entangled with Bob's particle. So,
> Bob has the same probabilities for finding spin up or down,

Right. In fact, when Alice_up meets Bob, and Alice_down meets Bob in the
parallel universe, they can both tell Bob their result, and the
direction in which they measured the spin. This makes no difference,
since Bob is now entangled with the Alice's that have definite results.
None of this makes any difference to the particle Bob measures, because,
by the definition of locality, nothing has interacted with Bob's
particle, so it must be in the same spin state as when it was produced.

> except that he can now measure the state of his particle by performing
> a measurement on Alice, by asking her what she found for her spin.

That is not a measurement, that is making a prediction based on the
conservation of angular momentum.

> It's not true that before Bob knows what Alice has found that only one
> of the two version's of Alice has arrived and that the information of
> her spin state is then already present in Bob's sector. This is not
> true in the MWI, decoherence simple means that you can't demonstrate
> the existence of the two versions of Alice via an interference
> experiment. But the inability to do so, doesn't by itself imply that
> only one version really exists.

I don't think you have fully understood the scenario I have outlined.
There is no collapse, many worlds is assumed throughout. Alice splits
according to her measurement result. Both copies of Alice go to meet
Bob, carrying the other particle of the original pair. Since they both
have now met Bob, the split that Alice occasioned has now spread to
entangle Bob as well as the rest of her environment. So there are now
two worlds, each of which has a copy of Bob, and an Alice, who has a
particular result. Locality says that Bob's particle is unchanged from
production, so when he measure its spin, he splits into two copies,
according to spin up or spin down. Since Alice is standing beside him,
she also becomes entangled with his result. But Alice already has a
definite result in each branch, so we now have four branches: with
results 'up-up', 'up-down', 'down-up', and 'down-down'. However, only
the 'up-down' and 'down-up' branches conserve angular momentum. How do
you rule out the other branches?

Bruce

[Bruce Kellett]

That is not what the formalism of the Schrödinger equation says. According to the SE, the number of worlds is exactly equal to the number of components in the superposition. These 'infinitely many' worlds are a fantasy. Besides, they do absolutely nothing towards explaining the violations of Bell's inequality.

The question is, how does Bob with Alice_up not get an up result, contradicting conservation of angular momentum.

Because each world obeys conservation of angular momentum.

The world in which Alice and Bob both get an 'up' result does not obey conservation of angular momentum. How do you exclude that world?

Exactly the problem with Bruno's model.  He says it recovers things like linearity and superposition - but beyond that it's not clear that it can recover QM.  He calls this "the white rabbit problem" as though it will be confined to a few peculiarities.

Yes, that is the point I have been trying to make for a long time. Bruno does not have a theory that eliminates non-locality by appealing to many worlds. He just hopes that by claiming it often enough people will come to believe it.

Similarly, how does Bob with Alice_down not get a down result. Since the measurement axes are explicitly aligned in this case, the 'up-up' and 'down-down' observations are forbidden. Appealing to an infinity of worlds is not going to help.

They don't really need to be infinite, just very numerous so that when we repeat some experiment for which the Born rule predicts 1/pi or other irrational number, we won't get results in our finite number of tests that are inconsistent with it.

You are not getting it, Brent! There is only one EPR pair made in this scenario.

No, Bruce, you're not getting. It your stuck in Everett/Dewitt version of many worlds in which there is branching from one to two to many.  Imagine an ensemble of worlds which "splits" into two ensembles when Alice makes her measurement.

Why should I imagine any such thing? That is not in the formalism of the SE, that is not many worlds as widely understood. But even if you imagine infinitely many ensembles of whatever you like, that gets you no nearer to an explanation of the irreducible non-locality.

Alice and Bob each measure their separate particles, and get either up or down, with 50% each way. Once Alice has measured and takes her 'up' result to Bob, he has to make a separate measurement. According to AM conservation he can't get 'up' also (in this world) since Alice has presented him with an 'up' result. What prevents him getting 'up'? That is still a 50% chance, after all, according to the wave function. The point of this scenario is that the only possibility for Bob after Alice brings him an 'up' result is 'down'. What stops the 'up' possibility for his measurement?

't Hooft's superdeterministic model simply says that in this case the particles are originally produced with spins in the previously agreed measurement direction. In other words, the 'previously agreed' direction was determined from the time of the big bang. Maudlin in his Facebook discussion with 't Hooft makes it clear that he thinks this is not a well-formulated position. It is not a matter of freedom of the will in choosing setups and orientations, because these can be chosen according to the digits of pi after the 10,000,000th.

They can only be chosen that way by physically computing and choosing that number; events determined since the Big Bang.

Or anything else, and the initial conditions at the big bang could not have covered all possibilities - at least not in any believable way.

But we can't test all possibilities.  Alice and Bob can only do the experiments determined by the past state of the universe, i.e. those determined by the Big Bang.  I don't know what's "unbelievable" about that - it's what Laplace et al once believed about the world.

Superdeterminism is a red herring here. 't Hooft explicitly rejects many words, so his arguments do not apply to the case I am presenting, which is developed in an explicit no-collapse, many worlds context.

I understand that.  I just noted it as another no-collapse model.

Superdeterminism is a collapse model.

If many worlders are to explain the time-like case I have outlined, they are going to have to work quite hard to avoid the notion of some influence at a distance.

In Bruno's model the "influence at a distance" is determing which world you're in.

If that means anything at all, it is still non-local because Bruno has to rule out the worlds in which angular momentum is not conserved;  he has not shown how he can do this. If it is simply that you cannot find yourself in a world in which AM is not conserved, then that is just an unabashed appeal to magic, since such worlds have not been shown not to exist.

Right.   They haven't been shown not to exist, or even be rare, in the plenum of Bruno's Everything Computable.  It has been shown empirically that we never experience one.

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

Bruce

[Bruce Kellett]

Non-locality just means that there is a non-local influence -- what happens to one member of an entangled pair influences the behaviour of the other. No model is proposed for how this happens, because any local causal model would have to be of the 'hidden variable' type, and Bell has ruled out such local hidden variable accounts. The 'Quantum Mechanics is incomplete' route is ruled out. Maudlin explores this in considerable detail in his book.

The problem becomes particularly apparent if you consider an EPR experiment with time-like separation. Let Alice prepare an EPR pair in her laboratory, then measure the spin of one of the pair in some defined direction. She then takes the other member of the EPR pair down the corridor to her partner, Bob, and gets him to measure the spin projection in the same direction. If the two particles are independent,

then both measurements give 50/50 chances for up/down.

OK. But they are not independent. After her measurement she is in a class of worlds with some definite result for both particle, with respect to the base up/down.

There is no 'class of worlds'. There are two worlds, one corresponding to each of the possible results for Alice's measurement.

After Alice measures her particle, she splits into Alice_up and Alice _down according to her result. Both copies then go to Bob's laboratory, which by then has also split according to Alice's result.

OK.

So Alice_up meets Bob, but when he measures his particle, he still has 50/50 chances of either result.

I don't think so. Only if he got the time to do it before Alice splits has not rich him.

Locality says unequivocally that what I say is correct: the particle that Alice presents to Bob (in each world) is in exactly the same spin state as when produced.

But he would propagate a possibly "violating Bell" result to a different Alice, just by tyhe lienarity of the tensor products and evolution.

I don't understand this comment. Alice and Bob have communicated, she has told him her measurement angle and the result she observed. All of this before he makes his measurement. But locality says that the fact that he has this information cannot influence the measurement he is about to make, so he still splits according to 'up' and 'down', and Alice becomes entangled with his result along with him. Unfortunately, this also involves combinations of results that violate angular momentum conservation.

Unfortunately, the only result that is consistent with spin conservation is that if Alice got 'up', he must get 'down', and vice verse (remember that the measurements are aligned by design).

Yes.

Since Alice_up can't meet a Bob_up, there must be a non-local influence that determines Bob's result according to which Alice he meets. This is not removed be assuming no collapse and many worlds.

Of course, with time-like separation, the results can be explained by a local hidden variable, but no such explanation is available for space-like separated measurements, and the same explanation must be available for both cases.

But it is. Because the Alice and Bob moves locally, causally and lives always in the partition dictated by the result of ùeasurement, which propagate locally. In a pure space-like separation, you cannot even defined the identity of the observers with respect to their counterparts.

Bullshit. I have taken great care to design a scenario in which the participants are always alongside each other so that they have no doubt about the identity of their counterparts.

Since non-locality is still present for time-like separations, it must be present in all cases. So many worlds do not eliminate non-locality in Bell-pair measurements.

It does not eliminate the apparent non-locality, or Bell's results, but it eliminate the "physical action at a distance".

What has 'physical action at a distance' got to do with it? Non-locality involves instantaneous influence at a distance. Physical action at this distance would be a local theory. Read Maudlin's book!

Bruce

[smitra]

The splitting as an apparent nonlocal aspect to it, which is due to a
common cause effect, the spins were entangled, and that entanglement
happened when the spins were created due to a local interaction in the
past.

If you then let Alice and Bob measure the space-like separated spins,
they'll split up, and that happens in a correlated way, because the
spins are correlated. It is just the MWI variant of Bertlmann's socks

Saibal

[Bruce Kellett]

Yes, the entangled spin zero state was created in the past.

> If you then let Alice and Bob measure the space-like separated spins,
> they'll split up, and that happens in a correlated way, because the
> spins are correlated. It is just the MWI variant of Bertlmann's socks

That is not correct. The correlation you seems to be relying on is
non-local once the particles have separated. As Bell pointed out,
Bertlmann's socks are the wrong way to look at it! Besides, my variation
was to look at time-like separated measurements so that one could keep
explicit track of the splitting into separate worlds -- Bob and Alice,
in their various versions, are always in the same world as each other.
This eliminates the confusion that seems to being used to escape the
fact of non-locality.

Bruce

[agrays...@gmail.com]

On Sunday, November 12, 2017 at 11:15:33 AM UTC-7, John Clark wrote:

On Sun, Nov 12, 2017 at 1:01 AM, <agrays...@gmail.com> wrote:

​> ​

What is your definition of non-realistic? 

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed. So not everything in a definite state must be observed, by detectors or conscious entities. OTOH, when an electron is prepared for a double slit experiment, it is in a superposition of states; that is, NOT in a definite state. If it were in a definite state, we'd observe the classical probability distribution. So quantum experiments, and QM in general to the extent it relies on superposition of states, is NONREALISTIC, whereas the macro world is generally REALISTIC. I can't speak to why the macro world is realistic.

 

A photon ​hits a horizontally polarizing filter and the universe splits in two if Many Worlds is right, in one the photon makes it through the filter and the inhabitants of that world conclude it is 100% horizontally polarized , in the other world it doesn't get through the filter and they conclude it must have been 100% vertically polarized, but in the world before the split, before it hit the filter, the inhabitants of that world would conclude (if they believed in Many Worlds) that the photon did not have any one definite polarized state at all.     

​

​>> ​

That is not unique to the MWI. In a accelerating  ​Einsteinian universe such as ours energy is not conserved at the cosmological level.

​> ​

There was some unique condition that gave rise to our universe.

​The multiverse may have always existed, if so then nothing, unique or otherwise, gave rise to it,​

 

You're conflating Multiverse with the MWI. In the former, OUR universe emerged due to unique, unknown initial conditions from an entity which, if it exists, is likely infinite in age and extent. In the MWI, universes allegedly emerge when Joe the Plumber shoots an electron at a slitted screen. The two situations are in no way comparable, and the latter seems hugely overblown IMO. So where the energy comes from in the MWI cannot be easily dismissed by the lack of global energy conservation in GR, or by referring to unknowns related to the emergence of our universe from a hypothetical Multiverse.

 

 

​> ​

MWI has it happening wily-nily when someone performs a slit experiment in a lab (and uncountably many times). Hardly a conservative interpretation IMO.  

​Many Worlds is very conservative if the mathematics doesn't say ​

​anything about a wave collapse. And it doesn't.

​>> ​

they can't even say what is observation is. ​

​> ​

I can. They can. In a SG experiment, e.g., an observation occurs when the electron's spin state is aligned, or anti-aligned to the magnetic field. 

​Observation is the wrong word if no observer is involved, then its just a change and a change is the criteria Many Worlds uses. 

Agreed that "observation" is misleading when there is no consciousness involved in a quantum experiment. We should speak of detectable changes recorded by instruments; aka "measurements".

 

In MWI everything that can happen does happen, so when a photon approaches 2 slits the universe splits and one photon goes through the right slit and one goes through the left slit. If after that the photons hit a photographic plate (or a brick wall) then the photons no longer exist in either universe and so they merge back together into one universe and this merger causes the interference lines. If instead after passing the slits there is no photographic plate (or brick wall) and the photons are allowed to continue on into infinite space then the 2 universes remain different and remain separated forever.

So if David Deutsch takes a right turn at an intersection, there's another identical David Deutsch in another identical universe who takes a left turn? I can't disprove it, but why would anyone of sound mind want to assert it? 

The universe splits because there is a difference, in one the photon went through the left slit and in another it went through the right slit, and the wave function never collapses it just keeps on going. And there is nothing special about me, I split just like everything else in the universe, the fact that I am conscious is irrelevant.  That's another great advantage of Many Worlds, unlike Copenhagen it doesn't need to explain what consciousness is or how it works because consciousness has nothing to do with it.   

As I previously pointed out, the alleged collapse of the wf has nothing to do with consciousness regardless of what Bohr or others might have speculated in the early days of QM. As Feynman clearly explained, you can have a detector recording outcomes, and if the detector is designed to determine which-way, the interference will be destroyed. In other words, we can have quantum observations without any conscious "observer".

 

​>> ​

Can only a person make a observation or can a cockroach collapse the wave function too?

​> ​

Feynman is conclusive on this point. No person or cockroach needed; just an instrument to record the result.

​If an instrument is anything that can exist in at least 2 states then I would be fine with that, but that sounds much more like Many Worlds than Copenhagen. ​All that's needed is a change, any change, it need not be anything as dramatic as a change in something as complex as a brain.

​> ​

Does every event require an observer or instrument to witness it? I think not. 

