Why Explore the Bohmian Interpretation of Quantum Mechanics?

[Careful]

Jambaugh : of course a test particle at rest with respect to a Friedmann frame gives rise to a physically distinct solution than one moving with respect to it (obviously one should correctly calculate the back reaction on the geometry). In your argument, you implicitely boost the gravitational degrees of freedom too (moreover, your speed is by far not close enough to the speed of light with respect to an average cosmic frame in order to generate measurable gravitational waves for a Friedmann observer ``at rest''). Regarding your FTL issue... GR itself is such a non-local theory, providing for non-local correlations between field configurations which have spacelike separations; although of course no signals can travel faster than light (in the dynamical metric): but nevertheless these correlations may be thought of in terms of ``action at a distance''.

 

[jambaugh]

Sorry, but it seems a bit self-contradictory to me. Can you explain it in more detail, in a manner that does not look self-contradictory?

BTW, I like very much how you distinguish the philosophical issues from the operational ones.

The "problems" I see are with regard to how well it is presented and how understandable it is not what is actually said. The problem is that relativistic QM is seldom used except in the context of relativistic QFT.

In short the problems of which I speak are ones of presentation and not content. More discussion and research is also needed in making clear the nature of the gauge constraints one may and must impose in a more general context than QFT. I think the operational interpretation can be further "relativized" i.e. expressed in terms of relative frequency of events rather than absolute probabilities of specific outcomes. But as yet this opinion is unsubstantiated.

Regards,
James
P.S. I'm off to my sister's for the weekend and there is no broadband internet so I won't have a chance to read-reply until Monday.
Later All!
JEB

 

[ueit]

2. True. Still, BM as a specific theory IS nonlocal. In fact, in
http://xxx.lanl.gov/abs/quant-ph/0703071
I argue that ANY formulation of QM (with or without hidden variables) must be nonlocal in some sense. Essentially, this is because you cannot avoid use of a wave function (or some substitute for it), which is a nonlocal object.

In the paper "Bohmian Mechanics and the Meaning of the Wave Function", chapter 9, Durr argues that the universal wave function given by a solution of the Wheeler-de Witt equation is stationary, therefore it is not non-local in the sense that, by virtue of being changeless, it cannot transfer any information whatsoever, faster than light or not. The conditional wave function is non-local, but this is an artifact of dropping the constraints the universal wave function imposes on the whole system. In other words, non-locality is the price to pay for introducing free-choice in an otherwise deterministic theory. This step might be necessary for extracting useful predictions from the theory but need not be seen as a characteristic of the theory itself.

Regarding to your paper I see no reason one cannot describe a particle trajectory based only on the universal wave function (which is a constant) and the initial particle configuration at big-bang (which is supposedly known to the particle) disregarding what other particles are presently doing. Even if not elegant, this is an example of local algorithm for QM.

 

[Fra]

But let me ask you a question:
What would you think about an alternative interpretation of CLASSICAL mechanics that claims that particle trajectories and objective reality do not exist even in classical mechanics?
That such an interpretation is possible see:
http://xxx.lanl.gov/abs/quant-ph/0505143

IMO, classical mechanics as a theory has a more idealized view of reality than QM. In many cases this makes perfect effective sense. But the same philosophical issues are still there of course from a realistic point of view. Just as there are issues in improved theories. Because when we speak of "in classical mechanics" and "in quantum mechanics" we are really just talking about models. The reality is and was the same.

From my point of view - it's seems again your ontological perspective that seems to lead to this questions (at least that's how I see it). I do not ask what is X. I ask, what knowledge do I have about X. And it's hard to not ask the next question: What do I know about the validity of my supposed "information of X".

If I am for a second to take on a more obsessive philosophical attitude, even in Newtons days I'd say that strictly speaking things are not completely definite between "measurements". But in the classical case, that attitude would suggest a cure more costly than, what ignoring the tiny issue does. The investment in a more complex model, should be "payed for" by the benefit in increasing fitness.

It's due to our different philosophies, but in my opinion I can only guess what a possible trajectory might be. In cases where I have massive confidence in things, this guess will be more or less dead on to any test mesurement. Like in the classical mechanics domain, and thus for effiency reasons there is not need to talk about "guessing" (even though that, strictly speaking is what we are doing) when our experience repeatadly shows that our guesses are more or less dead on each time. So we say we can "predict the trajectory", when it really means that we are guessing, but the guess is so qualified that it becomes only a silly formality to insist on calling it a guess.

I'm not sure if I got your point by this comment, if not let me know.

/Fredrik

 

[Fra]

But you highlight an important issue! Of course quantum mechanics as it stands, doesn't make sense either. For several reasons. One is that quantum mechanics axioms expects a definite answer to the question, what do we know about X. It ignores the next question : What do we know, about the validity of what we know. That next question loosely speaking is what leads to second quantization. Of course, why should't be ask the same question again, and get the third quantization?

There seem to be an induction step here, triggered by something. I think this triggering point can be formalized, and put into the theory. This is more radical that QM as it stands, but I think it will resolve part of your issue? But probably not in the way you want.

/Fredrik

 

[Fra]

what do we know about X. It ignores the next question : What do we know, about the validity of what we know. That next question loosely speaking is what leads to second quantization. Of course, why should't be ask the same question again, and get the third quantization?

There seem to be an induction step here, triggered by something. I think this triggering point can be formalized, and put into the theory. This is more radical that QM as it stands, but I think it will resolve part of your issue? But probably not in the way you want.

Just to expand on the ideas, this might have seemed cryptical.

One question that spontaneously should appear when seeing this, is ones of general convergent properties, and when do we know when to goto the next step. Ie it seems a bit ad hoc at first. But that is just because it's a special case, in the general case it all makes more sense.

In the abstracted generalisation of this, what I argue in favour of is one gets into modelling the models. And one can talk about "exciting the model" to the next level. And the beauty is that there might be a way to define this evolution of models in terms of natural data processing. Ie. it may turn out this is not as ad hoc as one might first suspect. One would be able to have probabilistic qualifyers between models, that clearly explains why certain models are preferred over others. One sees that this seems to have no end (except in special cases) and thus is some kind of ongoing evolution. And this can provide unification on a very fundamental level.

While this is possibly more strange than ordinary QM, it may solve some of the issues with it and where I think we agree. Still I see no problem so picture these abstractions as real. It's just that I find the abstractions much easier to handle than specific cases.

/Fredrik

 

[Fra]

IMO, classical mechanics as a theory has a more idealized view of reality than QM. In many cases this makes perfect effective sense. But the same philosophical issues are still there of course from a realistic point of view.

In the light of the above comments, one major reason I personally don't like the classical mechanistic realism philosophy is that it suggests static models, that if right, gives a very nice description, but when it's wrong it makes the task to evolve the model very complicated.

