A Tumulka on Bohmian QED

[A. Neumaier]

Roderich Tumulka (a long-time Bohmian) demonstrates in his newest preprint,

• R. Tumulka, A Vision for a Bohm-Style Theory of Quantum Electrodynamics, arXiv:2409.07784.

that for the interpretation QED, the Bohmian interpretation has nothing to offer (apart from speculation called vision), and that the renormalization problem (which needs to be addressed in any serious interpretation of QED) is still completely unsolved on the interpretation level.

 

[Demystifier]

for the interpretation QED, the Bohmian interpretation has nothing to offer

Is it his words or your words?

 

[A. Neumaier]

Is it his words or your words?

I cited the source of the paper so that you can find out for yourself.

 

[Demystifier]

I have read the paper even before you posted it, and I didn't see that Tumulka is in any sense negative about BM. I guess you see in it what you want to see.

 

[A. Neumaier]

I have read the paper even before you posted it, and I didn't see that Tumulka is in any sense negative about BM.

Of course he isn't, since it is his main field of research.

But one needs to read between the lines. (Renormalized) QED and Bohmian mechanics both exist for now slightly more than 70 years. While QED was and still is a magnificent success, with a huge number of applications, Tumulka's paper documents the fact that the Bohmian version of it is still at the level of mere ideas and conjectures only, none of them really working, and without any change of this in sight.

 

[Demystifier]

and that the renormalization problem (which needs to be addressed in any serious interpretation of QED) is still completely unsolved on the interpretation level

In my opinion, renormalization on the interpretation level is best understood with Wilson philosophy, according to which QED (and the whole Standard Model) is just a long-distance effective theory, emerging from some unknown more fundamental theory formulated with entirely different degrees of freedom. From this point of view trying to find a Bohmian formulation of QED is misguided. The Bohmian formulation should be applied to this more fundamental theory, which makes it a part of a larger, more ambitious and more difficult problem of finding a better theory beyond the Standard Model.

 

[A. Neumaier]

The Bohmian formulation should be applied to this more fundamental theory, which makes it a part of a larger, more ambitious and more difficult problem of finding a better theory beyond the Standard Model.

This makes it even more speculative than Tumulka's alrady vague vision....

 

[Demystifier]

This makes it even more speculative than Tumulka's alrady vague vision....

It is, but it gives me a peace of mind, because then in practice I can just use quantum theory on an instrumental level, without a need to think about the details of Bohmian mechanics, and yet having a vague but intuitive picture of what might go on at a more fundamental level. For me, quantum interpretations are just tools for intuitive thinking. This particular tool works for me pretty well. But I use other tools (other interpretations) as well, whenever it helps me to grasp some aspects of quantum theory intuitively.

 

[Demystifier]

When I evaluate various interpretations of QM, I try to use the principle of charity.
https://en.wikipedia.org/wiki/Principle_of_charity

 

[apostolosdt]

In my opinion, renormalization on the interpretation level is best understood with Wilson philosophy, according to which QED (and the whole Standard Model) is just a long-distance effective theory, emerging from some unknown more fundamental theory formulated with entirely different degrees of freedom. From this point of view trying to find a Bohmian formulation of QED is misguided. The Bohmian formulation should be applied to this more fundamental theory, which makes it a part of a larger, more ambitious and more difficult problem of finding a better theory beyond the Standard Model.

Sorry, but which Wilson are you referring to? Not Kenneth, I presume.

 

[Demystifier]

Sorry, but which Wilson are you referring to? Not Kenneth, I presume.

Kenneth Wilson, of course, did not not talk about Bohmian mechanics, but his approach to renormalization can be used in Bohmian mechanics as well. Sorry for using the p-word (philosophy), I know that this word irritates you.

 

[apostolosdt]

Kenneth Wilson, of course, did not not talk about Bohmian mechanics, but his approach to renormalization can be used in Bohmian mechanics as well. Sorry for using the p-word (philosophy), I know that this word irritates you.

I appreciate your understanding of my... caprice with "philosophy" in a physics context. But still, my question genuinely holds: Which Wilson are you referring to? For I googled the name and a lot of philosophers under "Wilson" came up. Looks like the name is quite popular among philosophers. My wild guess is in connection with the term "principle of charity" (never heard before, though). Is it Neil Wilson? Just curious.

 

[Demystifier]

If I wrote "approach" instead of "philosophy", would it look more like Kenneth to you?

