Insights Interview with Astrophysicist: Adam Becker - Comments

[Greg Bernhardt]

Greg Bernhardt submitted a new PF Insights post

Interview with Astrophysicist: Adam Becker

Continue reading the Original PF Insights Post.

 

[fresh_42]

We should make his book a mandatory read for all who want to debate or turn a debate into the 1,001st take of a Bohemian Rapsody - introduction test to prove it included! The last one which started by a harmless attempt by Shoshany to bring QM nearer to school kids:

"Quantum theory for high-school students"​

just turned into the obviously inevitable confrontation (post #8 fffff.)

I think it is weak on interpretation.

 

[Mentz114]

Do you have a view on the ‘reality’ of the wave function?

I think that there must be something in nature that approximately resembles the wave function, or that directly gives rise to something like a wave function.
[..]
Why do I think this? Because quantum physics works phenomenally well. It explains a huge diversity of phenomena to a breathtaking degree of accuracy. How could quantum physics possibly work so well if there weren’t something out in the world that it was accurately describing?
[..]
A theory that can do that has got to be latching on to some true fact about nature, even if it’s just in an indirect or approximate way.

I found your response to this question thought provoking, thank you.

Reference https://www.physicsforums.com/insights/interview-with-astrophysicist-adam-becker/

 

[Greg Bernhardt]

fyi, we should be receiving a few copies of his new book to give away very soon!

 

[Wes Tausend]

An excellent interview, Greg. Thanks.

I look forward to Dr. Becker's book showing up here in the boondocks. It seems I need a lot of historical background to see how the theories first developed to understand what they are and Dr. Becker seems to recognize this key to comprehension.

I don't possesses any higher math than some dusty trig. In that unfortunate aspect, I've seemed to reach a plateau with my layman's understanding of the relativities. Most quantum principles seem a lot more difficult to understand and especially incorporate into what might seem to be a simpler mechanical rendition like gravity. I hope to someday see a simpler natural explanation for atomic mechanism too. I ever harbor a secret suspicion that Nature is lazy and not so complicated after all.

So far I've read some info by Asimov and what might be a similar, but dated book, Quantum Reality: Beyond the New Physics by Nick Herbert. Herbert describes several perspectives that may lend themselves to simpler nucleic structure models; I hope more like the electron cloud and maybe even a incorporate a gravitational base.

Wes
...

 

[zonde]

Excellent read his new book. I become too intrigued so read it on my phone with kindle app.
It describes the path from the early days of quantum mechanics to the more modern times when questioning Bohr and Copenhagen interpretation become safer for professional career. He gives contexts for different periods and characters in his story that makes his book more interesting to read not to mention the sense of deeper understanding of historical context.

I will add one quote of Einstein that was new for me:
"When Philip Frank, a founding member of the Vienna Circle, asked Einstein about his philosophy of science, he was astonished to find that Einstein was not a positivist. Frank protested that Einstein had invented the positivist approach to physics in his theories of relativity. "A good joke should not be repeated too often." Einstein replied, much as he had to Heisenberg several years before."

 

[RUTA]

My experience with foundations of physics parallels Adam's, "And this asymmetry I’d found was a doozy: the philosophers of physics were, in general, quite well informed about physics, but the physicists were, by and large, wholly ignorant of philosophy, despite the fact that they were making philosophical claims when they dismissed questions about quantum foundations. As a result, the physicists were generally relying upon faulty philosophy when they answered such questions." In the nine courses I took on quantum mechanics, solid state physics, nuclear physics, quantum field theory, string theory, and particle physics, never once did any textbook or professor use the terms EPR paradox, Bell inequality, entanglement, measurement problem, delayed choice, quantum eraser, which-way twin-slit experiment, or quantum nonlocality. I received my PhD in physics in 1987, so hopefully things are better for young physicists today, but the asymmetry extends even here to PF today.

I've been researching, publishing and teaching in foundations of physics at Etown College for 30 years. I've given dozens of conference and public lectures on topics in this area, so I was particularly excited to see an online outlet become available for dissemination of "the cool stuff" in physics, i.e., PF Insights. I use these for my students in my GR and QM courses, and Ruth Kastner is currently writing a paper referencing two of them, but all of my PF Insights on foundations of physics topics were postdated (to hide them) and had the comments disabled. This sanction even included my Insights explaining papers published in Phys Rev Lett and Nature Comm. This is precisely the attitude towards foundations of physics in the physics community Adam decries.

As to Adam's particular take on the measurement problem, I hope he acknowledges in his book (which I will certainly read!) that the measurement problem is a non-starter for block universe views. For example, there is no "collapse of the wave function" or "non-unitary evolution of the wave function" in the block universe, since one is computing the probability amplitude in spacetime rather than the time evolution of a the wave function in configuration or Hilbert space. This is a psi-epistemic view rather than a psi-ontic view. I have a series of PF Insights explaining the implications of the block universe on foundations of physics starting with https://www.physicsforums.com/insig...ions-part-1-time-dilation-length-contraction/. These Insights have thousands of hits despite being duly"hidden" by the PF Admin.

