New experiments supporting Bohmian mechanics?

[PeterDonis]

The ones relating to expectation values of time correlation of position observables. They have been discussed many times in these very boards.

Then you should have no problem providing some specific references. Please do so.

 

[LeandroMdO]

Then you should have no problem providing some specific references. Please do so.

Here's a recent thread where this was discussed:
https://www.physicsforums.com/threads/an-argument-against-bohmian-mechanics.898028/

You were even an active participant in it.

 

[PeterDonis]

Here's a recent thread where this was discussed

Which is 24 pages long, and it was 5 months ago. If there are specific posts that illustrate what you're referring to, please link to them. I'm not going to wade through the whole thread to try and guess.

 

[LeandroMdO]

Which is 24 pages long, and it was 5 months ago. If there are specific posts that illustrate what you're referring to, please link to them. I'm not going to wade through the whole thread to try and guess.

Try the original post. It's really not that hard.

 

[PeterDonis]

Try the original post.

In other words, you are expressing your opinion that that thread never answered A. Neumaier's argument to your satisfaction? Ok. I don't see the point of rehashing a 24-page thread again. You've expressed your opinion.

It's really not that hard.

It's really not that hard to say what specific post you were referring to, yes. Then why did I have to request that three times before you did it?

Continuing to display this attitude will get you a warning.

 

[Demystifier]

The arguments that it isn't haven't been convincingly rebutted in my opinion.

Have you ever studied the theory of quantum measurements in BM? Try it, it's not that hard. You cannot understand why BM makes the same measurable predictions as standard QM if you don't understand what happens during a measurement. That's probably the main lesson of BM, but for some reason people repeatedly ignore it.

 

[LeandroMdO]

In other words, you are expressing your opinion that that thread never answered A. Neumaier's argument to your satisfaction? Ok. I don't see the point of rehashing a 24-page thread again. You've expressed your opinion.

What I would consider to be "an answer" would be a post pointing out the error in his calculation and how the calculation should be done correctly. There are many words in that thread, but no such calculation.

It's really not that hard to say what specific post you were referring to, yes. Then why did I have to request that three times before you did it?

I was very specific in what objection I was referring to: time correlations of position observables (which at first I assumed you would be familiar with since, as I said, you participated in threads that discussed it). The first post in the thread I linked to has a link to the paper with the argument. The issue of time correlations is also mentioned a few times in the first page of that thread. It takes only a trivial amount of effort to recognize this sort of thing. If you're unwilling to spend this minimal effort, that is fine: you don't even have to participate in any discussion if you don't want to.

Continuing to display this attitude will get you a warning.

Right, look, you were sounding a little exasperated there. If your reaction to the suggestion that you might be acting unreasonably is to threaten the use of mod powers, you might wish to ponder whether you should be wielding them at all. Little conflict of interest there.

 

[Demystifier]

What I would consider to be "an answer" would be a post pointing out the error in his calculation and how the calculation should be done correctly. There are many words in that thread, but no such calculation.

Here is a deal. I will make explicit correct calculation in Bohmian mechanics, provided that you first present a correct calculation of measurable time correlations in standard QM. In that way I will know at which level you understand measurable time correlations in standard QM, so that I can adjust my calculation to your level of understanding. And be careful, because the naive correlation function $$\langle\psi| x(t_1)x(t_2) |\psi\rangle$$ is not measurable.

 

[vanhees71]

Have you ever solved some problem without making a new testable prediction? I bet you have. In fact, you probably do that every day.

Or let me give some well-known examples you will probably appreciate:
1) Lagrangian or Hamiltonian mechanics make the same measurable predictions as Newtonian mechanics. Yet, they solve some problems of Newtonian mechanics. (Otherwise, why would anyone introduce them?)
2) Maxwell equations in the manifestly covariant F-form make the same measurable predictions as Maxwell equations in the non-covariant E-B-form. Yet, the covariant F-form solves some problems of the non-covariant form.
3) In QFT, a self-energy loop diagram is divergent, which is a problem. This divergence can be absorbed into a redefinition of the particle mass, which solves the problem. But this solution does not make any new testable prediction.

