I Ontology is to quantum theory what hardware is to computation theory

[Morbert]

No, locality means that there are no faster-than-light signals. The nonrelativistic interactions are described by instantaneous (potential) forces and thus violate locality by assumption.

But what if your Hamiltonian has no such terms? E.g. In a standard EPR thought experiment, the dynamics are such that no action Bob performs on his particle can instantaneously affect any expectation values or response rates re/ Alice's particle. This state of affairs can be obtained even without Lorentz invariance.

 

[Fra]

I would say the issue is that lorentz invariance or any other observer equivalence) is not defined for the "set of all possible bare/naked/intrinsics views" (which represents the ontologies) but for the views where these are inferred. This ia how lack of the "observed symmetries" isnt a problem per see.

Before their inference rules and relations are defined, the set of all views is i think no metric space. Ie. The notion of neighbourhood around an agent is not defined.

i would expect it to be the task of any such theory/paradigm to explain how a lorentz invariant "layers" is defined or emergent from the underlying set. [i expect all this to start happen at some extreme temperature however where spacetime may not be defined aa 4d yet. ]

/Fredrik

 

[physika]

Yes, but the question is how to represent the real stuff (such as electron) with a mathematical object. If you represent it by a wave function, then you must have collapse (unless you accept many worlds), which leads to non-locality and Lorentz violation. If you say that it is not represented by a wave function, then you should say something about representing real stuff with another mathematical object. And yet people like @martinbn refuse to say anything concrete of this sort. For me they are non-realists at least in some weak sense, not by claiming that reality doesn't exist (which would be a strong non-realism), but by refusing to say something about the mathematical object that represents this real stuff.

.
how could it be described (or represented) if it is not even defined (not the value) i.e. "what is" the thing/object/entity, we do not know if it is a particle or a wave or an excitation of the field.
and by the way the representation by a mathematical object would be something else, not an ontological problem per se.
what mathematical object it will be, will be seen later.I will return later with the Lorentz Invariance.

.

 

[Demystifier]

how could it be described (or represented) if it is not even defined (not the value) i.e. "what is" the thing/object/entity, we do not know if it is a particle or a wave or an excitation of the field.

We don't know what it is, but we have some ideas what it might be. We can represent our ideas.

 

[gentzen]

Somehow in the debate with philosophers you have the problem that they don't understand that non-relativistic QM of course violates Lorentz invariance, simply because it's a non-relativistic theory.

Somehow "philosophers" seems to be used here as a "stand-in" for people eager to discuss QM without proper understanding of the underlying physics. In an actual discussion between some real philosopher and some real physicist, it is much harder to decide who is responsible for the debate going nowhere. See for example this discussion between Tim Maudlin (a philosopher) and Lev Vaidman (a physicist):

The debate starts at 36:20 and gets stopped at 44:33 (by a moderator). My link above starts at 39:00, where the debate gets hot. In this debate, Tim Maudlin defends more or less Demystifier's position, while Lev Vaidman defends an idea that I personally first learned about from A. Neumaier's book.

(*) Or maybe I do. The thermal interpretation by @A. Neumaier might be the only realistic interpretation in this sense, but AFAIK this interpretation is not published in any peer reviewed journal.

What exactly would be different, if he would publish it in a peer reviewed journal? It is an interpretation (mostly in the orthodox/Copenhagen spirit), so the reviewers certainly won't reject it for having its own set of issues. If he would try to publish it in a physics journal, then he would probably be forced to use less words, and focus more on what is different to other interpretations. Is it this what you are hoping for? If he would try to publish it in a philosophy journal, then his many words would probably be no problem at all. The only difference to the current state would then be that he could not continue to revise and enlarge his paper again and again (like he did with his latest paper). In this respect, I admit that his book was indeed very helpful for me, because it was a stable target that I could read from start to finish, and then be done with it. (In fact, I still hope that he will publish his second planned book at some point, so that I can read and enjoy it just like his first book, as a stable whole.)

Or is it more that as long as it is not published in a peer reviewed journal, it is not a stable target for reference or attack in peer reviewed papers?

 

[Fra]

"what is" the thing/object/entity, we do not know if it is a particle or a wave or an excitation of the field.

Or maybe neither of those?

Those terms all come with a classical tang.

It is tempting wheen seeking abstractions is to restrict oneself to the common "classical ontologies". You might as well ask, what "is" a field or particle anyway? We only think we know because of classical ideas where one implicitly adds the newtonian behaviour to the ontologies.