​I think every observation requires a observer to witness a change, and Copenhagen requires an observation to trigger the collapse of the wave function.

 Not for macro events as pointed out above, or even quantum events. Detectors to record changes are sufficient as "observers". 

Many Worlds just requires a simple change to trigger a split, a change in anything, and nothing triggers 

the collapse o

​f​

the wave function

​ because the mathematics doesn't even hint at such a thing happening, the Copenhagen people just tacked that on.

Not exactly true IMO. When the measurement occurs, the probability becomes unity for the value of the measurement, implying collapse of the probability density to a delta function. 

 

Somebody said that Many Worlds is cheap on assumptions but expensive in universes and I think that's true, I'm a fan because universes are cheaper than assumptions. ​

Thanks for an interesting discussion. 

  John K Clark

[agrays...@gmail.com]

On Sunday, November 12, 2017 at 11:24:15 PM UTC-7, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:15:33 AM UTC-7, John Clark wrote:

On Sun, Nov 12, 2017 at 1:01 AM, <agrays...@gmail.com> wrote:

​> ​

What is your definition of non-realistic? 

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed. So not everything in a definite state must be observed, by detectors or conscious entities. OTOH, when an electron is prepared for a double slit experiment, it is in a superposition of states; that is, NOT in a definite state. If it were in a definite state, we'd observe the classical probability distribution. So quantum experiments, and QM in general to the extent it relies on superposition of states, is NONREALISTIC, whereas the macro world is generally REALISTIC. I can't speak to why the macro world is realistic.

FWIW, I left out an important reason why some systems are in definite states, like macro systems, and others not, such as quantum systems prepared for measurements. It's likely related to whether the systems in question are ISOLATED.

[Bruno Marchal]

In mechanism, the status is decided, but still untractable.

It is a pity you continue to claim that many worlds eliminates the need for non-locality.

Sorry but you continue to mix two different theories. 

And quantum mechanics is a deterministic local theory. The non locality and the indeterminacies are explained to be apparent in each branche, but without any action at a distance, as you can see when you develop the experiment in all branches (that is with theuniversal  wave).

We have discussed this, and it seemed to me you were OK with the fact that QM does not imply physical action at a distance (even withot transmission of information),. All I said is that QM does not imply that. And it is open problem if Digital Mechanism is true.

Bruno

Bruce

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[Bruno Marchal]

You are playing with word. "instantaneous influence at a distance" is another terming for "physical action at a distance".

I read and quoted already Maudlin; he says exactly what we are saying here: there is "non locality", but without any instantaneous action at a distance once you eliminate the collapse of the wave. 

The violation of Bell's inequality only show that each branch is non local, and that there *would* be action at a distance, if they were unique. But none are unique, and in the global picture, the appearance of non-locality and indeterminacy is explained in term of only causal interaction propagating at speed < c.

Bruno

Bruce

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[Bruno Marchal]

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state. 

Bruno

Bruce

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[Bruce Kellett]

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

Bruce

[agrays...@gmail.com]

On Sunday, November 12, 2017 at 11:50:00 PM UTC-7, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:24:15 PM UTC-7, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:15:33 AM UTC-7, John Clark wrote:

On Sun, Nov 12, 2017 at 1:01 AM, <agrays...@gmail.com> wrote:

​> ​

What is your definition of non-realistic? 

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed. So not everything in a definite state must be observed, by detectors or conscious entities. OTOH, when an electron is prepared for a double slit experiment, it is in a superposition of states; that is, NOT in a definite state. If it were in a definite state, we'd observe the classical probability distribution. So quantum experiments, and QM in general to the extent it relies on superposition of states, is NONREALISTIC, whereas the macro world is generally REALISTIC. I can't speak to why the macro world is realistic.

FWIW, I left out an important reason why some systems are in definite states, like macro systems, and others not, such as quantum systems prepared for measurements. It's likely related to whether the systems in question are ISOLATED.

If you find collapse of the wf anathema, instead of the MWI why not just assume the branches that aren't measured in this world, dissipate into the environment as I think Decoherence theory postulates?  MWI doesn't tell us what will be measured in this or any other particular world, so what's the downside to this hugely simpler way of avoiding collapse? 

[Brent Meeker]

It's that last point I don't understand.  Why isn't conservation of angular momentum a condition in every world.  It's something separate from QM.  I'd say there is non-locality even when Bob's measurement is time-like because there is correlation with no physical causal link.   The "common cause" of conserved angular momentum is not an explanation because that doesn't work in the space-like case and there's no reason to suppose QM is different in the two cases.

Brent

[John Clark]

On Mon, Nov 13, 2017 at 1:24 AM, <agrays...@gmail.com> wrote:

​>

​>> ​

​

What is your definition of non-realistic? 

​>> ​

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

​> ​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed.

​That's just stating as a fact the​ very thing we're debating. Was the Earth-Moon ever in one definite state? If MWI is right the answer is no, it was always in a huge number of states, every state that was not forbidden by the laws of physics. If Copenhagen is right then Earth-Moon system was in no state at all for billions of years until somebody made a measurement and the fuzziness collapsed into one sharp definite state. Exactly what does and does not constitutes a measurement the Copenhagen people leave as a exercise for the reader.

 

​> ​

OTOH, when an electron is prepared for a double slit experiment, it is in a superposition of states; that is, NOT in a definite state.

​The MWI can give a pretty good explanation why big things like the Earth-Moon system and a small things like an electron behave so differently, but to my mind Copenhagen is much less successful at doing that.   ​

​> ​

You're conflating Multiverse with the MWI.

​

You can't have the MWI without the Multiverse, and if there is a Multiverse then the MWI explains a lot.

​ ​

There are about 10^80 atoms in the observable universe and obviously there is a finite number of ways 10^80 atoms can be arranged in a sphere with a radius of 13.8 billion light years; so if the

​entire ​

universe (not to be confused with the observable universe) is infinite then at a very large but still finite distance things must repeat and there is a universe identical to our own, and at another hyper large distance there is a universe identical to ours except that the freckle on my right thumb is on my left thumb instead. And at a even greater distance one second after a John Clark hits send on a message identical to this one all the air molecules in the room he is in go to the other side of the room due to random thermal vibrations and that John Clark suffocates. Bizarre events like that are not impossible just very very unlikely, but if the universe is really infinite then everything that doesn't violate the laws of physics will happen, and the Many World people say that's what the wave function is trying to tell us, everything that can happen will happen.      

​> ​

where the energy comes from in the MWI cannot be easily dismissed by the lack of global energy conservation in GR,

​Why Not? Energy conservation is not a logical necessity, it was just a empirical fact that we found that seemed to be always true, until it wasn't. Twenty years ago we discovered the universe was accelerating.  ​

​> ​

Agreed that "observation" is misleading when there is no consciousness involved in a quantum experiment. We should speak of detectable changes recorded by instruments; aka "measurements".

​Measurement is an even worse word to use than observation because it implies not only information​

 

​but meaning, and you can's have meaning without a mind and you can't have a mind without a brain and you can't have a brain without atoms arranged in ​certain patterns. Many Worlds strips things down to their bare essentials, no need to worry about observation or measurement or information or meaning or consciousness, all that's needed is a change. 

​> ​

So if David Deutsch takes a right turn at an intersection, there's another identical David Deutsch in another identical universe who takes a left turn? I can't disprove it, but why would anyone of sound mind want to assert it? 

​Because  the bizarre outcome of experiments forces me to conclude the universe is not of sound mind; if I were God I probably would have just stuck with Newton but unfortunately I didn't get the job.  I admit the MWI is stark raving mad, but the big question is it crazy enough to be true?  Whatever the truth turns out to be you can be certain it will seem nuts to all bipedal hominids that evolved to be good at hunting game on the African Savanna and not good at probing the mysteries of the quantum world. ​

 

​> ​

you can have a detector recording outcomes, and if the detector is designed to determine which-way, the interference will be destroyed. In other words, we can have quantum observations without any conscious "observer".

Yes, and that gives more support to many Worlds than Copenhagen. In the MWI when the electron passes the slits the universe splits and if the which way information is retained then there must be a physical difference between the two universes because information is physical, and so they remain split and no interference pattern is seen. However if after the split the which way information is subsequently erased then there is no longer a physical difference between the two and the universes merge back together. But there are still indications the electron went through slot X and a equally strong indications the electron went through slot Y, and so we have a interference pattern. The reason we see this bizarre behavior in a electron but not a baseball is that a electron is just one simple particle and so the difference between the two universes is very small , so it you're very clever you can with delicate experiments get them to merge back together again, but a baseball is made up of about 10^25 particles so the difference between the universes is 10^25 larger, so it would be 10^25 times harder to do the same thing with a baseball. So in the MWI we see splitting far more often than merging, but it does happen,   

 

​>> ​

Many Worlds just requires a simple change to trigger a split, a change in anything, and nothing triggers 

the collapse o

​f​

the wave function

​ because the mathematics doesn't even hint at such a thing happening, the Copenhagen people just tacked that on.

​> ​

Not exactly true IMO. When the measurement occurs, the probability becomes unity for the value of the measurement, implying collapse of the probability density 

 

 

​I ​

know

​,​

that's what I'm talking about

​.​

 

T​

he

​ ​

Copenhagen people tacked on that a measurement (whatever that is)

​ collapses the function to just one thing. But why? The mathematics doesn't say why and the

Copenhagen people

​ certainly didn't derive it, they just waved their hands and said that it does. Many World people say the mathematics mean what it says and they don't tack a collapse or anything else onto it that is not inherent to the mathematics itself.​

 

​> ​

Thanks for an interesting discussion. 

​And thank you, I enjoyed it too.

John K Clark​

 

 

[Bruce Kellett]

On 14/11/2017 10:01 am, Brent Meeker wrote:

On 11/13/2017 1:40 PM, Bruce Kellett wrote:

On 14/11/2017 2:07 am, Bruno Marchal wrote:

On 12 Nov 2017, at 23:05, Bruce Kellett wrote:

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state.

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

It's that last point I don't understand.  Why isn't conservation of angular momentum a condition in every world.  It's something separate from QM.

Yes, sorry, I seem to have got my negatives confused! There is no reason to suppose (in the time-like case proposed) that 'up-up' or 'down-down' combinations are impossible, and such combinations of results would violate conservation of angular momentum.

I'd say there is non-locality even when Bob's measurement is time-like because there is correlation with no physical causal link.   The "common cause" of conserved angular momentum is not an explanation because that doesn't work in the space-like case and there's no reason to suppose QM is different in the two cases.

You are quite right here. The time-like and space-like separated measurements must give the same results, and have the same explanation. Common cause explanations don't work because space-like separations rule them out. My reason for considering time-like separation is that in that case one can precisely control the number of branches of the MWI involved, so that Alice and Bob are in the same branch when the crucial measurement is made. Thus there is no confusion over separate worlds that have to be matched up according to AM conservation when they finally meet -- they are always together, so there is no 'matching up' issue.

Bruce

[John Clark]

On Mon, Nov 13, 2017 at 4:40 PM, <agrays...@gmail.com> wrote:

​> ​

If you find collapse of the wf anathema, instead of the MWI why not just assume the branches that aren't measured in this world, dissipate into the environment as I think Decoherence theory postulates?  MWI doesn't tell us what will be measured in this or any other particular world, so what's the downside to this hugely simpler way of avoiding collapse?

​How is everything except one value dissipating any different from everything collapsing into one value? And what does nature consider to be a measurement and what does it not? A change is simpler than a measurement and a theory without an assumption is simpler than a theory that needs an assumption. I say we don't really need an assumption of collapse (or dissipation) so get rid of it.

John K Clark

​

 

 

[agrays...@gmail.com]

On Monday, November 13, 2017 at 4:41:02 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 4:40 PM, <agrays...@gmail.com> wrote:

​> ​

If you find collapse of the wf anathema, instead of the MWI why not just assume the branches that aren't measured in this world, dissipate into the environment as I think Decoherence theory postulates?  MWI doesn't tell us what will be measured in this or any other particular world, so what's the downside to this hugely simpler way of avoiding collapse?

​How is everything except one value dissipating any different from everything collapsing into one value?

How is everything except one value in this world (the others dissipating into the environment), WORSE than conjuring a multitude of universes for the other values to be measured? I fail to see anything "conservative" about this pov. When you pull a slot machine, is it really conservative to assert 10 million other universes come into being (along with the player!) for the other unrealized outcomes in this universe?

 

And what does nature consider to be a measurement and what does it not? A change is simpler than a measurement and a theory without an assumption is simpler than a theory that needs an assumption. I say we don't really need an assumption of collapse (or dissipation) so get rid of it.

By replacing Decoherence with MWI seems to raise hugely more insoluble problems than simply using the Decoherence model of dissipation of the unrealized outcomes. 

John K Clark

​

 

 

[Brent Meeker]

Decoherence implies small cross terms in the density matrix (which implies small measure in the given basis) but it doesn't say anything about "dissipating" the diagonal terms that represent possible outcomes.

Brent

[John Clark]

On Mon, Nov 13, 2017 at 8:01 PM, <agrays...@gmail.com> wrote:

​> ​

How is everything except one value in this world (the others dissipating into the environment), WORSE than conjuring a multitude of universes for the other values to be measured?

​One theory makes an assumption and the other, being more conservative, does not.​

 

 

​> ​

When you pull a slot machine, is it really conservative to assert 10 million other universes come into being (along with the player!) for the other unrealized outcomes in this universe?

​If the universe is really infinite, not just very very big but INFINITE, then somewhere in that infinite universe there must be a collection of atoms that behaves in a Johnkclarkian way that observes every one of the 10 million states a slot machine can be in; and that's more than just conservative, there is no other way it could be. 

 And if the multiverse is infinite then it wouldn't be a case of a branch coming into being but of determining which branch a rational observer is in. Based on known information many worlds assigns a complex number to every branch and the degree of certainty a rational agent would have for believing to be in that branch can be obtained by squaring the absolute value of that complex number. This is called The Born Rule.  

​> ​

By replacing Decoherence with MWI seems to raise hugely more insoluble problems than simply using the Decoherence model of dissipation of the unrealized outcomes. 

