Do particles have well-defined positions at all times?

[Fredrik]

Double-slit experiments are about ensembles.

So?

When we put a detector at each slit to ensure that every particle in the ensemble has a well-defined position, the interference pattern changes. Why would it change if the particles already had well-defined positions?

 

[strangerep]

So? [...]

In the course of this thread, I've come to realize that my perspective on these things is in fact a stripped-down and modified version of Ballentine. Following Occam's principle of disregarding all inessential crud, I had also tacitly disregarded some of the extra "explanatory" material in SI which (imho) is inessential or misleading. The statement about "a particle having some position" is one of these, since I don't find the notion of "particle" helpful and I always translate it into a field picture. But of course, this is then different from what Ballentine was saying in print.

To avoid further confusion, I guess I should stop talking about "pure" SI. :-)

Edit: If it's not diverting your thread too much, suppose the title were modified to read "Do fields have well-defined positions at all times?", what would the answer be?

 

[Fra]

Edit: If it's not diverting your thread too much, suppose the title were modified to read "Do fields have well-defined positions at all times?", what would the answer be?

This raises some quite interesting questions like, IS a field "positioned" relative to spacetime in the first place (then how is "PURE spacetime" inferred?), or is spacetime simply a way of INDEX a field (whatever a field is; but I'm thinking in terms of some abstract data acquired from a communication channel).

This immediately suggest a deeper link, where there is a conceptual problem to even talk about "PURE spacetime". If spacetime is an INDEX, then it's an INDEX of something else. I can't imagine there is such thing as a pure index unless you again resort to some realism.

You referred to some old thread where this was discussed, I don't know which it was. Do you have a link? Maybe some of this is already discussed and it could be interesting to reveiw what was said.

/Fredrik

 

[Fredrik]

A classical field is a section of some kind of vector bundle over spacetime. In QFTs, we have to talk about operator-valued distributions instead. In every theory I'm familiar with, a field is some kind of function (in the very general sense) which isn't associated with any particular point in spacetime. So it wouldn't make sense to attribute the property of "having a well-defined position" to the field itself.

However, in a one-particle theory such as quantum Klein-Gordon theory, it makes sense to say that the "one-particle states" are really states of the field. Some of those states can be described as having approximately well-defined positions. So while a field can't be said to have a position, some of its states can.

I suspect that even that last part can be false in theories of massless particles, or theories with interactions, but I don't know QFT well enough to really understand this.

 

[strangerep]

[...] So it wouldn't make sense to attribute the property of "having a well-defined position" to the field itself.

Agreed.

However, in a one-particle theory such as quantum Klein-Gordon theory, it makes sense to say that the "one-particle states" are really states of the field. Some of those states can be described as having approximately well-defined positions. So while a field can't be said to have a position, some of its states can.

But not a state corresponding to a quasi-monochromatic plane wave incident upon a double-slit...

 

[strangerep]

You referred to some old thread where this was discussed, I don't know which it was. Do you have a link? Maybe some of this is already discussed and it could be interesting to reveiw what was said.

I was referring (I think) only to the moderately-recent threads in which Arnold Neumaier debated with Meopemuk about slits, particles, fields, etc. Some of this was in Meopemuk's thread in the IR forum, and some of it was here. But I don't think it wandered into the sort of question you're posing:

[...] IS a field "positioned" relative to spacetime in the first place (then how is "PURE spacetime" inferred?), or is spacetime simply a way of INDEX a field (whatever a field is; but I'm thinking in terms of some abstract data acquired from a communication channel).

The only vague thoughts I have on this are to think in terms of the radar method in GR.
If you have a copy of Misner, Thorne & Wheeler, look at figs 1.2 and 1.3 which seek to synthesize a mathematical picture of spacetime from interaction events. This suggests to me that we should be thinking in terms of acceleration and covariant Frenet-Serret equations to obtain a more intrinsic picture of such interactions (and hence correlations).
But this is more speculative than I'm willing to pursue on PF. :-)

 

[Demystifier]

So?

When we put a detector at each slit to ensure that every particle in the ensemble has a well-defined position, the interference pattern changes. Why would it change if the particles already had well-defined positions?

Because the detector modifies these positions?

 

[Fredrik]

Because the detector modifies these positions?

If all particles have well-defined positions, then half the particles will pass through each slit, regardless of whether there are detectors there. But the interference pattern depends on whether the detectors are there or not. So the answer can't be just that the detectors move the particles. There must be something more to it than that.

 

[Fra]

If you have a copy of Misner, Thorne & Wheeler, look at figs 1.2 and 1.3 which seek to synthesize a mathematical picture of spacetime from interaction events

Yes, something in that direction (and even farther) is what I mean (I don't have that book.)

This suggests to me that we should be thinking in terms of acceleration and covariant Frenet-Serret equations to obtain a more intrinsic picture of such interactions (and hence correlations).
But this is more speculative than I'm willing to pursue on PF. :-)

I agree its speculative relative to the mainstream theories, but from a more intellectual point of view, if you analyse this, consider how our world view is actually inferred, and then add the idea that matter also infers it's world view in an analogous way as per some physical inference process, then it's not speculative. Somehow I am forced to face these questions. There is nowhere to hide.

To ignore them and replace de factor inferred elements of theory, with elements of structural realism, THAT is IMHO at least logically MORE speculative (because it corresponds to a wilder extrapolation from raw data than what I suggest).

