A question about quantum entanglement

[Matterwave]

Well, there are always debates about the best way to formulate a theory from basic principles (see the reference above to Höhn's article).

Lucas.

You can certainly debate anything, but SR is generally formulated on the constancy of the speed of light and the equal validity of all inertial frames of reference ("relativity principle"). This was given by Einstein in 1905 and I don't see a ton of debate on trying to change that. Time dilation is a consequence of those 2 postulates.

 

[Fra]

I disagree: we do understand why there is the phenomena of time dilation in special relativity.

You can certainly debate anything, but SR is generally formulated on the constancy of the speed of light and the equal validity of all inertial frames of reference ("relativity principle"). This was given by Einstein in 1905 and I don't see a ton of debate on trying to change that. Time dilation is a consequence of those 2 postulates.

Of course, we can explain time dilation, cleanly and logically from the postulates, since 1905. Few theories are as clear and clean as SR.

But the conceptual problem still today is that while the no preferred observer is extremely intuitive. The light postulate, while technically simple, is by no means obvious or intuitive. But any debate on that, would not be of the form that the postulated is "wrong" in the validated experimental domains, it would likely be that maybe it can be formally relaxed and that it's "status" of postulate or axiom, could be REPLACED by some evolutionary principle or some attractor, based on some other principles that are in fact as intutive as the no preferred observer principle. That would bring deeper understanding, not just a reformulation into "new variables". But so far this is not existing as mature science. This is what i referred to.

/Fredrik

 

[Fra]

and maybe Barandeis "spooky action at a time" (indivisible non-markovian processes). Though I don't know how "well established" they are.

I agree with this hook. This was discussed in other threads. Barandes is making good contributions, but the picture he provides is critically incomplete still to serves as a resolution. The specific part is a missing first principle new reconstruction of the transition probabilitites (gamma). So far, they are only inferred from the hilbert picture via the correspondence. The gamma matrices hides the mystery, to complete the resolution, I think we need to explain how the gamma matrices evolve; my I see all possibilities for his program to be completed in that way. But that is also not on the table yet.

/Fredrik

 

[Sambuco]

You can certainly debate anything, but SR is generally formulated on the constancy of the speed of light and the equal validity of all inertial frames of reference ("relativity principle"). This was given by Einstein in 1905 and I don't see a ton of debate on trying to change that. Time dilation is a consequence of those 2 postulates.

Sure, that's precisely why I said that no one is looking for an underlying mechanism to "explain" time dilation in special relativity!

This does not happen in quantum mechanics, where the prediction of entanglement and the violation of Bell's inequalities are not usually accepted at face value, but rather an additional mechanism is sought to "explain" it.

Lucas.

 

[PeterDonis]

no one is looking for an underlying mechanism to "explain" time dilation in special relativity!

the prediction of entanglement and the violation of Bell's inequalities are not usually accepted at face value, but rather an additional mechanism is sought to "explain" it.

I think the difference here is that time dilation in SR is not an observable--it's something that's calculated by assuming a particular inertial frame. The actual observable is the relativistic Doppler shift. I don't think people just accept the relativistic Doppler shift without looking for some kind of underlying mechanism.

Similarly, in the case of QM, Bell inequality violations are an observable, so people want to look for an underlying mechanism.

 

[Fra]

Elevating something to a postulate or axiom, means that within the theory, it is something you do not further need to explain. But a theory (regardless how well corroborated it is) is never more intuitive or understandable than the plausibility of it's the postulates it rests on. As I see it postulates is a form of hidden implicit fine tuning of the "theory space", which is at theoryspace level rather than fine tuning initial conditions within a given dynamical system.

The light postulate is not intuitively obvious in SR.

In QM there are also several non-intuitive postulates/axioms, introducting hilbert spaces and perhaps worst, the time evolution postulates of the hamiltonian operator for a close system. There is a huge amount of what i conceptually see as "fine tuning" hidden in the hamiltonian and the hilbert space structure.

Just like I advocate naturalness in initial conditions, the ambition is tha a good theory should be built in at least reasonable postulates as well, that is ideally intutitive.

