I What is the current perspective on quantum interpretation?

[PeterDonis]

I'm obviously disregarding objects like "Tachyons" since they are not compatible with causation as understood in modern science.

This is a very strong claim. Do you have any references to back it up? (And yes, there are plenty of peer-reviewed papers discussing tachyons.)

 

[Tendex]

This is a very strong claim. Do you have any references to back it up? (And yes, there are plenty of peer-reviewed papers discussing tachyons.)

You mean you are not aware of the issues of tachions regarding causality? You even mentioned them so I don't know how my mentioning them for the purposes of restricting my claim to particles different from tachyons is stronger than yours or requires references. Can you explain?

 

[Tendex]

Go ahead and perform mentally the experiment you proposed with photons and tachyons, dou you think it makes sense?

 

[PeterDonis]

You mean you are not aware of the issues of tachions regarding causality?

I mean that if you want to make claims about such things, you need to provide specific references to back up your claims.

Go ahead and perform mentally the experiment you proposed with photons and tachyons, dou you think it makes sense?

Sure. My experiment was one-way.

 

[vanhees71]

The quantum correlations are indeed realized just as predicted by non-relativistic QM (which equals QFT for low energy phenomena as in this case). So, the mystery here has nothing to do with QM vs. QFT vs. SR. All these theories are compatible with the observed results (more so than you might suspect, see this article for example). The mystery resides in the desire for a causal mechanism responsible for those correlations and that is assumed to function per the causal structure of M4 per "local realism." No one has that answer.

Photons for sure cannot be described with non-relativistic QM. There is no mystery at all. Only the philosophers have problems. Minimal interpreters have none ;-))).

 

[RUTA]

Photons for sure cannot be described with non-relativistic QM. There is no mystery at all. Only the philosophers have problems. Minimal interpreters have none ;-))).

Here is an experiment with photons in the Bell triplet state violating the CHSH inequality: D. Dehlinger and M.W. Mitchell, ``Entangled photons, nonlocality, and Bell inequalities in the undergraduate laboratory,'' American Journal of Physics 70(9), 903--910 (2002).

 

[vanhees71]

Yes, and it's in full accordance with QED! No mystery!

 

[RUTA]

But why in accord with "local realism"?, the correlations show it to be the wrong classical recipe.

Exactly, that's the mystery. So, the various interpretations propose various causal mechanisms that violate local realism in various ways to account for the correlations. Then the proponents of a given interpretation argue why they think the manner by which their interpretation violates local realism makes sense. So far, no one has produced an interpretation that has garnered consensus support. The most popular "interpretation" is no interpretation, i.e., Shut up and calculate (the Copenhagen interpretation per Mermin). See this poll: M. Schlosshauer, J. Kofler, and A. Zeilinger, ``A snapshot of foundational attitudes toward quantum mechanics,'' Studies in the History and Philosophy of Modern Physics 44, 222–230 (2013). \url{https://arxiv.org/abs/1301.1069}.

Thus, some foundationalists have taken to proposing a principle explanation rather than a constructive explanation of quantum entanglement, as Einstein did with special relativity (SR). In SR, we still don't have a constructive account of time dilation and length contraction, but no one cares anymore. Everyone long ago gave up on theories of the luminiferous aether and the textbooks simply show how everything in SR follows from the relativity principle applied to the measurement of c (with some additional mathematical assumptions like linearity). For example, Jeff Bub says the non-Boolean algebraic structure of Hilbert space is fundamental a la the non-Euclidean geometric structure of spacetime. But no principle account has garnered consensus support yet either. We've published a few papers in the past two years using the relativity principle applied to the measurement of Planck's constant h to derive the joint probabilities for the Bell states. That might have more success, since everyone is happy with SR and we're following the example of SR exactly. We'll see :-)

 

[RUTA]

Yes, and it's in full accordance with QED! No mystery!

As I keep saying, the formalism itself is the source of the mystery, not the resolution of the mystery. As we show in our papers, the conservation law at work for the Bell spin states when Bob and Alice are making different spin measurements holds only on average. It is explicitly violated on a trial-by-trial basis. What kind of causal mechanism is responsible for that kind of conservation? So, the formalism does not resolve the mystery, the fact that it works is the mystery.

 

[vanhees71]

I'd say we have understood a phenomenon if our theories agree with the observations. I don't know what else you mean by "understanding".

I don't understand what you are referring to when you say the conservation laws hold only on average. According to standard Q(F)T angular momentum is conserved, and it's conserved on an event-by-event basis. I'm not aware of any observation disproving this.

 

[RUTA]

I'd say we have understood a phenomenon if our theories agree with the observations. I don't know what else you mean by "understanding".

That is why you don't understand the mystery and you keep posting, "The formalism works, what else do you want?" For those who want to know why the formalism works, you have provided nothing.

I don't understand what you are referring to when you say the conservation laws hold only on average. According to standard Q(F)T angular momentum is conserved, and it's conserved on an event-by-event basis. I'm not aware of any observation disproving this.

Read this paper https://www.nature.com/articles/s41598-020-72817-7 and you'll understand what I'm talking about.

 

[Fra]

The mystery resides in the desire for a causal mechanism responsible for those correlations

Agreed.