So main main issue with many of the classical models is that they lack flexbility. As it also seen in nature, the animals that are survivors aren't necessarily the ones that have the biggest teeth, it's the one that are masters in adaption.

My estimate from the beginning is that everything in my experience suggest that understanding changes, and models change, as new data arrives. Thus, an important property of any model or strategy is an element of efficient evolution. Thus it leads me to suggest model the model.

In this respect the classical modelling, are not impossible or wrong as such, they just seem to me inefficient.

/Fredrik

 

[jambaugh]

Jambaugh : of course a test particle at rest with respect to a Friedmann frame gives rise to a physically distinct solution than one moving with respect to it (obviously one should correctly calculate the back reaction on the geometry). In your argument, you implicitely boost the gravitational degrees of freedom too (moreover, your speed is by far not close enough to the speed of light with respect to an average cosmic frame in order to generate measurable gravitational waves for a Friedmann observer ``at rest'').

I beg your pardon, I wasn't paying close enough attention to your premise, the Friedmann model. But even so, the assertion of uniform distribution of matter on the cosmological scale needn't preclude large regions of near vacuum on the intergalactic scale. In said regions near asymptotically flat GR and local SR is implied by the GR behind the Friedmann model.

Regarding your FTL issue... GR itself is such a non-local theory, providing for non-local correlations between field configurations which have spacelike separations; although of course no signals can travel faster than light (in the dynamical metric): but nevertheless these correlations may be thought of in terms of ``action at a distance''.

Careful about calling GR a "non-local theory" in light of the qualification you are correctly making about casual signals vs non-local correlations. Maxwell's theory is just as much a "non-local theory" as you get the same type of "non-local" correlations. They are implied by the boundary conditions of the exemplar thought experiments. It just gets more difficult to see the local causal nature of such in GR since all interactions imply conditions on the gravitational source term T_{\mu\nu} and so it is far more difficult to see a propagating change in the gravitational field. (Hence gravity waves are very hard to observe as compared to EM waves).

You may at best bring up the "absence of impossibility" in GR for e.g. large scale topological defects (wormholes et al) from allowing global causality violations.

But I am here making the distinction that Bhom's pilot waves necessarily causally propagate back in time within SR. (On the scale where SR is valid even given a larger scale Friedmann cosmology) Note that even with your Friedmann hypothesis, given local SR still applies you can still (assuming you can effect and be affected by Bhomian pilot waves) build a sequence of backward in time Bhomian signals which will then be back in time in all frames. Ultimately this shows that these pilot waves are necessarily non-observable (which is usually already assumed by those positing them).

The critical point is that they are removable from the physics without affecting any predictions of empirical experiments. They are not part of the physical theory but rather elements of a model or "mystical" speculations depending on how seriously their ontological status is taken.

And another more subtle point, once you allow local causality violation even if you give the objects special status as unobservable to allow no practical "time telephones" you run into difficulty giving their objective physical state any meaning since it can be revised by future events. It was this objective physical state of reality for which they are introduced in the first place.

The very purpose for which they are posited is then denied them. The only way then to reconcile their objective status is to introduce an additional meta-time, then you get oscillating causal loops and finally you end up with something on the order of Everett's many-worlds. I admit that Everett's ontology is self consistent but so is the postulate that we are dreams in the mind of God. Neither of these nor Bhom's pilot wave "model" say anything useful within in the epistemological discipline of science.

Regards,
James

 

[ueit]

And another more subtle point, once you allow local causality violation even if you give the objects special status as unobservable to allow no practical "time telephones" you run into difficulty giving their objective physical state any meaning since it can be revised by future events. It was this objective physical state of reality for which they are introduced in the first place.

BM is a deterministic theory, meaning the future is uniquely determined by the past. All events, past or future, were fixed by the initial conditions at the big-bang. So I don't see how future events can "revise" anything.

 

[Careful]

Jambough: the only thing I was saying is that the physics in the limit of v -> c of a particle moving in a gravitational field (one could measure the speed of the particle with respect to a notion of time which makes the gravitational field approximately stationary) is not well represented by imagining the particle to move in Minkowski spacetime, that is all.

Maxwell's theory with nontrivial currents becomes only ``locally causal'' through selection of the retarded Green's function (and by eventually adding positive energy waves); however it does not provide a locally causal model for localized carriers of the EM field. It is important here to realize that the notion of local causality originated from observing electromagnetic disturbances to propagate at the speed of light in vacuum, but nowhere has it been observed that the gravitational field to which these disturbances couple need to obey locally causal physics (as this is enforced by choosing boundary conditions) and actually it won't in a de Sitter universe.

Anyway, there is a non-local aspect about the current formulation of quantum mechanics, and unless we believe in photons reading minds of distant apparati (which I don't) - or hinge upon shortcomings in experiments - we have to believe in nonlocality (you are willing to give up realism). Of course this implies that there exist signals which we cannot measure yet, but nevertheless go faster than light, but I would hardly call that ``something useless'': people only started ``measuring atoms'' less than a century ago, but the concept has been around for more than 2000 years.


Careful

 

[jambaugh]

BM is a deterministic theory, meaning the future is uniquely determined by the past. All events, past or future, were fixed by the initial conditions at the big-bang. So I don't see how future events can "revise" anything.

This mental picture of all past and future as a fixed state is a useless arguing point. I can argue that I can flap my arms and fly. You can't disprove it because I am predetermined to never actualize this ability. It redefines the word "can" and "ability" to be meaningless.

It is the same problem moral philosophers have with ethics and (quasi)deterministic models of human behavior. It is pardoxically used to justify relaxing punishment for criminal behavior rather than more consistently being used to say that the choice of punishment we make is just as predetermined.

In short the use of such argument in context is self contradictory in that choice is a priori assumed in the very foundation of the argument. You can't say the value of the observable you choose to measure is predetermined because everything is predetermined (implicitly including your choice). The "because" here is meaningless because you must change contexts from this hypothesized globally determined states in the very semantics of the language in which you express the physics.

There is in fact a subtle category error built into such arguments. Even asserting metaphysically such a globally deterministic state, one recasts the concept of choosing to execute an experiment in terms of metachoice of circumstances where such an experiment is determined to occur. It then just as certainly leads to questions about whether the metachoice exists which will find in the deterministic clockwork of the universe the appearance of backward in time causality.

The very notion of cause and effect and hence determinism is premised on external free choices in the operational verification of cause and effect. Determinism must always be relative to a system epi-system cut and is meaningless in a universal context (except as "religious" dogma).

Without it all you get semantically is correlation and the ordering of cause and effect is all together meaningless. You can adopt such a world picture but it doesn't fit into quantum theory. The "bras" in quantum theory correspond to an experimenter causing e.g. an electron to be emitted which he knows from past experience will always affect one type of detector (the dual "ket") and never affect specific others (the dual "kets" of orthogonal "bras").