One excellent example, that is one foundational postulate is the "no preferred observer" or "no preferred frame". That is I think something that most would agree is indeed plausible, as the opposite would simple be unnatural and required an explanation.

Alot of other things, have a long way to reach that level of plausibiliity.

/Fredrik

 

[Morbert]

As an aside: There are analogous interpretational debates around special and general relativity. See e.g. substantivalist vs relationalist spacetime, or kinematical vs dynamical/neo-Lorentzian accounts. I suspect they are not as energetic as QM debates because relativity doesn't assault our notion of a primitive ontology to anywhere near the same degree.

 

[FactChecker]

The light postulate is not intuitively obvious in SR.

After precise experiments that measured the speed of light as c, no matter what the velocity of the test platform was, I think it was somewhat natural to consider.

 

[Sambuco]

I think the difference here is that time dilation in SR is not an observable--it's something that's calculated by assuming a particular inertial frame. The actual observable is the relativistic Doppler shift. I don't think people just accept the relativistic Doppler shift without looking for some kind of underlying mechanism.

Similarly, in the case of QM, Bell inequality violations are an observable, so people want to look for an underlying mechanism.

Interesting! I'd never thought of it that way.

Lucas.

 

[Fra]

After precise experiments that measured the speed of light as c, no matter what the velocity of the test platform was, I think it was somewhat natural to consider.

Empirically well motivated from alot of experiments yes. But understanding a deeper explanation for the specific empirical facts, and their domain of validity is what is missing.

/Fredrik

 

[Roberto Pavani]

But understanding a deeper explanation for the specific empirical facts,

Even if a deeper explanation existed, it would itself rest on postulates, merely shifting the question one level down.

BTW SR is a little OT for "entanglement topic"

 

[FactChecker]

Empirically well motivated from alot of experiments yes. But understanding a deeper explanation for the specific empirical facts, and their domain of validity is what is missing.

Mathematically, with very reasonable/desirable assumptions, there are only two possibilities, and only one with a constant speed of light. The assumption of relativity will only allow Galilean relativity (all inertial frames share a universal time) or Einsteinian relativity (constant speed of light in a vacuum).
(See https://arxiv.org/abs/physics/0302045 )
When experiments implied a constant speed of light, there was only one mathematical solution.

 

[Paul Colby]

Even if a deeper explanation existed, it would itself rest on postulates, merely shifting the question one level down.

It may well happen that this deeper understanding will be even less understandable in the sense that people find QM at the moment. I see no reason a more inclusive theory would improve the current situation. In fact, I expect the opposite.

 

[Fra]

Mathematically, with very reasonable/desirable assumptions, there are only two possibilities, and only one with a constant speed of light. The assumption of relativity will only allow Galilean relativity (all inertial frames share a universal time) or Einsteinian relativity (constant speed of light in a vacuum).
(See https://arxiv.org/abs/physics/0302045 )
When experiments implied a constant speed of light, there was only one mathematical solution.

The fallacy here is that here you over-extrapolate the acutual domain of corroboration (human scale observation) to apply universally, all the way from creation of the universe[which we cant observe]. This is what is often labeled the "cosmological fallacy".

I fully agree that the theory as it stands it probably the simplest possible mathematical formulation that is consistent with the known physics, but not necessarily the least speculative or most natural. Technical over-extrapolating evidence is "speculation".

The obvious other option is that; the invariants we do observe are some asymptotic or attractor state of some more wild process of physics from the early creation (including genesis of spacetime) what we do not understand.

It is a valid question though, to ask: Why on earth make this so complicated and sort of "speculate" about what unobserved things that might have been going on before the limit of what we can see? My motivation for that is that if this succeeds, maybe we can reduce the number of free parameters, and find "explanations" to all the things that are "froezen" on the observable limit from our perspective, that today we are fine tuning.

It may well happen that this deeper understanding will be even less understandable in the sense that people find QM at the moment. I see no reason a more inclusive theory would improve the current situation. In fact, I expect the opposite.