...and that is assumed to function per the causal structure of M4 per "local realism." No one has that answer.

Maybe this part of the question is where it goes wrong? Is the question wrong and there is no answer, or didn't anyone just find the answer yet?

/Fredrik

 

[Fra]

Exactly, that's the mystery. So, the various interpretations propose various causal mechanisms that violate local realism in various ways to account for the correlations. Then the proponents of a given interpretation argue why they think the manner by which their interpretation violates local realism makes sense. So far, no one has produced an interpretation that has garnered consensus support.

Agreed here as well.

However lack of consens support is not something one should care about for a problem of this difficulty. It even seems likely that "most of the community" are likely to have a hard time to accept novel ideas initially. If not, the problem should have been solved already.

The Qbism angle, I hinted in a previous post, if taken seriosuly spontaneously spawns a whole new can of worms that is hard to ignore, and separate from the initial more "simple concepts".

/Fredrik

 

[Sunil]

The mystery resides in the desire for a causal mechanism responsible for those correlations and that is assumed to function per the causal structure of M4 per "local realism." No one has that answer.

I disagree. The mystery resides in the quasi-religious status of the thesis that relativistic symmetry is fundamental and not simply emergent. Relativity has to be about space and time because we are so clever that we are able to understand very fundamental properties of space and time.

Instead, emergent relativity would leave us with boring distortions of clocks and rulers which play no fundamental role at all, and the difference to the Newtonian world is that with those distorted rulers and clocks we have no chance to measure space and time distances accurately. This picture of the world is boring, not mysterious. But physicists like mystery - this is what has fascinated them when they have, in impressive childhood years, looked at popular descriptions of relativity.

To preserve classical causality as it was in pre-relativistic time has also nothing to do with mystery. The Goedel universe or wormholes are much better candidates for those who love mysticism.

The answer is well-known, but rejected because it means a return to quite old, boring metaphysics, and requires the rejection of mysticism.

 

[vanhees71]

That is why you don't understand the mystery and you keep posting, "The formalism works, what else do you want?" For those who want to know why the formalism works, you have provided nothing.

The formalism works, because it is based on observations. That's how the scientific method successfully works since Galilei et al.

I'll have a look at your paper.

 

[Tendex]

Sure. My experiment was one-way.

Tachyons are compatible with SR and are part of many speculative theories that are routinely published in peer-reviewed journal as there are many publications about speculative quantum gravity theories or time travel theories(which also informs about the the quality decay of modern day journals), but they are not so far compatible with QFT or the Standard model, once again due to problems with causality and coherence with any physical scientific theory that arise when admitting FTL communication,(it might surprise you but FTL signaling is not considered a good thing for a theory, go figure). So it is perfectly sensible to leave those speculative entities outside a serious discussion about quantum theories without having to collect the massive bibliography about it. You can google tachyon as easily as anyone if you need a quick access to such references.

Anyway, back to your experiment to test FTL signaling, if it is one-way, how would you tell that the particle detected first is not the light signal, and therefore no FTL? You have to have some synchronization convention for the times at departure and detection, no? Unless you are only considering galilean relativity and then there is nothing special about a signal traveling FTL.

 

[Tendex]

I disagree. The mystery resides in the quasi-religious status of the thesis that relativistic symmetry is fundamental and not simply emergent. Relativity has to be about space and time because we are so clever that we are able to understand very fundamental properties of space and time.

Instead, emergent relativity would leave us with boring distortions of clocks and rulers which play no fundamental role at all, and the difference to the Newtonian world is that with those distorted rulers and clocks we have no chance to measure space and time distances accurately. This picture of the world is boring, not mysterious. But physicists like mystery - this is what has fascinated them when they have, in impressive childhood years, looked at popular descriptions of relativity.

To preserve classical causality as it was in pre-relativistic time has also nothing to do with mystery. The Goedel universe or wormholes are much better candidates for those who love mysticism.

The answer is well-known, but rejected because it means a return to quite old, boring metaphysics, and requires the rejection of mysticism.

Aren't you ignoring the fact that the correlations observed(in quantum experiments) are not compatible with classical, pre-relativistic time correlations?

 

[Fra]

To preserve classical causality as it was in pre-relativistic time has also nothing to do with mystery.

Perhaps we are talking about different things? Perhaps it was my flawed interpretation and i don't get what you guys are talking about. I thought RUTA meant that the "open issue" (mystery, is just a word?) is to to find an explanation of the correlations observed in entanglement. And if possible an explanation that obeys local realism. I think explanations are possible, but they the premises in "local realism" is wrong to start with. Nevertheless, and "explanation" is wanted.

We know QM works, but as long as we do not understand it properly, its explanatory value is limited.

This I agree with. I see no mysticism here?

/Fredrik

 

[vanhees71]

Exactly! There's no mysticism and an "explanation", namely quantum theory (QM is only an approximation for non-relativistic situations). I don't know what "local realism" is, because I don't know of any clear definition of "realism", and about "locality" we have a lot of debates here. For me locality means that space-like separated events cannot be in a cause-effect relation and that the interactions between particles are described by a Hamilton density which is built by the field operators and their derivatives at one space-time point such that the microcausality constraint holds for all local observables. Usually QT is understood, not to be "realistic" by philosophers though it's the most "realistic" theory we have, and we don't know anything that contradicts its. So for me QT is indeed realistic, because it describes all yet observed objective facts of Nature.