Something *weakly* related in this direction is also this

The principle of relative locality
by Giovanni Amelino-Camelia, Laurent Freidel, Jerzy Kowalski-Glikman, Lee Smolin
" We propose a deepening of the relativity principle according to which the invariant arena for non-quantum physics is a phase space rather than spacetime. Descriptions of particles propagating and interacting in spacetimes are constructed by observers, but different observers, separated from each other by translations, construct different spacetime projections from the invariant phase space. Nonetheless, all observers agree that interactions are local in the spacetime coordinates constructed by observers local to them. This framework, in which absolute locality is replaced by relative locality, results from deforming momentum space, just as the passage from absolute to relative simultaneity results from deforming the linear addition of velocities. Different aspects of momentum space geometry, such as its curvature, torsion and non-metricity, are reflected in different kinds of deformations of the energy-momentum conservation laws. These are in principle all measurable by appropriate experiments. We also discuss a natural set of physical hypotheses which singles out the cases of momentum space with a metric compatible connection and constant curvature.
"
-- http://arxiv.org/abs/1101.0931

I like to be more radical than that, but I think there are fragments of good thinking in that paper. In particular the acknowledgment that "spacetime" is something that is inferred by each observer. This is a fundamental key insight. But I think we could be far more radical and analysing it deeper than just thinking in terms of inference from momentum.

/Fredrik

 

[Varon]

Yes, something in that direction (and even farther) is what I mean (I don't have that book.)


I agree its speculative relative to the mainstream theories, but from a more intellectual point of view, if you analyse this, consider how our world view is actually inferred, and then add the idea that matter also infers it's world view in an analogous way as per some physical inference process, then it's not speculative. Somehow I am forced to face these questions. There is nowhere to hide.

To ignore them and replace de factor inferred elements of theory, with elements of structural realism, THAT is IMHO at least logically MORE speculative (because it corresponds to a wilder extrapolation from raw data than what I suggest).

Something *weakly* related in this direction is also this

The principle of relative locality
by Giovanni Amelino-Camelia, Laurent Freidel, Jerzy Kowalski-Glikman, Lee Smolin
" We propose a deepening of the relativity principle according to which the invariant arena for non-quantum physics is a phase space rather than spacetime. Descriptions of particles propagating and interacting in spacetimes are constructed by observers, but different observers, separated from each other by translations, construct different spacetime projections from the invariant phase space. Nonetheless, all observers agree that interactions are local in the spacetime coordinates constructed by observers local to them. This framework, in which absolute locality is replaced by relative locality, results from deforming momentum space, just as the passage from absolute to relative simultaneity results from deforming the linear addition of velocities. Different aspects of momentum space geometry, such as its curvature, torsion and non-metricity, are reflected in different kinds of deformations of the energy-momentum conservation laws. These are in principle all measurable by appropriate experiments. We also discuss a natural set of physical hypotheses which singles out the cases of momentum space with a metric compatible connection and constant curvature.
"
-- http://arxiv.org/abs/1101.0931

I like to be more radical than that, but I think there are fragments of good thinking in that paper. In particular the acknowledgment that "spacetime" is something that is inferred by each observer. This is a fundamental key insight. But I think we could be far more radical and analysing it deeper than just thinking in terms of inference from momentum.

/Fredrik

Fra. As one of the fierciest Copenhagenists. Pls. comment on this thread:

https://www.physicsforums.com/showthread.php?t=501244

where your namesake Fredrik (aka Wolverine) stated that a correct analysis of Copenhagen gives the conclusion that either the state vector is describing Many Worlds or Statatistical (Ensemble) Interpretation which refutes everything you said because in both there is no need for observers. So defend yourself against his all consuming idea.

 

[Fra]

I'll comment later when I've read those threads what superhero Fredrik writes. I didn't follow the threads you refer to. More later.

Also note that I am not a pure copenhagenist. It may seem like I am close to it, and I am, but the classical copenhagen view only describes things from the point of view of a classical observer. In this case, I agree it's close to an ensemble view. But the point is that my objection is that the "ensemble view" makes sense ONLY in the case of a classical observer.

Now, the generic observer (say an atom), is IMO not classical. So the original Bohr view, is a special case. What I try to do, is to keep what I THINK is part of the core spirit, but extend it to non-classical observers.

/Fredrik

 

[strangerep]

Something *weakly* related in this direction is also this

The principle of relative locality
by Giovanni Amelino-Camelia, Laurent Freidel, Jerzy Kowalski-Glikman, Lee Smolin

[...]
-- http://arxiv.org/abs/1101.0931

I like to be more radical than that, but I think there are fragments of good thinking in that paper. In particular the acknowledgment that "spacetime" is something that is inferred by each observer. This is a fundamental key insight. But I think we could be far more radical and analysing it deeper than just thinking in terms of inference from momentum.

I looked through that paper when it came out. (I also recall a brief thread about it in the BSM forum.) I'm ok with it while they talk about momentum and interactions, but then they postulate something like canonical conjugates of momenta in section III and assume these must be positions (IIUC). I don't see that this is justified. I would have thought that a better generalization is to express dynamics as momenta and acceleration (and maybe jerk) in the formulation. Their step back to a standard phase space seems insufficiently justified, imho.

 

[Demystifier]

If all particles have well-defined positions, then half the particles will pass through each slit, regardless of whether there are detectors there.

True.

But the interference pattern depends on whether the detectors are there or not.

True.

So the answer can't be just that the detectors move the particles. There must be something more to it than that.

Not necessarily true. The following scenario is also logically possible:
The presence of the detector may influence the motion of the particle not only on the position of the detector, but also behind the detector, in the "interference region". That influence may be such that, when an ensemble of particles is considered, the interference pattern is destroyed.