My colleagues in philosophy and mathematics (Silberstein and McDevitt) and I have a book forthcoming with Oxford UP on a block universe approach to physics called "Beyond the Dynamical Universe" (already available in the UK, available in the US next month). Here is a link to a low-level introduction on the OUP authors' blog https://blog.oup.com/2018/03/gods-eye-view-of-reality/. Besides resolving the puzzle of the Big Bang, the flatness problem, the horizon problem, the low entropy problem, and the conundrums of quantum nonlocality, block universe physics denies the need for non-baryonic dark matter and dark energy. This also allows for an empirical approach to quantum gravity and unification. In short, we lay the blame for the current impasse of fundamental physics and foundations of physics at the feet of dynamical thinking. We also argue that, as Adam found himself, there is a need for collaboration between physicists and philosophers on these matters. This interview on PF is at least a small step in that direction.

 

[zonde]

In short, we lay the blame for the current impasse of fundamental physics and foundations of physics at the feet of dynamical thinking. We also argue that, as Adam found himself, there is a need for collaboration between physicists and philosophers on these matters.

Adam is arguing against positivism. And positivism has been discussed among philosophers and so there are things that philosophers can bring to the table.
Have there been similar discussions about adynamical/dynamical thinking among philosophers?

 

[RUTA]

Have there been similar discussions about adynamical/dynamical thinking among philosophers?

The dynamical bias runs deep, even those who interpret QM via future boundary conditions resort to terminology such as “retrocausality,” “completed transactions” and “backwards causation.” I just attended special sessions on foundations of physics at the APS March Meeting earlier this month where Ken Wharton and I gave the only talks on the adynamical approach. [Aside: Ken only recently himself replaced the term “retrocausality” with “all-at-once view.”] Since philosophers of physics tend to follow physicists, there are very few of them who study adynamical approaches. Huw Price is a notable exception, having written a book on retrocausality (Price, H. (1996). Time’s Arrow and Archimedes Point: New Directions for the Physics of Time. Oxford University Press, Oxford) and used the term “global constraint” in a spatiotemporal sense in Price, H. (2008). Toy models for retrocausality. Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 39(4):752–61. David Albert worked with Aharonov and Vaidman on weak values corresponding to the Two-State Vector Formalism (Y. Aharonov, et al., Phys. Rev. Lett. 60, 1351 (1988)). Peter Evans is another philosopher who has written on this topic (Evans, P. (2015). Retrocausality at no extra cost. Synthese, 192(4):1139–55). I’m sure there are more, sorry I don’t have their names. [Aside: Ruth Kastner has reanimated (if you will) the use of future boundary conditions in her approach: Kastner, R. (2013). The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility. Cambridge University Press, Cambridge.] Replacing the so-called Newtonian Schema Universe (current way we explain, term from Smolin) with the Lagrangian Schema Universe (block universe way to explain, term from Wharton) is an enormous change in what it means to explain something; probably rivaling the change from Aristotelian to Newtonian thinking. Such ideas can take decades to mature. Aharonov et al. introduced the Two-State Vector Formalism in 1964 and according to Wikipedia that idea originated with Watanabe in 1955. Fifty years later (we introduced Relational Blockworld in 2005 at New Directions) time-symmetric QM finally evolved to fully adynamical thinking (block universe patterns per adynamical global constraints). So, adynamical thinking is relatively nascent.

 

[Peter Morgan]

Have there been similar discussions about adynamical/dynamical thinking among philosophers?

The philosophy of QFT seems generally more open to thinking about a block world than is the philosophy of non-relativistic QM, because dynamical evolution has to be equally describable in any boosted frame (not everyone feels forced to a block world by Lorentz invariance, but it's not easy to dismiss it as a possible ontology.)

 

[zonde]

The dynamical bias runs deep, even those who interpret QM via future boundary conditions resort to terminology such as “retrocausality,” “completed transactions” and “backwards causation.”

Bringing in retrocausality takes the discussion even further away from topic of this thread. I'm not going to discuss it in this thread.

Such ideas can take decades to mature.

I agree that it takes decades for philosophical ideas to mature, but then it takes more decades to find out if they can contribute for development of scientific knowledge.
But I do not think that blockworld by itself changes anything just like switching from cartesian coordinates to spherical coordinates won't give any new statements about physical configuration we describe with these coordinate systems. There are other features in your approach that you exclusively associate with blockworld. But I don't. As this can open some offtopic discussion I rather stop here.

 

[RUTA]

I agree, we don't want to discuss blockworld per se here, that would be off topic. And, I agree that for most physics blockworld has nothing new to offer. I've purchased Adam's book on audio and will start listening to it this weekend. I'll post any of my responses here. Of course, in that context adynamical thinking is highly relevant, as you'll see.

 

[vanhees71]

There's a (positive) review on Becker's book in today's issue of Nature

https://www.nature.com/articles/d41586-018-03793-2

 

[DrChinese]

And although it is not the source you'd normally go to for suggestions on a science book, this review of Adam's book appeared a few days ago... in the Wall Street Journal.

https://www.wsj.com/articles/what-is-real-review-quarks-and-quandaries-1521234605

 

[Peter Morgan]

https://www.wsj.com/articles/what-is-real-review-quarks-and-quandaries-1521234605

"Whether he has chosen to wear the right uniform will be for future readers to judge."