There is a difference between having different mathematical techniques to formulate and solve problems in theoretical physics. Concerning your examples it's very clear that it makes sense to study all three topics as a theoretical physicist, because

(1) Lagrangian and Hamiltonian mechanics (or in other words the least-action principle) offers analytical methods to solve Newtonian mechanics (but I don't see which problems it solves for Newtonian mechanics since it's in itself a closed consistent mathemtical theory) like Noether's theorem etc. From a practical point of view it also facilitates the derivation of equations of motion in arbitrary coordinates. For the progress of science it was very important in directing away the view from the murky concept of forces to more general dynamical laws in terms of local interactions mediated by fields, and it's applicable for a much wider range of theories than Newtonian mechanics (field theory, relativistic physics) and leads to a heuristic way to formulate QT (canonical quantization, group-theoretical approaches, $C^*$ algebras of observables etc. etc.)

(2) Whether you formulate Maxwell theory in terms of the manifestly covariant or the (1+3) formalism in which form it has been discovered doesn't make any difference. It's the very same mathematical theory.

(3) is a completely different case. It's part of the very definition of perturbative QFT as a physical theory. Without it you can't make contact to experiment beyond the tree-level results of perturbation theory. I'd say it's integral and undispensible part of the theory, without which you can't make any sense of the mathematically murky concept of ill-defined products of distribution valued operators.

In contradistinction to these 3 examples of different equivalent formulations of the same theory or the (admittedly only FAPP) solution of a mathematically ill-defined model Bohmian mechanics doesn't add anything to QT in terms of a physical theory. Everything you can observe according to QT (and in accordance with all hitherto made observations and stringent experimental tests of QT) you can derive from QT without adding any fictitious and unobservable trajectories. It's an empty academic exercise to calculate these trajectories without any physical consequences.

 

[Demystifier]

(2) Whether you formulate Maxwell theory in terms of the manifestly covariant or the (1+3) formalism in which form it has been discovered doesn't make any difference. It's the very same mathematical theory.

So what's the point of introducing a manifestly covariant formalism once you already know the traditional non-covariant one? It doesn't make new predictions, so what's the point of it? (I am just trying to force you to give a reason which, with a minor modification, can also be applied to BM. )

 

[vanhees71]

Well, the point of it is to have a much better understanding of the structure of the theory and it helps to solve the puzzle of "Electrodynamics for moving bodies" (as Eisntein's famous paper about SRT was titled in 1905). BTW you can write classical E&M in manifest covariant form also in terms of the Riemann-Silberstein vector which is very elegant, but as I said, all this is still the very same theory as has been written down by Maxwell after a cumbersome detour through very complicated mechanical models ;-).

Again, I don't see any merit of the additions of BM to QT compared to the standard formulation. To the contrary it makes the standard formulation way more complicated and adds (unnecessary!) problems in the case of relativistic QFT, which is problematic enough without additional useless problems by itself.

 

[Demystifier]

Well, the point of it is to have a much better understanding of the structure of the theory and it helps to solve the puzzle of "Electrodynamics for moving bodies" (as Eisntein's famous paper about SRT was titled in 1905). BTW you can write classical E&M in manifest covariant form also in terms of the Riemann-Silberstein vector which is very elegant, but as I said, all this is still the very same theory as has been written down by Maxwell after a cumbersome detour through very complicated mechanical models ;-).

So, you agree that a new theoretical insight does not always need to give new measurable predictions? Good, keep it in mind when thinking about BM!

Again, I don't see any merit of the additions of BM to QT compared to the standard formulation. To the contrary it makes the standard formulation way more complicated and adds (unnecessary!) problems in the case of relativistic QFT, which is problematic enough without additional useless problems by itself.