​You're assuming there actually are unrealized outcomes, its true you can only see one outcome but that's exactly what is to be expected if you are duplicated along ​with all those other other outcomes. The point is you can't explain why they dissipate, Many Worlds can't explain it either but it doesn't need to because it says there are no

unrealized outcomes

​.

 John K Clark​

 

[agrays...@gmail.com]

On Monday, November 13, 2017 at 4:22:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 1:24 AM, <agrays...@gmail.com> wrote:

​>

​>> ​

​

What is your definition of non-realistic? 

​>> ​

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

​> ​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed.

​That's just stating as a fact the​ very thing we're debating. Was the Earth-Moon ever in one definite state? If MWI is right the answer is no, it was always in a huge number of states, every state that was not forbidden by the laws of physics. If Copenhagen is right then Earth-Moon system was in no state at all for billions of years until somebody made a measurement and the fuzziness collapsed into one sharp definite state. Exactly what does and does not constitutes a measurement the Copenhagen people leave as a exercise for the reader.

Brent can correct me if I am wrong, but I think every macro system, although comprised of a huge number of individual constituents, is in one definite state; namely, the combined states of its constituents, and this is because each constituent state has interacted with the environment. That is, the lack of ISOLATION is the condition for the existence of this macro definite state. OTOH, when, say, electrons are prepared for a slit experiment, they are ISOLATED, and this gives rise to the superposition of states, which is where the system is NOT in any definite state of the states comprising the superposition. Thus, if I am correct, the Earth-Moon system was, indeed, in a definite state when it formed, even though there were no "observers" of any type to witness it. I contend that your understanding of what's necessary for an "event" to exist or occur, is seriously incorrect. 

[agrays...@gmail.com]

On Monday, November 13, 2017 at 4:22:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 1:24 AM, <agrays...@gmail.com> wrote ​

​> ​

You're conflating Multiverse with the MWI.

​

You can't have the MWI without the Multiverse, and if there is a Multiverse then the MWI explains a lot.

​ ​

There are about 10^80 atoms in the observable universe and obviously there is a finite number of ways 10^80 atoms can be arranged in a sphere with a radius of 13.8 billion light years; so if the

​entire ​

universe (not to be confused with the observable universe) is infinite then at a very large but still finite distance things must repeat and there is a universe identical to our own, and at another hyper large distance there is a universe identical to ours except that the freckle on my right thumb is on my left thumb instead. And at a even greater distance one second after a John Clark hits send on a message identical to this one all the air molecules in the room he is in go to the other side of the room due to random thermal vibrations and that John Clark suffocates. Bizarre events like that are not impossible just very very unlikely, but if the universe is really infinite then everything that doesn't violate the laws of physics will happen, and the Many World people say that's what the wave function is trying to tell us, everything that can happen will happen.    

The concept of Multiverse and Many Worlds come from entirely different contexts and theories, so the idea that they are somehow connected or related strikes me a patently false. Moreover, the idea that if the universe is infinite (in some parameter; spatial extent, age, whatever), then anything that can happen, will happen, is IMO unproven and almost certainly false. For example, we know that irrational numbers exist, but in an infinite string of digits representing some irrational number, there are no repetitions of any subset strings. But there should be according to your conjecture.

[agrays...@gmail.com]

Or look at it this way; if your conjecture were true, it would be impossible for irrational numbers to exist, since recurring repetitions of subset strings would be impossible to avoid.

[Brent Meeker]

On 11/13/2017 8:25 PM, agrays...@gmail.com wrote:

On Monday, November 13, 2017 at 4:22:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 1:24 AM, <agrays...@gmail.com> wrote:

​>

​>> ​

​

What is your definition of non-realistic? 

​>> ​

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

​> ​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed.

​That's just stating as a fact the​ very thing we're debating. Was the Earth-Moon ever in one definite state? If MWI is right the answer is no, it was always in a huge number of states, every state that was not forbidden by the laws of physics. If Copenhagen is right then Earth-Moon system was in no state at all for billions of years until somebody made a measurement and the fuzziness collapsed into one sharp definite state. Exactly what does and does not constitutes a measurement the Copenhagen people leave as a exercise for the reader.

Brent can correct me if I am wrong, but I think every macro system, although comprised of a huge number of individual constituents, is in one definite state; namely, the combined states of its constituents, and this is because each constituent state has interacted with the environment. That is, the lack of ISOLATION is the condition for the existence of this macro definite state. OTOH, when, say, electrons are prepared for a slit experiment, they are ISOLATED, and this gives rise to the superposition of states, which is where the system is NOT in any definite state of the states comprising the superposition.

This is looking at it wrong.  A superposition is a definite state, it's just not an eigenstate of the basis you've chosen.  I'd say a macroscopic object is never in a (knowable) definite state because it's continually interacting with the rest of the environment.  The Bucky Ball experiment shows that even radiating some IR photons in enough to destroy interference effects.  So macroscopic objects have definite (FAPP) states in the classical sense, but that's not the same as a ray in Hilbert space.

Brent

Thus, if I am correct, the Earth-Moon system was, indeed, in a definite state when it formed, even though there were no "observers" of any type to witness it. I contend that your understanding of what's necessary for an "event" to exist or occur, is seriously incorrect. 

--

[agrays...@gmail.com]

On Monday, November 13, 2017 at 10:46:23 PM UTC-7, Brent wrote:

On 11/13/2017 8:25 PM, agrays...@gmail.com wrote:

On Monday, November 13, 2017 at 4:22:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 1:24 AM, <agrays...@gmail.com> wrote:

​>

​>> ​

​

What is your definition of non-realistic? 

​>> ​

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

​> ​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed.

​That's just stating as a fact the​ very thing we're debating. Was the Earth-Moon ever in one definite state? If MWI is right the answer is no, it was always in a huge number of states, every state that was not forbidden by the laws of physics. If Copenhagen is right then Earth-Moon system was in no state at all for billions of years until somebody made a measurement and the fuzziness collapsed into one sharp definite state. Exactly what does and does not constitutes a measurement the Copenhagen people leave as a exercise for the reader.

Brent can correct me if I am wrong, but I think every macro system, although comprised of a huge number of individual constituents, is in one definite state; namely, the combined states of its constituents, and this is because each constituent state has interacted with the environment. That is, the lack of ISOLATION is the condition for the existence of this macro definite state. OTOH, when, say, electrons are prepared for a slit experiment, they are ISOLATED, and this gives rise to the superposition of states, which is where the system is NOT in any definite state of the states comprising the superposition.

This is looking at it wrong.  A superposition is a definite state, it's just not an eigenstate of the basis you've chosen. 

 

I like that formulation. I was reacting to Clark's comment that a system in a superposition of states is not in any state comprising the superposition, and thus, in this context, contradicted REALISM.

.  

I'd say a macroscopic object is never in a (knowable) definite state because it's continually interacting with the rest of the environment.  The Bucky Ball experiment shows that even radiating some IR photons in enough to destroy interference effects.  So macroscopic objects have definite (FAPP) states in the classical sense, but that's not the same as a ray in Hilbert space.

I meant that any macro state is definite, albeit always fluctuating. Not in a superposition.

[smitra]

Whether Bob and Alice are really in the same worlds has to be considered
very carefully within a precise model. If Bob is modeled as a robot with
it's conscious thoughts defined by some bitstring stored in his
electronic brain and similarly in case of Alice, then decoherence does
not lead to a splitting in the bitstring sector. While the atoms out of
which the logical units are made out of do decohere, the logical states
are macroscopic states that can be "0" or "1" , and Bob as defined by
its bistring specifying it's subjective state can be simply factored out
of the complete quantum state.

Within this model, Bob does not decohere until that time he is told what
Alice has found. Now, one may consider modeling Alice and Bob in some
other way, such that the information what Alice has found does affect
Bob's subjective state before he is told anything, and the probabilities
will then change. So, here the splitting happens differently and there
is again nothing nonlocal going on.

Bob becoming localized in Alice's sector due to decoherence is a local
process, I don't think there is disagreement about that. But if Bob is
completely localized then there is no splitting anymore, as the
splitting has already happened. The whole concept of "splitting" is only
an effective concept, in reality you only have the states of Bob, Alice,
and the rest of the universe evolving in time due to local interactions,
and Bob's and Alice's states are going to be correlated.


Saibal

[Bruce Kellett]

You're floundering. Whether Bob and Alice are robots, bitstrings, or
flesh and blood human beings, they get split by being entangled with the
environment and the experimental result. What they know or don't know is
entirely secondary. Once they are split by being entangled with a
particular result, that is that -- nothing can change that, and their
knowledge is secondary.

> Within this model, Bob does not decohere until that time he is told
> what Alice has found.

That is simply not true. Decoherence is not subject to a particular
person's knowledge. When Alice and Bob are next to each other, they are
jointly entangled with a particular result.

> Now, one may consider modeling Alice and Bob in some other way, such
> that the information what Alice has found does affect Bob's subjective
> state before he is told anything, and the probabilities will then
> change. So, here the splitting happens differently and there is again
> nothing nonlocal going on.
>
> Bob becoming localized in Alice's sector due to decoherence is a
> local process, I don't think there is disagreement about that.

Decoherence is a local process, of course. But Alice brings, say an 'up'
result, to Bob, who is then entangled with the world in which Alice got
'up'. He then measures his part of the entangled pair, and both Alice
and Bob together become entangled with the result -- 'up' or 'down'
according to which branch one considers. If everything is completely
local, there is no way to avoid the cases in which both Bob and Alice
report 'up-up' or 'down-down'. Both of these possibilities violate
angular momentum conservation. You have not given any account, local or
other, that forbids these particular combinations of results from occurring.

> But if Bob is completely localized then there is no splitting anymore,
> as the splitting has already happened. The whole concept of
> "splitting" is only an effective concept, in reality you only have the
> states of Bob, Alice, and the rest of the universe evolving in time
> due to local interactions, and Bob's and Alice's states are going to
> be correlated.

Sure, splitting is occasioned by entanglement with the results of the
experiment (It is real, not simply 'effective'). This is local, and not
under our control, but without non-locality for the entangled pair, some
of the Alice-Bob combinations see impossible results.

Bruce

[smitra]

I think that this needs to be discussed in more detail. Decoherence
does not cause a superposition to get reduced to either one of the two
possible outcomes. Given what Bob knows, he cannot locate himself in
either sector. If this were not true then given everything Bob is aware
of, he could get to better odds than 50-50 for guessing the spin. But
that implies information transfer to something his brain can access.

So, it boils down to decoherence acting on a microscopic degrees of
freedom, while brains and computers must be robust systems that would
not function well if they would be affected by such effects. Thermal
noise would make computing impossible.

If you have robust bitstrings that are only going to be affected by
information present in the environment at a sufficiently coarse grained
level, then that bitstring is never going to pick up any information
about Alice's result other than via direct communication or any leakage
of information e.g. if Bob is in to cold reading, or if there are other
correlations at the macroscopic level that Bob can exploit.

So, we have two decohered parallel worlds, but Bob is mentally identical
in the two sectors despite decoherence having split his body. As long as
he cannot access that information, he is the same person in both
sectors.

Saibal


If Alice and Bob are computers and whatever they are aware of is
contained in a bitstring, then it follows that anything one isn't aware
of, but is different in the two sectors cannot be present in the
bitstring. Otherwise Bob could know Alice's result before asking her or
measuring his own spin. At least, you cannot rule this out.

All that decoherence does is that the Alice

[Stathis Papaioannou]

On Mon, 13 Nov 2017 at 8:54 am, Bruce Kellett <bhke...@optusnet.com.au> wrote:

I don't think you have fully understood the scenario I have outlined.
There is no collapse, many worlds is assumed throughout. Alice splits
according to her measurement result. Both copies of Alice go to meet
Bob, carrying the other particle of the original pair. Since they both
have now met Bob, the split that Alice occasioned has now spread to
entangle Bob as well as the rest of her environment. So there are now
two worlds, each of which has a copy of Bob, and an Alice, who has a
particular result. Locality says that Bob's particle is unchanged from
production, so when he measure its spin, he splits into two copies,
according to spin up or spin down. Since Alice is standing beside him,
she also becomes entangled with his result. But Alice already has a
definite result in each branch, so we now have four branches: with
results 'up-up', 'up-down', 'down-up', and 'down-down'. However, only
the 'up-down' and 'down-up' branches conserve angular momentum. How do
you rule out the other branches?

When you put something in the cupboard and come back later to get it, why, under MWI, is it still there?

--

Stathis Papaioannou

[Bruno Marchal]

I have no clue what you mean. The singlet state guaranties the conservation of angular momentum in all worlds. The singlet state describes an infinity of "worlds",  and in each of them there is conservation of angular momentum, and it has a local common cause origin, the same in all worlds.

Bruno

Bruce

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

[Bruno Marchal]

On 13 Nov 2017, at 22:40, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:50:00 PM UTC-7, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:24:15 PM UTC-7, agrays...@gmail.com wrote:

On Sunday, November 12, 2017 at 11:15:33 AM UTC-7, John Clark wrote:

On Sun, Nov 12, 2017 at 1:01 AM, <agrays...@gmail.com> wrote:

​> ​

What is your definition of non-realistic? 

Nonrealistic means ​when something is not being observed it doesn't exist in any one definite state.​

 

​

You have to be careful here. For example, when the Earth-Moon system formed, it existed in a definite state, but was NOT observed. So not everything in a definite state must be observed, by detectors or conscious entities. OTOH, when an electron is prepared for a double slit experiment, it is in a superposition of states; that is, NOT in a definite state. If it were in a definite state, we'd observe the classical probability distribution. So quantum experiments, and QM in general to the extent it relies on superposition of states, is NONREALISTIC, whereas the macro world is generally REALISTIC. I can't speak to why the macro world is realistic.

FWIW, I left out an important reason why some systems are in definite states, like macro systems, and others not, such as quantum systems prepared for measurements. It's likely related to whether the systems in question are ISOLATED.

If you find collapse of the wf anathema, instead of the MWI why not just assume the branches that aren't measured in this world, dissipate into the environment as I think Decoherence theory postulates? 