Now your point is well taken that this does appear resolve the objection I have to the Bohm pilot waves propagating back in time, i.e. that it is only partial resolutions of this universal system which appear to have this behavior due to the nature of how the piece of the whole is resolved. But then again this relativizes the "objective reality" one is trying to latch onto.

If it makes you sleep better to imagine this universal wave function is "out there" instead of just an imaginary construct then great. I've no real problem with other people's belief systems be they this or say "intelligent design" just so long as they don't try to call it science.

Regards,
James Baugh

 

[Anonym]

Now your point is well taken that this does appear resolve the objection I have to the Bhom pilot waves propagating back in time

Please write Bohm.

Dany.

 

[jambaugh]

Jambough: the only thing I was saying is that the physics in the limit of v -> c of a particle moving in a gravitational field (one could measure the speed of the particle with respect to a notion of time which makes the gravitational field approximately stationary) is not well represented by imagining the particle to move in Minkowski spacetime, that is all.

All particles move "in a gravitational field" but ok let's take your premise. How can you tell in terms of operational measurements whether this gravitatonal field is "approximately stationary". Do not forget that there are gauge degrees of freedom in the definition of "the gravitational field". It is exactly those gauge degrees of freedom we are talking about here.

The Friedmann universe is identical to a whole host of "skewed Friedmann universes" in so far as empirical observations are concerned. In solving Einstein's equations for the Friedmann cosmology you must invoke gauge conditions with make this one way speed of light "measurement" ontologically meaningful but not distinct operationally from the distinct "skewed" cases.

In the end you still get the implication that FTL signals (as defined in each case) can be used to send signals back in time due to this gauge symmetry. If you deny this symmetry exists you invalidate GR and must replace it with another theory. Maybe that one better conforms to experiment in which case of course my arguments are no longer valid as they are premised on the correctness of local SR which is implied by regional GR.

Maxwell's theory with nontrivial currents becomes only ``locally causal'' through selection of the retarded Green's function (and by eventually adding positive energy waves); however it does not provide a locally causal model for localized carriers of the EM field. It is important here to realize that the notion of local causality originated from observing electromagnetic disturbances to propagate at the speed of light in vacuum, but nowhere has it been observed that the gravitational field to which these disturbances couple need to obey locally causal physics (as this is enforced by choosing boundary conditions) and actually it won't in a de Sitter universe.

One needn't select one of the advance vs retarded solutions to sources field equations to invoke "local causality" in Maxwell theory. One needs only invest the two with the correct interpretation. Take the simple case of a moving charged particle which is given an impulsive boost.
You get advanced and retarded solutions and one is the field resulting from the acceleration while the other is the field necessary to induce the acceleration assuming no external force was utilized. The advanced field is the component of the total EM field which would be absorbed by the sources acceleration. In short they are components of a classical scattering problem where you solve for the IN and OUT EM field uniquely defined by the behavior of the scattering center.

Then when you look at a charged particle in uniform motion you have both advanced and retarded fields present and canceling so that you get the frame boosted Coulomb field which "appears" non-local only because the electron is constantly effecting and being affected by the local field. The Coulomb field presupposes the uniform motion of the particle into the infinite past.

I beg to differ w.r.t. gravitation. de Sitter or no. The same principles apply as in EM but with the difficulty in that all matter is a source term so it is impossible to effect a change in motion of a particle without bringing another source into conjunction with the particle. It relates to the spin-2 nature as well since we can't neutralize the sources to mask them. There is thus no way to independently affect sources of gravitation. Thus even simple seemingly local assertions about a source term, say that a mass receives an impulsive force, are not local in that to effect such an impulse you need to transport momentum to the event and that momentum is also a source.

I can't see where de Sitter makes any difference as you still have the same local Einsteinian field equations and the same regional correspondence to the general case (with cosmological constant if necessary).

Anyway, there is a non-local aspect about the current formulation of quantum mechanics, and unless we believe in photons reading minds of distant apparati (which I don't) - or hinge upon shortcomings in experiments - we have to believe in nonlocality (you are willing to give up realism). Of course this implies that there exist signals which we cannot measure yet, but nevertheless go faster than light, but I would hardly call that ``something useless'': people only started ``measuring atoms'' less than a century ago, but the concept has been around for more than 2000 years.

The non-local aspects in quantum mechanics are not causal but conceptual.

In the case of Bell's derivation of his inequality he used non-locality as one means to ensure the measured variables are independent.
This needn't be the means of this assumption. We need only assume there exists some pair of commuting variables. You then with Bell's other assumptions get the inequality and you then with QM are able to entangle those variables and violate the inequality. It is those other assumptions which are negated in the reducto ad absurdum argument.

You should know what I think about wave function collapse as well. I use the analogy of lotto ticket expectation value collapse. It is an instantaneous update of our knowledge which we (may) index via spatial coordinates and not of physical entities located at said coordinates.

W.r.t the FTL BIT signals, it doesn't imply signals we cannot measure yet but rather that we fundamentally cannot measure period (assuming the very quantum theory one is "interpreting" by invoking these "signals".).

To measure the objects sending these signals we would then be able to either empirically prove Bell's inequality in contradiction to experience and to the predictions of QM or again require they have the same quantum nature in an extended quantum theory. We would then need "pilot waves" for the pilot waves. Where does it end?
[/QUOTE]

 

[jambaugh]

Please write Bohm.

Dany.

Pardon my transposing, I need to do a few drills so the o key gets hit before the h when I get going fast. I'll be careful in future.
R. J. B.

 

[Careful]

All particles move "in a gravitational field" but ok let's take your premise. How can you tell in terms of operational measurements whether this gravitatonal field is "approximately stationary". Do not forget that there are gauge degrees of freedom in the definition of "the gravitational field". It is exactly those gauge degrees of freedom we are talking about here.

If you want it very strict : - say - the preferred spaces in a static universe; you can carefully relax this condition furthermore. Moreover, in line of my argument it is irrelevant how to determine such frame operationally; but I guess you can retrieve the metric in free space by studying deviations in light paths (and reflection times) between different free falling mirrors (and by defining your units).

In the end you still get the implication that FTL signals (as defined in each case) can be used to send signals back in time due to this gauge symmetry.

Yeh, so what ? Is that against observation ? What if special relativity is only valid for elementary particles with velocity almost up to c (but not quite) in almost empty space ?

One needn't select one of the advance vs retarded solutions to sources field equations to invoke "local causality" in Maxwell theory.

Of course one does.