There's a book signing in New York on April 3rd, https://www.facebook.com/events/420267451764873/, which is part of a regular lecture series, https://nyphilsci.wordpress.com/201...ation-doesnt-work-and-why-its-popular-anyhow/. I know at least one other person who's going, so I'm toying with going myself. Anyone else interested? Frankly, I need a little impetus, because the story I'm seeing, particularly what seems an excessive focus on Copenhagen, doesn't do much for me (Copenhagen is interesting as history, but not much as a basis for new work, particularly for me, working on QFT).

EDIT: Adam's current list of events is at http://freelanceastrophysicist.com/talks/

 

[Peter Morgan]

A more interesting review, more philosophically academic, from the APS Division of Quantum Information, March 16th: http://thequantumtimes.org/2018/03/book-review-what-is-real-by-adam-becker/. This makes me more interested in seeing his lecture on April 3rd.

EDIT: I'm going.

 

[RUTA]

From The Quantum Times review:

“The truth, of course, is that (contrary to what many people, even many physicists, seem to believe) quantum mechanics does not describe electrons in this way. Instead of N wave-like disturbances in a field, the theory describes a system of N electrons as a single wave-like disturbance in an abstract, 3N-dimensional space whose connection to ordinary three-dimensional physical reality is, at best, completely obscure.”

This is another issue that the Lagrangian, block universe approach to QM clears up easily. By computing a probability amplitude for a specific outcome (path integral uses future boundary conditions), the formalism is moved out of configuration space and into spacetime. Now you can understand QM as providing distributional frequencies in spacetime, i.e., the relative frequencies of experimental outcome patterns in the block universe. And the confusing nature of the time-evolved wavefunction mentioned above is revealed as nothing more than an epistemological constraint of the ant’s-eye view. In other words, as ants we don’t know which particular outcome will occur in any given trial, thus the need for configuration space in a time-evolved approach.

 

[atyy]

There's a (positive) review on Becker's book in today's issue of Nature

https://www.nature.com/articles/d41586-018-03793-2

There's a (mixed, but overall positive) review by Mélanie Frappier on Becker's Book in today's Science.

http://science.sciencemag.org/content/359/6383/1474.1

""... nontechnical primers are not the place for fastidious philosophical distinctions. They should, however, be careful not to create straw men. ...

By suggesting that, for all practical purposes, these physicists defended the same position, Becker—like so many before him—ends up portraying the Copenhagen interpretation as a single, internally inconsistent doctrine. His uncharitable account makes it difficult not to conclude that these physicists were at best unsophisticated instrumentalists, at worst self-serving hypocrites. ...

Despite an oversimplified treatment of the philosophical issues at play, What Is Real? offers an engaging and accessible overview ... who like Einstein, wonder if the Moon is still there when no one is looking."

 

[vanhees71]

Well, this review is, however, also a bit besides the point. I've not read Becker's book, but to think that any of the physics problems, some seem still to claim to be existent, could be solved by philosophy is wishful thinking. There's not a single example in the history of science in the modern sense (which with about 400 years is however not that old yet) where philosophical considerations have solved any physical problem. The progress has been made by a mutual interaction between experiments/observations, model and theory building as well as, in my opinion often underpreciated, progress in mathematics.

There is, as far as I can see, no measurement problem, because quantum theory is successfully used to predict experimental results and to suggest new experiments to test and clarify it. The philosophical quibbles between Bohr and Einstein haven't lead to anything interesting in physics before Bell hasn't found a way to reformulate the philosophical opinions of the two in terms of a scientifically well-defined theoretical statement (Bell's inequality must hold if a local deterministic hidden-variable theory can reproduce the probabilities of QT), which in turn lead to high-precision experiments due to technological progress in AMO physics. The outcome is very clear: If there is a deterministic HV theory that could reproduce the probabilistic predictions of QT (which in fact were shown to be correct, and the Bell inequality is violated as predicted by QT!) it must be non-local, and it's obviously hard to produce non-local HV theories in accordance with Einstein causality. All we have that is compatible with experiment and in accordance with causality in the sense of SRT is relativistic local QFT (and classical relativistic field theories of continua, which however are to be seen as effective theories of macroscopic systems), but no non-local relativistically causal HV theory.

The case of Bohm is in a way indeed tragic, and of course one should not intermingle political opinions with scientific questions. That said, however, it should be pretty clear that Bohmian-de-Broglie pilot wave theory is not very much appreciated in the physics community because Bohm had unwanted political views in his time, but because it is of not much use. The point is that it works to a certain extent for non-relativistic QT but there's no satisfactory reinterpretation of relativistic local QFT in its sense. Also the claimed Bohmian trajectories seem not to be observable, at least it's not unambigously clear how to measure them. The rest of the interpretation just reproduces the probabilistic statements of the (minimal) standard interpretation, and the minimal standard interpretation (also known as statistical interpretation) is just a flavor of Copenhagen where all the philosophical mumbo-jambo of some of its followers is stripped off bringing bare bones of physically observable facts into the focus, i.e., there is a theory that predicts the probabilistic outcomes of measurements in real-world labs very well, and that's it.