If you ask from the stance of inference, what is a "field", its not as clear anymore. Instead from that stance other things are more clear, that are simultaneously not clear in classical ontology.

I think each ontology comes with implicit assumptions on behaviour. Same goes for geometrical ontologies. Gaming ontologies. We can call it a "dice" or a "random walker".. the evolution of rhe dice or evolution of the geometry... different abstractions or ontologies but serving compatible purposes and thinking tools (a term demystifiers uses alot). I am not a fan of geometrical ontologies, i prefer those or gaming.

/Fredrik

 

[martinbn]

...
See for example this discussion between Tim Maudlin (a philosopher) and Lev Vaidman (a physicist):

The debate starts at 36:20 and gets stopped at 44:33 (by a moderator). My link above starts at 39:00, where the debate gets hot. In this debate, Tim Maudlin defends more or less Demystifier's position, while Lev Vaidman defends an idea that I personally first learned about from A. Neumaier's book.
...

I watched the ten mins you suggested and my impression is different. I agree it seems that Tim Maudlin defends the usual Bohm-Bell possition. Lev defends more or less standard QM possition. But the whole collapse of the debate seem to me to come from the fact that "be-able" is not precisely defined.

 

[WernerQH]

Or maybe neither of those?

Those terms all come with a classical tang.

It is tempting wheen seeking abstractions is to restrict oneself to the common "classical ontologies". You might as well ask, what "is" a field or particle anyway? We only think we know because of classical ideas where one implicitly adds the newtonian behaviour to the ontologies.

Exactly. Quite a few here on PF insist that the idea of wave-particle duality is outdated, and everything is fine when you talk about quantum objects and field excitations instead. But the duality is still there. When you want to emphasize continuity, you turn to "fields", when discreteness is essential, you say "excitations". Is the emission of radiation a continuous or a discontinuous process? The experimental evidence seems to be overwhelmingly clear, but some theorists (perhaps because of their love for differential equations) still insist on it being continuous because of Schrödinger's equation.

I am not a fan of geometrical ontologies, i prefer those or gaming.

My preferences are the exact opposite. But this should not distract from an interesting discussion.

 

[vanhees71]

Indeed, there's no duality but one consistent picture called quantum field theory. Of course, radiative processes are continuous. There are no "quantum jumps" in Q(F)T!

 

[WernerQH]

Indeed, there's no duality but one consistent picture called quantum field theory. Of course, radiative processes are continuous. There are no "quantum jumps" in Q(F)T!

I also detest quantum jumps, when they refer to e.g. collapsing wave functions. But how can you insist on talking about a series of detector clicks as something continuous?

 

[vanhees71]

It depends of course on the time resolution. If you resolve the "click" of, e.g., a Geiger counter with an oscilloscope you'll see that it's a continuous signal:

https://lcamtuf.coredump.cx/geiger/old/old/

 

[Morbert]

In an actual discussion between some real philosopher and some real physicist, it is much harder to decide who is responsible for the debate going nowhere. See for example this discussion between Tim Maudlin (a philosopher) and Lev Vaidman (a physicist):

It's Tim's fault. Always. His writings are frustrating to read. E.g. here he makes a comment about labels falling off boxes that shows he simply hasn't developed the intuition for these kinds of discussions at the level of public outreach he engages in.

 

[WernerQH]

It depends of course on the time resolution. If you resolve the "click" of, e.g., a Geiger counter with an oscilloscope you'll see that it's a continuous signal:

https://lcamtuf.coredump.cx/geiger/old/old/

So you dismiss the essential microscopic event causing the click of the Geiger counter?

Perhaps the rivers of ink which have been expended discussing the nature of the 'continuous' over the centuries, from Aristotle to Heidegger, have been wasted. Continuity is only a mathematical technique for approximating very finely grained things. The world is subtly discrete, not continuous. The good Lord has not drawn the world with continuous lines: with a light hand, he has sketched it in dots, like Seurat.

(Carlo Rovelli, emphasis added)

 

[physika]

Or maybe neither of those?

Those terms all come with a classical tang.

It is tempting wheen seeking abstractions is to restrict oneself to the common "classical ontologies". You might as well ask, what "is" a field or particle anyway? We only think we know because of classical ideas where one implicitly adds the newtonian behaviour to the ontologies.

If you ask from the stance of inference, what is a "field", its not as clear anymore. Instead from that stance other things are more clear, that are simultaneously not clear in classical ontology.