One needs only invest the two with the correct interpretation. Take the simple case of a moving charged particle which is given an impulsive boost.
You get advanced and retarded solutions and one is the field resulting from the acceleration while the other is the field necessary to induce the acceleration assuming no external force was utilized. The advanced field is the component of the total EM field which would be absorbed by the sources acceleration. In short they are components of a classical scattering problem where you solve for the IN and OUT EM field uniquely defined by the behavior of the scattering center.

Euh that doesn't make any sense to me. The retarded field exists without any acceleration. Moreover, if no external force is used, there is no acceleration at all for a single electron (there is enough discussion on that point in the literature concerning the Lorentz Dirac equation).

Then when you look at a charged particle in uniform motion you have both advanced and retarded fields present and canceling so that you get the frame boosted Coulomb field which "appears" non-local only because the electron is constantly effecting and being affected by the local field. The Coulomb field presupposes the uniform motion of the particle into the infinite past.

Euh, for an electron at rest (or uniform motion), the Coulomb field = Field strength arising from the RETARDED propagator.

I can't see where de Sitter makes any difference as you still have the same local Einsteinian field equations and the same regional correspondence to the general case (with cosmological constant if necessary).

Gravitons are plane wave solutions of the linearized field equations around a flat background metric; hence the local causality principle simply follows from the well known causality theorems for hyperbolic partial differential equations. If I linearize around de Sitter, I get different null geodesics (expanding congruences) and hence different causality properties.

The non-local aspects in quantum mechanics are not causal but conceptual.

That doesn't make any sense to me (and denying the reality of the measurement of Alice, being Bob, doesn't really help in making progress IMO).

For the rest, you basically say : nothing real can correspond to the quantum waves -->> what is the use of BM ? Again, why do you think the first thing is true at all ?? Some people would say particles are not reall at all, but merely localized field exitations, and that it is the wave which is fundamental (Einstein was one of them).

 

[jambaugh]

If you want it very strict : - say - the preferred spaces in a static universe; you can carefully relax this condition furthermore. Moreover, in line of my argument it is irrelevant how to determine such frame operationally; but I guess you can retrieve the metric in free space by studying deviations in light paths (and reflection times) between different free falling mirrors (and by defining your units).

W.r.t. recovering the metric, it doesn't uniquely define an inertial frame. The local Lorentz group IS the invariance group of the local metric.

W.r.t. the operational meaning being irrelevant, then if this is necessarily so then by the same failure of operational distinction then the point made if requiring this argument is also operationally meaningless.

Yeh, so what ? Is that against observation ? What if special relativity is only valid for elementary particles with velocity almost up to c (but not quite) in almost empty space ?

I don't know what you mean about "velocity almost up to c" unless you are selecting a specific inertial frame. Either the 4-velocity is a unit vector or a null vector.

Let's see if I can reproduce your reasoning:
a) There's a preferred inertial frame.
b) The relativity group is approximately the Lorentz group (or has a Lorentz subgroup).
c) The action of the relativity group is approximately linear on local space-time coordinates and 4-momenta.
d) These "approximations" loose precision the farther one gets from the preferred inertial frame.
e) These divergence from SR is sufficient to imply FTL signals in the preferred frame never result in backward in time signals in any inertial frames.

Is this a good summary or have I misunderstood?

Of course one does.

Let us see...

Euh that doesn't make any sense to me. The retarded field exists without any acceleration. Moreover, if no external force is used, there is no acceleration at all for a single electron (there is enough discussion on that point in the literature concerning the Lorentz Dirac equation).

Yes, I used the accelerated case as an example because the advanced and retarded solutions are distinct... see below.

Euh, for an electron at rest (or uniform motion), the Coulomb field = Field strength arising from the RETARDED propagator.

And also the field strength arising equivalently from the ADVANCED propagator. The situation is time symmetric.

Gravitons are plane wave solutions of the linearized field equations around a flat background metric; hence the local causality principle simply follows from the well known causality theorems for hyperbolic partial differential equations. If I linearize around de Sitter, I get different null geodesics (expanding congruences) and hence different causality properties.

I would rather you said, Gravitons are as yet not well defined hypothesized quanta which may be approximately resolved in terms of plane-wave solutions around...

Firstly let's stick to classical gravitational waves until such time as a reasonable QG theory is presented. Secondly even photons do not uniquely correspond to plane wave phenomena. That is just one of the many bases into which they may be resolved.

Thirdly, your linearization around de Sitter has the same well known causality theorems for hy. p.d.e.s when you look at them in terms of equivalent pdes in the 1+4 dimensional flat space in which the de Sitter manifold is a unit pseudo-sphere. The characteristics of the equations may project onto curves on the pseudo-sphere rather than "straight lines" but they have the same local topology and no qualitative distinction in the global setting w.r.t. causality. Asymptotically they are the same and hence they are the same with regard to local causal structure.

That doesn't make any sense to me (and denying the reality of the measurement of Alice, being Bob, doesn't really help in making progress IMO).

Let me make it clear. Say you are observing that "the electron" within a one particle system to be in a specific region of space. You are not making a local observation when you couple this with the "one particle system" assumption because there is an implicit rejection of cases where you observe an electron as stated and additionally do not observe an electron elsewhere.

It is not that the measurement (a local action) causes a global effect, but rather your system definition causes you to reject those cases or globally prevent those cases where distant electron counts correlate to the count of 1 or 0 at the given local.

The restriction to outcomes where only one particle is ever detected globally (globally in the sense of a larger region then you are resolving locales) is a non-local conceptual constraint when you consider the idealized system with fixed total=1 particle number.

The physical locality of the situation is seen when you consider two subsequent such global measurements of particle counts at all locals.
You will never see physically observable quantities causally propagate FTL (according to the current theory).

For the rest, you basically say : nothing real can correspond to the quantum waves -->> what is the use of BM ? Again, why do you think the first thing is true at all ?? Some people would say particles are not reall at all, but merely localized field exitations, and that it is the wave which is fundamental (Einstein was one of them).

I would phrase it differently:
Nothing observable can correspond to the quantum waves -->>...

As to why I believe this beyond the causality arguments I've made...
I look most often to Bell inequality violation in QM and EPR experiments.
There is in my opinion a much simpler derivation of Bell's inequality which doesn't require any locality issues be brought up per se, but rather only that you can actually find commuting observables. Bell's inequality is simply the triangle inequality when you assume:
a) An objective state of reality prior to measurement.
b) That the probabilities of outcomes derive from a probability measure over the set of states of reality.
c) That two measurements can be made without the outcome of one affecting the other (usually handled by spatially separating them and using locality arguments but not necessarily done this way).

I believe (c) and that (b) necessarily follows from (a) and the assertion that the measurement is causally determined by the prior state.

