It’s hard to regard physics since Bohr as stagnant, when that same period gave us the standard model (and then string theory, which physicists do generally regard as a great advance, but not one that has yet become testable). Maybe the positivistic quantum theory of Bohr has to reach the era of gauge fields and branes, before the right postquantum ontology can be identified.
Some say string theory is even less testable than some of the more sophisticated proposals for many worlds, transactional interpretation, or some of the retrocausal interpretations, assuming some type of ‘spooky action at a distance’, etc., is inevitable. So it does not yet seem clear that it will prove to be an advance at all. Especially as delayed choice quantum ‘eraser’ experiments have been delivering quite interesting results in recent years that although not necessarily refuting Copenhagenists certainly introduce bizarre complications into their model. See https://physics.fullerton.edu/~hal/Delayed-15.pdf
There’s more to physics than the general quantum-mechanical framework. There is the specific ensemble of forces and particles that we find in nature, with all their various properties, including quantities like masses and couplings. The standard model tied most of that into a single equation, using the new concept of gauge fields (Yang-Mills); and string theory gives us a framework of possible worlds in which such quantities take definite values in each world, and it does so in a mathematically deep way. Those two steps each constitute enormous progress.
The “Copenhagen interpretation” is the one way that we know how to use quantum theory, that actually works; while the other interpretations are ontological ideas of varying degrees of vagueness, whose viability has to be tested against the best specific theory we have, and which are, so far, all lacking in some way.
I don’t think it was ever in question there’s more to physics than the ‘quantum-mechanical framework’? I am not quite sure what you are trying to get at with the first paragraph. Surely it should be clear by now with regards to advances in neutrino physics, etc., that the standard model is incomplete? It could very well be that some future advancement will make string theory redundant or require modifications, etc.
And in any case by no means are ‘gauge fields‘, ‘string theory’, etc., widely accepted as general relativity for example (which in itself has different camps of supporters on certain matters), or widely accepted to have constituted ‘enormous progress’, that is after all why there is even a serious audience for the first book.
In regards to your second paragraph, I will make my remarks clear, the delayed choice quantum ‘eraser’ experimental results have conclusively shown, at the very least, that the Copenhagen interpretation, and slight variants thereof, do not produce the most parsimonious results. Of course that does not constitue a refutation either as the equations ‘still work’, but they certainly have convinced and continue to convince serious people that there’s more to the story. And it’s the meaning we attach to those equations that allow for an integrative understanding, they may indeed be ‘ideas of varying degrees of vagueness’ but that includes all interpretations.
For example, the fact that the Schrodinger equation, in linear or nonlinear forms, ‘works’, does not automatically imply that the current theory, of anything involving the equation, is more privileged than some other theory. Unless experimental results decisively falsify said theories.
I am not quite sure what you are trying to get at with the first paragraph.
That physics has not stagnated.
by no means are ‘gauge fields‘ … widely accepted to have constituted ‘enormous progress’
This is a gap in your understanding. Unlike string theory, gauge fields are at the heart of empirical progress in modern particle physics. All the forces other than gravitation are described by gauge theory. (Maudlin has even proposed that the fiber bundles of gauge theory offer a new approach to metaphysics, an alternative to universals. I don’t know if the idea makes sense, but it’s creative and engaged with the facts.)
the delayed choice quantum ‘eraser’ experimental results have conclusively shown, at the very least, that the Copenhagen interpretation, and slight variants thereof, do not produce the most parsimonious results
The parsimonious approach to all quantum experimental results is the one which interprets them in terms of observable properties being described by Hilbert space operators, the quantum probability calculus, etc. Yes, if you want a theory that tells you what reality is, in a way that doesn’t refer to observation, you’ll need something else. You are welcome to develop the ideas of Bohm, Everett, Penrose, Cramer, etc. But none of those theories is presently good enough to replace quantum orthodoxy.
I don’t think any reader of LW believe physics in general has stagnated? With recent developments, well covered in mass media, in gravity waves, neutrinos, cosmology, etc., I don’t think there’s anyone with honest intentions in danger of genuinely believing no progress in physics has occurred at all.
Is there some hidden danger you’ve spotted?
On ‘gauge fields’ like I said the theory is nowhere nearly as widely supported as general relativity, which I use as the reference point for ’enormous progress’, among many examples. Considering that there are fringe people that reject even the ‘empirical contribution’ it should not be a surprise that the set of people that reject either the ‘theoretical or empirical contribution’, or some other aspect, is larger.
Your final sentence seems logically unrelated with the quote?