I think each ontology comes with implicit assumptions on behaviour. Same goes for geometrical ontologies. Gaming ontologies. We can call it a "dice" or a "random walker".. the evolution of rhe dice or evolution of the geometry... different abstractions or ontologies but serving compatible purposes and thinking tools (a term demystifiers uses alot). I am not a fan of geometrical ontologies, i prefer those or gaming.

/Fredrik

Obvious.

Yesterday I was going to edit, but it is something implicit, nobody wants to restrict themselves conceptually, I was going to put "X" or "Y" as the other option, because the "classical analogies" thing is already so hackneyed, nobody wants to waste time, endlessly on it (useless talk), excuses for others to write more.

 

[Demystifier]

What exactly would be different, if he would publish it in a peer reviewed journal?

If it was published, I would not have doubts whether I should include it on the list of "official" interpretations.

 

[Demystifier]

Of course, radiative processes are continuous.

Continuous but random. Is there an explicit equation in standard quantum theory which describes a continuous random process? (I saw such equations in stochastic theories, but they are not a part of standard quantum theory.)

 

[Fra]

My preferences are the exact opposite. But this should not distract from an interesting discussion.

The two stances can interestingly charactereized liek this...

in the geometrical/manifold ontology, the "information" guiding the random walker is I think naturally thought of as existing somehow objectively, independently of the random walker (delocalized over the whole manifold). (Unless there is a feedback, like in General relativity, but we can't handle that in QFT - which I think is a hint)

=> Here all random walkers, can be thought of as "walking" the same "objective" manifold module observer symmetry transformations. But we have trouble to understand, how a single random walker can LEARN about the whole manifold, just by walking without distoring the very same during the inference process? The idea is that the do NOT infer anything, they just exist and the manifold parameters and all information is fine tuned, without explanation. We can imagine a sort of closed explanation, which makes it in a certain sense "simple", but requires fine tuning. But this is why i do not like it, it has low explanatory value, it's more a "description".

in the dice/gaming ontology, the "information" guiding the player, is encoded in the dice, which is naturally thought of as beeing encoded and controlled locally along with the player itself. Ie. the dice is encoded locally, and presumably the result of an inference on it's own history of interactions. So the dice is ideally always "explained" in terms of inference. And the idea is naturally also in gaming that players are evolutionary selected, so only those with good dices survive. Those that doesn't are not banned, but not abundant.

=>The problem is to understand how the dices of a multiplayer game evolve, and does there spontanesouly appear nash type equilbirums? Can we make more progress here, without the same fine tuning? And does these have any physical significance? Theser are open questions (just like finding a fine tuning answer of previous type).

/Fredrik

 

[jbergman]

In interpretations of quantum mechanics there are two types of physicists: those who care about ontology and those who don't. The ontologists, or realists, want to know what is the world made of. The non-realists, on the other hand, think that this question is not relevant to physics.

Usually the two types of physicists don't understand each other. A realist can't understand how a physicist may not care about what is the physical world made of. A non-realist, on the other hand, can't understand how a serious scientist may care about the metaphysical notion of "reality" that does not have any practical consequences.

To help mutual understanding between the two types of physicists, I would like to propose an analogy, or at least a good metaphor. The two types of physicists are somewhat like the two types of computer scientists; those who care about hardware and those who don't.

Suppose that you ask how a computer program works. There are two kinds of explanation one can give to you. One explanation is something like - there is an electric current flowing through the microchip, which consists of many transistors, where each transistor is made of silicon in a pnp configuration, ... This explains how the computer works at the hardware level. The other explanation, on the other hand, will completely ignore the hardware and explain you the algorithm of the specific computer app; it explains how the computer program works at the software level.

The software guy will tell you that it is the computation algorithm that really explains how the program works, while the hardware implementation is not really important for understanding from the point of view of computation theory. The hardware guy will tell you that only understanding the hardware gives you the true understanding how the computer really works. The hardware guy gives you an ontological explanation, while the ontology is irrelevant to the software guy.

Of course, both the hardware guy and the software guy are right in some sense. And more importantly, there is no really any controversy about that, it's not that hardware guys and software guys don't understand each other. They only put more emphasis on different aspects of computation theory, which are complementary to each other.

Likewise, I believe, that two ways of thinking in quantum foundations are also complementary to each other. Realists and non-realists in quantum theory are analogous to hardware guys and software guys in computation theory. I believe that this way of thinking about realists and non-realists can help in better mutual understanding between them.

The problem with this analogy is there is always another layer. For instance, the hardware guy might not know the physics behind the components he uses.

Like Sean Carroll often says, at some point there are probably just brute facts that we have to accept as true until we have reason to believe there is something deeper.