(a) seems to be the most intuitively obvious but so to was the assumption of absolute time pre SR. Parse the classical notion of "state" more closely and note that it had an operational meaning since it is classically assumed that all properties can be independently measured and thus the state of reality can in principle be empirically determined. Once you invalidate this classical assumption you find that "objective reality" is not quite physically meaningful. In quantum theory you start with measurements and forget about states. The "wave functions" "state vectors" "kets" etc which are best labeled "mode vectors" are representatives of classes of systems which have been measured with respect to a certain maximal observable. Maximal no longer being "complete" in the classical sense of defining a state.

BTW I am also one of those people who say "particles are not real" (rather I would say they are actual pheonmena as opposed to e.g. the conceptual status of the wave functions representing them.)
But I also give the same status to the "fields". They are all pheomena, out there but not reducible to "transitions between states of reality". Ultimately "an electron" is the causal correlation between "electron emitters" and "electron detectors". Similarly for photons et al.

What then are the wave functions? They are representations of equivalence classes of such emitters or detectors, said representations giving also information about partial correlations between inequivalent emitter-detectors. When you propagate a wave-function you are simply specifying how under the given dynamics earlier and later acts of emission yield equivalent behavior with respect to measurements in the future of both acts. All is expressed in terms of the actual empirical elements, the measurements (provided you don't additionally tack on an ontological interpretation of the wave function).

Given then that this operational interpretation by its formulation addresses any and all questions of what can be observed (given the theory itself specifies limits via the uncertainty principle), then adding another level of ontological interpretation can at "best", add nothing or at "worst" predict deviations from the predictions of QM. Even so said deviations can still be recast in purely operational terms.

I assert that this is a great virtue in physics. Sticking to the operational language forces one to ask the right questions (those which can be empirically tested) an not to waste time on artificial distinctions.

With regard to Bohmian interpretation I'll ask Mammy to summarize my position:
http://www.obcgs.com/firstwomen/mammy.jpg
"It just ain't physics! It ain't PhysICS! It ain't PHYsics!"

 

[Careful]

Jambaugh, you miss the first two points entirely although I have explained how GR allows you to speak in those terms, so I am not going to come back to this again. Of course, the Lorentz group is a local symmetry group of GR, but then on the natural bundle of orthonormal frames or as a subgroup of the Diff_0.
About the accelerated case, your original ``point'' was that the distinction between the retarded and advanced propagator doesn't matter which is false in case you include background radiation (which is what I did in the first place) or more than one particle. Concerning your de Sitter argument, of course this theorem remains valid (but then with respect to the de Sitter metric) which of course differs locally from the Minkowskian one. May I ask you what your definition of locally causal is anyway ?

 

[ueit]

This mental picture of all past and future as a fixed state is a useless arguing point.

Nevertheless, this is the picture BM (and any deterministic theory) gives us. If you disagree with it there is no point to object to the theory on other grounds, as all your arguments are bound to be circular (sooner or later you'll make an appeal to "free choice" or something of that sort which is the logical opposite of determinism).

I can argue that I can flap my arms and fly. You can't disprove it because I am predetermined to never actualize this ability. It redefines the word "can" and "ability" to be meaningless.

That's not exactly true. I can disprove it because it is against the physical law.

It is the same problem moral philosophers have with ethics and (quasi)deterministic models of human behavior. It is pardoxically used to justify relaxing punishment for criminal behavior rather than more consistently being used to say that the choice of punishment we make is just as predetermined.

This doesn't mean the argument is not sound. We may not like it but it may still be true.

In short the use of such argument in context is self contradictory in that choice is a priori assumed in the very foundation of the argument. You can't say the value of the observable you choose to measure is predetermined because everything is predetermined (implicitly including your choice). The "because" here is meaningless because you must change contexts from this hypothesized globally determined states in the very semantics of the language in which you express the physics.

I disagree. Even if I am not able to "choose" to do a measurement, I can observe it unfolding. I still can notice correlations between what I do (freely or not) and what the outcome is and do science.

There is in fact a subtle category error built into such arguments. Even asserting metaphysically such a globally deterministic state, one recasts the concept of choosing to execute an experiment in terms of metachoice of circumstances where such an experiment is determined to occur. It then just as certainly leads to questions about whether the metachoice exists which will find in the deterministic clockwork of the universe the appearance of backward in time causality.

The very notion of cause and effect and hence determinism is premised on external free choices in the operational verification of cause and effect. Determinism must always be relative to a system epi-system cut and is meaningless in a universal context (except as "religious" dogma).

Without it all you get semantically is correlation and the ordering of cause and effect is all together meaningless. You can adopt such a world picture but it doesn't fit into quantum theory. The "bras" in quantum theory correspond to an experimenter causing e.g. an electron to be emitted which he knows from past experience will always affect one type of detector (the dual "ket") and never affect specific others (the dual "kets" of orthogonal "bras").

For calculating experimental results one have to use the wave function of a subsystem. This has all the required properties including the experimenter's "free choice" so no contradiction with QM exists. However, I see no reason why BM cannot be applied to the experimenter himself. It is a logical step to make regardless of what philosophical questions it may produce.

Now your point is well taken that this does appear resolve the objection I have to the Bohm pilot waves propagating back in time, i.e. that it is only partial resolutions of this universal system which appear to have this behavior due to the nature of how the piece of the whole is resolved. But then again this relativizes the "objective reality" one is trying to latch onto.

If it makes you sleep better to imagine this universal wave function is "out there" instead of just an imaginary construct then great. I've no real problem with other people's belief systems be they this or say "intelligent design" just so long as they don't try to call it science.

You have a really strange position here. You tell me to go to the "intelligent design" camp because I pointed an error in your line of reasoning. In BM the future is fixed, period. This has nothing to do with my "belief system". If you think that the deterministic nature of BM is contrary to science then say so. If you have a reason to believe that BM cannot be applied to a human brain/mind then please state clearly what that reason is. If not, stop using the "free choice" assumption when dealing with a deterministic theory. At most, you could argue for some type of statistical independence between various parts of an experiment (like detectors' settings in an EPR experiment), but never for the possibility of multiple outcomes from the same initial state.

 

[jambaugh]

Nevertheless, this is the picture BM (and any deterministic theory) gives us. If you disagree with it there is no point to object to the theory on other grounds, as all your arguments are bound to be circular (sooner or later you'll make an appeal to "free choice" or something of that sort which is the logical opposite of determinism).

The problem is that the determinism of the "theory" which then in principle means the deterministic outcome of say the z-spin measurement of an electron which has just previously been measured with x-spin -1/2, disallows any actual prior experiment which would observe the variables determining this event. It is a "theory" about empirically invisible entities. Which is why I keep comparing it to e.g. theology.

Now "determinism" can be defined in two contexts. They way you're using it is in the sense that the universe as a whole is a clockwork. QM (in its purely operational form) can be also defined as "deterministic" in a weaker form in that any (possible) outcome of any measurement may be assured by suitable prior actions. You can cause any effect you choose given enough prior warning.