It's also not clear to me, why one makes Bohr the main culprit. Although guilty of having produced a lot of philosophical gibberish with notions as "complementarity", he usually was the one who argued with the hard physics facts. It's, e.g., not so clear to me, whether he agreed to the collapse conjecture, which is the most problematic ingredient, in clear contradiction to Einstein causality (and thus rightfully criticized by Einstein as "spooky action at a distance"). Interestingly Einstein also did not think very favorably about the Bohm-de-Broglie pilot-wave idea. If there is a main culprit of the "Copenhagen gang" it was Heisenberg, who was pretty dogmatic too. Ironically he got the interpretation of the uncertainty relation wrong. Bohr had to correct him, but unfortunately Heisenberg's first paper on the subject somehow stuck, and even today statements are made in textbooks that the uncertainty relatation is about the impossibility of accurately measure observables rather than the impossibility to prepare states for which the standard deviations of incompatible observables are small for all of them.

So the main problems with QT today, if there are any, are because of philosophical gibberish and imprecisely formulated claims. The real problem with QT today from a physics point of view, still is the unsolved problem to find a compatible quantum theory of gravitation rather than artificial philosophical issues on some apparent measurement problem.

 

[atyy]

@vanhees71 - congratulations on such a long post on philosophy! I think you are addicted to philosophy

 

[vanhees71]

Maybe, there's a masochistic side in me

 

[fresh_42]

Maybe, there's a masochistic side in me

Blame it on the heritage.

 

[Lord Jestocost]

In the interview, Adam Becker says:

“What is Real? is about the unfinished quest for the meaning of quantum physics. We have this beautiful theory, quantum mechanics, and it’s astonishingly accurate. But it’s not at all clear what that theory is saying about the nature of the world around us. It must be saying something about that world—there must be something in nature that resembles the mathematics of quantum mechanics, otherwise why would the theory work so well? But there’s no clarity or consensus among physicists about what, exactly, quantum physics is saying about reality. This is very strange, especially given that quantum mechanics is over 90 years old.”

What is here very strange? It is strange that still today many try to squeeze something REAL out of the “quantum physics” tube. Quantum physics has nothing to say about the nature per se of the world around us. It’s about object-subject relations. And why should there be consensus among physicists? To ask “What, exactly, is quantum physics saying about reality?” is a biased question. It implicitly assumes – without trying to go to the bottom - that there is something like REALITY.

In the interview, Adam Becker says:

"The closest thing we have to a consensus about any of this is the Copenhagen interpretation. But the Copenhagen interpretation isn’t really a single coherent set of ideas about quantum mechanics—it’s a family of mutually-contradictory ideas, none of which adequately solve the measurement problem or answer the other questions at the heart of quantum theory. This is all the more strange given that reasonable alternatives to Copenhagen have existed for decades.“

What questions are at the heart of quantum theory? To my mind, such questions merely arise when people have the feeling that quantum theory “threatens” their personal psychological predispositions or philosophical beliefs. The “Copenhagens” were clearly aware of this.

 

[vanhees71]

Quantum theory describes a tremendous part of the real world (or at least that part we can observe and objectively investigate, anyway). To say it's "not real" is simply rediculous. The word "real" is spoiled by philosophers to a degree that you cannot use it anymore in scientific discussions since its meaning has been put into the state of maximum entropy (mess) ;-)). SCNR.

 

[Lord Jestocost]

Quantum theory describes a tremendous part of the real world (or at least that part we can observe and objectively investigate, anyway).

To say that "quantum theory describes a tremendous part of the real world" is your personal "interpretation". That was my point.

 

[atyy]

What is here very strange? It is strange that still today many try to squeeze something REAL out of the “quantum physics” tube. Quantum physics has nothing to say about the nature per se of the world around us. It’s about object-subject relations. And why should there be consensus among physicists? To ask “What, exactly, is quantum physics saying about reality?” is a biased question. It implicitly assumes – without trying to go to the bottom - that there is something like REALITY.

Copenhagen usually assumes the existence of reality. There is the classical/quantum cut, and the classical side (measurement outcomes) is reality. The terminology is bad, so one could also call the cut the macro/micro cut or the real/non-real cut.

 

[fresh_42]

To say that "quantum theory describes a tremendous part of the real world" is your personal "interpretation". That was my point.

... expressing it with a machine that relies on QM and is on the brink of a revolution, which will rely even more on it.

 

[vanhees71]

To say that "quantum theory describes a tremendous part of the real world" is your personal "interpretation". That was my point.

No, it's a well-established fact by a plethora of high-accuracy measurements of all kinds of systems from the high-energy-particle experiments at the LHC over quantum optics, atomic, nuclear physics to condensed-matter physics. That's not simply a personal interpretation of a single physicist!

 

[vanhees71]

Copenhagen usually assumes the existence of reality. There is the classical/quantum cut, and the classical side (measurement outcomes) is reality. The terminology is bad, so one could also call the cut the macro/micro cut or the real/non-real cut.

The cut is also only in certain flavors of Copenhagen! There's no clear definition of it, and there's no known limit to the validity of quantum theory also for macroscopic systems. It's only a technical problem of state preparation preventing us from measuring "quantum properties" of macroscopic objects. In any case there are some empirical examples that prove the existence of predicted quantum effects like entanglement, as for example the experiment entangleling vibration modes of diamonds over some distance (working even at room temperature on a usual lab desk).

 

[Peter Morgan]

The outcome is very clear: If there is a deterministic HV theory that could reproduce the probabilistic predictions of QT (which in fact were shown to be correct, and the Bell inequality is violated as predicted by QT!) it must be non-local, and it's obviously hard to produce non-local HV theories in accordance with Einstein causality.