 

[Lord Jestocost]

I don't know what "local realism" is, because I don't know of any clear definition of "realism", and about "locality" we have a lot of debates here.

That's relatively simple. As Simon Gröblacher, Tomasz Paterek, Rainer Kaltenbaek, Caslav Brukner, Marek Zukowski, Markus Aspelmeyer and Anton Zeilinger put it in “An experimental test of non-local realism” ( Nature, vol. 446, pages 871–875 (2007))

“Most working scientists hold fast to the concept of 'realism' - a viewpoint according to which an external reality exists independent of observation. But quantum physics has shattered some of our cornerstone beliefs…..

Physical realism suggests that the results of observations are a consequence of properties carried by physical systems. It remains surprising that this tenet is very little challenged, as its significance goes far beyond science. Quantum physics, however, questions this concept in a very deep way. To maintain a realistic description of nature, non-local hidden-variable theories are being discussed as a possible completion of quantum theory.”

 

[Fra]

I don't know what "local realism" is, because I don't know of any clear definition of "realism", and about "locality" we have a lot of debates here.

I agree that just these definitions of these terms drives a lot of the discussions on their own.

What I assumes RUTA mean here, is the definitions in the premises of Bells theorem. Ie. those that assumes a causal relation between the hidden variable and the probability associated to Alice and Bob.

Its my opinion, that the fact the nonone yet explained correlations using the premises of bells theorem, is beacuse it likely isnt' possible at all. But maybe there are other explanations, that have more explanatory value than QM as it stands, that does have some form of realism, but not the form of realism as defined by bell.

Personally, my own "understanding" of this, satisfies me, but it also unavoidably spawns NEW questions that must be asked. In this sense, the consensus of QM as it stands is not satisfactory. That does NOT mean however that i am looking for old school determinism or bell type realism. There are other options.

/Fredrik

 

[Fra]

“Most working scientists hold fast to the concept of 'realism' - a viewpoint according to which an external reality exists independent of observation. But quantum physics has shattered some of our cornerstone beliefs…..

But it seems even the attempts at precise definitions, become dependent on interpretations. For example, for some of us, the notion of "existing independent of observation" is just a metaphysical notions. This is why for me; the closest thing to realism lies in say the "invariants" of the symmetries in the observer classes. But such definitions presumes the existence of such symmetry transformations. To defined something as independent of observation, means its not inferrable, and to me that is a no no.

But them I am sure others will disagree with me and yet interpret the definition differently.

/Fredrik

 

[PeterDonis]

The answer is well-known

Really? Someone has a well-tested, experimentally confirmed theory in which Lorentz invariance is not fundamental, but emergent? Please provide a reference.

 

[RUTA]

The formalism works, because it is based on observations. That's how the scientific method successfully works since Galilei et al.

The articulation of the mystery: "What is the nature of reality/causal mechanism such that the formalism maps so well to the experimental outcomes?"

Your response: "The formalism maps so well to the outcomes because the formalism maps so well to the outcomes."

Do you understand that your response provides absolutely nothing for resolving the mystery? I can't make it any clearer than that.

 

[PeterDonis]

they are not so far compatible with QFT or the Standard model, once again due to problems with causality and coherence with any physical scientific theory that arise when admitting FTL communication

You can have tachyons without admitting FTL communication. But I agree that there are issues with having tachyons in a QFT that no one has figured out how to resolve.

if it is one-way, how would you tell that the particle detected first is not the light signal, and therefore no FTL?

Because you have two different kinds of detectors, one that only detects light signals and one that only detects whatever postulated FTL signal carrier you are using.

You have to have some synchronization convention for the times at departure and detection, no?

No. Both departure events are the same event--both emission devices are co-located in space and emit their signals at the same instant.

Both detection events are on the same timelike worldline, since the detectors are also co-located in space and are at rest relative to each other. So the time ordering of the detection events is invariant and does not require any simultaneity convention.

Bear in mind, I am not saying anyone actually has an FTL signaling device that could pass the test I'm describing. I'm just saying that testing whether a device that is claimed to do FTL signaling, actually does it, is a straightforward experimental test and does not require having any particular theory about how FTL signaling works or how it should not be possible. Of course our current theories of relativity and QFT predict that it is not possible and any such test would fail. But that does not make the test itself impossible or not well-defined.

 

[Tendex]

Because you have two different kinds of detectors, one that only detects light signals and one that only detects whatever postulated FTL signal carrier you are using.

Such a detector would allow to measure the speed of light in a one-way experiment then.

No. Both departure events are the same event--both emission devices are co-located in space and emit their signals at the same instant.

Both detection events are on the same timelike worldline, since the detectors are also co-located in space and are at rest relative to each other. So the time ordering of the detection events is invariant and does not require any simultaneity convention.

I'm referring to the simultaneity convention between emission and detection in view of what I say above about detectors.