In the MWI (= multiverse, = non-collapse), the dissipation is a (bad) terming for "entanglement with the environment".  If you have a superposition of some particle up + down, and that particle interact with some unknown passing particles, that you lost, from your point of view, the superposition is lost, as you would need the other particle to recover the interference of the initial particles. That is why it is hard to make macroscopic object interfere: they leak to easily to the environment, including to you, which is akin to a measurement. I use the expression "the superposition is contagious to the environment": the "dissipitation" is about the pure state, which behave like a mixed state when it has not been isolated enough.

Bruno

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

[agrays...@gmail.com]

I think my conjecture above is incorrect. Although finite strings of any length would repeat in an infinite random string, they would not repeat at regular intervals that would cause the original string to fail to represent an irrational number. OTOH, I think we can agree that necessary repetitions of whatever in a FINITE universe cannot be expected. Thus, if our universe is finite in extent and number of particles, there will be no automatic or expected repeats of anything. I submit that our universe is, indeed, finite (observable and unobservable regions) because it is FINITE IN AGE.

[Brent Meeker]

On 11/14/2017 6:18 AM, Bruno Marchal wrote:

On 13 Nov 2017, at 22:40, Bruce Kellett wrote:

On 14/11/2017 2:07 am, Bruno Marchal wrote:

On 12 Nov 2017, at 23:05, Bruce Kellett wrote:

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state.

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

I have no clue what you mean. The singlet state guaranties the conservation of angular momentum in all worlds. The singlet state describes an infinity of "worlds",  and in each of them there is conservation of angular momentum, and it has a local common cause origin, the same in all worlds.

But it's not a sufficient 'hidden' variable to explain the space-like correlation of measurements.

Brent

[Bruce Kellett]

On 15/11/2017 1:18 am, Bruno Marchal wrote:

On 13 Nov 2017, at 22:40, Bruce Kellett wrote:

On 14/11/2017 2:07 am, Bruno Marchal wrote:

On 12 Nov 2017, at 23:05, Bruce Kellett wrote:

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state.

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

I have no clue what you mean. The singlet state guaranties the conservation of angular momentum in all worlds. The singlet state describes an infinity of "worlds",  and in each of them there is conservation of angular momentum, and it has a local common cause origin, the same in all worlds.

Tell me what you don't understand and I will attempt to explain it more clearly, as I did when Brent asked about the confusion of negatives in my final sentence above. (I meant that, given locality, there are branches in the above scenario that violate angular momentum conservation.)

Local common cause explanations (aka 'Bertlmann's socks') have been known not to give the correct quantum correlations since at least Bell's time.

Bruce

[John Clark]

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

​> ​

the lack of ISOLATION is the condition for the existence of this macro definite state.

​A baseball made of 10^25 atoms ​has 10^25 times more ways to interact with the environment than a single atom does, so we'd expect to see a baseball in just one state about 

 

​10^25 times less often than we do in a single atom.​

 

​> ​

The concept of Multiverse and Many Worlds come from entirely different contexts and theories,

​I don't think anybody was even talking about the Multiverse before 1957 when Hugh Everett introduced the idea of Many Worlds, and Evert's idea won't work without the Multiverse. ​ That doesn't sound entirely different to me.

 

​> ​

For example, we know that irrational numbers exist

Do we?  We know that mathematicians can use the language of mathematics to write stories about irrational numbers

​,​

but nobody has ever seen a irrational number

​of​

 anything in the physical world. And we know that a English professor can write stories about The Lord Of The Rings, but noddy has ever seen

​​

Frodo Baggins

​ 

or The Shire.

 

​> ​

if your conjecture were true, it would be impossible for irrational numbers to exist, since recurring repetitions of subset strings would be impossible to avoid.

 

​If the ​

conjecture

​is​

 true

​ then there might be a infinite number of Turing Machines in the Multiverse but they couldn't communicate with each other and none of them would have a infinite amount of tape. So any real Turing Machine in the Multiverse is certain to eventually stop, not for any software reason but because of hardware failure. Eventual any real Turing machine will get a command like "move the read/wright head one box to the left write a 1 in the box and then change to state 6.02*10^23" but it will be unable to move one box to the left became it is already at the end of the tape and there is no more matter in the observable universe to extend it. If no physical process can produce them that 

seems to me a pretty good indication that the physical universe doesn't need irrational numbers (or even real numbers). Many Worlds is a theory about physics not mathematics so the philosophic debate about the existence or nonexistence of irrational numbers ​

has no bearing on existence or nonexistence of

​ Many Worlds.​

 John K Clark

[agrays...@gmail.com]

On Tuesday, November 14, 2017 at 3:32:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

Any macro object is in a definite state -- not a superposition of states -- at every moment in time, but obviously the state is constantly fluctuating due to interactions with its constituents and entities external to it. Due to the huge number of constituents, we can't write it down explicitly,

 

​> ​

the lack of ISOLATION is the condition for the existence of this macro definite state.

​A baseball made of 10^25 atoms ​has 10^25 times more ways to interact with the environment than a single atom does, so we'd expect to see a baseball in just one state about 

 

​10^25 times less often than we do in a single atom.​

 

​> ​

The concept of Multiverse and Many Worlds come from entirely different contexts and theories,

​I don't think anybody was even talking about the Multiverse before 1957 when Hugh Everett introduced the idea of Many Worlds, and Evert's idea won't work without the Multiverse. ​ That doesn't sound entirely different to me.

Multiverse arose in the context of string theory, after Everett's MWI. The difference between Multiverse and MWI is striking and obvious. For example, the former has nothing to do with Joe the Plumber shooting an electron at a slit in a lab and creating an awesome (uncountable!) number of NEW universes.

 

​> ​

For example, we know that irrational numbers exist

Do we? 

Of course. It has been proven that pi and e are not rational. It's also been proven that the irrationals are dense in the reals; that is, many "more" irrationals than rationals; the difference between countable and uncountable infinities. 

 

We know that mathematicians can use the language of mathematics to write stories about irrational numbers

​,​

but nobody has ever seen a irrational number

​of​

 anything in the physical world. And we know that a English professor can write stories about The Lord Of The Rings, but noddy has ever seen

​​

Frodo Baggins

​ 

or The Shire.

 

​> ​

if your conjecture were true, it would be impossible for irrational numbers to exist, since recurring repetitions of subset strings would be impossible to avoid.

 

​If the ​

conjecture

​is​

 true

​ then there might be a infinite number of Turing Machines in the Multiverse but they couldn't communicate with each other and none of them would have a infinite amount of tape. So any real Turing Machine in the Multiverse is certain to eventually stop, not for any software reason but because of hardware failure. Eventual any real Turing machine will get a command like "move the read/wright head one box to the left write a 1 in the box and then change to state 6.02*10^23" but it will be unable to move one box to the left became it is already at the end of the tape and there is no more matter in the observable universe to extend it. If no physical process can produce them that 

seems to me a pretty good indication that the physical universe doesn't need irrational numbers (or even real numbers). Many Worlds is a theory about physics not mathematics so the philosophic debate about the existence or nonexistence of irrational numbers ​

has no bearing on existence or nonexistence of

​ Many Worlds.​

I am not sufficiently knowledgeable about Turing machines to comment. HOWEVER, if you prefer, forget about number theory and consider the FINITE AGE of our universe, the observable and unobservable regions. It's been expanding for 13.8 billion years, so its spatial extent must be FINITE. This undercuts your argument about infinite repetitions of whatever. 

 

 John K Clark

[Brent Meeker]

On 11/14/2017 3:17 PM, agrays...@gmail.com wrote:
> HOWEVER, if you prefer, forget about number theory and consider the
> FINITE AGE of our universe, the observable and unobservable regions.
> It's been expanding for 13.8 billion years, so its spatial extent must
> be FINITE.

That only shows that the the finite piece we can see was finite in the
beginning.  It the universe were always infinite, the piece we can see
would still be finite.

Brent

[agrays...@gmail.com]

On Tuesday, November 14, 2017 at 4:17:29 PM UTC-7, agrays...@gmail.com wrote:

On Tuesday, November 14, 2017 at 3:32:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

Any macro object is in a definite state -- not a superposition of states -- at every moment in time, but obviously the state is constantly fluctuating due to interactions with its constituents and entities external to it. Due to the huge number of constituents, we can't write it down explicitly,

The "one" state I have been referring to, is, obviously, the resultant of all the states of its constituent particles, probably their tensor product., and fluctuating with time. 

[Bruce Kellett]

I don't understand the significance of your question. Why wouldn't things remain stable in MWI? After all, the whole world, as it is, becomes entangled with the particular branching event.

Bruce

[Bruce Kellett]

On 15/11/2017 12:44 am, smitra wrote:
> On 14-11-2017 09:23, Bruce Kellett wrote:
>> On 14/11/2017 5:51 pm, smitra wrote:
>>
>>> Within this model, Bob does not decohere until that time he is told
>>> what Alice has found.
>>
>> That is simply not true. Decoherence is not subject to a particular
>> person's knowledge. When Alice and Bob are next to each other, they
>> are jointly entangled with a particular result.
>
> I think that this needs to be discussed in more detail. Decoherence
> does not cause a superposition to get reduced to either one of the two
> possible outcomes. Given what Bob knows, he cannot locate himself in
> either sector. If this were not true then given everything Bob is
> aware of, he could get to better odds than 50-50 for guessing the
> spin. But that implies information transfer to something his brain can
> access.

One of the strongest arguments for MWI was that it eliminates the
concept of a conscious observer from the interpretation of quantum
mechanics. This is seen to be particularly important in quantum
cosmology, but it is relevant everywhere. You seem to be wanting to turn
the clock back and make consciousness, and conscious knowledge of
events, central to your interpretation.

The branches form under decoherence for every quantum event. Whether you
know about it or not, or know the result of the experiment, is
irrelevant. Schrödinger's cat is definitely dead in one branch, and
definitely alive in the other, whether you open the box or not.

That is MWI in standard QM. If you want to propose another theory in
which consciousness is central, then that is up to you. But you have to
show that your alternative theory reproduces all the observed results of
quantum mechanics before you can say that you are right and everyone
else is wrong.

> So, it boils down to decoherence acting on a microscopic degrees of
> freedom, while brains and computers must be robust systems that would
> not function well if they would be affected by such effects. Thermal
> noise would make computing impossible.
>
> If you have robust bitstrings that are only going to be affected by
> information present in the environment at a sufficiently coarse
> grained level, then that bitstring is never going to pick up any
> information about Alice's result other than via direct communication
> or any leakage of information e.g. if Bob is in to cold reading, or if
> there are other correlations at the macroscopic level that Bob can
> exploit.
>
> So, we have two decohered parallel worlds, but Bob is mentally
> identical in the two sectors despite decoherence having split his
> body. As long as he cannot access that information, he is the same
> person in both sectors.

And the rock on the ground outside the laboratory is the same in both
decohered worlds. That is irrelevant to the existence of such worlds in
MWI. As I said, Bob's knowledge or lack of knowledge is irrelevant to
the fact that locality implies there are worlds in which angular
momentum is not conserved in the scenario that I have outlined.

Bruce

[Brent Meeker]

On 11/14/2017 3:17 PM, agrays...@gmail.com wrote:

On Tuesday, November 14, 2017 at 3:32:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

Any macro object is in a definite state -- not a superposition of states -- at every moment in time,

This is misleading "a superposition of states" implies a pure state represented in some basis other than one in which it's an eigenstate.  A classical object is never in a state like that, because it is always entangled  with a lot of other objects.  Since those entanglements are unknowable, whatever basis we choose to represent the object will not include those entanglements and the density matrix we use will be a mixed state, one that represents all those entanglements (if it represents them at all) as statisicaly interactions that can just be averaged over.

but obviously the state is constantly fluctuating due to interactions with its constituents and entities external to it.

It's interaction with them means that it is entangled with them and has no pure state that does not also include them.  Regarding the object by itself is already implicitly averaging over or otherwise neglecting those entanglements.

Brent

[Russell Standish]

On Wed, Nov 15, 2017 at 11:05:22AM +1100, Bruce Kellett wrote:
>
> One of the strongest arguments for MWI was that it eliminates the concept of
> a conscious observer from the interpretation of quantum mechanics.

I disagree. The strongest argument is that it removes the need for a
mysterious nonunitary physical collapse process (that may or may not
be driven by a conscious observer).

A conscious observer (or rather just observer, really) is still
required to define the branches of the MWI, be that mediated by Zeh's
decoherence process, or otherwise. To eliminate observers entirely
requires solving the preferred basis problem without reference to an
observer or observation.


--

----------------------------------------------------------------------------
Dr Russell Standish Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Senior Research Fellow hpc...@hpcoders.com.au
Economics, Kingston University http://www.hpcoders.com.au
----------------------------------------------------------------------------

[agrays...@gmail.com]

On Tuesday, November 14, 2017 at 6:31:20 PM UTC-7, Brent wrote:

On 11/14/2017 3:17 PM, agrays...@gmail.com wrote:

On Tuesday, November 14, 2017 at 3:32:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

Any macro object is in a definite state -- not a superposition of states -- at every moment in time,

This is misleading "a superposition of states" implies a pure state represented in some basis other than one in which it's an eigenstate.  A classical object is never in a state like that,

Isn't that what I wrote; that a macro object is not in a superposition of states? You go on to more precisely define the state it is in.

[agrays...@gmail.com]

On Tuesday, November 14, 2017 at 6:49:33 PM UTC-7, Russell Standish wrote:

On Wed, Nov 15, 2017 at 11:05:22AM +1100, Bruce Kellett wrote:
>
> One of the strongest arguments for MWI was that it eliminates the concept of
> a conscious observer from the interpretation of quantum mechanics.

I disagree. The strongest argument is that it removes the need for a
mysterious nonunitary physical collapse process (that may or may not
be driven by a conscious observer).

A conscious observer (or rather just observer, really) is still
required to define the branches of the MWI, be that mediated by Zeh's
decoherence process, or otherwise. To eliminate observers entirely
requires solving the preferred basis problem without reference to an
observer or observation.

According to Feynman one doesn't need a conscious observer to perform a measurement, just a detector to record the result. Have I misinterpreted his conclusion? TIA. 