Moreover, such influence of the detector on the particle far from the detector may even be local, provided that there IS something more propagating from the position of the detector. But what that "more" could be? Well, we certainly don't know what, if anything, it IS. Yet, Bohmian mechanics provides the simplest known answer what that COULD be. It could be the wave function itself, propagating according to the Schrodinger equation. In this view, the particle and the wave function are separate objectively existing entities, where the latter influences the motion of the former.

Or to quote John Bell:
“Is it not clear from the smallness of the scintillation on the screen that we have to do
with a particle? And is it not clear, from the diffraction and interference patterns, that the
motion of the particle is directed by a wave? De Broglie showed in detail how the motion
of a particle, passing through just one of two holes in screen, could be influenced by waves
propagating through both holes. And so influenced that the particle does not go where the
waves cancel out, but is attracted to where they cooperate. This idea seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored.”

 

[Varon]

I'll comment later when I've read those threads what superhero Fredrik writes. I didn't follow the threads you refer to. More later.

Also note that I am not a pure copenhagenist. It may seem like I am close to it, and I am, but the classical copenhagen view only describes things from the point of view of a classical observer. In this case, I agree it's close to an ensemble view. But the point is that my objection is that the "ensemble view" makes sense ONLY in the case of a classical observer.

Now, the generic observer (say an atom), is IMO not classical. So the original Bohr view, is a special case. What I try to do, is to keep what I THINK is part of the core spirit, but extend it to non-classical observers.

/Fredrik

Here's the arguments.

What does |u>+|v> mean to you?

For Fredrik/Wolverine, He believes it can only mean the following two cases:

1. |u>+|v> means that the there are (at least) two copies of the system, one of which is in state |u> and the other in state |v>?

2. |u>+|v> doesn't actually represent the properties of the system, but is just a part of a mathematical formalism that can be used to calculate probabilities of possible results of experiments.

The first case is Many worlds, the second case is Ensemble Interpretation. He believes other Copenhagen variant just try to be something else but is really Many worlds or Ensemble Interpretation at the core. Anyway. How do you understand |u>+|v>?

 

[yoda jedi]

I have always thought that this idea isn't even consistent with the standard version of QM, so I was really surprised when I found this quote in Ballentine's 1970 article "The statistical interpretation of quantum mechanics":

In contrast, the Statistical Interpretation considers a particle to always be at some position in space, each position being realized with relative frequency $|\psi(\vec r)|^2$ in an ensemble of similarly prepared experiments.​

Later in the article he admits that we don't know if this is really the case, but he insists that this view isn't inconsistent with QM. I would like to know if he's right.

Is there an argument that proves that particles don't have well-defined positions at all times? Aren't there experiments for which the assumptions "the particle is either here or there" and "the particle is in a superposition of here and there" give us different predictions?

well-defined values is a statement of the modal approach.

..."physical systems at all times possesses a number of well-defined physical properties, i.e. definite values of physical quantities.."




and no collapse.


.

 

[Fredrik]

The presence of the detector may influence the motion of the particle not only on the position of the detector, but also behind the detector, in the "interference region". That influence may be such that, when an ensemble of particles is considered, the interference pattern is destroyed.

Right, but then we can at least conclude that the wavefunction doesn't just describe the statistical distribution of particles with well-defined positions. It has some other significance as well.

I think we're closing in on an answer to my original question: There is no known argument or experiment that can completely rule out the possibility that particles have well-defined positions at all times, but we can rule out the possibility that the only significance of the wavefunction is to describe the statistical distribution of particles with well-defined positions.

This makes me wonder if I've been thinking about Bohmian mechanics in the wrong way. I've been thinking that it's a different theory that makes the same predictions as QM, but this makes me think that it should (or at least can) be viewed as a genuine interpretation of QM. It seems that you can add some Bohmian assumptions on top of QM to turn the theory into something that might be a description of what actually happens, without changing the theory's predictions. It might be a description of a purely fictional universe, but at least it's a description of something. This is exactly what I think an "interpretation of QM" should do.

 

[Demystifier]

Right, but then we can at least conclude that the wavefunction doesn't just describe the statistical distribution of particles with well-defined positions. It has some other significance as well.

I think we're closing in on an answer to my original question: There is no known argument or experiment that can completely rule out the possibility that particles have well-defined positions at all times, but we can rule out the possibility that the only significance of the wavefunction is to describe the statistical distribution of particles with well-defined positions.

This makes me wonder if I've been thinking about Bohmian mechanics in the wrong way. I've been thinking that it's a different theory that makes the same predictions as QM, but this makes me think that it should (or at least can) be viewed as a genuine interpretation of QM. It seems that you can add some Bohmian assumptions on top of QM to turn the theory into something that might be a description of what actually happens, without changing the theory's predictions. It might be a description of a purely fictional universe, but at least it's a description of something. This is exactly what I think an "interpretation of QM" should do.

Yes, I think I can agree with all that.

 

[A. Neumaier]

This makes me wonder if I've been thinking about Bohmian mechanics in the wrong way. I've been thinking that it's a different theory that makes the same predictions as QM, but this makes me think that it should (or at least can) be viewed as a genuine interpretation of QM. It seems that you can add some Bohmian assumptions on top of QM to turn the theory into something that might be a description of what actually happens, without changing the theory's predictions. It might be a description of a purely fictional universe, but at least it's a description of something. This is exactly what I think an "interpretation of QM" should do.

Indeed, and the literature on Bohmian mechanics shows that this can be done in lots of essentially different ways, which are not equivalent in terms of the underlying Bohmian reality.