I'm sure there are physicists (perhaps working in condensed matter) who do not see any merit in introducing covariant F-formalism in electrodynamics, but see it as making electrodynamics look more complicated. If somebody does not see a merit, it doesn't mean that there isn't any. To see the merit, one must first look at things from a different perspective. Perhaps covariant electrodynamics does not have a merit from condensed matter perspective, but it does from high-energy perspective. Perhaps BM does not have a merit from a perspective of making predictions, but it does from what-is-going-on-when-we-do-not-observe perspective. The latter perspective is perhaps more philosophical than scientific, but it is a legitimate perspective used by some people, even if you are not one of them.

 

[vanhees71]

Well, I don't know, what sense it makes to discuss about things you can never check. You cannot check what happens with something when you are not looking without looking. As you see, already the experiment description is contradictory in itself. This has nothing to do specifically with quantum theory but for observations within any model of nature.

 

[Denis]

Well, I don't know, what sense it makes to discuss about things you can never check.

Different interpretations are different starting points for future theory development. Because different interpretations have different weak points, and attempts to solve these problems often lead to proposals to modify the theory.

Say, one solution of the measurement problem is to introduce a physical collapse into the theory. Which is a modification of quantum theory and can be tested.

Similarly, BM also has weak points where one can look for modifications of QT. One place is quantum equilibrium. There may be some non-equilibrium effects somewhere. Another one is that the velocity becomes infinite near the zeros of the wave function. This asks for a regularization. And such a regularization will probably get rid of the zeros.

 

[vanhees71]

I'll not argue about the interpretational issues. The final statement is strange to me. What do you define as "velocity" here? I'm not aware with anything that's in anyway problematic with velocity in QM, which is defined as $p/m$, I'd guess.

 

[Denis]

I mean the velocity of the Bohmian particle, as defined by the guiding equation. So, no, it has nothing to do with p/m measurements.

 

[vanhees71]

Is it an observable quantity? If not, why is it a problem? Is it the same issue as in the WKB approximation at the "classical turning point"? If so than it's no issue at all, because the classical approximation breaks down there.

 

[Denis]

Is it an observable quantity? If not, why is it a problem?

For positivists like you it is not a problem. For those who think that a physical theory has to describe reality, it is a problem if something supposed to describe something real becomes, somewhere, infinite. Even if the infinity itself is only at a harmless place where the probability to appear is zero.

And my point was that the solution of this problem - even if only a problem for those interested in reality instead of observables only - will probably lead to a different sub-quantum theory with equations and solutions which differ from QT, even in its observable effects, so that, after this, you can come back and find out if that modified theory is better than QT.

With your self-restriction not to care about non-observable problems you restrict yourself from participation in the creation of such sub-quantum theories, which solve problems of different interpretations. Ignorance of problems means, first of all, refusal to participate in their solution. Your choice.

 

[berkeman]

If your reaction to the suggestion that you might be acting unreasonably is to threaten the use of mod powers, you might wish to ponder whether you should be wielding them at all. Little conflict of interest there.

Please rest assured that all the Mentors are watching your posts in this thread. It may not be Peter that gives that warning...

 

[LeandroMdO]

Here is a deal. I will make explicit correct calculation in Bohmian mechanics, provided that you first present a correct calculation of measurable time correlations in standard QM. In that way I will know at which level you understand measurable time correlations in standard QM, so that I can adjust my calculation to your level of understanding. And be careful, because the naive correlation function $$\langle\psi| x(t_1)x(t_2) |\psi\rangle$$ is not measurable.

I have no doubt that you could show how to calculate a different correlation function and have the results agree between BM and QM. But I'm not interested in other correlation functions: I'm interested in $$\langle\psi| x(t_1)x(t_2) |\psi\rangle$$. It's not like it's some esoteric thing, after all, $$\langle 0| T x(0)x(t_1) |0\rangle$$ for instance is just the two-point function for a 0+1-dimensional field theory, a quantity that can certainly be probed.

You told me that the A. Neumaier's calculation for the expectation value of this observable in BM was incorrect, and that if the calculation is done correctly the discrepancy disappears. That's certainly a possibility I'm willing to entertain. But now you tell me that not all observables are "measurable". I don't know what that word means. When you say "$$\langle\psi| x(t_1)x(t_2) |\psi\rangle$$ is not measurable", do you mean that you can't think of a way to measure it, or do you have a demonstration that it cannot be measured? Can you show me how to classify observables between "measurable" and "not measurable" ones, and then show that all of those in the first group agree between BM and QM?