I bring up this distinction because this weak determinism can be empirically tested and is operationally meaningful. But your sort of clockwork determinism cannot be given such meaning because it is asserting that the outcome of any possible measurement of a given instance of a system is a priori determined. You can't actually measure prior variables which will predict all outcomes of any measurement. You can at best actualize a prediction of one of the measurements as via measuring a second system totally entangled with the one in question.

Thus specifically you measuring the half of an entangled pair, or any other prior systems going all the way back to the big bang, cannot tell me the outcome of a specific measurement I will choose to make without me first telling you which measurement I will make. You can't send me a complete list of "if you measure A you will see a, if you measure B you will see b..."

You seem to be arguing that there is an invisible version of such a list "out there" in the form of a universal wave function. I can't see such an assertion as other than "mystic belief".

That's not exactly true. I can disprove it because it is against the physical law.

But you must understand. In reality I can fly but when I do so I will be invisible and you see only projection of my body which just appears to be standing there. The projection is so perfect it even will affect both light and material particles. But the real me... my pilot wave... is flying.

Pardon my facetiousness... but you can only prove that a hypothesized physical law's predictions disallow what I described. I, to be intentionally difficult, will just hypothesize a physical law which doesn't. How do we weigh and compare such laws? By empirical test if we wish to call our methods science. If such a law as you invoke has been confirmed by empirical data that confirmation is only about the observable predictions of that law, namely the empirical meaning of "me flapping my arms and flying" and NOT my assertions about reality behind what is empirically visible.

Granted this example didn't fit well the point I was making. You have the weak form of determinism I mentioned which allows you to disprove my claim without being invalidated by my resistance to the test. (And if the weak form I stated is inconsistent with the strong form it may yet be modified and still allow this example's invalidation.)

This doesn't mean the argument is not sound. We may not like it but it may still be true.

It is not its truth I criticize, rather its inconsistent application of the premise. The person is arguing that the relevant decision maker should make a reasoned choice based on the premise that people cannot make reasoned choices but rather only react to their environment. It also fails to consider that part of that environment is the social judicial policy.

I was implying your determinism argument is similarly inconsistent. But now upon consideration I think I must back-peddle.

I disagree. Even if I am not able to "choose" to do a measurement, I can observe it unfolding. I still can notice correlations between what I do (freely or not) and what the outcome is and do science.

But you can't choose what you observe, its predetermined. For all you know there is a strong correlation between what you will be predetermined to observe and the behavior of that observation. I'm trying to say that invoking this determinism doesn't tell you anything about what you aren't actually observing, unless you assume an independence of choice in contradiction to the assumed determinism. It is either self contradictory or it again all reverts back to operationalism. You only talk about what is observed and "the reality" component is outside the domain of science.

[addendum] On a more conciliatory note, I offer a weaker statement. I can say rather that it is sufficient for any empirical predictions to stick to descriptions of what the outcomes of measurements we choose (or are predestined) to make and thus the rest extends outside the domain of science. By its sufficiency nothing is added by reality hypotheses.

For calculating experimental results one have to use the wave function of a subsystem. This has all the required properties including the experimenter's "free choice" so no contradiction with QM exists. [...

The point is that those predictions for the subsystem (which is the QM theory, not just consistent with it) are all causally local and self consistent. I asserted that the wave function itself when given ontological status is not. You say this is "cured" by viewing the wave-function as part of a global deterministic ontological model. I asserted that you can't invoke this choice negating "cure" while still allowing the choice. However I back-peddle here as well and concede the issue.

You I take it would argue that there is sufficient "randomness" between the variables determining the property to be measured which variation is uncorrelated with those subsystem variables determining the outcome of the measurement so as to allow a statistical inference over many isomorphic trials.

I concede then that my "determinism invalidates implicit choice in defining experimental measurement" doesn't hold up. It is after all the circumstance we see in astrophysics. We can make statistical inferences in looking at many astronomical objects without the need to "choose" from where in the universe we watch or "choose" via active preparation the initial conditions of e.g. two colliding galaxies.

Very well. I will henceforth restrict my objections to ("strong") determinism to only the issue of operational meaning.

...] However, I see no reason why BM cannot be applied to the experimenter himself. It is a logical step to make regardless of what philosophical questions it may produce.

Yes. But I see no distinction between giving the wave functions ontological status and calling it BM vs treating the wave functions as mathematical constructs and calling it e.g. (Copenhagen) QM.

You have a really strange position here. You tell me to go to the "intelligent design" camp because I pointed an error in your line of reasoning.

Firstly I didn't tell you to go to the "intelligent design" camp, nor did I bring up "intelligent design" out of malice for loosing an argument. I brought up intelligent design as another example of a belief system insisting on being granted status as a scientific theory when it is in fact based on beliefs about reality beyond what can be observed.

In BM the future is fixed, period. This has nothing to do with my "belief system".

BM is not a belief system? It doesn't posit metaphysical assertions? Does it not in fact posit metaphysical assertions outside the domain of what may be empirically tested? Is not this "fixed future, period." assertion just such an example?

If you think that the deterministic nature of BM is contrary to science then say so.

Right. I so say...or rather said above with regard to its lack of operational meaning of some of its assertions.

If you have a reason to believe that BM cannot be applied to a human brain/mind then please state clearly what that reason is.

In so far as BM doesn't disagree with operationally interpreted QM I see no reason to distinguish it as particularly inapplicable to the human brain/mind.
[deleted a long meaningless speech.]
I just don't see any fruitful results from any quantum analysis of the brain.[deleted second long tangential speech.] We can discuss my opinions about applying quantum methods to psychology in another setting if you wish.

If not, stop using the "free choice" assumption when dealing with a deterministic theory.

I shall as I think you've quite well countered it in the context I was trying to apply it. I would go so far as to say I may have been guilty of sophistry.

At most, you could argue for some type of statistical independence between various parts of an experiment (like detectors' settings in an EPR experiment), but never for the possibility of multiple outcomes from the same initial state.

On this last I'm not quite clear what you mean. I at least must try to rephrase it so as to remove implicit assumptions I deny. You say "initial state" I say initial mode of preparation. (Our distinct meanings given to the wave function) Given that mode (a class of instances) you can have (across many instances) multiple outcomes of identical modes provided the outcome is a measurement for an observable for which that mode is not an eigen-mode. Clearly in a single instance you can only measure one observable and see only one outcome of that measurement. If that's what you mean I can't see how I led you to believe I would think otherwise.