This means that the Bohmian approach drives out the devil with Beelzebub - instead of an interpretation problem one now has the problem of finding out which one of the infinitely many possibilities is realized. With the additional torment that according to the official claim that Bohmian mechanics makes exactly the same experimental predictions as quantum mechanics there cannot be any experimental decision between these potential realities.

The only way to discriminate between these different variants of the Bohmian interpretations is on the basis of subjective criteria such as simplicity - unless one assumes that there are situations where a system is not in quantum equilibrium, in which case the experimental predictions differ both from each other and from standard quantum mechanics.

 

[Fra]

I've been unusually busy lately, but I think I roughly understand your question and this is what I think (I didn't read all the past thereads you refer to).

Here's the arguments.

What does |u>+|v> mean to you?

For Fredrik/Wolverine, He believes it can only mean the following two cases:

1. |u>+|v> means that the there are (at least) two copies of the system, one of which is in state |u> and the other in state |v>?

2. |u>+|v> doesn't actually represent the properties of the system, but is just a part of a mathematical formalism that can be used to calculate probabilities of possible results of experiments.

The first case is Many worlds, the second case is Ensemble Interpretation. He believes other Copenhagen variant just try to be something else but is really Many worlds or Ensemble Interpretation at the core. Anyway. How do you understand |u>+|v>?

|u>+|v> first of all is a symbolic notation since you are not just implying a state, you are implying that it's constructed by means of an addition. I can comment on this, because this is independent from the other (your main) question about what this means.

Your first question, then I think the state vector represents the observing systems current state of information about the observed system. This is physically encoded in the physical state of the observing system.

Now to comment further on this: does this mean there exists many worlds? No, not IMO, unless you by world means "inferred world", then yes. However I find it almost profane language to call it many worlds. I would rather say there are many observers! AND these observers are INTERACTING - this is exactly why it makes no sense to talke about many worlds as in many universes.

The different "apparent worlds" are just the different views, held by each observer.

About the second detail; the addition, that means to me that |u>+|v> is the information state you get when you the observing system tries to update |u> with |v> in a sense where they have equal confidence. IE. somehow your information tells you two conflicting things, BUT you are confident enough to konw that even though the information contains internal tension; the information is confident. This comvined information state is what it is.
One thing I also consider an open question is to describe this inference process (mathematiclally).

For example when you combine two momentum eigenvectors; and then tries to infere position, then you get the weird superposition statistics because there exists a transformation in between.

My view is to view the observers structure instantly as a SET of several different classical microstructures, that are related by data transformation relations (think data compression). And the total information capacity of this set is determined by the complexity(or mass) of the observing system. This means that there is a phenomena where the observing system, subject to a constant stream of data, are force to select and evolve NEW structures in the set of microstructures for an "optimal representation", observing systems that fail to do this will be decomposed and this not populate the world we see. Another effect is that due to the limiting information capacity, the observing system constantly needs to bleed off information (throw away) information at thte same rate unless it can increase it's mass (this can happen too! but this will complicate this even more so I ignore it here). Now the distribution of the thrown away information will be random (contain no information) as measured relative to the observing system itself (here associate BH radiation and info paradox) but it WILL genereally contain information relativge to a complex outside observer that is complexy enough to DECODEe it.

In essence plenty of the interactions could potentially be explainedi nterms of this "discarded information" which looks like it contains no info form the inside, but not from the outside.

Herein lies the points where the constructiong of entropic fources meets the information paradox problem. A BH also "discards information" - hawking radiation, but according to WHICH measure does it or does it not contain any information? I propose a (so far conceptual at least) resolution.

But the details are all in progress.

So to your original question I think we have one world, but many observers. The state vector of system B relative observer O. So each wavefunctio nneeds to indfexes, the system which is "describes" and the system that encodes the description.

The ensemble view avoids this problems and just talks about the abstract ensemble. and this makes perfect sense in many cases! Such as when we have a classical laboratory and a particle experiment! But, the ensemble view IMO fails to make any sense in the more general cases I tried to elaborate.

/Fredrik

 

[Varon]

I've been unusually busy lately, but I think I roughly understand your question and this is what I think (I didn't read all the past thereads you refer to).



|u>+|v> first of all is a symbolic notation since you are not just implying a state, you are implying that it's constructed by means of an addition. I can comment on this, because this is independent from the other (your main) question about what this means.

Your first question, then I think the state vector represents the observing systems current state of information about the observed system. This is physically encoded in the physical state of the observing system.

Now to comment further on this: does this mean there exists many worlds? No, not IMO, unless you by world means "inferred world", then yes. However I find it almost profane language to call it many worlds. I would rather say there are many observers! AND these observers are INTERACTING - this is exactly why it makes no sense to talke about many worlds as in many universes.

The different "apparent worlds" are just the different views, held by each observer.

Fra. Can you consider this statement of yours a postulate of your Extra Copenhagen understanding: "The different "apparent worlds" are just the different views, held by each observer."? I was reviewing your messages for an hour in old archives here trying to get similar statement but this is the same first time you mentioned it. In your previous views. You were saying that Copenhagen is a special case applying to the cases where an infinitely complex classical observer observes a small subsystem, while you believe that there should many observers (explaining Wigner friend paradox for example). So this is your punchline. That these many observers of yours is nothing but what many worlds called branches? Right? Again you said this motto: "The different "apparent worlds" are just the different views, held by each observer."

Btw.. Michael Lockwood has similar ideas althought in his views, the different "apparent worlds" are just the different views, held by each conscious Mind. It's called the Many Minds Interpretations favored by Many Worlders..