Bear in mind, I am not saying anyone actually has an FTL signaling device that could pass the test I'm describing. I'm just saying that testing whether a device that is claimed to do FTL signaling, actually does it, is a straightforward experimental test and does not require having any particular theory about how FTL signaling works or how it should not be possible. Of course our current theories of relativity and QFT predict that it is not possible and any such test would fail. But that does not make the test itself impossible or not well-defined.

The test is of course not impossible if you are willing to consider galilean relativity or Lorent ether theory or some version of Bohmian mechanics and the like as some people in this very thread. According to QFT the result is always going to be negative, that's for sure. Scientific experiments are usually done to discard one theory versus some other. If one does detect such FTL influences it is up to the experimenter to decide whether this means special relativistic theories are wrong and recover Galilean ones, or interpret it as relativistic QFT must admit a breakup of causality, the last option is more problematic as it means breaking with all scientific knowledge based on causality including the rationale of being able to make predictions besides creating contradiction with the way QFT is constructed.

 

[edmund cavendish]

Important to keep this sub thread alive. Only referencing the issue of the observer and the observed Bishop Berkeley via Heisenberg there is plenty to consider..to be is to be perceived is still relevant. As Penrose says we may need a whole new physics between the quantum and classical worlds. Enjoying contributing down both lines.

 

[PeterDonis]

Such a detector would allow to measure the speed of light in a one-way experiment then.

Not without a simultaneity convention. Remember, all that is being "measured" in my scenario is the time order of the two arrivals--light signal vs. claimed "FTL" signal. In my scenario, the speed of the signals is not being measured; only in which order they arrive. That very limited measurement does not require a simultaneity convention, while a measurement of speed would.

I'm referring to the simultaneity convention between emission and detection in view of what I say above about detectors.

No such convention is required for the very limited measurement I am describing. See above.

The test is of course not impossible if you are willing to consider galilean relativity or Lorent ether theory or some version of Bohmian mechanics and the like as some people in this very thread.

The test I have described, as I have already said, does not require having or adopting any theory at all. It is a purely empirical measurement of a very limited result, the order in which two signals arrive.

 

[Sunil]

Aren't you ignoring the fact that the correlations observed(in quantum experiments) are not compatible with classical, pre-relativistic time correlations?

There is no such fact. The realist interpretations need an absolute time (that means a hidden preferred frame) but have no causal influences into the past. So, they follow the same type of causal restrictions as in classical physics.

Perhaps we are talking about different things? Perhaps it was my flawed interpretation and i don't get what you guys are talking about. I thought RUTA meant that the "open issue" (mystery, is just a word?) is to to find an explanation of the correlations observed in entanglement. And if possible an explanation that obeys local realism. I think explanations are possible, but they the premises in "local realism" is wrong to start with. Nevertheless, and "explanation" is wanted.

We know QM works, but as long as we do not understand it properly, its explanatory value is limited.

This I agree with. I see no mysticism here?

What I name mysticism is the rejection of principles and concepts of common sense without necessity.

We have, today, explanations for quantum as well as relativistic effects which are not at all in conflict with the principles of common sense, as known from classical physics. Since the invention of dBB theory, we know that we can have a continuous trajectory in the configuration space. We know since Bell's theorem that the speed of light cannot be the upper limit of causal influences, but have no need to give up realism or causality. We have known from the start but "forgotten" that we don't have to give up Newtonian absolute space and time, but can explain relativistic effects by distortions of clocks and rulers, and that Lorentz symmetry is a property of a wave equation, which allows to construct Doppler-shifted solutions. We have an epistemic interpretation of the wave function (Caticha). That QT is not local, ok, not nice, but it is something shared with Newtonian gravity. One may not like it, but so what? There is room for future theories to replace QT with a local (but not Einstein-local) theory, similarly to the replacement of Newtonian gravity by general relativity.

Given that such an interpretation of modern physics exists, there is no necessity to give up any of the key elements of classical physics.

The rejection of classical elements of explanation, like causal explanations for observed correlations, is standard part of mystical theories.

Really? Someone has a well-tested, experimentally confirmed theory in which Lorentz invariance is not fundamental, but emergent? Please provide a reference.

Let's start with the classical theory of sound waves, with the equation $\square u = (\frac{1}{c^2}\partial_t^2 - \Delta) u = 0$, with the speed of the wave being c. It is simple mathematics to see that the Lorentz transformation with that c of a solution of that equation gives the Doppler-shifted solution of the same equation. So, the equation has Lorentz symmetry. And it is emergent because there is no such Lorentz symmetry on the atomic level.

But we can also consider the fundamental level.

Schmelzer, I. (2012). A Generalization of the Lorentz Ether to Gravity with General-Relativistic Limit. Advances in Applied Clifford Algebras 22(1), 203-242, resp. arxiv:gr-qc/0205035

It gives, in some limit, the Einstein equations in harmonic coordinates, which is the field-theoretic variant of GR. Which is quite well-tested, not? While the EEP holds exactly in the theory itself (derived from action equals reaction symmetry), the SEP holds only in the limit, thus, is emergent. So, full relativistic symmetry is emergent. Moreover, the theory is interpreted as a classical condensed matter theory, with continuity and Euler equations, and the gravitational field is interpreted as density, average velocity and stress tensor of an ether. The analogy to usual condensed matter theories, without any Lorentz symmetry on the fundamental atomic level suggests that something similar, without any relativistic symmetry, has to be done there too. Given that the theory is not even renormalizable, it makes sense only as an effective theory too.