Well I can't imagine that you fail to understand my points about operational meaning and I've conceded the point about "choice" so I don't think, as much as I like "hearing" myself "speak" that I can add any more to the discussion.
You're probably weary of me as well so I'll read your replies and endeavor only respond to append brief clarifications. Thanks for the debate and especially for revealing a weakness in my arguments.

Regards,
James Baugh

 

[ueit]

The problem is that the determinism of the "theory" which then in principle means the deterministic outcome of say the z-spin measurement of an electron which has just previously been measured with x-spin -1/2, disallows any actual prior experiment which would observe the variables determining this event. It is a "theory" about empirically invisible entities. Which is why I keep comparing it to e.g. theology.

So, what interpretation of QM is free from "empirically invisible entities"?

Now "determinism" can be defined in two contexts. They way you're using it is in the sense that the universe as a whole is a clockwork. QM (in its purely operational form) can be also defined as "deterministic" in a weaker form in that any (possible) outcome of any measurement may be assured by suitable prior actions. You can cause any effect you choose given enough prior warning.

My issue with this "weak determinism" is that its logical consistency is questionable. We are ourselves quantum systems, part of the environment and we obey the same constraints as the system under study. It has to be proven from inside the studied theory, not assumed, that a certain action is possible. For example, if you study gravity by orbiting around earth, you cannot just assume that you can change orbit at will. If you have no massive object at hand you are bound to deterministically follow the same orbit for ever.

Or consider an EPR experiment. Say that one proposes a theory stipulating that an entangled pair is only emitted when a signal from the would-be absorbers is recieved. Now, you cannot just assume that the detector orientations are free parameters because the spin of the entangled particles is a function of the detector's state.

I bring up this distinction because this weak determinism can be empirically tested and is operationally meaningful. But your sort of clockwork determinism cannot be given such meaning because it is asserting that the outcome of any possible measurement of a given instance of a system is a priori determined. You can't actually measure prior variables which will predict all outcomes of any measurement. You can at best actualize a prediction of one of the measurements as via measuring a second system totally entangled with the one in question.

Thus specifically you measuring the half of an entangled pair, or any other prior systems going all the way back to the big bang, cannot tell me the outcome of a specific measurement I will choose to make without me first telling you which measurement I will make. You can't send me a complete list of "if you measure A you will see a, if you measure B you will see b..."

You seem to be arguing that there is an invisible version of such a list "out there" in the form of a universal wave function. I can't see such an assertion as other than "mystic belief".

I actually agree with you that assuming hard determinism (HD) is useless from a scientific stand point. However, I did not assume HD but I pointed out that it is inescapable if BM is true. One cannot have BM and not have HD. So, if one wants to do an internal critique of BM one has to agree, for the sake of the argument, with HD.

[addendum] On a more conciliatory note, I offer a weaker statement. I can say rather that it is sufficient for any empirical predictions to stick to descriptions of what the outcomes of measurements we choose (or are predestined) to make and thus the rest extends outside the domain of science. By its sufficiency nothing is added by reality hypotheses.

It depends on what you mean by sufficient. Science evolves and models that propose unobservable mechanisms can be useful in the long run. There are also entities that could be required for logical/mathematical consistency.

Very well. I will henceforth restrict my objections to ("strong") determinism to only the issue of operational meaning.

See my objections to weak determinism above.

Firstly I didn't tell you to go to the "intelligent design" camp, nor did I bring up "intelligent design" out of malice for loosing an argument. I brought up intelligent design as another example of a belief system insisting on being granted status as a scientific theory when it is in fact based on beliefs about reality beyond what can be observed.

OK, I'm sorry for misunderstanding what you were saying and giving a hasty answer. The difference between ID and HD is that ID-ers make a set of very unparsimonious assumptions (that a omnimax god exists and the bible is his word and it is absolutely true) while BM makes a pretty simple assumption, that the quantum particles move from place to place on a deterministic trajectory. This hypothesis in turn implies HD as a logical conclusion.

BM is not a belief system? It doesn't posit metaphysical assertions? Does it not in fact posit metaphysical assertions outside the domain of what may be empirically tested? Is not this "fixed future, period." assertion just such an example?

As I said before, I just assume, for the sake of the argument that BM is true. My point is that you cannot criticize BM by denying that the future is fixed, because the later is implied by the former.

Right. I so say...or rather said above with regard to its lack of operational meaning of some of its assertions.

OK.

In so far as BM doesn't disagree with operationally interpreted QM I see no reason to distinguish it as particularly inapplicable to the human brain/mind.
[deleted a long meaningless speech.]
I just don't see any fruitful results from any quantum analysis of the brain.[deleted second long tangential speech.] We can discuss my opinions about applying quantum methods to psychology in another setting if you wish.

I agree with you on this. I only pointed out that we are part of this universe and subject to the same laws. If these laws are deterministic, so are we. You cannot have a deterministic interpretation of QM and free choice unless that choice comes from somewhere else (soul?)

On this last I'm not quite clear what you mean. I at least must try to rephrase it so as to remove implicit assumptions I deny. You say "initial state" I say initial mode of preparation. (Our distinct meanings given to the wave function) Given that mode (a class of instances) you can have (across many instances) multiple outcomes of identical modes provided the outcome is a measurement for an observable for which that mode is not an eigen-mode. Clearly in a single instance you can only measure one observable and see only one outcome of that measurement. If that's what you mean I can't see how I led you to believe I would think otherwise.

I meant that, an initial bohmian state (wave function + configuration) "fixes" the future, a rephrasing of my previous point.

Well I can't imagine that you fail to understand my points about operational meaning and I've conceded the point about "choice" so I don't think, as much as I like "hearing" myself "speak" that I can add any more to the discussion.
You're probably weary of me as well so I'll read your replies and endeavor only respond to append brief clarifications. Thanks for the debate and especially for revealing a weakness in my arguments.

I thank you for your answers as well. My only remaining question is related to the logical consistency of weak determinism.

Regards,
Andrei Bocan

 

[jambaugh]

So, what interpretation of QM is free from "empirically invisible entities"?

Basically the "operational interpretation" I much earlier described which I believe is the same as the Copenhagen. What mathematical objects which do not directly correspond to laboratory actions of preparation/measurement/selective detection are not granted status other than as mathematical objects.

My issue with this "weak determinism" is that its logical consistency is questionable. We are ourselves quantum systems, part of the environment and we obey the same constraints as the system under study. It has to be proven from inside the studied theory, not assumed, that a certain action is possible. For example, if you study gravity by orbiting around earth, you cannot just assume that you can change orbit at will. If you have no massive object at hand you are bound to deterministically follow the same orbit for ever.

Hmmm... I'm not sure I see your point here. My thought was that if you give me an early enough head's-up on e.g. your future plan to measure the z-spin of an electron, I can make sure the electron is there with a specific momentum and z-spin value. I didn't see any special logical issues in this.
The ability to prepare a system in a given mode was I though a foundational assumption in QM.