 

[apostolosdt]

If I wrote "approach" instead of "philosophy", would it look more like Kenneth to you?

It looks like I've caused sort of sidetrack in your thoughts, for which I apologize.

In one of your previous posts here, the passage "...QED (and the whole Standard Model) is just a long-distance effective theory, emerging from some unknown more fundamental theory formulated with entirely different degrees of freedom..." you used does sound like Kenneth to anyone knowing sth about the subject, but that "interpretation" term fuzzed the text a bit.

I've nothing against philosophy per se; in fact, being Greek, I've been exposed to enough philosophy at school. But I cannot overstate my stance that physics is an experimental science that may help us know about the world, but not revealing the truth about the world. That's what Feynman so emphatically repeated. And yet, "interpretation" implies "knowing the truth;" that's irritating to me, yes it is.

 

[Demystifier]

And yet, "interpretation" implies "knowing the truth;" that's irritating to me, yes it is.

I don't see it this way. For me, interpretation implies having an idea what truth might be.

 

[A. Neumaier]

Kenneth Wilson, of course, did not not talk about Bohmian mechanics, but his approach to renormalization can be used in Bohmian mechanics as well.

Where is a published example of the use of the renormalization approach in Bohmian mechanics?

 

[Demystifier]

Where is a published example of the use of the renormalization approach in Bohmian mechanics?

Why do you ask? Would you like to read it, or are you just hoping that I will say that there isn't any?

 

[PeterDonis]

Why do you ask? Would you like to read it, or are you just hoping that I will say that there isn't any?

The way for you to find out which of these possibilities is correct is to answer the question. Please do so. I would be interested to see the answer too.

 

[Demystifier]

In my "Bohmian mechanics for instrumentalists" I used a Wilsonian way of thinking to argue that one does not need to worry about the details of Bohmian mechanics. To my knowledge, in a Bohmian context there is no paper that uses Wilsonian renormalization in a technical sense.

 

[A. Neumaier]

Why do you ask? Would you like to read it, or are you just hoping that I will say that there isn't any?

As you know I read quite a number of publications on Bohmian mechanics! But I haven't seen one on the topic you mentioned, so I was asking (ns would have read it). Your answer showed that renormalization is so far not applied in Bohmian mechanics, except as an excuse not to have to think deeper about the foundations, because

one does not need to worry about the details of Bohmian mechanics.

That's why I don't worry about Bohmian mechanics at all; it is just a carpet under which to sweep all nontrivial problems....

 

[Demystifier]

As you know I read quite a number of publications on Bohmian mechanics! ...
That's why I don't worry about Bohmian mechanics at all;

Why do you read it, if you don't worry about it?

 

[A. Neumaier]

Why do you read it, if you don't worry about it?

What a question! Worry is a poor guide for choosing what to read.

I read to be informed about possible progress.

 

[Demystifier]

I read to be informed about possible progress.

So you think Bohmian interpretation has a potential? If so, could you explain why you think so? You often say what you don't like about BM, which is fine, but perhaps now you could say what you like about it.

 

[A. Neumaier]

So you think Bohmian interpretation has a potential? If so, could you explain why you think so? You often say what you don't like about BM, which is fine, but perhaps now you could say what you like about it.

Its Plus is that it is a deterministic theory. Thus it makes predictions for the single case, which is necessary for today's experiments on single atoms, electrons, or nanodevices. These are not covered by the statistical interpretations without making ad hoc additions.

Its big (and at present devastating) Minus is that it cannot handle naturally relativistic theories, including renormalization issues. That's why I was curious about hearing that

Kenneth Wilson, of course, did not not talk about Bohmian mechanics, but his approach to renormalization can be used in Bohmian mechanics as well.

Unfortunately, it was a false alarm....

 

[Demystifier]

I see. You are disappointed with BM because you have high expectations of it, higher than it can actually produce.

 

[haushofer]

Its big (and at present devastating) Minus is that it cannot handle naturally relativistic theories, including renormalization issues. That's why I was curious about hearing that

But isn't that potentially interesting? If you want a theory of quantum mechanics that's ontologically sound, you run into problems with relativity, just like e.g. Maxwell's theory of electromagnetism and the rejection of the ether run into trouble with Galilean relativity.