A microscopic model for some parts of that ether has been developed in

Schmelzer, I. (2009). A Condensed Matter Interpretation of SM Fermions and Gauge Fields, Found. Phys. 39(1) 73-107, resp. arxiv:0908.0591.

It does not have any relativistic symmetry.

 

[Fra]

What I name mysticism is the rejection of principles and concepts of common sense without necessity.

I see.

the principles of common sense, as known from classical physics.
..
The rejection of classical elements of explanation, like causal explanations for observed correlations, is standard part of mystical theories.

Ok, at least i know what you mean. For me however, "common sense" does not equal classical physics. Some things suggested by quantum mechanics, for example that that action of agents are causally determined by its subjective probability, rather than hidden variable, is MORE SENSIBLE than classical physics. I have been giving this a lot of considerations over time, and although before my first QM course, I admitt that I had also another view. But this is revised, and common sense today means something else for me.

I also consider, if anything, that influences on actions are not instant to be very common sense. In this sense, Newtons physics is not very sensible at all.

Regarding necessity, for me, that is not rooted in "interpretations only", the necessity is rooted in trying to understand the open questions in physics. Such as unifying forces and QM and gravity etc. And when thinking about what for quite some time, I have come to the conclusion that this problem is entangled with the foundational problems of QM. This is the motivation for my "necessity".

Reinterpretations, that make no ambition to the open problems however, is in my eyes unneccessary, or are constrained to ease of mind only.

/Fredrik

 

[PeterDonis]

Let's start with the classical theory of sound waves, with the equation $\square u = (\frac{1}{c^2}\partial_t^2 - \Delta) u = 0$, with the speed of the wave being c.

The equation you give is indeed Lorentz invariant, but it is not "the classical theory of sound waves". The classical theory of sound waves predicts, correctly, that the speed of sound waves is different in a frame in which the medium in which the waves are propagating is moving than it is in a frame in which the medium is at rest. The equation you wrote does not predict that.

Schmelzer, I. (2012). A Generalization of the Lorentz Ether to Gravity with General-Relativistic Limit. Advances in Applied Clifford Algebras 22(1), 203-242, resp. arxiv:gr-qc/0205035

You will find plenty of previous discussions of Schmelzer's work here on PF. The fact that the GR limit of this theory is well-tested, since GR itself is well-tested, does not mean the theory as a whole is well tested. To test the theory itself would require testing in a regime where its predictions differ from GR. No such testing has been done.

 

[Sunil]

The equation you give is indeed Lorentz invariant, but it is not "the classical theory of sound waves". The classical theory of sound waves predicts, correctly, that the speed of sound waves is different in a frame in which the medium in which the waves are propagating is moving than it is in a frame in which the medium is at rest. The equation you wrote does not predict that.

The equation is, of course, for a homogeneous medium in its rest frame. Real media are inhomogeneous, so that this is only an approximation. But this is not in contradiction with Lorentz invariance of the equation. You can use Galiean transformation in SR too, and you will also obtain a different equation.

You will find plenty of previous discussions of Schmelzer's work here on PF. The fact that the GR limit of this theory is well-tested, since GR itself is well-tested, does not mean the theory as a whole is well tested. To test the theory itself would require testing in a regime where its predictions differ from GR. No such testing has been done.

I have tried to find something, but probably used wrong search items given that I have found almost nothing.

I disagree with your idea about testing. One should not use a historical accident of which theory was proposed earlier to evaluate their experimental support. All what counts is what both theories predict, and if this agrees with observation. From this point of view, this theory is as well tested as GR.

BTW, it is not my point that the theory is well-tested. The point is that there is an interpretation of modern physics compatible with common sense, without any trace of mysticism. As for the quantum domain, as for the relativistic domain, and both being compatible with each other.

 

[Tendex]

There is no such fact. The realist interpretations need an absolute time (that means a hidden preferred frame) but have no causal influences into the past. So, they follow the same type of causal restrictions as in classical physics.

The fact is that the probabilities obtained in quantum experiments can never be achieved by classical correlations(whatever hidden varaibles are used including preferred frame with distorted clocks and rulers), so how come there is no such fact?
Also in any scientific theory they are going to follow the same type of causal restrictions, this is a pre-requisite for making sense of observations and making predictions that can be checked by later observations so you must be missing my point about correlations.

 

[martinbn]

I have tried to find something, but probably used wrong search items given that I have found almost nothing.

I disagree with your idea about testing. One should not use a historical accident of which theory was proposed earlier to evaluate their experimental support. All what counts is what both theories predict, and if this agrees with observation. From this point of view, this theory is as well tested as GR.

BTW, it is not my point that the theory is well-tested. The point is that there is an interpretation of modern physics compatible with common sense, without any trace of mysticism. As for the quantum domain, as for the relativistic domain, and both being compatible with each other.