[Bruce Kellett]

On 15/11/2017 12:49 pm, Russell Standish wrote:
> On Wed, Nov 15, 2017 at 11:05:22AM +1100, Bruce Kellett wrote:
>> One of the strongest arguments for MWI was that it eliminates the concept of
>> a conscious observer from the interpretation of quantum mechanics.
> I disagree. The strongest argument is that it removes the need for a
> mysterious nonunitary physical collapse process (that may or may not
> be driven by a conscious observer).

I said "one of the strongest"! I know that you want to define QM from
the idea of observer moments. I don't think that this will work, and the
usual consensus is that one of the strengths of MWI is the elimination
of the conscious observer.

> A conscious observer (or rather just observer, really) is still
> required to define the branches of the MWI, be that mediated by Zeh's
> decoherence process, or otherwise. To eliminate observers entirely
> requires solving the preferred basis problem without reference to an
> observer or observation.

That is not true. The basis problem is solved by Zurek's einselection --
the preferred basis is the one that is stable against further
decoherence. Observers have nothing to do with it. In Zurek's account,
it is the fact that the results of interactions, be they measurements or
not, are recorded multiple times in the environment via decoherence,
that is the mark of an irreversible quantum event.

Bruce

[Brent Meeker]

And "recorded" may not bring the right picture to mind.  It is recorded
even if the information is radiated away into space.  The future light
cone is part of the environment.  But this makes me wonder if there are
degrees of this entanglement information.  Even though there are lot of
copies of Alice's results in the immediate vicinity, at a distance of
few billion light years the information is spread very thin, so there is
uncertainty as to whether it is entangled or not at that distance.  So,
if you are sufficiently far away, is there no longer any fact of the
matter about which result Alice got?  This might be a connection to the
quantization of spacetime, since at sufficiently time-like separated
points the propagation of from one superspace foliation to another must
satisfy an uncertainty principle.

Brent

[Russell Standish]

On Wed, Nov 15, 2017 at 02:46:21PM +1100, Bruce Kellett wrote:
> On 15/11/2017 12:49 pm, Russell Standish wrote:
> > On Wed, Nov 15, 2017 at 11:05:22AM +1100, Bruce Kellett wrote:
> > > One of the strongest arguments for MWI was that it eliminates the concept of
> > > a conscious observer from the interpretation of quantum mechanics.
> > I disagree. The strongest argument is that it removes the need for a
> > mysterious nonunitary physical collapse process (that may or may not
> > be driven by a conscious observer).
>
> I said "one of the strongest"! I know that you want to define QM from the
> idea of observer moments. I don't think that this will work, and the usual
> consensus is that one of the strengths of MWI is the elimination of the
> conscious observer.

Where's your evidence that this is the usual concensus? Who argues for it?

>
> > A conscious observer (or rather just observer, really) is still
> > required to define the branches of the MWI, be that mediated by Zeh's
> > decoherence process, or otherwise. To eliminate observers entirely
> > requires solving the preferred basis problem without reference to an
> > observer or observation.
>
> That is not true. The basis problem is solved by Zurek's einselection -- the
> preferred basis is the one that is stable against further
> decoherence.

I understand that the idea of einselection is still rather
controversial, but be that as it may, I can't see how it solves the
preferred basis problem. Consider an experiment where the experimenter
may choose between inserting a circularly polarised file, or a
linearly polarised one. The preferred basis (selected by einselection)
will depend on that choice. In MWI, we normally assume that there are
two branches of the universe with different choices made by the
experimenter. Unless there is some sort of superdeterminism in play,
where the experimenter does not have the freedom to choose. But
superdeterminism is certainly not a popular idea.

> Observers have nothing to do with it. In Zurek's account, it is the fact
> that the results of interactions, be they measurements or not, are recorded
> multiple times in the environment via decoherence, that is the mark of an
> irreversible quantum event.

If you put a system in contact with a completely symmetric heat bath,
there will be no preferred basis selected by einselection. The only
way for a basis to emerge is if there are system constraints of some
sort. I would argue that the only way these constraints could arise in
a Multiverse (which is symmetric by construction) is by considering
the environment from the point of view of some observer, ie the basic
symmetry breaking mechanism.

[Bruce Kellett]

True. The loss of interference due to radiation of IR photons from
buckeyballs means that information does not have to be 'recorded' in a
concrete sense -- it just has to be available somewhere, even if
recovery is not practicable.

> The future light cone is part of the environment. But this makes me
> wonder if there are degrees of this entanglement information. Even
> though there are lot of copies of Alice's results in the immediate
> vicinity, at a distance of few billion light years the information is
> spread very thin, so there is uncertainty as to whether it is
> entangled or not at that distance.

There is no distance parameter in the wave function for entanglement! So
distance makes no difference.

> So, if you are sufficiently far away, is there no longer any fact of
> the matter about which result Alice got? This might be a connection
> to the quantization of spacetime, since at sufficiently time-like
> separated points the propagation of from one superspace foliation to
> another must satisfy an uncertainty principle.

Why? I don't see a particular connection here.

Bruce

[Bruce Kellett]

On 15/11/2017 5:02 pm, Russell Standish wrote:
> On Wed, Nov 15, 2017 at 02:46:21PM +1100, Bruce Kellett wrote:
>> On 15/11/2017 12:49 pm, Russell Standish wrote:
>>> On Wed, Nov 15, 2017 at 11:05:22AM +1100, Bruce Kellett wrote:
>>>> One of the strongest arguments for MWI was that it eliminates the concept of
>>>> a conscious observer from the interpretation of quantum mechanics.
>>> I disagree. The strongest argument is that it removes the need for a
>>> mysterious nonunitary physical collapse process (that may or may not
>>> be driven by a conscious observer).
>> I said "one of the strongest"! I know that you want to define QM from the
>> idea of observer moments. I don't think that this will work, and the usual
>> consensus is that one of the strengths of MWI is the elimination of the
>> conscious observer.
> Where's your evidence that this is the usual concensus? Who argues for it?

Most people, indirectly if not directly. I am thinking of MWI proponents
such as Deutsch and Wallace. Wallace puts it like this "Some have argued
that he measurement problem of quantum mechanics gives us reason to
abandon the picture of science as describing an observer-independent
world....". He does not accept this view. The general view of scientific
realism consists in the belief that the objective external world is
independent of the observer. The thinking is related to Bell's assertion
that: "Measurement should never be introduced as a primitive process in
a fundamental mechanical theory like classical or quantum mechanics..."
Measurement, observation, observers are all related concepts in this
context.

>>> A conscious observer (or rather just observer, really) is still
>>> required to define the branches of the MWI, be that mediated by Zeh's
>>> decoherence process, or otherwise. To eliminate observers entirely
>>> requires solving the preferred basis problem without reference to an
>>> observer or observation.
>> That is not true. The basis problem is solved by Zurek's einselection -- the
>> preferred basis is the one that is stable against further
>> decoherence.
> I understand that the idea of einselection is still rather
> controversial,

Not really. See Schlosshauer's paper and book.

> but be that as it may, I can't see how it solves the
> preferred basis problem. Consider an experiment where the experimenter
> may choose between inserting a circularly polarised file, or a
> linearly polarised one. The preferred basis (selected by einselection)
> will depend on that choice.

That is a common misconception, but the angle selected for the
polarizer, or the S-G magnet in a spin measurement, is not a selection
of a measurement basis. The measurement is actually the observation
whether or not the photon/particle passes the filter. It is then an
inference from the observation of a point on a screen, or the firing (or
failing to fire) of a detector of some sort, that the
polarization/spin-component was such and such. You don't actually
measure anything in the selected orientation, you only ever measure
whether the particle passed the filter or not. So the actual measurement
is just a position measurement (position on a screen), and the
measurement basis is the position (pointer) basis.

> In MWI, we normally assume that there are
> two branches of the universe with different choices made by the
> experimenter.

That is really an oversimplification. It is done because it is simpler
to work with two-state systems, and position measurements are of a
continuous variable, so are not neatly two-valued.

> Unless there is some sort of superdeterminism in play,
> where the experimenter does not have the freedom to choose. But
> superdeterminism is certainly not a popular idea.

No, superdeterminism does not have many advocates.

>> Observers have nothing to do with it. In Zurek's account, it is the fact
>> that the results of interactions, be they measurements or not, are recorded
>> multiple times in the environment via decoherence, that is the mark of an
>> irreversible quantum event.
> If you put a system in contact with a completely symmetric heat bath,
> there will be no preferred basis selected by einselection.

The environment of a measurement or an interaction is not generally a
symmetric heat bath. If you measure a spin component (space
quantization) you get one of two spots on a screen downstream of the S-G
magnet. These are not symmetric wrt the rest of the environment. In one
world the irreversible record is of an upper spot. In the other world it
is of the lower spot. The distinction is not lost because of symmetry.
The basis for the measurement is the position basis, because that is
stable against further decoherence. The angle of the S-G magnet is not
the measurement basis.

> The only
> way for a basis to emerge is if there are system constraints of some
> sort. I would argue that the only way these constraints could arise in
> a Multiverse (which is symmetric by construction) is by considering
> the environment from the point of view of some observer, ie the basic
> symmetry breaking mechanism.

The observer is not a general symmetry breaking mechanism. The many
worlds in QM are not symmetric anyway.

Bruce

[scerir]

>> And "recorded" may not bring the right picture to mind. It is

[Bruce, I guess]

>True. The loss of interference due to radiation of IR photons from
>buckeyballs means that information does not have to be 'recorded' in a
>concrete sense -- it just has to be available somewhere, even if
>recovery is not practicable.

"The superposition of amplitudes is only valid if there is no way to know,
even in
principle, which path the particle took. It is important to realize that this
does not
imply that an observer actually takes note of what happens. It is sufficient
to destroy
the interference pattern, if the path information is accessible in principle
from the
experiment or even if it is dispersed in the environment and beyond any
technical
possibility to be recovered, but in principle 'still out there'."
--Anton Zeilinger, (Rev. Mod. Phys., 1999, p. S-288)

[Bruno Marchal]

The existence (or not) of irrational numbers is independent of the existence of a physical universe. Numbers are not physical objects, unless you postulate a vey special metaphysics making them so. But then you might describe it, perhaps.

Bruno

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[Bruno Marchal]

On 15 Nov 2017, at 00:17, agrays...@gmail.com wrote:

On Tuesday, November 14, 2017 at 3:32:08 PM UTC-7, John Clark wrote:

On Mon, Nov 13, 2017 at 11:52 PM, <agrays...@gmail.com> wrote:

​> ​

I think every macro system, although comprised of a huge number of individual constituents, is in one definite state;

​No object large enough to see with ​

your unaided ​can is in one definite state, that is to say can be described with a single quantum wave function, with the possible exception of a

Bose–Einstein condensate

​, and even then it would be so small ​it would be at the limits of visibility. And you're not going to see one in everyday life unless you visit a lab that can cool things down to less than a millionth of a degree above absolute zero that is needed to make a 

Bose–Einstein condensate

​.​

  Incidentally

unless  ​

ET

​exists and is also interested in physics research that lab you're visiting is

 the coldest place in the universe

​.​

 

 

Any macro object is in a definite state -- not a superposition of states -- at every moment in time, but obviously the state is constantly fluctuating due to interactions with its constituents and entities external to it. Due to the huge number of constituents, we can't write it down explicitly,

 

​> ​

the lack of ISOLATION is the condition for the existence of this macro definite state.

​A baseball made of 10^25 atoms ​has 10^25 times more ways to interact with the environment than a single atom does, so we'd expect to see a baseball in just one state about 

 

​10^25 times less often than we do in a single atom.​

 

​> ​

The concept of Multiverse and Many Worlds come from entirely different contexts and theories,

​I don't think anybody was even talking about the Multiverse before 1957 when Hugh Everett introduced the idea of Many Worlds, and Evert's idea won't work without the Multiverse. ​ That doesn't sound entirely different to me.

Multiverse arose in the context of string theory, after Everett's MWI. The difference between Multiverse and MWI is striking and obvious.

To my knowledge, "multiverse" is the terming given by David Deutsch for the Many-Worlds. Then, String Theory has used that terming in its context, but it could have used "many-World". String theory is a special application of QM.

For example, the former has nothing to do with Joe the Plumber shooting an electron at a slit in a lab and creating an awesome (uncountable!) number of NEW universes.

 

​> ​

For example, we know that irrational numbers exist

Do we? 

Of course. It has been proven that pi and e are not rational. It's also been proven that the irrationals are dense in the reals; that is, many "more" irrationals than rationals; the difference between countable and uncountable infinities. 

The rational are dense, but countable. The real are not countable. But this is mathematics, not physics. You need some metaphysical or theological hypothesis to talk about the existence or non-existence of a mathematical object in a physucal reality, or vice versa. See my work for an explanation that if Mechanism is true in cognitive science, then, there is 0 physical universe, as arithmetic emulate all dreams, and the physical apperances emerges from "number's dream" statistic. It seems you assume Aristotle metaphysics, which assumes that there is a primary/primitive/non-derivable Physical Universe.

Bruno

 

We know that mathematicians can use the language of mathematics to write stories about irrational numbers

​,​

but nobody has ever seen a irrational number

​of​

 anything in the physical world. And we know that a English professor can write stories about The Lord Of The Rings, but noddy has ever seen

​​

Frodo Baggins

​ 

or The Shire.

 

​> ​

if your conjecture were true, it would be impossible for irrational numbers to exist, since recurring repetitions of subset strings would be impossible to avoid.

 

​If the ​

conjecture

​is​

 true

​ then there might be a infinite number of Turing Machines in the Multiverse but they couldn't communicate with each other and none of them would have a infinite amount of tape. So any real Turing Machine in the Multiverse is certain to eventually stop, not for any software reason but because of hardware failure. Eventual any real Turing machine will get a command like "move the read/wright head one box to the left write a 1 in the box and then change to state 6.02*10^23" but it will be unable to move one box to the left became it is already at the end of the tape and there is no more matter in the observable universe to extend it. If no physical process can produce them that 

seems to me a pretty good indication that the physical universe doesn't need irrational numbers (or even real numbers). Many Worlds is a theory about physics not mathematics so the philosophic debate about the existence or nonexistence of irrational numbers ​

has no bearing on existence or nonexistence of

​ Many Worlds.​

I am not sufficiently knowledgeable about Turing machines to comment. HOWEVER, if you prefer, forget about number theory and consider the FINITE AGE of our universe, the observable and unobservable regions. It's been expanding for 13.8 billion years, so its spatial extent must be FINITE. This undercuts your argument about infinite repetitions of whatever. 