 

[martinbn]

But isn't that potentially interesting? If you want a theory of quantum mechanics that's ontologically sound, you run into problems with relativity, just like e.g. Maxwell's theory of electromagnetism and the rejection of the ether run into trouble with Galilean relativity.

It may be interesting but it is a big problem, because there is no third option. You either have relativity or Galilean relativity. If you cannot make your theory relativistic, then you have to go back to Galilean relativity, and explain all the experiments that confirm relativity. Not sure if the last one is even possible.

 

[A. Neumaier]

I see. You are disappointed with BM because you have high expectations of it, higher than it can actually produce.

No.

I am disappointed with BM because I have high expectations of satisfying foundations of physics, which (as shown by the practice of the last 70 years) must include satisfying foundations of relativistic quantum field theory.

BM (also over 70 years old) still doesn't meet these standards, so I have very low expectations of it. But I get curious when new claims are made that could affect this assessment. Unfortunately, always false alarms....

 

[Demystifier]

No.

I am disappointed with BM because I have high expectations of satisfying foundations of physics, which (as shown by the practice of the last 70 years) must include satisfying foundations of relativistic quantum field theory.

BM (also over 70 years old) still doesn't meet these standards, so I have very low expectations of it. But I get curious when new claims are made that could affect this assessment. Unfortunately, always false alarms....

So you have low expectations of BM, fine. Is there an interpretation of quantum theory (including relativistic QFT) of which you have much higher expectations?

 

[A. Neumaier]

So you have low expectations of BM, fine. Is there an interpretation of quantum theory (including relativistic QFT) of which you have much higher expectations?

Yes. My thermal interpretation, in the form introduced in my new book

• A. Neumaier and D. Westra, Algebraic Quantum Physics, Vol. 1: Quantum mechanics via Lie algebras, de Gruyter, Berlin 2024.

I am quite happy: The book is now fully published -- today I got a printed copy of the book!

It features a mathematically rigorous but still physically lucid account of quantum mechanics from the point of view of symmetries, including its foundations.

Though this book does not feature relativistic QFT, the compatibility of the thermal interpretation with QFT is shown in my earlier book.

• A. Neumaier, Coherent Quantum Physics: A Reinterpretation of the Tradition, de Gruyter, Berlin 2019.

 

[Demystifier]

Ok, is there is any other interpretation for which you have high expectations?

About the thermal interpretation, in your opinion, does it have some weaknesses?

 

[A. Neumaier]

Ok, is there is any other interpretation for which you have high expectations?

The shut-up-and-calculate interpretation! It says that anything goes as long as it respects the formalism and is suggestive to the audience. The difficulty there is to make the 'suggestive' watertight. The attempt to do so led me to the thermal interpretation.

About the thermal interpretation, in your opinion, does it have some weaknesses?

I leave the answer to this question to those who have a less biased view than me. In any case, your attempt to shoot it down 5 years ago didn't convince me of having substance.

 

[Demystifier]

The shut-up-and-calculate interpretation! It says that anything goes as long as it respects the formalism and is suggestive to the audience. The difficulty there is to make the 'suggestive' watertight. The attempt to do so led me to the thermal interpretation.

I see. My instrumental Bohmian mechanics can be seen in a similar way, as an attempt to reformulate the shut-up-and-calculate interpretation to a form that makes it more suggestive to the audience. The result, at least, is suggestive to me, just as the thermal interpretation is suggestive to you.

 

[haushofer]

It may be interesting but it is a big problem, because there is no third option. You either have relativity or Galilean relativity. If you cannot make your theory relativistic, then you have to go back to Galilean relativity, and explain all the experiments that confirm relativity. Not sure if the last one is even possible.

Is that really the only way? To use Bell's words, aren't we lacking imagination?

But I see your point.

 

[martinbn]

Is that really the only way? To use Bell's words, aren't we lacking imagination?

But I see your point.

What other way could there be? No Einsteinian relativity and no Galilean relativity? Then it would be more difficult. You need to reconcile a few centuries of physics with it.

 

[Demystifier]

What other way could there be? No Einsteinian relativity and no Galilean relativity? Then it would be more difficult. You need to reconcile a few centuries of physics with it.