[Moderator's note: First sentence of response deleted.]
The theory goes like this: add new terms with new parameters to the lagrangian of the old theory and you get a new theory which coincides with the old when the parameters are equal to zero. Then take credit for all the successes of the old theory without any new prediction tested by observation. Then add your preferred philosophical mumbo jumbo that supports your prejudices on how nature should be and write a paper. Anyone can do this in an infinitely many ways. How can this be used as an argument against the old theory!

 

[Tendex]

Not without a simultaneity convention. Remember, all that is being "measured" in my scenario is the time order of the two arrivals--light signal vs. claimed "FTL" signal. In my scenario, the speed of the signals is not being measured; only in which order they arrive. That very limited measurement does not require a simultaneity convention, while a measurement of speed would.
No such convention is required for the very limited measurement I am describing. See above.
The test I have described, as I have already said, does not require having or adopting any theory at all. It is a purely empirical measurement of a very limited result, the order in which two signals arrive.

Well first you are assuming certain things before the experiment, you seem to be discarding spacelike paths since, for all we have discussed before about setting up a scenario to observe a causal, timelike order of arrival of signals if causality is not granted and you can have signals detected before being emitted, etc, order is inmaterial in the spacelike case and you claim to only be testing an order. So you are considering only timelike, causal paths.
Now you have to be able to distinguish the signals at arrival to identify one as the light signal and assign it an arrival order with respect to a "supposed FTL" signal, you said you had a detector that only detected light signals without measuring their speed or any reference to their characteristic speed in vacuum, well, how does it do it? You either have to assume light isotropy or not, if you don't any of the signals could arrive first and be a light or sublight signal, if you do assume isotropy we are back to the need of a simultaneity convention and a roundtrip test.

 

[Sunil]

Ok, at least i know what you mean. For me however, "common sense" does not equal classical physics. Some things suggested by quantum mechanics, for example that that action of agents are causally determined by its subjective probability, rather than hidden variable, is MORE SENSIBLE than classical physics.

Ok, I also take some modern interpretations of classical physics, like the objective Bayesian interpretation of probability (Jaynes) and their reinterpretation of thermodynamics so that entropy is a measure of information about a state and not of the state itself, also as more compatible with common sense.

And the actually best interpretations of QT, which are imho stochastic ones, can be also considered to be more compatible with common sense than the determinism of classical physics.

But if you need a one-liner to explain what means common sense, to refer to classical physics remains a good idea, despite such differences.

I also consider, if anything, that influences on actions are not instant to be very common sense. In this sense, Newtons physics is not very sensible at all.

Yes, but this is the sort of problem to be left to future research. Already Newton himself has not liked this aspect of his theory, but he had to leave it to future research. Same situation now with the quantum non-locality. One can leave it to future research to find some theory with some limiting speed for that quantum non-locality too. That such a local replacement of QT cannot be Einstein-local is clear. I'm not sure if the experimental limit of $> 10^4 c$ has been improved by recent Bell tests or not. But I agree that some local theory with much larger limiting speed would be preferable from point of view of common sense.

Regarding necessity, for me, that is not rooted in "interpretations only", the necessity is rooted in trying to understand the open questions in physics. Such as unifying forces and QM and gravity etc. And when thinking about what for quite some time, I have come to the conclusion that this problem is entangled with the foundational problems of QM. This is the motivation for my "necessity".

Reinterpretations, that make no ambition to the open problems however, is in my eyes unneccessary, or are constrained to ease of mind only.

But all the common sense principles are also candidate principles for fundamental theories. Once a problem is to unify QT and RT, then finding interpretations of both compatible with the same common sense principles already gives a common set of principles for both theories, which defines a guiding rule for a unification.

 

[Sunil]

This, and the paper are stupid. The theory goes like this: add new terms with new parameters to the lagrangian of the old theory and you get a new theory which coincides with the old when the parameters are equal to zero. Then take credit for all the successes of the old theory without any new prediction tested by observation. Then add your preferred philosophical mumbo jumbo that supports your prejudices on how nature should be and write a paper. Anyone can do this in an infinitely many ways. How can this be used as an argument against the old theory!

First, I would recommend you to learn how to behave in a scientific discussion. Then, if you think you can do this in "infinitely many ways", feel free to prove it by publishing papers in this way. We live in "publish or perish" times, not? So, this would be a chance for you to learn how to get (not) published.

If you would have read the paper, you would have seen that it follows a very different path. It starts with a few general assumptions which have nothing to do with GR at all, and then the most general Lagrangian compatible with those principles is derived.

It seems that you don't understand how the competition of theories work, or at least should work according to the scientific method. A new theory does not take credit from old theories if it also makes the same empirical predictions as the old ones. Science works by empirical falsification, not by taking away successful tests from some theories and giving it to another one.

A theory can be criticized for its various problems, among them singularities and incompatibility with other established principles (local energy conservation) and theories (quantum theory). A new theory is important for this type of criticism if it is compatible with those principles resp. theories.

Last but not least, you would better learn that it is not possible simply to add own preferred metaphysics to some theory. With the exception of degradation of the theory by positivism or solipsism - you can add both without problems because all you have to do is to throw away something. But you cannot simply add, say, realism or causality.