About the second detail; the addition, that means to me that |u>+|v> is the information state you get when you the observing system tries to update |u> with |v> in a sense where they have equal confidence. IE. somehow your information tells you two conflicting things, BUT you are confident enough to konw that even though the information contains internal tension; the information is confident. This comvined information state is what it is.
One thing I also consider an open question is to describe this inference process (mathematiclally).

For example when you combine two momentum eigenvectors; and then tries to infere position, then you get the weird superposition statistics because there exists a transformation in between.

My view is to view the observers structure instantly as a SET of several different classical microstructures, that are related by data transformation relations (think data compression). And the total information capacity of this set is determined by the complexity(or mass) of the observing system. This means that there is a phenomena where the observing system, subject to a constant stream of data, are force to select and evolve NEW structures in the set of microstructures for an "optimal representation", observing systems that fail to do this will be decomposed and this not populate the world we see. Another effect is that due to the limiting information capacity, the observing system constantly needs to bleed off information (throw away) information at thte same rate unless it can increase it's mass (this can happen too! but this will complicate this even more so I ignore it here). Now the distribution of the thrown away information will be random (contain no information) as measured relative to the observing system itself (here associate BH radiation and info paradox) but it WILL genereally contain information relativge to a complex outside observer that is complexy enough to DECODEe it.

In essence plenty of the interactions could potentially be explainedi nterms of this "discarded information" which looks like it contains no info form the inside, but not from the outside.

Herein lies the points where the constructiong of entropic fources meets the information paradox problem. A BH also "discards information" - hawking radiation, but according to WHICH measure does it or does it not contain any information? I propose a (so far conceptual at least) resolution.

But the details are all in progress.

So to your original question I think we have one world, but many observers. The state vector of system B relative observer O. So each wavefunctio nneeds to indfexes, the system which is "describes" and the system that encodes the description.

The ensemble view avoids this problems and just talks about the abstract ensemble. and this makes perfect sense in many cases! Such as when we have a classical laboratory and a particle experiment! But, the ensemble view IMO fails to make any sense in the more general cases I tried to elaborate.

/Fredrik

 

[PhilDSP]

The only way to discriminate between these different variants of the Bohmian interpretations is on the basis of subjective criteria such as simplicity - unless one assumes that there are situations where a system is not in quantum equilibrium, in which case the experimental predictions differ both from each other and from standard quantum mechanics.

Unless, of course, some variant of de Broglie theory (assuming that is more general in conception than Bohmian mechanics) succeeds in deriving a new observation of some sort that becomes experimentally verified. So apparently its real potential value lies in becoming more descriptive than any other QM discipline.

 

[Fra]

Fra. Can you consider this statement of yours a postulate of your Extra Copenhagen understanding: "The different "apparent worlds" are just the different views, held by each observer."?

Almost but not quite. The problem is this: If one takes really seriously what I suggest, then it suggest that quantum mechanics with the fixed hilbert spaces and deterministic unitary evolution is not the correct description for the general case! This is why what I suggest is not "just" an interpretation.

In particular, the "apparent worlds" are INCONSISTENT with each other unless you add interactions. This is a new idea that doesn't exist in the old interpretation. So just trying to keep QM formalism intact and then say that the different views correspond to different observers, does not make sense as it would correspond to different CLASSICAL worlds; in violation with what we see. Classical means, means there are many classical observers but they all agree. This why it's not so simply to just add this to the old interpretation.

I'm proposing also new physical mechanisms.

But what you suggest is in the right direction.

You were saying that Copenhagen is a special case applying to the cases where an infinitely complex classical observer observes a small subsystem, while you believe that there should many observers (explaining Wigner friend paradox for example). So this is your punchline. That these many observers of yours is nothing but what many worlds called branches? Right? Again you said this motto: "The different "apparent worlds" are just the different views, held by each observer."

Well, almost, but it really depends what you mean by many worlds. As far as I know, most people into that view, are not thinking in terms of itneracting worlds. My "apparent worlds" are interacting. This is probably the main difference.

Btw.. Michael Lockwood has similar ideas althought in his views, the different "apparent worlds" are just the different views, held by each conscious Mind. It's called the Many Minds Interpretations favored by Many Worlders..

I'm aware of the many minds, but I haven't seen anything serious about it. I've just seen some vague ideas.

The obvious problem with many observers is that you run into an apparent subjectivity. I am not ignoring this, I'm trying to explain how effective objectivity and effective reality emerges when interacting observer negotiate. What I know so far the so called "many minds" doesn't provide any mechanism or ideas of mechanisms for this at all. At least nothing I'm aware of?

But loosely speaking "many observers" is the directing in which i thinking, rather than many worlds. BUT, in the special domain of QM where it's tested, say particle experiments. Then I think the statistical ensemble interpretation is pretty close to my view. But this does not generalize to cases where the ensenble isn't established or known, due to time or information capacity constraints, it's this generalisation I have in mind.

Note that since I am talking about interacting observers! this is NOT just like the branches of the many worlds. It contains much more mechanisms (which of course I have not explained in detail because it's still things in progress).

Many worlds, is considered to be a pure interpretation.

In my interacting observer view, the unitary evolution is just an EXPECTED evolution. Which means in a real interaction it's just the differential evolution (think tangentspace) that is unitary. But the entire space deforms during the finite evolution.

/Fredrik

 

[Fra]

In your case. Does a state vector represent all the properties of a single system? Superhero Fredrik said "Obviously, there are only two answers: yes and no. I've been arguing that "yes" implies many worlds." ... "I have also been arguing that "no" defines the statistical/ensemble/Copenhagen interpretation. So Fra, is your answer yes or no? Again, Does a state vector represent all the properties of a single system in your case?