 

[WernerQH]

guiding the random walker

You presuppose the (continuous!) existence of a "random walker" or "player". @vanhees71 assumes the continuous existence of electrons and photons ("field excitations") at least for some interval of time. But I consider only the creation and destruction events as real. The QFT formalism just describes the statistical correlations between these events.

 

[Fra]

You presuppose the (continuous!) existence of a "random walker" or "player". @vanhees71

Actually I do not.

But those discussions doesn't belong here I think. The above was a simplified view with those good points left out.

(In my own view, the continuum is an "approximatation", not the other way around, for this reason I even think standard probability theory is problematic, because the real number isn't justified, it is a valid embedding however. But I confusing the physical and mathemtatical complextions, is probably why we sit here today with so much divergences in our theories. The alternative to continum probability, would be combinatorics and permutations etc, but for complex systems that just gets unmanagable. Like Boltzmanns entropy, counting complexions)

/Fredrik

 

[Fra]

You presuppose the (continuous!) existence of a "random walker" or "player". @vanhees71 assumes the continuous existence of electrons and photons ("field excitations") at least for some interval of time. But I consider only the creation and destruction events as real. The QFT formalism just describes the statistical correlations between these events.

What is continous to one observer, may be discontinous to another one, and I see no problem with that. The wave collapse refers to the original observer, the decoherence does not. These two views does not have to match.

/Fredrik

 

[Fra]

The problem with this analogy is there is always another layer. For instance, the hardware guy might not know the physics behind the components he uses.

Like Sean Carroll often says, at some point there are probably just brute facts that we have to accept as true until we have reason to believe there is something deeper.

The version of this I subscribe to is that at some point, I (or genereally, the agent) are simply unable to formulate further questions, this is the layer where the turtles stop, which one can consider as an axiomatic status. The problem is thta this layer, will probably depend on the observer. Which is my each observer stops seeing turtles at different levels, which also seems to be the trouble when trying to form observer equivalence.

/Fredrik

 

[Structure seeker]

I'd like to come back to this point:

Wave functions are not observables. Their only meaning is to provide the probabilities (probability distributions) for the outcome of measurements via Born's rule.

I do not think you are in the position to determine what is and is not the meaning of the wave function. If it turns out from experiments that it also has another meaning, you'd have to accept it I suppose. And interference is due to the wavefunction, doesn't it have a meaning there as well?

I follow the consistent history interpretation, that wavefunction collapse is just entanglement with the macroscopic measurement device. That means your measurements of observables are merely wavefunctions entangled with a macroscopic object. Due to that entanglement, as far as I understand the interpretation, the Schrodinger equation squashes the wavefunction to a small point-like classical value of the quantum property. But the essence of what it is is still a wavefunction. In my definition of what is real, the entanglement in fact means that "the value of the measured observable" is not independent of the state of the measuring device so it is only real if you word it as "the value of the observable as measured by the measuring device" which then should be interpreted as "the wavefunction is [some formula] in the device and [the value] of the measured object" but then described as density matrix.

I thought that's also what quantum physics tells, that classical reality is dependent on the measurement setting, isn't that right?

But as I see it: quantum reality, the wavefunction, is not measurable without affecting it but all the more real.

 

[Simple question]

The debate starts at 36:20 and gets stopped at 44:33

Fantastic example of a debate between a hardware guy (Tim) and a software guy (Lev) !

The thing is even when beable are precisely defined, as computer-circuit and computer-users are, some software guy cannot care less. It would not be an issue if the software guy did not made grand (hand-wavy) claims about the result they claim which are factually incorrect.

But I think this thread is more about elucidating the importance of ontologies.
The software guy also has an ontology, and his own high-level beable (like quine) could even be fun as hell. So this is a result of some sort. But that ontology is not the claimed one anymore. It is computing "science", not computer science.

Again, when taken to task, by pinpointing that the result is not great or even blatantly false, then the software guy will say that it can also represent "hardware stuff", even "user stuff". And this is mostly true. But then when the hardware guy explain that this does not need a explaining, because it exists first, and actually retrofitting the hardware schematics into the software space just change the ontological level (37:40)

The problem with this analogy is there is always another layer. For instance, the hardware guy might not know the physics behind the components he uses.

Actually I think the analogy precisely address that issue.
Claims about ontologies, are not about "being first" (instead of derivative/emergent), or being "more grounded" (instead of philosophical). Those claims are precisely there to stop the infinite regress at a level where "reality" gets asserted.