 

[Sunil]

The fact is that the probabilities obtained in quantum experiments can never be achieved by classical correlations(whatever hidden varaibles are used including preferred frame with distorted clocks and rulers), so how come there is no such fact?

Of course, the trajectories of dBB theory differ from classical trajectories. But what would be the point of this, if we nonetheless have to same classical configuration space describing reality? The quantum equations are equations quite similar to classical equations, so that the difference is not that big.

Also in any scientific theory they are going to follow the same type of causal restrictions, this is a pre-requisite for making sense of observations and making predictions that can be checked by later observations so you must be missing my point about correlations.

Yes, I'm completely missing your point about correlations. If you have in mind violations of the Bell inequalities, they can be easily obtained in a classical scenario if the measurement on one side causally influences the state of the other side.

The causal restrictions of classical theory and relativistic theory are quite different, in classical theory FTL causal influences are not forbidden, in relativity they are forbidden.

 

[Tendex]

Of course, the trajectories of dBB theory differ from classical trajectories. But what would be the point of this, if we nonetheless have to same classical configuration space describing reality? The quantum equations are equations quite similar to classical equations, so that the difference is not that big.

I'm not following your answer, here is where I had in mind BI violations.

Yes, I'm completely missing your point about correlations. If you have in mind violations of the Bell inequalities, they can be easily obtained in a classical scenario if the measurement on one side causally influences the state of the other side.

The causal restrictions of classical theory and relativistic theory are quite different, in classical theory FTL causal influences are not forbidden, in relativity they are forbidden.

In classical theory with just Galilean relativity FTL influences are no big deal and don't affect causality in any way since the speed of light is not a maximum,so they shouldn't require a theory that constructs probabilities in a different way than the classical real probabilities, however quantum theory does require it to obtain better predictions.

 

[vanhees71]

That's relatively simple. As Simon Gröblacher, Tomasz Paterek, Rainer Kaltenbaek, Caslav Brukner, Marek Zukowski, Markus Aspelmeyer and Anton Zeilinger put it in “An experimental test of non-local realism” ( Nature, vol. 446, pages 871–875 (2007))

“Most working scientists hold fast to the concept of 'realism' - a viewpoint according to which an external reality exists independent of observation. But quantum physics has shattered some of our cornerstone beliefs…..

Physical realism suggests that the results of observations are a consequence of properties carried by physical systems. It remains surprising that this tenet is very little challenged, as its significance goes far beyond science. Quantum physics, however, questions this concept in a very deep way. To maintain a realistic description of nature, non-local hidden-variable theories are being discussed as a possible completion of quantum theory.”

If this is understood as physical realism, I don't understand, why quantum physics "questions this concept in a very deep way." The only thing that quantum physics disproves is determinism, which is just the concept of classical physics. QT indeed discribes "properties carried by physical systems", and one property is that these properties are not describable by a deterministic theory but that there is inherent randomness. What's "real" in this simple sense is described in QT by the states, whose meaning and only meaning is to give the probabilities for the outcome of measurements made on a system prepared in a specific state. One must just forget about the classical picture of determinism, and there's no quibble anymore!

 

[vanhees71]

The articulation of the mystery: "What is the nature of reality/causal mechanism such that the formalism maps so well to the experimental outcomes?"

Your response: "The formalism maps so well to the outcomes because the formalism maps so well to the outcomes."

Do you understand that your response provides absolutely nothing for resolving the mystery? I can't make it any clearer than that.

The point is that there is no mystery. It's just an outcome of our investigations in physics that nature is not deterministic but has to be described by a probabilistic theory named QT. That the formalism maps so well to the observations is not trivial, as you seem to suggest. It's just amazing, in how simple a way we can describe almost everything with a mathematical theory, but to find such a description is only possible through observations and finding (with some luck ;-)) the right mathematical model to describe them with a quite sparse set of fundamental "postulates". If there is any mystery, it's the question, why these mathematical descriptions work so well, as was famously asked by Wigner.

 

[Morbert]

The articulation of the mystery: "What is the nature of reality/causal mechanism such that the formalism maps so well to the experimental outcomes?"

Your response: "The formalism maps so well to the outcomes because the formalism maps so well to the outcomes."

Do you understand that your response provides absolutely nothing for resolving the mystery? I can't make it any clearer than that.

Physical theories will always have a nomological character. Even in classical physics, we can e.g. ask why one Hamiltonian is more successful than another Hamiltonian.

 

[Fra]

If there is any mystery, it's the question, why these mathematical descriptions work so well, as was famously asked by Wigner.

I can share this statement and but probably unlike Wigner, I think the question is sensible. I suspect Wigner puts it as a rethorical question.

The response to the unreasonable effectiveness of mathematics is something Smolin treated in books. Its a foundational questions for science and physics. Effectively asking, why are the laws what they are? Also this is related to

In the context of evolving law, Lee Smolin pulls another favourite quotation from 1891 of Charles Sanders Pierce, which is the.

"To suppose universal laws of nature capable of being apprehended by the mind and yet having no reason for their special forms, but standing inexplicable and irrational, is hardly a justifiable position. Uniformities are precisely the sort of facts that need to be accounted for … Law is par excellence the thing that wants a reason.
...
Now the only possible way of accounting for the laws of nature and for uniformity in general is to suppose them results of evolution.”
-- https://www.jstor.org/stable/pdf/27896847.pdf

Smolin also suggests the unreasonable effectiveness of mathematics is because its limited, rather than universal.