 

 John K Clark

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[Bruno Marchal]

OK, but not instantaneously. This might be the point where we disagree in the interpretation of the Non-collapse theory. 

Bruno

Bruce

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[Bruno Marchal]

If the the explanation is based on hidden variable, per branch, then there will be non-locality. But the many universe are not really hidden variable in the sense of EPR-Bell's, which assumes Alice and Bob have the same identity and keep it, when they do the space-like measurement, but it seems to me that this is a wrong interpretation of the singlet state when we suppress any possible collapse. If Alice and Bob are space-like separated, they will later only access to the Bob and Alice they will locally be able to interact with, and those are "new" people, not the original couple. 

Bruno

Brent

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[Bruno Marchal]

Everett use the theory of Mechanism for consciousness, and yes, that
is the main reason to prefer MWI than an hardly intelligible action of
consciousness on matter, but I think Saibal was using only the usual
first person/third person distinction, that Mechanism implied (if I
got his point).

Bruno

>
>
>> So, it boils down to decoherence acting on a microscopic degrees of
>> freedom, while brains and computers must be robust systems that
>> would not function well if they would be affected by such effects.
>> Thermal noise would make computing impossible.
>>
>> If you have robust bitstrings that are only going to be affected by
>> information present in the environment at a sufficiently coarse
>> grained level, then that bitstring is never going to pick up any
>> information about Alice's result other than via direct
>> communication or any leakage of information e.g. if Bob is in to
>> cold reading, or if there are other correlations at the macroscopic
>> level that Bob can exploit.
>>
>> So, we have two decohered parallel worlds, but Bob is mentally
>> identical in the two sectors despite decoherence having split his
>> body. As long as he cannot access that information, he is the same
>> person in both sectors.
>
> And the rock on the ground outside the laboratory is the same in
> both decohered worlds. That is irrelevant to the existence of such
> worlds in MWI. As I said, Bob's knowledge or lack of knowledge is
> irrelevant to the fact that locality implies there are worlds in
> which angular momentum is not conserved in the scenario that I have
> outlined.
>
> Bruce
>

[agrays...@gmail.com]

As "Multiverse" is now usually used, it refers to the multitude of possible universes with different basic parameters that might exist in parallel as claimed by String Theory, whereas the way Many Worlds is used it refers to the (uncountable!) universes allegedly automatically created when Joe the Plumber goes into a lab and shoots an electron at, say, a double slit. The two types of multiple worlds are conceptually different, hugely different, and that was all I was asserting. To claim that the two concepts are somehow the same is a common error, and egregiously misleading to equate them.  

For example, the former has nothing to do with Joe the Plumber shooting an electron at a slit in a lab and creating an awesome (uncountable!) number of NEW universes.

 

​> ​

For example, we know that irrational numbers exist

Do we? 

Of course. It has been proven that pi and e are not rational. It's also been proven that the irrationals are dense in the reals; that is, many "more" irrationals than rationals; the difference between countable and uncountable infinities. 

The rational are dense, but countable. The real are not countable. But this is mathematics, not physics. You need some metaphysical or theological hypothesis to talk about the existence or non-existence of a mathematical object in a physucal reality, or vice versa. See my work for an explanation that if Mechanism is true in cognitive science, then, there is 0 physical universe, as arithmetic emulate all dreams, and the physical apperances emerges from "number's dream" statistic. It seems you assume Aristotle metaphysics, which assumes that there is a primary/primitive/non-derivable Physical Universe.

Why are you splitting hairs? Clark questioned whether irrational numbers exist. I asserted their existence has been proven, obviously in the context of mathematics and mathematical logic. I didn't assert, and wouldn't, that they exist in the physical world, any more than I would assert you can find a perfect triangle in the physical world.  

I am  interested in your opinion that, as I contend,  the universe we inhabit, must be finite in spatial extent since it is finite in age. This is the elephant in the room that no one wants to discuss, apparently. 

[Brent Meeker]

But decoherence is a statistical effect.  If the probability of
interacting with the wave function at great distance becomes very small,
then decoherence is operationally ineffective - you can't, at that
distance, recover enough information to say which way Alice's
measurement turned out.  And the reason for that (maybe) is that the
foliation of spacetime has too much uncertainty over that interval.
Maybe this is empirically ruled out by the lensing of  distant
galaxies...I'll have to think about it.

Brent

[Russell Standish]

On Wed, Nov 15, 2017 at 07:33:12AM -0800, agrays...@gmail.com wrote:
>
>
> On Wednesday, November 15, 2017 at 7:51:09 AM UTC-7, Bruno Marchal wrote:
> >
> >
> > On 15 Nov 2017, at 00:17, agrays...@gmail.com <javascript:> wrote:
> >
> >
> > Multiverse arose in the context of string theory, after Everett's MWI. The
> > difference between Multiverse and MWI is striking and obvious.
> >
> >
> >
> > To my knowledge, "multiverse" is the terming given by David Deutsch for
> > the Many-Worlds. Then, String Theory has used that terming in its context,
> > but it could have used "many-World". String theory is a special application
> > of QM.
> >
>

> *As "Multiverse" is now usually used, it refers to the multitude of

> possible universes with different basic parameters that might exist in
> parallel as claimed by String Theory, whereas the way Many Worlds is used
> it refers to the (uncountable!) universes allegedly automatically created
> when Joe the Plumber goes into a lab and shoots an electron at, say, a
> double slit. The two types of multiple worlds are conceptually different,
> hugely different, and that was all I was asserting. To claim that the two
> concepts are somehow the same is a common error, and egregiously misleading

> to equate them. *
>

Multiverse can refer to any of the ensembles, depending on the
author. String theorists will be referring to the string lanscape, as
you observe, but for say someone like David Deutsch, Multiverse refers
to the Many Wolds of MWI. I think Deutsch coined the term originally.

Yes it is important to distinguish the difference ensembles, as in
Tegmark's classification of multiverses. IIRC, the string landscape
is a level 2 multiverse and the many worlds a level 3 multiverse.



>
> *I am interested in your opinion that, as I contend, the universe we

> inhabit, must be finite in spatial extent since it is finite in age. This

> is the elephant in the room that no one wants to discuss, apparently. *
>

As Brent explained, if the universe is infinite in extent at t=0, it
remains infinite in extent at finite times.

[agrays...@gmail.com]

On Wednesday, November 15, 2017 at 12:55:18 PM UTC-7, Russell Standish wrote:

On Wed, Nov 15, 2017 at 07:33:12AM -0800, agrays...@gmail.com wrote:
>
>
> On Wednesday, November 15, 2017 at 7:51:09 AM UTC-7, Bruno Marchal wrote:
> >
> >
> > On 15 Nov 2017, at 00:17, agrays...@gmail.com <javascript:> wrote:
> >
> >
> > Multiverse arose in the context of string theory, after Everett's MWI. The
> > difference between Multiverse and MWI is striking and obvious.
> >
> >
> >
> > To my knowledge, "multiverse" is the terming given by David Deutsch for
> > the Many-Worlds. Then, String Theory has used that terming in its context,
> > but it could have used "many-World". String theory is a special application
> > of QM.
> >
>
> *As "Multiverse" is now usually used, it refers to the multitude of
> possible universes with different basic parameters that might exist in
> parallel as claimed by String Theory, whereas the way Many Worlds is used
> it refers to the (uncountable!) universes allegedly automatically created
> when Joe the Plumber goes into a lab and shoots an electron at, say, a
> double slit. The two types of multiple worlds are conceptually different,
> hugely different, and that was all I was asserting. To claim that the two
> concepts are somehow the same is a common error, and egregiously misleading
> to equate them. *
>

Multiverse can refer to any of the ensembles, depending on the
author. String theorists will be referring to the string lanscape, as
you observe, but for say someone like David Deutsch, Multiverse refers
to the Many Wolds of MWI. I think Deutsch coined the term originally.

 Yes, Deutsch. AG

Yes it is important to distinguish the difference ensembles, as in
Tegmark's classification of multiverses. IIRC, the string landscape
is a level 2 multiverse and the many worlds a level  3 multiverse.  



>
> *I am  interested in your opinion that, as I contend,  the universe we
> inhabit, must be finite in spatial extent since it is finite in age. This
> is the elephant in the room that no one wants to discuss, apparently. *
>

As Brent explained, if the universe is infinite in extent at t=0, it
remains infinite in extent at finite times.

But if it tunnels into existence at t=0, how can it be infinite in extent? I find that egregiously hard to imagine, plus the fact that one has to use QM to explain the tunneling, and that, ipso facto, seems to imply it's infinitesimally small in spatial extent t=0 at . AG 

[Brent Meeker]

On 11/15/2017 7:04 AM, Bruno Marchal wrote:

On 14 Nov 2017, at 21:15, Brent Meeker wrote:

On 11/14/2017 6:18 AM, Bruno Marchal wrote:

On 13 Nov 2017, at 22:40, Bruce Kellett wrote:

On 14/11/2017 2:07 am, Bruno Marchal wrote:

On 12 Nov 2017, at 23:05, Bruce Kellett wrote:

What really annoys me is the continued claim that many worlds eliminates the need for non-locality. It does not, and neither Bruno nor anyone else has ever produced a valid argument as to how many worlds might restore locality.

But nobody has proved that there is non locality in the MWI. EPR-BELL proves non-locality apparant in each branch, but the MWI avoids the needs of action at a distance to explains them. Once Alice and Bob are space-separated, their identity are independent. It makes no sense to talk of each of them like if they were related, (unless you correlate them with a third observer, etc) If they do measurement, some God could see that they are indeed no more related, but if they decide to come back to place where they can compared locally their spin, they will always get contact to the corresponding observer with the well correlated spin. The independent Alice and Bob will never meet because they can't belong to the same branch of the multiverse, by the MWI of the singlet state. So Mitra is right. Although Bertlmann's socks are tyically not working for Bell's violation in a MONO-universe, it works again in the MWI, applied in this case to the whole singlet state.

Bell has proved non-locality in MWI, every bit as much as in each branch separately. You appear not to have grasped the significance of the scenario I have argued carefully. Alice and Bob are not space-like separated in the scenario I outlined. Alice and Bob are together in the same laboratory when the second measurement is made. They are necessarily in the same world before, and branch in together according to Bob's result. Your mumbo-jumbo about them only being able to meet in appropriate matching branches does not work here, because they are always in the same branch. And there is no reason to suppose that their results in some of those branches do not violate conservation of angular momentum.

I have no clue what you mean. The singlet state guaranties the conservation of angular momentum in all worlds. The singlet state describes an infinity of "worlds",  and in each of them there is conservation of angular momentum, and it has a local common cause origin, the same in all worlds.

But it's not a sufficient 'hidden' variable to explain the space-like correlation of measurements.

If the the explanation is based on hidden variable, per branch, then there will be non-locality. But the many universe are not really hidden variable in the sense of EPR-Bell's, which assumes Alice and Bob have the same identity and keep it, when they do the space-like measurement, but it seems to me that this is a wrong interpretation of the singlet state when we suppress any possible collapse. If Alice and Bob are space-like separated, they will later only access to the Bob and Alice they will locally be able to interact with, and those are "new" people, not the original couple.

But that's the point of Bruce's version in which the measurements are time-like.  Alice and Bob will have continuity of identity and, as he argues, the explanation for the correlation of results being stronger than classical must be the same.

Brent

[Bruce Kellett]

Yes, there is a considerable body of experimental evidence to this
effect. It is not necessary to observe or record some information for
that to have observable quantum effects, as long it is "out there"
somewhere. Conscious observers are definitely secondary.

Bruce

[Bruce Kellett]

On 16/11/2017 1:55 am, Bruno Marchal wrote:

On 15 Nov 2017, at 00:55, Bruce Kellett wrote:

On 15/11/2017 12:47 am, Stathis Papaioannou wrote:

On Mon, 13 Nov 2017 at 8:54 am, Bruce Kellett <bhke...@optusnet.com.au> wrote:

I don't think you have fully understood the scenario I have outlined.
There is no collapse, many worlds is assumed throughout. Alice splits
according to her measurement result. Both copies of Alice go to meet
Bob, carrying the other particle of the original pair. Since they both
have now met Bob, the split that Alice occasioned has now spread to
entangle Bob as well as the rest of her environment. So there are now
two worlds, each of which has a copy of Bob, and an Alice, who has a
particular result. Locality says that Bob's particle is unchanged from
production, so when he measure its spin, he splits into two copies,
according to spin up or spin down. Since Alice is standing beside him,
she also becomes entangled with his result. But Alice already has a
definite result in each branch, so we now have four branches: with
results 'up-up', 'up-down', 'down-up', and 'down-down'. However, only
the 'up-down' and 'down-up' branches conserve angular momentum. How do
you rule out the other branches?

When you put something in the cupboard and come back later to get it, why, under MWI, is it still there?

I don't understand the significance of your question. Why wouldn't things remain stable in MWI? After all, the whole world, as it is, becomes entangled with the particular branching event.

OK, but not instantaneously. This might be the point where we disagree in the interpretation of the Non-collapse theory.

I think that the general idea is that the entanglement with the result spreads at the velocity of light -- inside the forward light cone. This spread of entanglement does not require that all objects in the forward light cone have explicitly interacted with the original event. The mathematics are quite clear on this point.

Bruce

[Brent Meeker]

On 11/15/2017 12:06 PM, agrays...@gmail.com wrote:
>
> But if it tunnels into existence at t=0, how can it be infinite in
> extent? I find that egregiously hard to imagine, plus the fact that
> one has to use QM to explain the tunneling, and that, ipso facto,
> seems to imply it's infinitesimally small in spatial extent t=0 at

A limitation of imagination.  Nothing about tunneling assumes a size.

Brent

[Bruce Kellett]

Is it? I thought it was a consequence of deterministic evolution
according to the Schrödinger equation.