I think that the more inclusive theory will necessariy be mathematically drastically more complex.
So it will probably be tecnically less understandable for those trying to make numerical work, but just like noone uses GR or SR to compute pool physics, they use newtonian mechanics, the current QM or QFT will remain the engineering tool of choice, that are and will remain excellent. A model with an order of magniture more complex algorithmic requirements will not add value here.

But I am not driven by such practical things, I am driven by a desired to understnad nature at the deepest level which is defined by some sort of naturalness. And for reasons of complexity regulations, this will not be an infinite regress. There will be a cutoff related to the "inferential scale". Similar to obswervational resolutions in high energy physics. Your accelerator energy will limit "how deep" you can see, and thats where it stops - naturally not abmigously.

But I am sure a better theory will be conceptually more understandable. Obviously my own confidence is this is supported by my own think and working on this for a long time. But from the perspective of the physics community there are still no answers.

/Fredrik

 

[FactChecker]

The fallacy here is that here you over-extrapolate the acutual domain of corroboration (human scale observation) to apply universally, all the way from creation of the universe[which we cant observe]. This is what is often labeled the "cosmological fallacy".

IMO, you are putting words into my mouth. I reasonably thought that we were discussing the SR theory of what is happening now, locally. That is how SR is usually discussed and applied.

I fully agree that the theory as it stands it probably the simplest possible mathematical formulation that is consistent with the known physics, but not necessarily the least speculative or most natural. Technical over-extrapolating evidence is "speculation".

There is less freedom in the mathematics than people think.

 

[Fra]

IMO, you are putting words into my mouth. I reasonably thought that we were discussing the SR theory of what is happening now, locally. That is how SR is usually discussed and applied.

I didnt mean todo that, but yes we were. But I thought we were disussing possible "explanations" beyond the descriptions, ie how can we "understand" what we know are "facts" here and now. And I suggested the logical possbility that the "explanations" to what is happening here now, locally - is not necessarily to be found "here and now", it maybe in the history of emergence. No matter what one "thinks", it seems a logical possibility. After all, what is the definition of the sup lim speed invariance before spacetime emerged?

/Fredrik

 

[Paul Colby]

But I am sure a better theory will be conceptually more understandable. Obviously my own confidence is this is supported by my own think and working on this for a long time. But from the perspective of the physics community there are still no answers.

By this view, why isn’t QM more understandable to you than classical physics? It’s clearly a better theory. All the things known about nature that bother you will remain true in any new theory. So why hope a new more complete theory will ease you? At best you can only expect to maintain a status quo.

 

[Fra]

By this view, why isn’t QM more understandable to you than classical physics? It’s clearly a better theory.

It is! It is superior in many ways, in particular as it takes the physics of measurement seriously, that you can't like in classical physics alway reduce the interaction strenght so that you can make inferences without disturbing the system. It also acknowledges that inferences can be complementeary and not independent.

Quantum theory as a "theory of measurements" is superior conceptually to classical mechanics. But many problems in QM, are inherited from CM as well. There is no "explanation" of this in classical physics either.

But the "revolution" is incomplete. QM for example considers "measurements" made from an external observer, or a massive asymptotic obsever.

If anything I wrote is interpreted as a wish to explain QM in terms of classical physics, then that is a misunderstnading.

So why hope a new more complete theory will ease you?

I am not talking about "more complete" in the sense Einstein and Bell did. I am talking about more complete as in taking the measurement EVEN more serious as a physical process. A measurement is not just "communication" it also has the end points, source and destimation, postprocessing and saturation issues. This is where it meets GR, as one needs to consider not just mesarurement as "commuinication" but also things like encoding and retention. Here the concept of mass must necessarily enter somehow.

/Fredrik

 

[PeterDonis]

the acutual domain of corroboration (human scale observation)

Um, no. Relativity, and our best current model in cosmology, have corroboration in domains well beyond "human scale observation".

I am sure a better theory will be conceptually more understandable.

This is your personal opinion, which you are entitled to, but it's getting way off topic.

 

[PeterDonis]

The thread topic has been sufficiently discussed, and the thread is closed. Thanks to all who participated.