Saying "you're asking a bad question" might be a perfectly fine response, but only with some more substantiation. Right now what I have is an indication that there is a class of observables whose expectation values disagree between BM and QM. I don't much care what that observable is because once a single one is found, even if it is "not measurable", the door is open for others, some of which might well be straightforward to measure.

Please rest assured that all the Mentors are watching your posts in this thread. It may not be Peter that gives that warning...

Of course. And I am watching you. You are entitled to think this irrelevant, but I question the seriousness of a physics forum that censors based on personal feelings and in-group bias. My impression was that this is a serious forum, but please do correct me if that impression was mistaken.

 

[berkeman]

My impression was that this is a serious forum, but please do correct me if that impression was mistaken.

No correction needed.

 

[PeterDonis]

You are entitled to think this irrelevant, but I question the seriousness of a physics forum that censors based on personal feelings and in-group bias.

Just to be clear: my objection was that you did not provide a specific reference (link to a specific post) when asked. It had nothing to do with "personal feelings" or "in-group bias". A request for a specific reference is in accordance with the PF rules, and the proper response is to provide one, not to say "it really isn't so hard" while refusing to specify what exactly you were referring to.

 

[Demystifier]

When you say "$$\langle\psi| x(t_1)x(t_2) |\psi\rangle$$ is not measurable", do you mean that you can't think of a way to measure it, or do you have a demonstration that it cannot be measured?

You can measure $x(t_1)$, and after that you can measure $x(t_2)$, and finally you can multiply the two values obtained by those two measurements. But this procedure is not the same as measurement of $x(t_1)x(t_2)$. In fact, the operator $x(t_1)x(t_2)$ is not even a hermitian operator, so it is not an observable. Only hermitian operators are observables, and only observables can be measured.

 

[Demystifier]

Well, I don't know, what sense it makes to discuss about things you can never check.

How about discussing things which can be checked in principle, but not in practice? E.g. string theory at the Planck scale, the nature of black-hole interior, or a macro system in which the entropy decreases? Does that make sense to you?

 

[LeandroMdO]

You can measure $x(t_1)$, and after that you can measure $x(t_2)$, and finally you can multiply the two values obtained by those two measurements. But this procedure is not the same as measurement of $x(t_1)x(t_2)$.

Indeed, but nobody suggested that one measure x(t_1) and then x(t_2). That is obviously inequivalent. However, there doesn't appear to be any fundamental difficulty in measuring or probing the correlation between x(t_1) and x(t_2) while leaving the positions themselves unmeasured. It's a matter of being creative in designing the proper experiment, unless it can be demonstrated that this is impossible. I don't think it's at all obvious that it should be impossible to measure a correlation between x(t_1) and x(t_2) without measuring either individually.

In fact, the operator $x(t_1)x(t_2)$ is not even a hermitian operator, so it is not an observable. Only hermitian operators are observables, and only observables can be measured.

Right, you have to use an appropriate symmetrization. x(t_1)x(t_2) + x(t_2)x(t_1) is Hermitian, and its naive expectation value in BM differs from that of QM. So the lack of Hermiticity is not the source of the discrepancy.

 

[vanhees71]

For positivists like you it is not a problem. For those who think that a physical theory has to describe reality, it is a problem if something supposed to describe something real becomes, somewhere, infinite. Even if the infinity itself is only at a harmless place where the probability to appear is zero.

And my point was that the solution of this problem - even if only a problem for those interested in reality instead of observables only - will probably lead to a different sub-quantum theory with equations and solutions which differ from QT, even in its observable effects, so that, after this, you can come back and find out if that modified theory is better than QT.

With your self-restriction not to care about non-observable problems you restrict yourself from participation in the creation of such sub-quantum theories, which solve problems of different interpretations. Ignorance of problems means, first of all, refusal to participate in their solution. Your choice.