One way to do something about this, vanhees71, is to ask for a manifestly Lorentz invariantly constructed random field that is equivalent to a quantum field. One finds that Einstein locality is indeed violated, but it's hard to object to a construction that is Lorentz invariantly constructed and that is equivalent to an empirically successful quantum field (specifically, quantized EM). I'll upload to here a current draft of a paper that derives from my EPL 87, 31002(2009) (the arXiv version is a couple of months old, as of now, and there's been lots of useful feedback from people on Facebook and from other correspondents since then; I intend to submit the paper to JMathPhys soon).
Once one knows how, one can say that it's not so hard.
I got to say that I think philosophy does something more than nothing for physics, though as in anything there's a lot that doesn't do much for me.

 

[atyy]

The cut is also only in certain flavors of Copenhagen!

The cut is in all flavours of Copenhagen.

There's no clear definition of it,

True, the cut is subjective.

and there's no known limit to the validity of quantum theory also for macroscopic systems. It's only a technical problem of state preparation preventing us from measuring "quantum properties" of macroscopic objects. In any case there are some empirical examples that prove the existence of predicted quantum effects like entanglement, as for example the experiment entangleling vibration modes of diamonds over some distance (working even at room temperature on a usual lab desk).

True, the cut can be shifted, so anything can be moved from the classical side of the cut to the quantum side of the cut.

However, you cannot put the whole universe, including all observers on the quantum side of the cut, with nothing left on the classical side. People try to do so, but that requires an attempted solution to the measurement problem, eg. Many Worlds or Bohmian Mechanics.

 

[zonde]

Well, this review is, however, also a bit besides the point. I've not read Becker's book, but to think that any of the physics problems, some seem still to claim to be existent, could be solved by philosophy is wishful thinking. There's not a single example in the history of science in the modern sense (which with about 400 years is however not that old yet) where philosophical considerations have solved any physical problem.

This is strawman attack. Philosophy is not rival to physics. Philosophy of science is concerned about physics solutions rather than physics problems.

The rest of the interpretation just reproduces the probabilistic statements of the (minimal) standard interpretation, and the minimal standard interpretation (also known as statistical interpretation) is just a flavor of Copenhagen where all the philosophical mumbo-jambo of some of its followers is stripped off bringing bare bones of physically observable facts into the focus, i.e., there is a theory that predicts the probabilistic outcomes of measurements in real-world labs very well, and that's it.

It is interesting that the author of Statistical interpretation clearly differentiates his interpretation from Copenhagen and describes it the way that can be viewed as generic HV interpretation (wavefunction is not a complete description of individual system).

 

[Lord Jestocost]

Copenhagen usually assumes the existence of reality...

Henry P. Stapp in “The Mindful Universe”:

“In the introduction to his book Quantum Theory and Reality the philosopher of science Mario Bunge (1967, p. 4) said:

The physicist of the latest generation is operationalist all right, but usually he does not know, and refuses to believe, that the original Copenhagen interpretation – which he thinks he supports – was squarely subjectivist, i.e., nonphysical.

Let there be no doubt about this point. The original form of quantum theory is subjective, in the sense that it is forthrightly about relationships among conscious human experiences, and it expressly recommends to scientists that they resist the temptation to try to understand the reality responsible for the correlations between our experiences that the theory correctly describes.”

The confusion arises when one begins to reason about “the experience of WHAT” - maybe, you can call the "WHAT" the "REALITY" in a metaphysical sense. Quantum theory is – so to speak - about that what’s in our head, the varying content of our consciousness. It has nothing to say about the WHAT. The WHAT is of inscrutable nature. And the tremendous fallacy to mistake the map – the content of our conscious – with the territory - the WHAT - leads to pseudo-questions at the heart of quantum theory.

 

[atyy]

Henry P. Stapp in “The Mindful Universe”:

“In the introduction to his book Quantum Theory and Reality the philosopher of science Mario Bunge (1967, p. 4) said:

The physicist of the latest generation is operationalist all right, but usually he does not know, and refuses to believe, that the original Copenhagen interpretation – which he thinks he supports – was squarely subjectivist, i.e., nonphysical.

Let there be no doubt about this point. The original form of quantum theory is subjective, in the sense that it is forthrightly about relationships among conscious human experiences, and it expressly recommends to scientists that they resist the temptation to try to understand the reality responsible for the correlations between our experiences that the theory correctly describes.”

The confusion arises when one begins to reason about “the experience of WHAT” - maybe, you can call the "WHAT" the "REALITY" in a metaphysical sense. Quantum theory is – so to speak - about that what’s in our head, the varying content of our consciousness. It has nothing to say about the WHAT. The WHAT is of inscrutable nature. And the tremendous fallacy to mistake the map – the content of our conscious – with the territory - the WHAT - leads to pseudo-questions at the heart of quantum theory.

As Bell said, presumably, you do not buy life insurance.

 

[vanhees71]

The cut is in all flavours of Copenhagen.
True, the cut is subjective.
True, the cut can be shifted, so anything can be moved from the classical side of the cut to the quantum side of the cut.

However, you cannot put the whole universe, including all observers on the quantum side of the cut, with nothing left on the classical side. People try to do so, but that requires an attempted solution to the measurement problem, eg. Many Worlds or Bohmian Mechanics.