Or consider an EPR experiment. Say that one proposes a theory stipulating that an entangled pair is only emitted when a signal from the would-be absorbers is recieved. Now, you cannot just assume that the detector orientations are free parameters because the spin of the entangled particles is a function of the detector's state.

Huh? As I was thinking of the definition the orientation of the detectors would have to be give to me before I prepared the pair of particles. I would then be able to assure a given pair of spin measurements. Whether the particles are entangled would be a secondary condition which is possibly (most probably) inconsistent with the type of assured outcome you are describing.

I actually agree with you that assuming hard determinism (HD) is useless from a scientific stand point. However, I did not assume HD but I pointed out that it is inescapable if BM is true. One cannot have BM and not have HD. So, if one wants to do an internal critique of BM one has to agree, for the sake of the argument, with HD.

Yes, You've convinced me I can't get an "internal" contradiction, and the desire for this HD is after all one of the main reasons given for considering BM.

It depends on what you mean by sufficient. Science evolves and models that propose unobservable mechanisms can be useful in the long run. There are also entities that could be required for logical/mathematical consistency.

Yes that is a weak piece of my argument. I can't really argue any case except certain basic preferred heuristics, dictating the conceptual path one might best take to get to a new and improved theory. The path that insight takes isn't predictable enough for the level of insistence I expressed.

OK, I'm sorry for misunderstanding what you were saying and giving a hasty answer. The difference between ID and HD is that ID-ers make a set of very unparsimonious assumptions (that a omnimax god exists and the bible is his word and it is absolutely true) while BM makes a pretty simple assumption, that the quantum particles move from place to place on a deterministic trajectory. This hypothesis in turn implies HD as a logical conclusion.

Yes, I used and exaggerated parallel of ID to really push the point.

As I said before, I just assume, for the sake of the argument that BM is true. My point is that you cannot criticize BM by denying that the future is fixed, because the later is implied by the former.

Right, I think we've now consensus between us on this.

I agree with you on this. I only pointed out that we are part of this universe and subject to the same laws. If these laws are deterministic, so are we. You cannot have a deterministic interpretation of QM and free choice unless that choice comes from somewhere else (soul?)

Yes. I think my invocation of "weak determinism" (in possibly modified form) does allow room for (even requires) free choice. (And I still believe much of the formulation of physics implicitly invokes choice in its language.)

Hmmm... I may see what you're getting at. Does the formulation imply that a a third party can prepare my intent and the system so that the outcome is different from my expectations. This brings up a big issue as to what concerning the person is really an observable. It's Schrodinger's cat all over again. I've some canned arguments but let's not start that here. Possibly another thread?

I meant that, an initial bohmian state (wave function + configuration) "fixes" the future, a rephrasing of my previous point.

OK.

I thank you for your answers as well. My only remaining question is related to the logical consistency of weak determinism.

I defined it on the spur of the moment so it may need some modification if there is a consistency issue. My main thought was any measurement or sequence of measurements of commuting observables could be a priori assured provided one is not appending additional constraints equivalent to specifying values of observables not commuting with those in question. (Such as requiring specific pairs of measurements and that the pair of systems be entangled.)

It is really nothing more than the assumption in QM that any given mode vector can be actualized.

If I understand your issue correctly, (that logical inconsistency could occur when you include the intending experimenter within the system of a second experimenter) is your objection any different than in a classical setting, saying you can tie my hands to prevent me from actualizing my intent to e.g. put the eight ball in the corner pocket? Thus the classical physics of pool is not weakly deterministic?

Regards,
James

 

[Demystifier]

For the most recent contribution to the program of answering the question "Why Bohm?" see
http://lanl.arxiv.org/abs/0706.2522

 

[jambaugh]

For the most recent contribution to the program of answering the question "Why Bohm?" see
http://lanl.arxiv.org/abs/0706.2522

I note in reading this paper that it promulgates the same misinterpretation of Orthodox (Copenhagen) QM, al la Bell's arguments.

However Bell’s theorem[4,2]showed that this problem
is inescapable for any interpretation of QM that admits the reality of measurement outcomes for space-like separated observers.

There is a grave distinction between the "reality of outcomes" and the dependence of outcomes on an underlying reality.

The distinction is in the totality of the reality assertion. A measurement is "real" in the exact meaning of "measurement" i.e. an amplification of a specific quantum variable to the scale at which its value can be described classically e.g. as a record on a measuring device. It is not the same as identifying that measurement with the totality of reality implicit in the state of reality picture for the physical system.

Bell showed that given a series of assumptions one can derive his famous inequality which contradicts the predictions of QM. One of those assumptions is local causality between acts of measurement. But another is that the a priori probabilities of the outcomes of these causally separated measurements derives from local objective states whether these states be observable or no. In essence He then showed that:

QM + Local Causality + Local Objective Reality, are incompatible. The author is making a grave mischaracterization in that in the Copenhagen interpretation it is the objective reality which is rejected (replaced with subjective actuality if you will) and hence local causality is not incompatible with QM.

See e.g. http://arxiv.org/html/quant-ph/9907027"
for a semantic analysis of the argument.

Indeed the no signaling theorem (see Eberhard 1978, Ghirardi, Rimini and Weber 1980, Jordan 1983, Shimony 1984, Redhead 1987, pp. 113-116 and 118) explicitly demonstrates that in so far as local causality is operationally defined it is a consequence of QM.

Any causality arguments in the context of "interpretations" of QM which still abide by the predictions of QM are like arguing "how many angels can dance on the head of a pin". (Something I let myself fall into earlier to my regret.)

So are there any "Why" 's out there which correctly characterize Copenhagen?

So far all that I've seen which is valid is either
I. "Personal philosophical preference" and
II. "It might somehow provide insight into new physics".
I assert the same is true vis versa with a stronger argument w.r.t. insight given operationalism is a powerful heuristic principle in physics. It helps one avoid hysteresis in ones conceptualization (which, I might add, Einstein used to great effect.)

Regards,
James Baugh

[Edit] P.S. This paper, by the way, is a very nice piece of work, or would be if (in my characterization) the BM "nonsense" were excised. But I don't see it as saying anything terribly ground breaking. Taking an operational approach it is clear that an ensemble average of his weakly observed normalized currents, for many systems by the very nature of the correspondence principle must approach the presented classical limit particle velocities. His assertion that an ensemble average must conform to the reality of an individual instance is predicated on the assertions of BM which he rightly qualifies. But absent these assertions the operational meaning is the same. One is taking an ensemble average and getting in the limit a classical description. Pushing the Bohmian part of it is to my mind no different than say ascribing a pressure to each particle of a (classical) gas because you can give the pressure of the ensemble operational meaning.
R., J. B.