> If the probability of interacting with the wave function at great
> distance becomes very small, then decoherence is operationally
> ineffective - you can't, at that distance, recover enough information
> to say which way Alice's measurement turned out.

If you build a big enough telescope and gather enough photons, you can
look through the laboratory window and read Alice's lab book over her
shoulder. There is nothing in current physics to say that this is
impossible in principle.

> And the reason for that (maybe) is that the foliation of spacetime has
> too much uncertainty over that interval. Maybe this is empirically
> ruled out by the lensing of distant galaxies...I'll have to think
> about it.

I think the evidence you are thinking of is the simultaneous arrival of
all frequencies from distant gamma bursters. This casts some doubt on
some granular models of space-time, but I doubt that it rules out all
such possibilities.

Bruce

[John Clark]

On Tue, Nov 14, 2017 at 6:17 PM, <agrays...@gmail.com> wrote:

​> ​

Any macro object is in a definite state

​That is incorrect. An electron an be in a single quantum state with just one associated wave function, 2 electrons can do the sane thing in superconductors they're called "Cooper pairs", and the same can also be true for several million atoms in a Bose–Einstein condensate but you have to cool them  to less than a millionth of a degree above absolute zero; but all the 10^25 atoms in a baseball have their own different wave function because unlike the atoms in a Bose–Einstein condensate all the atoms in a baseball are NOT entangled with each other, if they were a baseball would exhibit the same weird behavior as an electron.  That would certainly make for a more interesting game and might even be enough to turn me into a baseball fan.

Two atoms are quantum entangled entangled if they have the same wave function but it's a delicate condition and must be carefully isolated from the environment, the more atoms the more delicate it is, 10^25 atoms is so delicate we never see it.    

​>​

Multiverse arose in the context of string theory, after Everett's MWI. The difference between Multiverse and MWI is striking and obvious.

​Explain to me how ​

Everett's MWI

​ can work without the Multiverse.​ The fact that string theory also needs a Multiverse just give more support to Everett, or at least it would if there were any experimental evidence to indecate string theory was true,  

​>

​>>​

​

For example, we know that irrational numbers exist

​>> ​

Do we? 

​> ​

O

​​

f course. It has been proven that pi and e are not rational.

​Yes, in the language of mathematics there are stories about rational and irrational numbers and there are also stories about pi and e and you can prove that the stories abut irrationality are consistent with pi and e. And in the language of English there are stories about Harry Potter and it can be proven that Harry's aunt is named Petunia, but there is no proof that harry or Petunia exist in the physical world and there is no proof 

pi or e (not to be confused with the approximations of pi and e) have any effect on the laws of physics.  ​

 

 

It's also been proven that the irrationals are dense in the reals; that is, many "more" irrationals than rationals;

​And the stories also say there are many more  non-computable Real numbers ​

​than computable Real numbers, the set of computable numbers is not dense on the reals, its countably infinite with a cardinality of 

Aleph-naught

​. If a number is not computable, ​that is to say  unlike pi or e then is no procedure for even approximating it then I don't see how it cold be of any importance to physics. And I say again Many Worlds is a theory about physics not mathematics.  

What about the rational numbers, does physics need all of them? 

 The answer in not certain but we already have good reason to suspect that neither time nor space is continuous, although although we won't know for sure until we understand quantum gravity.  ​

 

​>> ​

there might be a infinite number of Turing Machines in the Multiverse but they couldn't communicate with each other and none of them would have a infinite amount of tape. So any real Turing Machine in the Multiverse is certain to eventually stop, not for any software reason but because of hardware failure. Eventual any real Turing machine will get a command like "move the read/wright head one box to the left write a 1 in the box and then change to state 6.02*10^23" but it will be unable to move one box to the left became it is already at the end of the tape and there is no more matter in the observable universe to extend it. If no physical process can produce them that 

seems to me a pretty good indication that the physical universe doesn't need irrational numbers (or even real numbers). Many Worlds is a theory about physics not mathematics so the philosophic debate about the existence or nonexistence of irrational numbers ​

has no bearing on existence or nonexistence of

​ Many Worlds.​

​> ​

I am not sufficiently knowledgeable about Turing machines to comment.

​All you need to know is that a Turing Machine is the simplest most fundamental form of computer that operates according to the known laws of physics, so if a Turning Machine can't do something then no computer can, and a Turing Machine can't calculate a single irrational number, not even if it makes use of all the matter in the observable universe, not even if it has infinite time to work on it. And that makes me think irrational numbers are not fundamentally important to the laws of physics or to our physical world.

 

​> ​

HOWEVER, if you prefer, forget about number theory and consider the FINITE AGE of our universe, the observable and unobservable regions. It's been expanding for 13.8 billion years, so its spatial extent must be FINITE. This undercuts your argument about infinite repetitions of whatever. 

​Right now the most popular Cosmological theory is inflation, if it's correct then the Big Bang was just a trivial occurrence  that happened 13.8 billion years ago in a infinitely old Multiverse.  ​

Alan Guth postulated a inflation field that decayed away in a process somewhat analogous to radioactive half life, and after the decay the universe expanded at a much much more leisurely pace. But then Andre Linde proved that for Guth's idea to work the inflation field had to expand faster than it decayed, Linde called it "Eternal Inflation". Linde showed that for every volume in which the inflation field decays away 2 other volumes don't decay. So one universe becomes 3, the field decays in one universe but not in the other 2, then both of those two universes splits in 3 again and the inflation field decays away in one and doesn't decay in 2 others, and it goes on forever. So what we call "The Big Bang" isn't the beginning of everything it's just the end of inflation in our particular part of the universe. So according to Linde this field created one Big Bang, then 2, then 4, then 8, then 16 etc in a unending process. Maybe in one of those universes Schrodinger's cat is dead and in another the cat is alive. 

​

It's interesting that first ​

Everett

​ needed the Multiverse to explain quantum ​weirdness, and then independently the string people discovered they needed the Multiverse in their struggle to develop quantum gravity, and then independent of the previous two the inflation people needed the Multiverse to explain the Big Bang. It seems like its all coming together, it makes me think the Multiverse might actually exist.   

John K Clark

 

 

[Russell Standish]

On Wed, Nov 15, 2017 at 10:54:51PM +1100, Bruce Kellett wrote:
> On 15/11/2017 5:02 pm, Russell Standish wrote:
> > On Wed, Nov 15, 2017 at 02:46:21PM +1100, Bruce Kellett wrote:

> > > I said "one of the strongest"! I know that you want to define QM from the
> > > idea of observer moments. I don't think that this will work, and the usual
> > > consensus is that one of the strengths of MWI is the elimination of the
> > > conscious observer.
> > Where's your evidence that this is the usual concensus? Who argues for it?
>
> Most people, indirectly if not directly. I am thinking of MWI proponents
> such as Deutsch and Wallace. Wallace puts it like this "Some have argued
> that he measurement problem of quantum mechanics gives us reason to abandon
> the picture of science as describing an observer-independent world....". He
> does not accept this view. The general view of scientific realism consists
> in the belief that the objective external world is independent of the
> observer. The thinking is related to Bell's assertion that: "Measurement
> should never be introduced as a primitive process in a fundamental
> mechanical theory like classical or quantum mechanics..." Measurement,
> observation, observers are all related concepts in this context.
>

Deutsch, I could believe would argue that. But Wheeler would be a
counter to that. I'm not that familiar with Wallace.

> > > > A conscious observer (or rather just observer, really) is still
> > > > required to define the branches of the MWI, be that mediated by Zeh's
> > > > decoherence process, or otherwise. To eliminate observers entirely
> > > > requires solving the preferred basis problem without reference to an
> > > > observer or observation.
> > > That is not true. The basis problem is solved by Zurek's einselection -- the
> > > preferred basis is the one that is stable against further
> > > decoherence.
> > I understand that the idea of einselection is still rather
> > controversial,
>
> Not really. See Schlosshauer's paper and book.
>

I haven't really followed the literature, but it strikes me that
problem is that ultimately einselection is not a unitary process, so
it has to be considered as the result of some sort of coarse graining
(which is, of course, due to the actions of the observer discretising
a continuous world), in much the same way as the second law of
thermodynamics emerges from a strictly reversible microscopic
dynamics.

I find it intriguing that the recent critique of Einselection by
Kastner is entitled "`Einselection' of Pointer Observables: the new
H-Theorem". The H-Theorem, as I'm sure you know, but for the benefit
of other lurkers is Bolzmann's mechanism of deriving the second law
from coarse graining the revrsible microscopic dynamics.

> > but be that as it may, I can't see how it solves the
> > preferred basis problem. Consider an experiment where the experimenter
> > may choose between inserting a circularly polarised file, or a
> > linearly polarised one. The preferred basis (selected by einselection)
> > will depend on that choice.
>
> That is a common misconception, but the angle selected for the polarizer, or
> the S-G magnet in a spin measurement, is not a selection of a measurement
> basis. The measurement is actually the observation whether or not the
> photon/particle passes the filter. It is then an inference from the
> observation of a point on a screen, or the firing (or failing to fire) of a
> detector of some sort, that the polarization/spin-component was such and
> such. You don't actually measure anything in the selected orientation, you
> only ever measure whether the particle passed the filter or not. So the
> actual measurement is just a position measurement (position on a screen),
> and the measurement basis is the position (pointer) basis.
>

But not all measurements are measurements of the position of
something. What about measuring the voltage of a circuit using an A->D
converter? Or the measurement of the momentum of a charged particle in
an electron multier?

> > In MWI, we normally assume that there are
> > two branches of the universe with different choices made by the
> > experimenter.
>
> That is really an oversimplification. It is done because it is simpler to
> work with two-state systems, and position measurements are of a continuous
> variable, so are not neatly two-valued.
>

The choice between circularly polarised filter and linear polarised
filters is binary. Obviously, there follows the choice of orientation,
which is continuous...

> > Unless there is some sort of superdeterminism in play,
> > where the experimenter does not have the freedom to choose. But
> > superdeterminism is certainly not a popular idea.
>
> No, superdeterminism does not have many advocates.
>
> > > Observers have nothing to do with it. In Zurek's account, it is the fact
> > > that the results of interactions, be they measurements or not, are recorded
> > > multiple times in the environment via decoherence, that is the mark of an
> > > irreversible quantum event.
> > If you put a system in contact with a completely symmetric heat bath,
> > there will be no preferred basis selected by einselection.
>
> The environment of a measurement or an interaction is not generally a
> symmetric heat bath.

If there is no experimenter, just an environment, then we must
consider all possible environments in superposition. That will have
maximal symmetry.

> If you measure a spin component (space quantization)
> you get one of two spots on a screen downstream of the S-G magnet. These are
> not symmetric wrt the rest of the environment.

That is because we're considering an SG experiment, with an SG
experimenter. That breaks the symmetry.

> In one world the irreversible
> record is of an upper spot. In the other world it is of the lower spot. The
> distinction is not lost because of symmetry. The basis for the measurement
> is the position basis, because that is stable against further decoherence.
> The angle of the S-G magnet is not the measurement basis.
>
> > The only
> > way for a basis to emerge is if there are system constraints of some
> > sort. I would argue that the only way these constraints could arise in
> > a Multiverse (which is symmetric by construction) is by considering
> > the environment from the point of view of some observer, ie the basic
> > symmetry breaking mechanism.
>
> The observer is not a general symmetry breaking mechanism.

I would argue that observation in a multiverse is a symmetry breaking
mechanism. In the multiverse, all possible outcomes of a measurement
exist as separate branches, and if all outcomes are equally likely,
there is a fundamental symmetry along that measurement axis. But the
action of observation fixes the outcome for a particular observer,
breaking that symmetry.

> The many worlds
> in QM are not symmetric anyway.
>

Not completely, but far more symmetric that the world we inhabit.

[agrays...@gmail.com]

Agreed. My imagination is not the be-all, or end-all of anything. But isn't it claimed that Einstein's field equations breakdown earlier than Planck time, and this is where QM must be invoked, when the universe is presumably very small in spatial extent?  Alternatively, doesn't tunneling assume QM, which is a theory about the micro world. As I recall the concept is limited to QM. AG

[Bruce Kellett]

On 16/11/2017 9:14 am, Russell Standish wrote:
> On Wed, Nov 15, 2017 at 10:54:51PM +1100, Bruce Kellett wrote:
>> On 15/11/2017 5:02 pm, Russell Standish wrote:
>>> On Wed, Nov 15, 2017 at 02:46:21PM +1100, Bruce Kellett wrote:
>>>> I said "one of the strongest"! I know that you want to define QM from the
>>>> idea of observer moments. I don't think that this will work, and the usual
>>>> consensus is that one of the strengths of MWI is the elimination of the
>>>> conscious observer.
>>> Where's your evidence that this is the usual concensus? Who argues for it?
>> Most people, indirectly if not directly. I am thinking of MWI proponents
>> such as Deutsch and Wallace. Wallace puts it like this "Some have argued
>> that he measurement problem of quantum mechanics gives us reason to abandon
>> the picture of science as describing an observer-independent world....". He
>> does not accept this view. The general view of scientific realism consists
>> in the belief that the objective external world is independent of the
>> observer. The thinking is related to Bell's assertion that: "Measurement
>> should never be introduced as a primitive process in a fundamental
>> mechanical theory like classical or quantum mechanics..." Measurement,
>> observation, observers are all related concepts in this context.
>>
> Deutsch, I could believe would argue that. But Wheeler would be a
> counter to that. I'm not that familiar with Wallace.

Wallace is a collaborator with Deutsch. I don't know what Wheeler would
say here> I think he was a believer in scientific realism -- reality
without an observer. But then, head counts don't really amount to much.

>>>>> A conscious observer (or rather just observer, really) is still
>>>>> required to define the branches of the MWI, be that mediated by Zeh's
>>>>> decoherence process, or otherwise. To eliminate observers entirely
>>>>> requires solving the preferred basis problem without reference to an
>>>>> observer or observation.
>>>> That is not true. The basis problem is solved by Zurek's einselection -- the
>>>> preferred basis is the one that is stable against further
>>>> decoherence.
>>> I understand that the idea of einselection is still rather
>>> controversial,
>> Not really. See Schlosshauer's paper and book.
>>
> I haven't really followed the literature, but it strikes me that
> problem is that ultimately einselection is not a unitary process, so
> it has to be considered as the result of some sort of coarse graining
> (which is, of course, due to the actions of the observer discretising
> a continuous world), in much the same way as the second law of
> thermodynamics emerges from a strictly reversible microscopic
> dynamics.