I'm not a positivist, but I'm a realist. It's almost a nuissance to discuss about "realism", because this is a notion that the philosophers have loaded with so much unsubstantiated meaning that nobody knows, what is discussed anymore. So what's "realistic" for a scientist? It's defined as reproducible objective and quantitative observations of phenomena in nature, no more no less.

Physics is an interplay between experiment and theory, and this interplay has lead to the discovery of quantum theory, which today is the most realistic theory we have about objectively observable phenomena in nature, and this theory tells us, taken away all the metaphysical additions of various interpretations that are supposed to solve some socalled problems with this discovery, that quantities are objectively indetermined, depending on the state a system is in. Given the Bell experiments of the recent decades together with the overwhelming success of local relativistic QFT, my conclusion is that the most realistic theory, which is QT in its minimal interpretation, in indeterministic. At the same time it describes all objective quantitative observations with an astonishing accuracy, and this makes it realistic in the sense of science.

I don't know, what you refer to when you talk about infinities. If you mean the infinities of perturbative relativistic QFT, then it's also a problem that is completely solved by modern renormalization theory with the physical interpretation of the abstract formalism provided by K. Wilson, Kadanoff et al. That physical theories have limitations in their validity is part of them being "realistic" and not some shortcoming! A bit overexaggerated one might say that finding out the limitations of validity of our theories is the very goal of ongoing scientific research, because this leads to its progress!

Of course, I don't believe that the current status of physical theory is the final answer. As long as there is no consistent formulation of gravity that must be wrong, but I don't believe that any progress can be made without new empirical facts guiding us into the right direction of theory building. To solve philosophical fake problems has never lead to any progress in the natural sciences. It was the great breakthrough of modern natural science to get rid of this "scholastic" idea. To solve a vague "problem of realism" or the socalled "measurement problem" hasn't furthered physical theory building, except by triggering a vigorous research program to test QT, and so far no limit of validity has been found. Although it's likely that one day we'll need a new even better theory, but we won't find it by speculations about philosophical problems but only by the very methodology of modern natural sciences, which is to test QT empirically with ever higher accuracy (implying of course that the same accuracy must be reached by theory in applying QT to the concrete description of these measurements).

 

[Demystifier]

Indeed, but nobody suggested that one measure x(t_1) and then x(t_2). That is obviously inequivalent. However, there doesn't appear to be any fundamental difficulty in measuring or probing the correlation between x(t_1) and x(t_2) while leaving the positions themselves unmeasured. It's a matter of being creative in designing the proper experiment, unless it can be demonstrated that this is impossible. I don't think it's at all obvious that it should be impossible to measure a correlation between x(t_1) and x(t_2) without measuring either individually.
Right, you have to use an appropriate symmetrization. x(t_1)x(t_2) + x(t_2)x(t_1) is Hermitian, and its naive expectation value in BM differs from that of QM. So the lack of Hermiticity is not the source of the discrepancy.

I still have no idea how one could measure any of the two things above in practice. But if you tell me how, I will tell you how standard and Bohmian QM make the same measurable predictions in that case.

 

[vanhees71]

How about discussing things which can be checked in principle, but not in practice? E.g. string theory at the Planck scale, the nature of black-hole interior, or a macro system in which the entropy decreases? Does that make sense to you?

Hm, is there any prediction of string theory that is observable in principle? Then it's of course well worth studying, because who knows what will be possible to test in practice in the future. 50 years ago nobody had believed that one can ever test Bell's ideas in practice, but it's almost common routine in the AMO labs today.

 

[Demystifier]

I'm not a positivist, but I'm a realist. It's almost a nuissance to discuss about "realism", because this is a notion that the philosophers have loaded with so much unsubstantiated meaning that nobody knows, what is discussed anymore. So what's "realistic" for a scientist? It's defined as reproducible objective and quantitative observations of phenomena in nature, no more no less.