I'd say there is a third answer, which is that the question is not clear enough to justify a yes/now. The answer is yes or no if you acknowledge the question as clear.

My answer is that I think the question is not clear enough. I'd like to say that the state vector represents the KNOWLEDGE of all properties (=EXPECTATIONS of) of a single system.

Because there IS no such THING as "the system itself", all you EVER have are KNOWLEDGE or EXPECTATIONS of this something. In fact to the observer, the expectations are as real as it gets.

However, in many cases (read where QM is tested) this KNOWLEDGE is infact inferred from several repetitive trials of indistinguishable systems. Meaning that the KNOWLEDGE of the individual system may be the same as the "ensemble view". Ie. you can VIEW the structure of the konwledge as an ensemble in the cases where the repetivive trial etc make sense.

But in cases where it does not make sense, I consider arbitrary time histories which also carry information, this also leads to an expectation. Not necessarily of the simple form that you have in the "statistical ensemble".

This is why in my view, the statistical ensemble view represents a special case. When it applies it's fine, but when it doesn't either you can look for something else or try to come up with answers that some has that "then science fails", which is IMO more like a cop-out attitude.

Also beside taking apart QM and Hilbert Space. Any problem with relativity in your interactive observers?

Except for the obvious fact that it remains on my burden to show explicitly that all this can be worked out - then conceptually there are no problems; on the contrary is the idea that this view also has an emergent spacetime where relativity comes as an naturally emergent symmetry.

/Fredrik

 

[Varon]

I'd say there is a third answer, which is that the question is not clear enough to justify a yes/now. The answer is yes or no if you acknowledge the question as clear.

My answer is that I think the question is not clear enough. I'd like to say that the state vector represents the KNOWLEDGE of all properties (=EXPECTATIONS of) of a single system.

Because there IS no such THING as "the system itself", all you EVER have are KNOWLEDGE or EXPECTATIONS of this something. In fact to the observer, the expectations are as real as it gets.

However, in many cases (read where QM is tested) this KNOWLEDGE is infact inferred from several repetitive trials of indistinguishable systems. Meaning that the KNOWLEDGE of the individual system may be the same as the "ensemble view". Ie. you can VIEW the structure of the konwledge as an ensemble in the cases where the repetivive trial etc make sense.

But in cases where it does not make sense, I consider arbitrary time histories which also carry information, this also leads to an expectation. Not necessarily of the simple form that you have in the "statistical ensemble".

This is why in my view, the statistical ensemble view represents a special case. When it applies it's fine, but when it doesn't either you can look for something else or try to come up with answers that some has that "then science fails", which is IMO more like a cop-out attitude.



Except for the obvious fact that it remains on my burden to show explicitly that all this can be worked out - then conceptually there are no problems; on the contrary is the idea that this view also has an emergent spacetime where relativity comes as an naturally emergent symmetry.

/Fredrik

You know what Fra, thinking about what you said and all. I think it has a big problem. Right now. We don't even know how to modify the Schroedinger equation in such a way as to provide for a dynamical collapse. Countless scientists and Nobelists have tried, but no one has succeeded in coming up with a really satisfactory proposal. Now what you are trying to do is not just one collapse, but dozens of collapses that also interacts! I think Pauli can say that it is "not even wrong". So meanwhile. I'll just entertain Many Worlds because your view is so arbitrary.. and you don't even have any mathematical proposal for it. If you are serious about it. Think about how this modification of the S.E. is done. Btw.. you must have known many failed attempts or proposals by the mainstream to provide for a dynamical collapse. Can you site those papers where they attempted it and failed (so we can see what problems and obstacles they encountered)? I still prefer it over the Schizopheniac Many Worlds but if there is almost no hope for resolution, then no choice but to go with the psycho MWI.

 

[Fra]

We don't even know how to modify the Schroedinger equation in such a way as to provide for a dynamical collapse.

Correct. This is why I said several times that I'm not doing pure interpretations. However, this "program" I'm into, implies a certain "interpretation". But the ultimate reason for preferring the interpretation is the success of the program.

But in fact, this is why it's worth considering. The pure interpretations, end up beeing the same mathematical formalism we have, and it provides NO further insights into unification and QG issues. So the "problems" you mentions, are just proving that this is non-trivial.

To excercise some lentght "interpretations" that in the end makes no further predictions than the current shut up and calculate formulation; then what is the point?

Countless scientists and Nobelists have tried, but no one has succeeded in coming up with a really satisfactory proposal.

Yes but this is IMO a VERY poor excuse for not doing ones own thinking :) Without the right attitude we will never succeed.

So I think I can do better than everyone else? Apparently. Yes I know I'm probably crazy, but sometimes you need to be a little bit crazy to try.

Every successful novel progress in the history of science has been backed up by a history of failures; this is entirely normal. It should not be seen as discouraging at all. Anyone who thinks he/she can't succeed just because everyone else failed probably doesn't have the right mindest for this undertaking in the first place.

This should not be confused with naivety though.

Think about how this modification of the S.E. is done.

That's exactly what I'm trying to do of course.

But before I make any bold proposals for new frameworks I have a lot more work to do.

But in short; the SE is most certainly correct as it stands, when you consider that it is a limiting case. Conceptually I've tried to explain it rouglhy, but the exact framework is in progress.

The whole point of conceptual view is a guide to finding the new framework. So I am constructive here.

This is in large contrast to those who try to find an interpretation of the existing already known! framework? What is the point?