/Fredrik

 

[PeterDonis]

The equation is, of course, for a homogeneous medium in its rest frame.

If it's only valid in one frame, it obviously is not Lorentz invariant, or indeed any kind of invariant.

this is not in contradiction with Lorentz invariance of the equation

This is nonsense. You are contradicting yourself.

it is not my point that the theory is well-tested. The point is that there is an interpretation of modern physics compatible with common sense

Schmelzer's theory is not just an interpretation; it makes different predictions from standard "modern physics", so it is a different theory, and must be judged as a different theory, not as "just an interpretation".

If you have in mind violations of the Bell inequalities, they can be easily obtained in a classical scenario if the measurement on one side causally influences the state of the other side.

Which is obviously impossible if the two measurements are spacelike separated. Which is the whole point of discussing the Bell inequalities in the first place.

 

[PeterDonis]

First, I would recommend you to learn how to behave in a scientific discussion.

This attitude has just earned you a warning and a thread ban.

 

[PeterDonis]

This, and the paper are stupid.

Statements like this should be avoided as they add nothing useful to the discussion.

 

[Tendex]

The test I have described, as I have already said, does not require having or adopting any theory at all. It is a purely empirical measurement of a very limited result, the order in which two signals arrive.

I'm not sure if I misinterpreted your meaning here. Performing such experiment is obviously possible without any previous commitment to this or that theory or theoretical assumption. However, interpreting it's result will be very different if you assume a simultaneity convention or if you reject constancy of light speed or any other assumption, IOW interpretation of an empirical test requires commitment to some assumption or to its rejection. Even interpreting if the difference of arrival of the signals is significant requires certain assumptions about the statistical error of the apparatus employed in detection, etc.

 

[Sunil]

If it's only valid in one frame, it obviously is not Lorentz invariant, or indeed any kind of invariant. ... You are contradicting yourself.

It's not the only one. You can take the sound-Lorentz-transformed coordinates of the rest frame and get other frames where the same equation holds. The only problem is that nobody will use such artificial coordinates. The context gives us a lot of other things, like light rays, to study sound waves in condensed matter theory, and these many other things don't follow that sound-Lorentz invariance. So, the sound together with the other environment has a preferred frame.

This does not contradict that the equation for the sound waves taken alone has that sound-Lorentz invariance.

The point is that there is an interpretation of modern physics compatible with common sense

Schmelzer's theory is not just an interpretation; it makes different predictions from standard "modern physics", so it is a different theory, and must be judged as a different theory, not as "just an interpretation".

In the limit $\Xi, \Upsilon\to 0$ it gives the Einstein equations in harmonic coordinates on $\mathbb{R}^4$, thus, the field-theoretic version of GR. Which is a standard version, and, for example, used by Donoghue et al for the quantization of GR as an effective field theory.

And it gives an ether interpretation of it.

Which is obviously impossible if the two measurements are spacelike separated. Which is the whole point of discussing the Bell inequalities in the first place.

No, it is not obviously impossible, it is impossible only if one accepts Einstein causality in its strong version (that means, not microcausality of QFT or signal causality) and rejects classical causality connected to a preferred frame.

 

[PeterDonis]

I'm not sure if I misinterpreted your meaning here.

I'm not either since you keep talking about things that have nothing to do with the experiment I proposed. See below.

interpreting it's result will be very different if you assume a simultaneity convention or if you reject constancy of light speed or any other assumption

No, it won't. As I have already said, the only "result" of the experiment I proposed is which signal arrives first. There is no measurement of speed or indeed any numerical value involved; it's just a simple choice between three discrete possibilities: A arrived before B, B arrived before A, or A and B arrived at the same instant. The time ordering is all along a single timelike worldline. No "interpretation" is required. No assumption about simultaneity or the speed of light or anything else is required.

Even interpreting if the difference of arrival of the signals is significant requires certain assumptions about the statistical error of the apparatus employed in detection, etc.

No, it doesn't. The three possible results are discrete alternatives--see above. There is of course a finite resolution to our comparison of arrival times of the two signals, but that just means the third discrete alternative, "A and B arrived at the same instant", has a finite "width", so to speak--if the two signals arrive within some small enough time interval of each other, our apparatus will tell us they arrived at the same instant even though that's not literally true. But this is not a matter of statistical error; it's just a matter of finite resolution, which will be true for any detector.

 

[PeterDonis]

the sound together with the other environment has a preferred frame.

Exactly.

This does not contradict that the equation for the sound waves taken alone has that sound-Lorentz invariance.

There is no such thing as "the sound waves taken alone". The sound waves don't exist without what you are calling the "environment". This makes it fundamentally different from light, which can travel through a vacuum. You can't just handwave away that fundamental physical difference.

In the limit

By this criterion, General Relativity is the same theory as Newtonian mechanics, since "in the limit" it makes the same predictions.

classical causality connected to a preferred frame.

If your theory has a preferred frame, what's the point of even talking about Lorentz invariance--or any other kind of invariance, for that matter?