Well, then you'd call the minimal interpretation not a Copenhagen flavor. Fine with with me, although I don't think that it is too much different from what's presented as "Copenhagen Interpretation" in standard textbooks. For me the minimal interpretation is mostly this "Copenhagen Interpretation" omitting the collapse (which is not needed and almost never realized in experiments, except it's necessary to take the effort to do so) and the classical-quantum cut, which is anyway not clearly defined as you agree about above. If you call to put a "classically" behaving macroscopic measurement device a "cut", it's just strange language, and that macroscopic measurement devices behave classically for me is rather explained by decoherence than by some fundamental quantum-classical cut.

 

[vanhees71]

This is strawman attack. Philosophy is not rival to physics. Philosophy of science is concerned about physics
solutions rather than physics problems.

My criticism against philosophy in QT is not that it doesn't solve any problems, but that they pretend that there are problems, where there are none and then confusing the subject by unclear definitions of prime notions like "reality". Thanks to philosophy (starting with the unfortunate EPR paper, which according to Einstein has not brought out his main concerns with QT which was more about inseparability due to entanglement, as he wrote in his Dialectica article of 1948 [*]) the word "reality" has almost lost its usability, because it is not clear anymore what exactly an author using it wants to say ;-)).

[*] A. Einstein, Quanten-Mechanik und Wirklichkeit, Dialectica 2, 320 (1948)
https://doi.org/10.1111/j.1746-8361.1948.tb00704.x

It is interesting that the author of Statistical interpretation clearly differentiates his interpretation from Copenhagen and describes it the way that can be viewed as generic HV interpretation (wavefunction is not a complete description of individual system).

Who is "the author"? Please try to cite clearly; if possible, I guess many in the forums appreciate also a link to a legal source of the paper.

 

[Demystifier]

My criticism against philosophy in QT is not that it doesn't solve any problems, but that they pretend that there are problems, where there are none

Scientific method can solve some problems, but scientific method, by itself, cannot determine what is a problem and what is not. Your criticism against philosophy in QT is a philosophy itself.

 

[Peter Morgan]

My criticism against philosophy in QT is not that it doesn't solve any problems, but that they pretend that there are problems, where there are none and then confusing the subject by unclear definitions of prime notions like "reality".

So, going back to your earlier comment,

The outcome is very clear: If there is a deterministic HV theory that could reproduce the probabilistic predictions of QT (which in fact were shown to be correct, and the Bell inequality is violated as predicted by QT!) it must be non-local, and it's obviously hard to produce non-local HV theories in accordance with Einstein causality.

do you consider that whatever nonlocality there is in QM/QFT is not a problem? Of course microcausality is satisfied, so there is not that kind of nonlocality, but still there is, say, Hegerfeldt nonlocality (for references relevant to that, please see https://www.facebook.com/max.derakshani/posts/10103068335632754?comment_id=10103069043593994 and the comments that follow). Personally, I agree that the modern focus of philosophers specifically on "reality", whatever that means beyond hammering the desk, is perhaps excessive — I prefer a rather heavier dose of empiricism and calibrated acceptance of current theories.

 

[Demystifier]

Maybe, there's a masochistic side in me

Many great physicists turn into philosophers later. Maybe you are getting old.

 

[vanhees71]

Scientific method can solve some problems, but scientific method, by itself, cannot determine what is a problem and what is not. Your criticism against philosophy in QT is a philosophy itself.

Well, in physics there are a lot of problems determined within physics itself and some are solved and some are unsolved. That there is a "measurement problem" in QT for me is disproven by evidence since experimentalists and theorists can very well design and analyze experiments using QT. If this is philosophy, that's fine with me ;-))).

 

[Demystifier]

Well, in physics there are a lot of problems determined within physics itself and some are solved and some are unsolved. That there is a "measurement problem" in QT for me is disproven by evidence since experimentalists and theorists can very well design and analyze experiments using QT. If this is philosophy, that's fine with me ;-))).

Define "physics itself". I think there is no such thing.

 

[RUTA]

I’ve been studying, researching, and teaching physics for nearly 40 years with one motive — to make ontological inferences and use those to create new theory. These motives are germane to foundations of physics, so I’ve been participating in that community for the past 24 years. Different physicists have different motives for putting in the hard work needed to do research in physics. Whether or not someone’s motives are “worthwhile” is purely a value judgment. If you’re not interested in foundations of physics, don’t participate in those discussions.

 

[vanhees71]

So, going back to your earlier comment,

do you consider that whatever nonlocality there is in QM/QFT is not a problem? Of course microcausality is satisfied, so there is not that kind of nonlocality, but still there is, say, Hegerfeldt nonlocality (for references relevant to that, please see https://www.facebook.com/max.derakshani/posts/10103068335632754?comment_id=10103069043593994 and the comments that follow). Personally, I agree that the modern focus of philosophers specifically on "reality", whatever that means beyond hammering the desk, is perhaps excessive — I prefer a rather heavier dose of empiricism and calibrated acceptance of current theories.

I couldn't sympathise more with poor Gross. It's hopeless to discuss with philosophers about the fact that local and microcausal relativistic QFT (as is applied with more success than wanted in the Standard Model) do not imply "spooky action at a distance", as claimed about QT in the EPR paper (which in fact Einstein was not quite satisfied with since he felt that his problems with QT are not well represented in this paper; his view becomes much clearer in his article in Dialectica 2, 320 (1948)). In fact, it's the collapse hypothesis of (some flavors of the) Copenhagen interpretation, which clearly contradicts the very construction of standard QFT and the meaning of the S matrix (see the first few chapters in Weinberg, QT of Fields, vol. 1, particularly the chapter on the linked-cluster theorem). Gross is of course referring to the state-of-the-art QFT of the 21st century and has as much problems with making sense of the EPR paper.