I think we should focus on solving OPEN problems, an not ONLY make up interpretations to theories in domains where they are absolutely excellent, and where the interpretations makes no difference.

Please give some example how the MWI aspires to add any insight to an open problems to physics?

/Fredrik

 

[Varon]

Correct. This is why I said several times that I'm not doing pure interpretations. However, this "program" I'm into, implies a certain "interpretation". But the ultimate reason for preferring the interpretation is the success of the program.

But in fact, this is why it's worth considering. The pure interpretations, end up beeing the same mathematical formalism we have, and it provides NO further insights into unification and QG issues. So the "problems" you mentions, are just proving that this is non-trivial.

To excercise some lentght "interpretations" that in the end makes no further predictions than the current shut up and calculate formulation; then what is the point?

Yes but this is IMO a VERY poor excuse for not doing ones own thinking :) Without the right attitude we will never succeed.

So I think I can do better than everyone else? Apparently. Yes I know I'm probably crazy, but sometimes you need to be a little bit crazy to try.

Every successful novel progress in the history of science has been backed up by a history of failures; this is entirely normal. It should not be seen as discouraging at all. Anyone who thinks he/she can't succeed just because everyone else failed probably doesn't have the right mindest for this undertaking in the first place.

This should not be confused with naivety though.

That's exactly what I'm trying to do of course.

But before I make any bold proposals for new frameworks I have a lot more work to do.

But in short; the SE is most certainly correct as it stands, when you consider that it is a limiting case. Conceptually I've tried to explain it rouglhy, but the exact framework is in progress.

The whole point of conceptual view is a guide to finding the new framework. So I am constructive here.

This is in large contrast to those who try to find an interpretation of the existing already known! framework? What is the point?

I think we should focus on solving OPEN problems, an not ONLY make up interpretations to theories in domains where they are absolutely excellent, and where the interpretations makes no difference.

Please give some example how the MWI aspires to add any insight to an open problems to physics?

/Fredrik

You make a lot of sense in this message! I found myself being limited by current interpretations that don't have enough degrees of freedom. They are too rigid. Can you cite other mainstream physicists who are working along the lines you mentioned? Like maybe Carlo Rivelli(?) or even Lee Smolin? Who else? What important papers did they publish along this line?

 

[Fra]

Unfortunately there is to my knowledge none that has published anything that is completely in the direction what I think needs to be done, but there are several peoples and programs that have fragments that point to this direction.

But the general direction I'm favouring is an inference perspective to physics, where the ultimate idea is that the laws of physics are nothing but natures own "rational infernece". Then this is combined by physical constraints on the inference system (hosted by the observing system).

Some ideas that at least RELATE to this (but which develops different later) you find here.

1) Ariel Caticha
http://www.albany.edu/physics/ariel_caticha.htm
His main idea is that the laws of nature are derivable from the rules of rational inference. Ie. that information about physical interactions between two systems in nature, can be understood as a rational inference on their behaviour. In his view rational inference = probability theory, and for the extension to non-commutative cases quantum theory.

How this relates to my view: the main idea that the laws of physical are "rational expectations" is right in line with I envision, but I think we Need to start the analysi much deeper. In particular to I reject the too naive usage of continuum based probability. I think we need to start at the discrete levels and not just jump into the limits. This is why the causal set program may have bigger potential. But the idea is that these programs might meed somewhere.

2) Lee Smolin (Roberto Unger angle)

Smolin is very scattered and writes about almost everything, but the part I like the most is his collaboration with R Unger (expert in social theory) where he argues that the idea of eternal and timless laws of physica is wrong. The laws of the universe are evolving. I won't repeat the argument here, but this is also in line with my thinking, and it merges well with the reconstruction of ratinal inference from discrete ordered and partitioned sets of sets. It ultimately means that the laws of physics are also the result of a rational inference. But I find that Smoling isn't radical enough, he doesn't go all the way.

3) Kevin Knuth
Foundations of Physical Law
http://knuthlab.rit.albany.edu/index.php/Program/Foundations

His idea is that natural law derives from ordering relations. The idea could be that order is naturally present in the chain of events that defines the observers knowledge. This is an abstract idea that aims to ultimatley infer the laws of nature, from ordering relations of set, combining them also with equivalence relations of sets. This is an abstract reasoning that takes place long before spacetime is defined.

This kind of research is important and may relate to what I have in mind. But what he does is very basic structures, I can not answer for what Knuth's vision of the more elaborated things are.

How this relates to my view: This reminds of some of basic structure I'm working with. The basic abstractions are sets of distinguishable events, as well as counter states, that represents memory structure (where information is encoded). Then I have sets of such sets, that are related by different encodings (fourier transform is just an example). This entire set is constrained by a complexity. A time history is ordered, but a reencoded history has a different order. This is why networks of order create complex sturcutres that can be interpreted as multidimensional. Then this entire set of sets is subjct to random walks as the networks of sets develop in different directions entirely depending on the data stream fed into it. But this research is so abstract that on first sight, I have to admit that it's hard to see how it connects to physics. This is why I thin that IF someone is working on this, and publish parts of it, it may be in mathematical papers.

4) String theory
While I do not like string theory as such, it may be interesting to associate to it since it's after all one of the main BTSM reasearch programs.

In string theory, the idea is to deduce the action of the system, from some form of string action, and different state of the string. But ultimately the origin of the string action is just a silyl association to the string as a mechanical litteral string, oscillating. Then you quantize etc.