EDIT: I realized you may have thought what I wrote were not Maudlin’s thoughts but my own, therefore I will state that I personally don’t believe physics in general has stagnated. And I will edit the essay to make it clear.
Who are these people that reject gauge theory? I wonder if we’re talking about the same thing. If I look at the list of Nobel Prizes for physics, I see prizes for gauge theory awarded in 1979, 1984, 1999, and 2004, and probably we should count a few other years like 2008 and 2013 too. In a modern understanding, even plain old electromagnetism is a gauge theory.
In the final quote, aren’t you saying that we already have better theories (more parsimonious) than quantum mechanics under the Copenhagen interpretation? Because that’s what I’m disagreeing with.
Hmm I guess if you consider electromagnetism as part and parcel, i.e. as a general theory of fields then I would agree. Perhaps it can be considered to be nearly universally accepted if so, though in that case it seems less like a new theory and more like a refinement of existing theories. I had in mind, to what you were referring to, a more limited scope of gauge fields as they apply to the more controversial QM foundational work, though perhaps you would consider those as tenuous extensions and not gauge theory proper.
We have experiments that demonstrate something other than the CI has the most parsimonious explanation, for that experiment. That doesn’t automatically imply such theories are more parsimonious overall. But it does imply there is a possibility.
I’m still not sure if we understand each other regarding the gauge fields. Do you agree that gluons, and W and Z bosons, exist? They are described by Yang-Mills fields, i.e. a kind of gauge field. They are gauge fields with nonabelian symmetry groups, whereas a Maxwell field like the electromagnetic field is an abelian gauge field.
The explanation of nuclear forces in terms of gauge fields was certainly fundamental progress in physics. But it is not generally understood as a change in the interpretation of quantum mechanics, though it does present specific new challenges, e.g. a Bohmian gauge field would seem to require choosing a particular gauge as the ontologically correct one, in the same way that Bohmian quantum fields in general require a preferred reference frame; and in both cases this is somehow against the spirit of the symmetry in question (gauge symmetry, Lorentz symmetry).
I don’t agree that there are particular experiments where one of the ontological interpretations offers the most parsimonious explanation. In the link you gave, it’s claimed that the transactional interpretation offers a more economical explanation of the delayed choice eraser. I don’t see it. To begin with, there doesn’t seem to be any clear principle telling us how to analyze a given experiment in terms of advanced and retarded waves. It seems to be up to the interpreter to figure out a story about which waves go where. I also don’t really understand how the Born rule emerges in the transactional interpretation. (But perhaps there are principles behind both of these, and I just haven’t seen them.)
By contrast, an instrumental or phenomenal or positivist approach to quantum mechanics is quite straightforward, because empirically it just boils down to conditional probabilities connecting observed events. It’s also more flexible because it doesn’t even require wavefunctions; it’s just as valid for a different formalism, like Heisenberg’s operator algebras. The downside is that it’s not giving you an observer-independent ontology.
I didn’t just say Copenhagen interpretation, because in people’s minds, the Copenhagen interpretation is often loaded with hermeneutic ballast that I might not agree with. So all I’m saying, is that an interpretation of quantum mechanics, which focuses on observed properties and makes no ontological assertions about anything else, is the most parsimonious interpretation we have.
My view on transactional interpretation, many worlds, etc., is that they are interesting and suggestive, but they all still have deficiencies when it comes to accounting for the full range of applications of quantum mechanics.
After some reflection I would have to say that most of what you write is sensible stuff. Though the definitions are the tricky part, like most discussions of physics when they get down into the weeds.
It is clear that something akin to gluons, W, and Z bosons must exist for the most elegant explanation, otherwise ridiculous complications will need to be introduced to fit observed phenomenon. But there’s always the danger of falling into the trap of thinking of these ‘objects’ as discrete entities, which I am not entirely convinced of. And so I will refrain from using the word ‘exist’.
If you mean ‘exist’ by a discrete object with a unique position persisting across some span of space-time, I’m not entirely sure they do.
Fields, or something akin to fields, clearly do, and so do macro objects of course, but I’m not even entirely convinced that electrons ‘exist‘ in the same sense as the above. They may ‘exist’ in the sense that information ‘exists’.
There‘s also Feynman’s half-in-jest proposal of a one electron universe, which I think has a grain, or several grains, of truth. If that helps you better understand my position.
Hermeneutic ballast is an excellent term! It’s definitely a more concise way of describing its oddities.
Ontological assertions may be avoidable even if some combination of ’spooky action at a distance’, ‘hidden variables’, etc., proved to be the case, but I just don’t see how anyone could make the argument without sacrificing parsimony.