Aristotelian?
https://www.sciencedirect.com/science/article/abs/pii/S0375960197001011

Let me explain in my own words. Galilean relativity says that 3-position is relative, 3-velocity is relative, but 3-acceleration is absolute. Aristotelian relativity says that 3-position is relative, but 3-velocity and 3-acceleration are absolute. Einstein-nonrelativistic Bohmian mechanics (ENBM) obeys Aristotelian relativity. Nevertheless, the classical limit of it obeys Galilean relativity. Einstein-nonrelativistic quantum mechanics (ENQM) in its standard form also obeys Galilean relativity. But ENQM has the measurement problem, so it seems that it is incomplete. ENBM is a possible completion of ENQM, according to ENBM Aristotelian relativity is fundamental while Galilean relativity is emergent, valid only at the statistical level.

How to generalize all this to Einstein-relativistic theories? The idea is that Einsteinian relativity is emergent in a similar way as Galilean relativity. How could that be? I have given some ideas in that direction in https://arxiv.org/abs/2205.05986 .

 

[gentzen]

The shut-up-and-calculate interpretation! It says that anything goes as long as it respects the formalism and is suggestive to the audience. The difficulty there is to make the 'suggestive' watertight. The attempt to do so led me to the thermal interpretation.

I really like this, because this was also the feeling I got from reading your 2019 book. When I had the challenge to describe the thermal interpretation to an outsider "in very few words," I decided to go with that feeling for the non-probability part:

Because of my interest in probability, I reviewed Arnold Neumaier's thermal interpretation.
(https://physicsoverflow.org/41990/f...-the-thermal-interpretation?show=43307#a43307)
As an interpretation of probability, it is an operative objective (model based) interpretation, which fixes both the better and lesser known issues of frequentism. As an interpretation of quantum mechanics, I would say it is a Copenhagen-like interpretation, which uses a better interpretation of probability, and pays more attention to details of preparation and measurement (i.e. less idealized) than usual.

(I am sufficiently deep into probability that I don't need to fall-back to feelings for that part.)

About the thermal interpretation, in your opinion, does it have some weaknesses?

I leave the answer to this question to those who have a less biased view than me. In any case, your attempt to shoot it down 5 years ago didn't convince me of having substance.

Everybody has a biased view, but maybe less biased than yours. Of course, Demystifier was interested in your answer, not in any objectively true or somehow less biased answer. Why did Demystifier try to shoot it down 5 years ago? What has your relation to Demystifier to do with QFT, and where are both your blind spots in that area?

Bohmian mechanics doesn't need QFT to get space back into QM. The thermal interpretation doesn't have obvious problems with QFT like Bohmian mechanics, but you hope to get spacetime and ontology from QFT. Now suddenly your requirements on QFT become much higher than it actually can satisfy in its current state. And this hope is also a significant departure from "shut-up-and-calculate" or "Copenhagen-like" interpretations.

For such interpretations, QM is a framework just like ordinary differential equations are a framework. You don't need to go to partial differential equations to get space and ontology into ordinary differential equations. OK, now after I have written this, I do see that the ontic character of time for ODEs can indeed be a problem, if you insist that only spacetime should have that ontic character. And that going to PDEs indeed helps with that issue.

 

[Morbert]

As an interpretation of quantum mechanics, I would say it is a Copenhagen-like interpretation, which uses a better interpretation of probability, and pays more attention to details of preparation and measurement (i.e. less idealized) than usual.

iirc the Thermal interpretation is more ambitious than Copenhagen-like interpretations. It attempts to recover the probabilistic character of quantum experiments from deterministic beables via something like the BBGK hierarchy (though I have never followed through in learning how).

 

[gentzen]

iirc the Thermal interpretation is more ambitious than Copenhagen-like interpretations.

How do you interpret "A Reinterpretation of the Tradition"? The tradition of BM or MWI? Certainly not! It means a reinterpretation of the orthodoxy.

Now what is the orthodoxy? Is it "shut up and calculate", Copenhagen, von Neumann QM, or ...? But von Neumann just tried to explain what Born and Heisenberg meant. The problem is that people misinterpreted Heisenberg and von Neumann in different ways. If I would try to "better explain" the thermal interpretation than A. Neumaier himself, I would probably suffer a similar fate like von Neumann or worse.

So I just tried to expain my own feeling instead. And I invite everybody to describe and explain their own feelings they got from reading A. Neumaier's papers and books.

 

[PeterDonis]

what is the orthodoxy?

There isn't one as far as QM interpretation is concerned. That's why QM interpretation is still an issue a century after QM as a mathematical model was developed.