That is not correct. einselection is entirely unitary. It is closely
related to the nature of the interaction Hamiltonian between the system
and the environment. There is no collapse involved. It is a question of
stability against further decoherence rather than anything else.

> I find it intriguing that the recent critique of Einselection by
> Kastner is entitled "`Einselection' of Pointer Observables: the new
> H-Theorem". The H-Theorem, as I'm sure you know, but for the benefit
> of other lurkers is Bolzmann's mechanism of deriving the second law
> from coarse graining the revrsible microscopic dynamics.

I am not familiar with this argument, but if he related einselection to
coarse graining, then he has missed the point.

Bruce

[Bruce Kellett]

On 16/11/2017 9:14 am, Russell Standish wrote:

On Wed, Nov 15, 2017 at 10:54:51PM +1100, Bruce Kellett wrote:

On 15/11/2017 5:02 pm, Russell Standish wrote:

but be that as it may, I can't see how it solves the
preferred basis problem. Consider an experiment where the experimenter
may choose between inserting a circularly polarised file, or a
linearly polarised one. The preferred basis (selected by einselection)
will depend on that choice.

That is a common misconception, but the angle selected for the polarizer, or
the S-G magnet in a spin measurement, is not a selection of a measurement
basis. The measurement is actually the observation whether or not the
photon/particle passes the filter. It is then an inference from the
observation of a point on a screen, or the firing (or failing to fire) of a
detector of some sort, that the polarization/spin-component was such and
such. You don't actually measure anything in the selected orientation, you
only ever measure whether the particle passed the filter or not. So the
actual measurement is just a position measurement (position on a screen),
and the measurement basis is the position (pointer) basis.

But not all measurements are measurements of the position of
something. What about measuring the voltage of a circuit using an A->D
converter?

A surrogate measurement of the position of a pointer on a voltmeter.

 Or the measurement of the momentum of a charged particle in
an electron multier?

Do you mean "electron multiplier"? Would than not be an energy measurement? Momentum of a charged particle is often measured by tracking the path of the charged particle in a magnetic field.

In MWI, we normally assume that there are
two branches of the universe with different choices made by the
experimenter.

That is really an oversimplification. It is done because it is simpler to
work with two-state systems, and position measurements are of a continuous
variable, so are not neatly two-valued.

The choice between circularly polarised filter and linear polarised
filters is binary. Obviously, there follows the choice of orientation,
which is continuous...

Whatever the choice of orientation, the outcome is binary, pass or not pass.

Unless there is some sort of superdeterminism in play,
where the experimenter does not have the freedom to choose. But
superdeterminism is certainly not a popular idea.

No, superdeterminism does not have many advocates.

Observers have nothing to do with it. In Zurek's account, it is the fact
that the results of interactions, be they measurements or not, are recorded
multiple times in the environment via decoherence, that is the mark of an
irreversible quantum event.

If you put a system in contact with a completely symmetric heat bath,
there will be no preferred basis selected by einselection.

The environment of a measurement or an interaction is not generally a
symmetric heat bath.

If there is no experimenter, just an environment, then we must
consider all possible environments in superposition. That will have
maximal symmetry.

"All possible environments in superposition"? That is seriously under-defined. Besides, that would only have a pseudo-symmetry.

If you measure a spin component (space quantization)
you get one of two spots on a screen downstream of the S-G magnet. These are
not symmetric wrt the rest of the environment.

That is because we're considering an SG experiment, with an SG
experimenter. That breaks the symmetry.

The environment breaks the symmetry. The environment may contain an experimenter, but need not. A camera would do the job.

In one world the irreversible
record is of an upper spot. In the other world it is of the lower spot. The
distinction is not lost because of symmetry. The basis for the measurement
is the position basis, because that is stable against further decoherence.
The angle of the S-G magnet is not the measurement basis.

The only
way for a basis to emerge is if there are system constraints of some
sort. I would argue that the only way these constraints could arise in
a Multiverse (which is symmetric by construction) is by considering
the environment from the point of view of some observer, ie the basic
symmetry breaking mechanism.

The observer is not a general symmetry breaking mechanism.

I would argue that observation in a multiverse is a symmetry breaking
mechanism. In the multiverse, all possible outcomes of a measurement
exist as separate branches, and if all outcomes are equally likely,
there is a fundamental symmetry along that measurement axis. But the
action of observation fixes the outcome for a particular observer,
breaking that symmetry.

In the first place, it is unlikely that all possible outcomes of an experiment are equally likely. But I think you are confusing symmetry breaking with the observer self-locating in one of the possible outcome worlds. That breaks the symmetry for him, perhaps. But he is not important for that, because any future developments in the separate worlds will break any residual symmetry. The observer is nothing more than just one possibility for such a future development.

The many worlds
in QM are not symmetric anyway.

Not completely, but far more symmetric that the world we inhabit.

Only in that the many worlds of QM contain more possibilities. Observers are not necessary for breaking this symmetry. The bottom line is that observation is not necessary for the existence of the world. Observation may tell us about this particular world, but that is secondary.

Bruce

[Brent Meeker]

It's just the large number of entanglements which keep us from
constructing and operator that reverses the decoherence.  That's what I
meant by statistical, as in stat mech.

>
>> If the probability of interacting with the wave function at great
>> distance becomes very small, then decoherence is operationally
>> ineffective - you can't, at that distance, recover enough information
>> to say which way Alice's measurement turned out.
>
> If you build a big enough telescope and gather enough photons, you can
> look through the laboratory window and read Alice's lab book over her
> shoulder. There is nothing in current physics to say that this is
> impossible in principle.

I'm not exactly saying it's impossible in the classical ideal.  I'm
thinking that the size of the telescope you need to collect enough
photons becomes on the order of the Hubble sphere at the Hubble radius
so it would be operationally impossible.  But on second thought, Alice
could amplify her result and send a signal of arbitrary power (photon
count).

Brent

[Brent Meeker]

On 11/15/2017 2:40 PM, agrays...@gmail.com wrote:

On Wednesday, November 15, 2017 at 2:37:02 PM UTC-7, Brent wrote:

On 11/15/2017 12:06 PM, agrays...@gmail.com wrote:
>
> But if it tunnels into existence at t=0, how can it be infinite in
> extent? I find that egregiously hard to imagine, plus the fact that
> one has to use QM to explain the tunneling, and that, ipso facto,
> seems to imply it's infinitesimally small in spatial extent t=0 at

A limitation of imagination.  Nothing about tunneling assumes a size.

Brent

Agreed. My imagination is not the be-all, or end-all of anything. But isn't it claimed that Einstein's field equations breakdown earlier than Planck time, and this is where QM must be invoked, when the universe is presumably very small in spatial extent? 

The part of the universe visible to us now (and any other finite patch) was very small.

Alternatively, doesn't tunneling assume QM, which is a theory about the micro world. As I recall the concept is limited to QM. AG

No.  It's  theory about the energy barrier between states.  It can be states of anything.

Brent

[Russell Standish]

On Thu, Nov 16, 2017 at 10:20:45AM +1100, Bruce Kellett wrote:
> On 16/11/2017 9:14 am, Russell Standish wrote:
> > But not all measurements are measurements of the position of
> > something. What about measuring the voltage of a circuit using an A->D
> > converter?
>
> A surrogate measurement of the position of a pointer on a voltmeter.
>

There is no d'Arsenval style meter here with a pointer, just an A->D
converter + whatever recording device you want to attach to it.

Where is the position measurement in that case?

> > Or the measurement of the momentum of a charged particle in
> > an electron multier?
>
> Do you mean "electron multiplier"? Would than not be an energy measurement?

The direction component of the momentum can be determined by the
orientation of the multiplier tube. At least that is the sort of setup
I seem to remember using during my honours thesis - of course at 30+
years ago, my memory of the details could be a bit unreliable.

> Momentum of a charged particle is often measured by tracking the path of the
> charged particle in a magnetic field.
>
> > > > In MWI, we normally assume that there are
> > > > two branches of the universe with different choices made by the
> > > > experimenter.
> > > That is really an oversimplification. It is done because it is simpler to
> > > work with two-state systems, and position measurements are of a continuous
> > > variable, so are not neatly two-valued.
> > >
> > The choice between circularly polarised filter and linear polarised
> > filters is binary. Obviously, there follows the choice of orientation,
> > which is continuous...
>
> Whatever the choice of orientation, the outcome is binary, pass or not pass.
>

Yes - but I was referring to what is the preferred basis, not the
experimental outcome.

>
> > > > Unless there is some sort of superdeterminism in play,
> > > > where the experimenter does not have the freedom to choose. But
> > > > superdeterminism is certainly not a popular idea.
> > > No, superdeterminism does not have many advocates.
> > >
> > > > > Observers have nothing to do with it. In Zurek's account, it is the fact
> > > > > that the results of interactions, be they measurements or not, are recorded
> > > > > multiple times in the environment via decoherence, that is the mark of an
> > > > > irreversible quantum event.
> > > > If you put a system in contact with a completely symmetric heat bath,
> > > > there will be no preferred basis selected by einselection.
> > > The environment of a measurement or an interaction is not generally a
> > > symmetric heat bath.
> > If there is no experimenter, just an environment, then we must
> > consider all possible environments in superposition. That will have
> > maximal symmetry.
>
> "All possible environments in superposition"? That is seriously
> under-defined. Besides, that would only have a pseudo-symmetry.
>

What is pseudosymmetry in this context? The only meaning that term
seems to have on the internet relates to when two crystals intergrow
(or "twin") giving rise to an apparent crystal symmetry. That doesn't
seem applicable here.

>
> > > If you measure a spin component (space quantization)
> > > you get one of two spots on a screen downstream of the S-G magnet. These are
> > > not symmetric wrt the rest of the environment.
> > That is because we're considering an SG experiment, with an SG
> > experimenter. That breaks the symmetry.
>
> The environment breaks the symmetry. The environment may contain an
> experimenter, but need not. A camera would do the job.

The camera merely decoheres the system, which remains in a superposition
of the two possible outcomes of the SG experiment. To break that
symmetry requires an observer looking at the photo plate, or
downloading the image from the camera's CCD and observing it on a screen.

>
> In the first place, it is unlikely that all possible outcomes of an
> experiment are equally likely. But I think you are confusing symmetry
> breaking with the observer self-locating in one of the possible outcome
> worlds.

Where is the confusion? Prior to self-location, the observer is in all
possible worlds, afterwards in just one.

> That breaks the symmetry for him, perhaps. But he is not important
> for that, because any future developments in the separate worlds will break
> any residual symmetry. The observer is nothing more than just one
> possibility for such a future development.
>

Einselection imposes no more symmetry breaking than the asymmetry
present in the environment. For that assymetry to get into the
environment requires conscious self-location (to use your term).

> > > The many worlds
> > > in QM are not symmetric anyway.
> > >
> > Not completely, but far more symmetric that the world we inhabit.
>
> Only in that the many worlds of QM contain more possibilities. Observers are
> not necessary for breaking this symmetry. The bottom line is that
> observation is not necessary for the existence of the world. Observation may
> tell us about this particular world, but that is secondary.
>

I still don't see that. See my response to your Stern-Gerlach camera
example above.

> Bruce

>
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[Brent Meeker]

On 11/15/2017 3:20 PM, Bruce Kellett wrote:

On 16/11/2017 9:14 am, Russell Standish wrote:

On Wed, Nov 15, 2017 at 10:54:51PM +1100, Bruce Kellett wrote:

On 15/11/2017 5:02 pm, Russell Standish wrote:

but be that as it may, I can't see how it solves the
preferred basis problem. Consider an experiment where the experimenter
may choose between inserting a circularly polarised file, or a
linearly polarised one. The preferred basis (selected by einselection)
will depend on that choice.

That is a common misconception, but the angle selected for the polarizer, or
the S-G magnet in a spin measurement, is not a selection of a measurement
basis. The measurement is actually the observation whether or not the
photon/particle passes the filter. It is then an inference from the
observation of a point on a screen, or the firing (or failing to fire) of a
detector of some sort, that the polarization/spin-component was such and
such. You don't actually measure anything in the selected orientation, you
only ever measure whether the particle passed the filter or not. So the
actual measurement is just a position measurement (position on a screen),
and the measurement basis is the position (pointer) basis.

But not all measurements are measurements of the position of
something. What about measuring the voltage of a circuit using an A->D
converter?

A surrogate measurement of the position of a pointer on a voltmeter.

When I've tried to think of measurements that are not position measurements, I come up with looking an emitter and seeing what color the photons are...a momentum measurement.

Brent

[agrays...@gmail.com]

On Wednesday, November 15, 2017 at 5:19:50 PM UTC-7, Brent wrote:

On 11/15/2017 2:40 PM, agrays...@gmail.com wrote:

On Wednesday, November 15, 2017 at 2:37:02 PM UTC-7, Brent wrote:

On 11/15/2017 12:06 PM, agrays...@gmail.com wrote:
>
> But if it tunnels into existence at t=0, how can it be infinite in
> extent? I find that egregiously hard to imagine, plus the fact that
> one has to use QM to explain the tunneling, and that, ipso facto,
> seems to imply it's infinitesimally small in spatial extent t=0 at

A limitation of imagination.  Nothing about tunneling assumes a size.

Brent

Agreed. My imagination is not the be-all, or end-all of anything. But isn't it claimed that Einstein's field equations breakdown earlier than Planck time, and this is where QM must be invoked, when the universe is presumably very small in spatial extent? 

The part of the universe visible to us now (and any other finite patch) was very small.

OK, but if everything we can measure, aka the visible universe, was hugely smaller in the past, what's the compelling reason to assume that the UN-observable universe was hugely larger at t=0, in fact infinite? It seems like an unwarranted conclusion when confronted with what measurements of the visible universe indicate. AG