Any philosopher would say that you are not a realist but a positivist. However, since you are not a philosopher but a scientist, who uses a scientific and not a philosophic language, you have a right to say that you are a realist and not a positivist.

The only problem is that you like to discuss philosophic questions with using scientific and not philosophic way of thinking. This is like discussing art with using scientific and not artistic way of thinking. If you try to explain the value of Mona Lisa by using a scientific way of thinking, it does not make much sense neither to artists nor to scientists.

 

[Demystifier]

Hm, is there any prediction of string theory that is observable in principle?

Yes, there are plenty of such predictions which should be visible at the Planck scale. Extra dimensions, particles with masses of the order of Planck mass, supersymmetry, ... These are generic predictions which do not depend on unknown details of string theory.

 

[vanhees71]

Hm, but then there should be a separate philosophy forum, which separates off the philosophical from the scientific parts of QT. There are Snow's two cultures getting separated into two unrelated universes the more both fields progress, and that's good. For me using philosophical methodology to QT is at least as non-sensical as the value of Mona Lisa by science only.

 

[zonde]

but I don't believe that any progress can be made without new empirical facts guiding us into the right direction of theory building.

Certainly

To solve a vague "problem of realism" or the socalled "measurement problem" hasn't furthered physical theory building, except by triggering a vigorous research program to test QT, and so far no limit of validity has been found. Although it's likely that one day we'll need a new even better theory, but we won't find it by speculations about philosophical problems but only by the very methodology of modern natural sciences, which is to test QT empirically with ever higher accuracy (implying of course that the same accuracy must be reached by theory in applying QT to the concrete description of these measurements).

To find a possible disagreement between the theory and experiment you need a test theory i.e. some sort of speculation where the theory might fail.
But the speculations have to be built on sound scientific basis and majority of speculations in QT (interpretations) are not of that type. BM is one example that is scientifically sound even if it currently does not propose possible limit of QT.

 

[atyy]

I'm not a positivist, but I'm a realist. It's almost a nuissance to discuss about "realism", because this is a notion that the philosophers have loaded with so much unsubstantiated meaning that nobody knows, what is discussed anymore. So what's "realistic" for a scientist? It's defined as reproducible objective and quantitative observations of phenomena in nature, no more no less.

Physics is an interplay between experiment and theory, and this interplay has lead to the discovery of quantum theory, which today is the most realistic theory we have about objectively observable phenomena in nature, and this theory tells us, taken away all the metaphysical additions of various interpretations that are supposed to solve some socalled problems with this discovery, that quantities are objectively indetermined, depending on the state a system is in. Given the Bell experiments of the recent decades together with the overwhelming success of local relativistic QFT, my conclusion is that the most realistic theory, which is QT in its minimal interpretation, in indeterministic. At the same time it describes all objective quantitative observations with an astonishing accuracy, and this makes it realistic in the sense of science.

I don't know, what you refer to when you talk about infinities. If you mean the infinities of perturbative relativistic QFT, then it's also a problem that is completely solved by modern renormalization theory with the physical interpretation of the abstract formalism provided by K. Wilson, Kadanoff et al. That physical theories have limitations in their validity is part of them being "realistic" and not some shortcoming! A bit overexaggerated one might say that finding out the limitations of validity of our theories is the very goal of ongoing scientific research, because this leads to its progress!

Of course, I don't believe that the current status of physical theory is the final answer. As long as there is no consistent formulation of gravity that must be wrong, but I don't believe that any progress can be made without new empirical facts guiding us into the right direction of theory building. To solve philosophical fake problems has never lead to any progress in the natural sciences. It was the great breakthrough of modern natural science to get rid of this "scholastic" idea. To solve a vague "problem of realism" or the socalled "measurement problem" hasn't furthered physical theory building, except by triggering a vigorous research program to test QT, and so far no limit of validity has been found. Although it's likely that one day we'll need a new even better theory, but we won't find it by speculations about philosophical problems but only by the very methodology of modern natural sciences, which is to test QT empirically with ever higher accuracy (implying of course that the same accuracy must be reached by theory in applying QT to the concrete description of these measurements).