And it seems ever more likely for that to be the case in the reality we live in, given recent trends in cosmology and black hole physics.
It’s hard to regard physics since Bohr as stagnant, when that same period gave us the standard model (and then string theory, which physicists do generally regard as a great advance, but not one that has yet become testable). Maybe the positivistic quantum theory of Bohr has to reach the era of gauge fields and branes, before the right postquantum ontology can be identified.
Some say string theory is even less testable than some of the more sophisticated proposals for many worlds, transactional interpretation, or some of the retrocausal interpretations, assuming some type of ‘spooky action at a distance’, etc., is inevitable. So it does not yet seem clear that it will prove to be an advance at all. Especially as delayed choice quantum ‘eraser’ experiments have been delivering quite interesting results in recent years that although not necessarily refuting Copenhagenists certainly introduce bizarre complications into their model. See https://physics.fullerton.edu/~hal/Delayed-15.pdf
There’s more to physics than the general quantum-mechanical framework. There is the specific ensemble of forces and particles that we find in nature, with all their various properties, including quantities like masses and couplings. The standard model tied most of that into a single equation, using the new concept of gauge fields (Yang-Mills); and string theory gives us a framework of possible worlds in which such quantities take definite values in each world, and it does so in a mathematically deep way. Those two steps each constitute enormous progress.
The “Copenhagen interpretation” is the one way that we know how to use quantum theory, that actually works; while the other interpretations are ontological ideas of varying degrees of vagueness, whose viability has to be tested against the best specific theory we have, and which are, so far, all lacking in some way.
I don’t think it was ever in question there’s more to physics than the ‘quantum-mechanical framework’? I am not quite sure what you are trying to get at with the first paragraph. Surely it should be clear by now with regards to advances in neutrino physics, etc., that the standard model is incomplete? It could very well be that some future advancement will make string theory redundant or require modifications, etc.
And in any case by no means are ‘gauge fields‘, ‘string theory’, etc., widely accepted as general relativity for example (which in itself has different camps of supporters on certain matters), or widely accepted to have constituted ‘enormous progress’, that is after all why there is even a serious audience for the first book.
In regards to your second paragraph, I will make my remarks clear, the delayed choice quantum ‘eraser’ experimental results have conclusively shown, at the very least, that the Copenhagen interpretation, and slight variants thereof, do not produce the most parsimonious results. Of course that does not constitue a refutation either as the equations ‘still work’, but they certainly have convinced and continue to convince serious people that there’s more to the story. And it’s the meaning we attach to those equations that allow for an integrative understanding, they may indeed be ‘ideas of varying degrees of vagueness’ but that includes all interpretations.
For example, the fact that the Schrodinger equation, in linear or nonlinear forms, ‘works’, does not automatically imply that the current theory, of anything involving the equation, is more privileged than some other theory. Unless experimental results decisively falsify said theories.
That physics has not stagnated.
This is a gap in your understanding. Unlike string theory, gauge fields are at the heart of empirical progress in modern particle physics. All the forces other than gravitation are described by gauge theory. (Maudlin has even proposed that the fiber bundles of gauge theory offer a new approach to metaphysics, an alternative to universals. I don’t know if the idea makes sense, but it’s creative and engaged with the facts.)
The parsimonious approach to all quantum experimental results is the one which interprets them in terms of observable properties being described by Hilbert space operators, the quantum probability calculus, etc. Yes, if you want a theory that tells you what reality is, in a way that doesn’t refer to observation, you’ll need something else. You are welcome to develop the ideas of Bohm, Everett, Penrose, Cramer, etc. But none of those theories is presently good enough to replace quantum orthodoxy.
I don’t think any reader of LW believe physics in general has stagnated? With recent developments, well covered in mass media, in gravity waves, neutrinos, cosmology, etc., I don’t think there’s anyone with honest intentions in danger of genuinely believing no progress in physics has occurred at all.
Is there some hidden danger you’ve spotted?
On ‘gauge fields’ like I said the theory is nowhere nearly as widely supported as general relativity, which I use as the reference point for ’enormous progress’, among many examples. Considering that there are fringe people that reject even the ‘empirical contribution’ it should not be a surprise that the set of people that reject either the ‘theoretical or empirical contribution’, or some other aspect, is larger.
Your final sentence seems logically unrelated with the quote?
EDIT: I realized you may have thought what I wrote were not Maudlin’s thoughts but my own, therefore I will state that I personally don’t believe physics in general has stagnated. And I will edit the essay to make it clear.