I've no clue what "Hegerfeldt nonlocality" is though. Do you have a reference (preferrable a physics one, where one has clear statements and a sufficient math density rather than some unclear philosophical gibberish) ;-)).

 

[vanhees71]

I’ve been studying, researching, and teaching physics for nearly 40 years with one motive — to make ontological inferences and use those to create new theory. These motives are germane to foundations of physics, so I’ve been participating in that community for the past 24 years. Different physicists have different motives for putting in the hard work needed to do research in physics. Whether or not someone’s motives are “worthwhile” is purely a value judgment. If you’re not interested in foundations of physics, don’t participate in those discussions.

I'm very interested in foundations of physics, but I don't think that philosophy helps to formulate the foundations clearly. To the contrary, philosophy tends to obscure clearly-defined notions (as "locality", "causality", etc) which have a very clear meaning and quantitative description in physics in terms of the most fundamental theories (relativistic local and microcausal QFT and GR).

 

[vanhees71]

Define "physics itself". I think there is no such thing.

Of course there are plenty of problems in physics completely unrelated to philosophy. If this was not the case there'd be no necessity for pure physics research anymore. Fortunately we are far from such a sad state!

Take as an example the discovery of quantum theory. There was a well-posed physics problem in the 19th century to find the spectral distribution of black-body radiation, whose solution lead to modern relativistic QFT (which is imho the first complete solution of the problem; Planck 1900 and Einstein 1917 being important steps towards this solution). This is a typical problem within the natural sciences with no philosophical pseudoproblem around: You simply didn't know the distribution of black-body radiation. Then it was measured with high accuracy at the PTR around 1900, and using the data Planck found the correct spectrum as an empirical formula. Then his problem was to derive it from theory, which was not possible using the then established classical electrodynamics, thermodynamics, and classical statistical physics. He found an ad-hoc explanation in terms of "energy quantization" (where energy is meant to be the exchange energy between the em. field and the cavity walls in Planck's idealized oscillator model). This left him (and also Einstein) quite unsatisfied. The next very important step was Einstein's kinetic-theory treatment of 1917, which lead to the discovery of spontaneous emission, which in fact we know today is not explainable other than by field quantization! This was finally the important notion for Dirac to come up with his annihilation-creation-operator formalism in 1927 (although Jordan had already quantized the em. field in the "Dreimännerarbeit" in 1926 before, but that was not noticed by the community; I've to read that paper carefully to figure out, to guess why).

Another example, which is more a theoretical problem, is the discovery of special relativity. The Maxwell theory of electromagnetism was more or less established at the end of the 19th century (mostly due to the creation and detection of electromagnetic waves by H. Hertz in 1887). There was, however, a theoretical problem, because the theory is not Galilei invariant. Of course, the common opinion at the time was the presence of a preferred frame of reference in terms of the restframe of the aether, but the attempts to empirically prove the latters existence failed. That's why many physicists and mathematicians like Fitzgerald, Lodge, Lorentz, Poincare, and finally Einstein were investigating this problem, which although purely theoretical is clearly a problem within physics as a natural science and not one of some philosophy.

 

[Peter Morgan]

I've no clue what "Hegerfeldt nonlocality" is though. Do you have a reference (preferrable a physics one, where one has clear statements and a sufficient math density rather than some unclear philosophical gibberish) ;-)).

From a few comments down the Facebook comment thread after the Facebook comment I mentioned above:

I'd offer either Hegerfedt's https://arxiv.org/abs/quant-ph/9809030 or his https://arxiv.org/abs/quant-ph/9806036, which link to the conference-published papers and which both cite what I think of as rather less clear papers from the 1970s and 1980s. These two papers include a helpfully more abstract presentation as a Theorem, with the conditions better stated.
My own take on this is that Hegerfeldt's nonlocality, by depending on analyticity deriving from a positive energy condition, is sui generis with the Reeh-Schlieder theorem, however it depends on much less mathematical structure than algebraic QFT, LQP, etc, so that even someone dismissive of the mathematics of algebraic QFT should have a hard time dismissing Hegerfeldt nonlocality.
However, as I say above [in the Facebook comment thread], we can face Hegerfeldt nonlocality with a reasonable degree of equanimity because it is compatible with Lorentz invariance. A further aspect, although this is not something that I would expect a QFTist to find compelling (but who knows?), is that boundary and initial conditions, which are by their very nature nonlocal, determine which (Lorentz invariant) propagator should be used in classical physics, with extensive consequences.

I should add that the philosopher I was engaging with there, Max Maaneli Derakhshani, has more-or-less refused to engage subsequently on the more careful, indeed more-or-less axiomatic, characterization of different kinds of locality. Hegerfeldt is essential reading, IMO, although if you know of something that more satisfyingly characterizes different kinds of nonlocality, I'll be very pleased to hear of it. Of course axiomatization is often disdained by physicists as "too much mathematics", which can be almost as much a smear as "too much philosophy". On the other hand, the best philosophy of QFT literature is almost indistinguishable from axiomatic QFT.