Wilson only solved fake philosophical problems. QED was successful before Wilson.

 

[Denis]

I'm not a positivist, but I'm a realist. It's almost a nuissance to discuss about "realism", because this is a notion that the philosophers have loaded with so much unsubstantiated meaning that nobody knows, what is discussed anymore. So what's "realistic" for a scientist?

Very simple, the scientist uses the definition of realism used in the relevant exact mathematical proofs. In this case, the most relevant proof is that of Bell's inequality, and the notion of realism used in this proof is sufficiently clear and precise.

And you obviously reject it. Given that you don't reject Einstein causality, and that realism and Einstein causality give Bell's inequality. Note also that what is used in the proof is also a very weak form of realism, namely the EPR criterion of reality. So, you have to reject even the EPR criterion of reality. So, no, you are not a realist, and naming yourself a realist is simply misleading.

It's defined as reproducible objective and quantitative observations of phenomena in nature, no more no less.

No. My dreams are also observations, phenomena, and some of them are repeatable too.

Physics is an interplay between experiment and theory, and this interplay has lead to the discovery of quantum theory, which today is the most realistic theory we have about objectively observable phenomena in nature, and this theory tells us, taken away all the metaphysical additions of various interpretations that are supposed to solve some socalled problems with this discovery, that quantities are objectively indetermined, depending on the state a system is in.

No, QT is not a realistic theory, there are some interpretations which are realistic, others are epistemic.

Given the Bell experiments of the recent decades together with the overwhelming success of local relativistic QFT, my conclusion is that the most realistic theory, which is QT in its minimal interpretation, in indeterministic.

Which is objectively false, because an explicit example of a deterministic realistic interpretation exists.

At the same time it describes all objective quantitative observations with an astonishing accuracy, and this makes it realistic in the sense of science.

No, this makes it phenomenological. A realistic theory should define a model of what really exists and what does not. QT in the minimal interpretation is not doing such a thing.

I don't know, what you refer to when you talk about infinities.

Take a look at the dBB formula for the velocity of a particle, by the guiding equation, and take a look at the limit of |v| at a zero of the wave function.

If you mean the infinities of perturbative relativistic QFT, then it's also a problem that is completely solved by modern renormalization theory with the physical interpretation of the abstract formalism provided by K. Wilson, Kadanoff et al.

Depends on what you mean by "completely solved". Of course, for people which follow common sense, QFT is completely satisfactory as an effective field theory, which, below some critical distance, will become invalid. They never expected that humans will be able to find out more than some large distance approximations. If you have in mind the problems of those who think Lorentz covariance is some fundamental truth or so, then it solves nothing. Because a theory which, below some critical length, will be replaced by a completely different unknown one, gives Lorentz covariance at best as some approximation. And theorems like Haag's theorem strongly suggest that there is no fundamental relativistic QFT. Nonrenormalizability of GR even more.

To solve a vague "problem of realism" or the socalled "measurement problem" hasn't furthered physical theory building, except by triggering a vigorous research program to test QT, and so far no limit of validity has been found.

Whatever, it was the consideration of such "philosophical" problems of QT which has given essentially the only interesting fundamental result - the violation of Bell's inequality. Following you, we would have found not even this result.

 

[vanhees71]

The EPR paper is very vague in stating what their criterion of reality is. The most famous sentence of this enigmatic paper (only Bohr's answer with the same title is more enigmatic ;-))

"If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity then there exists an element of physical reality to this quantity."

just says that a physical quantity only represents "an element of physical reality" if the system is prepared such that this quantity has a determined value. This is possible for any observable within quantum theory. The point, however, is that there's no state for which all observables have "an element of physical reality". So what? Does that make QT "unrealistic"? Of course not, because this prediction of QT, i.e., that observables may be undetermined, is well observed too. So where is the problem with "reality" here and why this should imply an incompleteness of QT, is enigmatic to me. The rest of the paper doesn't "disprove" QT but only QT with an additional "collapse assumption", and this we've discussed endlessly in this forum already!