Who are these people that reject gauge theory? I wonder if we’re talking about the same thing. If I look at the list of Nobel Prizes for physics, I see prizes for gauge theory awarded in 1979, 1984, 1999, and 2004, and probably we should count a few other years like 2008 and 2013 too. In a modern understanding, even plain old electromagnetism is a gauge theory.
In the final quote, aren’t you saying that we already have better theories (more parsimonious) than quantum mechanics under the Copenhagen interpretation? Because that’s what I’m disagreeing with.
Hmm I guess if you consider electromagnetism as part and parcel, i.e. as a general theory of fields then I would agree. Perhaps it can be considered to be nearly universally accepted if so, though in that case it seems less like a new theory and more like a refinement of existing theories. I had in mind, to what you were referring to, a more limited scope of gauge fields as they apply to the more controversial QM foundational work, though perhaps you would consider those as tenuous extensions and not gauge theory proper.
We have experiments that demonstrate something other than the CI has the most parsimonious explanation, for that experiment. That doesn’t automatically imply such theories are more parsimonious overall. But it does imply there is a possibility.
I’m still not sure if we understand each other regarding the gauge fields. Do you agree that gluons, and W and Z bosons, exist? They are described by Yang-Mills fields, i.e. a kind of gauge field. They are gauge fields with nonabelian symmetry groups, whereas a Maxwell field like the electromagnetic field is an abelian gauge field.
The explanation of nuclear forces in terms of gauge fields was certainly fundamental progress in physics. But it is not generally understood as a change in the interpretation of quantum mechanics, though it does present specific new challenges, e.g. a Bohmian gauge field would seem to require choosing a particular gauge as the ontologically correct one, in the same way that Bohmian quantum fields in general require a preferred reference frame; and in both cases this is somehow against the spirit of the symmetry in question (gauge symmetry, Lorentz symmetry).
I don’t agree that there are particular experiments where one of the ontological interpretations offers the most parsimonious explanation. In the link you gave, it’s claimed that the transactional interpretation offers a more economical explanation of the delayed choice eraser. I don’t see it. To begin with, there doesn’t seem to be any clear principle telling us how to analyze a given experiment in terms of advanced and retarded waves. It seems to be up to the interpreter to figure out a story about which waves go where. I also don’t really understand how the Born rule emerges in the transactional interpretation. (But perhaps there are principles behind both of these, and I just haven’t seen them.)
By contrast, an instrumental or phenomenal or positivist approach to quantum mechanics is quite straightforward, because empirically it just boils down to conditional probabilities connecting observed events. It’s also more flexible because it doesn’t even require wavefunctions; it’s just as valid for a different formalism, like Heisenberg’s operator algebras. The downside is that it’s not giving you an observer-independent ontology.
I didn’t just say Copenhagen interpretation, because in people’s minds, the Copenhagen interpretation is often loaded with hermeneutic ballast that I might not agree with. So all I’m saying, is that an interpretation of quantum mechanics, which focuses on observed properties and makes no ontological assertions about anything else, is the most parsimonious interpretation we have.
My view on transactional interpretation, many worlds, etc., is that they are interesting and suggestive, but they all still have deficiencies when it comes to accounting for the full range of applications of quantum mechanics.
Sorry for the late reply,
After some reflection I would have to say that most of what you write is sensible stuff. Though the definitions are the tricky part, like most discussions of physics when they get down into the weeds.
It is clear that something akin to gluons, W, and Z bosons must exist for the most elegant explanation, otherwise ridiculous complications will need to be introduced to fit observed phenomenon. But there’s always the danger of falling into the trap of thinking of these ‘objects’ as discrete entities, which I am not entirely convinced of. And so I will refrain from using the word ‘exist’.
If you mean ‘exist’ by a discrete object with a unique position persisting across some span of space-time, I’m not entirely sure they do.
Fields, or something akin to fields, clearly do, and so do macro objects of course, but I’m not even entirely convinced that electrons ‘exist‘ in the same sense as the above. They may ‘exist’ in the sense that information ‘exists’.
There‘s also Feynman’s half-in-jest proposal of a one electron universe, which I think has a grain, or several grains, of truth. If that helps you better understand my position.
Hermeneutic ballast is an excellent term! It’s definitely a more concise way of describing its oddities.
Ontological assertions may be avoidable even if some combination of ’spooky action at a distance’, ‘hidden variables’, etc., proved to be the case, but I just don’t see how anyone could make the argument without sacrificing parsimony.
And it seems ever more likely for that to be the case in the reality we live in, given recent trends in cosmology and black hole physics.