Probably I should add that Hegerfeldt is essentially a physicist.

 

[vanhees71]

The first cited paper investigates relativistic classical fields interpreting them in terms of first-quantized wave mechanics a la Schrödinger in the non-relativistic case. I don't think that in the year 2018 we still have to discuss why this doesn't work and why one has to employ relativistic quantum field theory to precisely cure this problem with apparent acausality. It's discussed in any textbook (see, e.g., Peskin-Schroeder).

 

[PeterDonis]

philosophy tends to obscure clearly-defined notions (as "locality", "causality", etc) which have a very clear meaning and quantitative description in physics in terms of the most fundamental theories (relativistic local and microcausal QFT and GR)

The way I read philosophers on this is that they are not so much questioning the precise quantitative descriptions as physics, as questioning whether they properly capture our intuitive sense of the ordinary language terms "locality", "causality", etc.

I agree with you that the latter quest is, in the end, a fool's errand, because if our ordinary language intuitions conflict with the precise quantitative physics that has been confirmed to umpteen decimal places by experiment, then what needs to change is our ordinary language intuitions, not the physics. But philosophers don't seem to like that very much, which is not surprising, since our ordinary language intuitions are the basis of their entire discipline.

 

[zonde]

Who is "the author"? Please try to cite clearly; if possible, I guess many in the forums appreciate also a link to a legal source of the paper.

Author is Ballentine. The book is Quantum Mechanics A Modern Development (1998). p47:
In classical mechanics the word “state” is used to refer to the coordinates and momenta of an individual system, and so early on it was supposed that the quantum state description would also refer to attributes of an individual system. ... However, such assumptions lead to contradictions (see Ch. 9), and must be abandoned.
The quantum state description may be taken to refer to an ensemble of similarly prepared systems. One of the earliest, and surely the most prominent advocate of the ensemble interpretation, was A. Einstein. His view is concisely expressed as follows [Einstein (1949), quoted here without the supporting argument]:
“The attempt to conceive the quantum-theoretical description as the complete description of the individual systems leads to unnatural theoretical interpretations, which become immediately unnecessary if one accepts the interpretation that the description refers to ensembles of systems and not to individual systems.”
and look at chapter 9.3. The Interpretation of a State Vector

 

[Peter Morgan]

The first cited paper investigates relativistic classical fields interpreting them in terms of first-quantized wave mechanics a la Schrödinger in the non-relativistic case. I don't think that in the year 2018 we still have to discuss why this doesn't work and why one has to employ relativistic quantum field theory to precisely cure this problem with apparent acausality. It's discussed in any textbook (see, e.g., Peskin-Schroeder).

One can't talk about relativistic quantum field theory "precisely", at least in 3+1-dimensions, except about free quantum fields, because interacting relativistic QFTs, again in 3+1-dimensions, only exist as asymptotic expansions, for which discussion is necessarily imprecise. In 1+1- or 2+1-dimensions, where there are models of the Wightman axioms, the Reeh-Schleider theorem is effectively the same as Hegerfeldt nonlocality.
To discuss free Wightman fields in 3+1-dimensions, one can consider as a simplest example the variance $\hat\phi_f^2$ of an observable $\hat\phi_f=\hat\phi_f^\dagger$ in the state $\frac{\langle 0|\hat\phi_g^\dagger\hat A\hat\phi_g|0\rangle}{\langle 0|\hat\phi_g^\dagger\hat\phi_g|0\rangle}$, that is, the expression $\frac{\langle 0|\hat\phi_g^\dagger\hat\phi_f^2\hat\phi_g|0\rangle}{(g,g)}=(f,f)+2\frac{(g,f)(f,g)}{(g,g)}$, where $(f,g)=\langle 0|\hat\phi_f^\dagger\hat\phi_g|0\rangle$ is a vacuum expectation value (which is enough to fix the Gaussian free field.)
This expression shows that the variance of the observable $\hat\phi_f$ is modified by the absolute value $|(f,g)|^2$ in the vector state $\hat\phi_g|0\rangle/\sqrt{(g,g)}$. Of course it is the case that measurements $\hat\phi_f$ and $\hat\phi_g$ commute if $f$ and $g$ are at space-like separation, but $|(f,g)|^2$ in general is non-zero. Another way to state this is that $[\hat\phi_f,\hat\phi_g|0\rangle\langle 0|\hat\phi_g]\not=0$ even if $f$ and $g$ are at space-like separation. This simple computation shows that the relationship of state preparation to measurement is different from the relationship between two measurements; it can be dismissed as about free fields, which can be said to be not physically relevant, and the Reeh-Schlieder theorem (which subsumes this simple computation) can be dismissed as about Wightman fields, which can also be said to be not physically relevant, however interacting QFT would agree that $[\hat\phi_f,\hat\phi_g|0\rangle\langle 0|\hat\phi_g]\not=0$ in general, so there seems to me to be a prima facie case for there being some value in identifying and characterizing different kinds of nonlocality, not only repeating "microcausality", powerful though that indubitably is.
Finally, you're right about the first Hegerfeldt paper I cited; in future I will cite only the second paper, which I think enough applies to the relativistic case as well as to the nonrelativistic case to be at least of historical interest to anyone who wishes to understand nonlocality/locality in QFT.