My generic view is to infer the action of a system from the rational action of the system, where the rational action is what follows from a random system just subject to the acquired self-constraints (such as ordering and equivalence relations of historical events). No classical action is needed. Also the "quantum" should be emergent as the structure of the system evolves from a single set to several non-commuting sets.

It is possible that string theory, may be a continuum limit of a deeper theory (without strings or more specifically without continuum objects at all; just sets of sets with inter-relations). The idea is that all interrelations would be understood from rational inference (almost the same as entropic reasoning).

5) Rovelli's LQG is not at all what I have in mind. When I started to read his book, during some of the first parts it started to converge to a picture I had where the networks would correspond to the observers information state; and that we would consider interacting networks. This would have been interesting to me, it could also connect at some point to te more abstract causal set views... but I later learning this is NOT Rovelli's vision.

Rovelli's RQM paper contains grains of excellent thinking, but again I find that because he wants to be conservative, he does not fully acknowledge his "no absolute relations" mantra. Because at some point he claims that communication is govergned by QM, and this is exactly the point where I find his reasoning looses coherence. But this is also because rovelli wants to find a "good interpretation" of QM, without changing it! But the outcome is not a good compromise IMO.

See http://arxiv.org/abs/quant-ph/9609002

--

My starting point, is a set of sets, that can be though of as (in constrast to classical statmech) a set of interacting microstructures, with a complexity conservation constraint. The microstructurs are related by different data encoding algorithms. When this structure is subject to new data, the data favours reallocations in this structure that can be understood as en entropic flow. New microstructures can be branched off at any time is situation demands. So there is NO static state space. The state space is always chancing. This is why expected changes are only relative to current state space. This is also why it's unitary (in the instant state space); there is simply no way to EXPECT the unexecpted. So unitarity is simpled to understand. It's no conicidene, or not magic tricks is needed to secure it. This is like when you move in a curved space; your tangent space is still always linear. There is an analogy here. Except that the structure of the embedding curved environment is unpredictable from the inside view; this is whay it's a true random walk, one step at a time.

But the difficulties start when these systems are interacting, then a selection will take place as there is a mutual interaction causing an evolution where at some point there may be a nash type equlibrium where systems maintain status quo (or approximately so). The task is to mathematically identify these equilibrium points, and the hope is obviously that the equilibrium points will prove to have a structure exactly fitting the standard model + of course include gravity and provide a GUT.

So in this view, there are no classical hamiltonian or lagrangians that are manually "quantized"! All there is are the logic of rationality (effectively serving as a selecting mechanics) then the effective hamiltonians will correspond to equilibrium points in this "game". Quantum logic automatically emerges out of this scheme as rational inference applied not to a single microstructure, but to sets of them (where they are related by information recodings), and constrained by "information capacity conservation".

/Fredrik

 

[Varon]

Thanks Fra for all the info. I'll take a look at them. Hope you won't be like Einstein spending half of his life chasing and solving and gaining nothing. This is because he lacked theoretical guiding principle in the latter half of his life. At least with GR, there is Equivalence Principle and this thought experiment of riding in a light wave in SR. So unless you have guiding principle (I don't know if this a right term). You may get nowhere. Lee Smolin mentioned that in String Theory they don't have guiding principle so it's possible they may face blank wall in later years turning it into a Theory of Nothing.

 

[Fra]

Lee Smolin mentioned that in String Theory they don't have guiding principle

I agree the guidind principles are essental indeed.

The key issue - from MY perspective - is that the meaning of the strings and the various string actions, lacks justification from the point of view of rational inference.

It's pretty much originating from the classical picture of a litteral string, blindly which you then quantize mechanically checking just for mathematical consistency. Then one found that there are several different theories, lots of dualities, but still there is no proper understanding what this is, beyond mathematical realtions. This is also I think the reason why there is no selection principle among the possible string backgrounds, there is even discussion of wether such a principle is needed or not. I find this highly confused, and it can't be covered up just by elegant mathematics.

IMHO, the string action and the string background, should be understood as a rational action, and definining the microstructure of the observer. So the "interacting observers" is what should provide the selection mechanism; the "moduli space" of backgrounds is then to be understood as the external picture; of a set of interacting strings (ie. strings observing each other), but that would suggest that not every point in the landscape is "populated" in the observer cluster; this the big size of the landscape is an illusion due to confusing mathematical possibilties with physical ones. But without this guide, the difference is not there. All there is are mathematical possibilities which isn't understood.

But in order to make sense out of it, one needs to do a complete reconstruction. The starting points of a classical string, has no justification at all in this picture.

/Fredrik

 

[Demystifier]

Right, but then we can at least conclude that the wavefunction doesn't just describe the statistical distribution of particles with well-defined positions. It has some other significance as well.

I think we're closing in on an answer to my original question: There is no known argument or experiment that can completely rule out the possibility that particles have well-defined positions at all times, but we can rule out the possibility that the only significance of the wavefunction is to describe the statistical distribution of particles with well-defined positions.

This makes me wonder if I've been thinking about Bohmian mechanics in the wrong way. I've been thinking that it's a different theory that makes the same predictions as QM, but this makes me think that it should (or at least can) be viewed as a genuine interpretation of QM. It seems that you can add some Bohmian assumptions on top of QM to turn the theory into something that might be a description of what actually happens, without changing the theory's predictions. It might be a description of a purely fictional universe, but at least it's a description of something. This is exactly what I think an "interpretation of QM" should do.

Perhaps now this can also be reconsidered from the point of view of a recent experiment already discussed here:
https://www.physicsforums.com/showthread.php?t=503861
https://www.physicsforums.com/blog.php?b=3077