Tim Maudling retry explaining it at 43:48, and the response is literally "you construct..."

No, you don't "construct". Nor does the hardware guy need to know about quantum fields. His hardware-ontology precisely define that its domain stop at some timing / frequency response/etc, even hardware-bugs!!! Gravity is useless to him, as well as QM. A bit a electronics and biology will do.

As usual, despite the facts observed in laboratory, that show that nature (yes that menial level of ontology) deal in non-local correlation, and probability conservation... this thread will inevitably turn into philosophical rambling about "fundamental randomness", and micro-causality.

Any discipline must be rooted in something, and science without some ontology is a chicken without head.

 

[A. Neumaier]

The thermal interpretation by @A. Neumaier might be the only realistic interpretation in this sense, but AFAIK this interpretation is not published in any peer reviewed journal.

Its published in a peer reviewed book!

 

[lightarrow]

The two types of physicists are somewhat like the two types of computer scientists; those who care about hardware and those who don't.

If, in QM, the "hardware" really existed, I would be realist

--
lightarrow

 

[Demystifier]

Its published in a peer reviewed book!

This link gives me a page in German with a password requirement, without any info about the book. Is there another link, like Amazon's?

 

[vanhees71]

I'd like to come back to this point:

I do not think you are in the position to determine what is and is not the meaning of the wave function. If it turns out from experiments that it also has another meaning, you'd have to accept it I suppose. And interference is due to the wavefunction, doesn't it have a meaning there as well?

In nearly 100 years no such other meaning ever materialized. That's the point of my argument. There were strong attempts to somehow circumvent the conclusion that Nature behaves irreducibly random from the very beginning of Born's probability interpretation, and all these attempts failed. The strongest argument against it was that what was vaguely defined in the infamous EPR paper and was much clarified by Einstein in his Dialectica article of 1948, but also this was refuted by the work of Bell and subsequently the experimental realization of the corresponding tests of Bell's inequality. Today it's very clear that Q(F)T is right and socalled local realistic theories are wrong. Together with the fact that relativistic local (=microcausal) QFT is, well, local "realism" must be refuted, i.e., these tests clearly show that the values of observables are not necessarily determined, if the system is not prepared in a state, where they are determined, and thus measurements on quantum systems have to be described by probabilities and statistics.

I follow the consistent history interpretation, that wavefunction collapse is just entanglement with the macroscopic measurement device. That means your measurements of observables are merely wavefunctions entangled with a macroscopic object. Due to that entanglement, as far as I understand the interpretation, the Schrodinger equation squashes the wavefunction to a small point-like classical value of the quantum property. But the essence of what it is is still a wavefunction. In my definition of what is real, the entanglement in fact means that "the value of the measured observable" is not independent of the state of the measuring device so it is only real if you word it as "the value of the observable as measured by the measuring device" which then should be interpreted as "the wavefunction is [some formula] in the device and [the value] of the measured object" but then described as density matrix.

This is all true (although I'd not talk about "the wave function" but about "the quantum state"). For all this I don't need any interpretation besides the minimal statistical one.

I thought that's also what quantum physics tells, that classical reality is dependent on the measurement setting, isn't that right?

"Classical reality" is an emergent phenomenon and originates from looking at coarse-grained collective observables, which tend to behave classical. If you look in more detail, you can also observe quantum phenomena on macroscopic objects. One of the most impressive observations is the observation of quantum fluctuations of the mirrors of the LIGO experiment, which are objects of mass in the 10kg range.

But as I see it: quantum reality, the wavefunction, is not measurable without affecting it but all the more real.

I don't know, what you mean by "quantum reality". The wave function itself is not measurable. You can only do statistics on ensembles and check the predictions for the probabilities of the outcome of these measurements.

 

[Lord Jestocost]

P. A. M. Dirac in “The Evolution of the Physicist’s Picture of Nature” (Scientific American Vol. 208, No. 5 (1963)):

“….. That is how quantum mechanics was discovered. It led to a drastic change in the physicist’s picture of the world, perhaps the biggest that has yet taken place. This change comes from our having to give up the deterministic picture we had always taken for granted. We are led to a theory that does not predict with certainty what is going to happen in the future but gives us information only about the probability of occurrence of various events. This giving up of determinacy has been a very controversial subject, and some people do not like it at all. Einstein in particular never liked it.”

 

[Demystifier]

In this debate, Tim Maudlin defends more or less Demystifier's position, while Lev Vaidman defends an idea that I personally first learned about from A. Neumaier's book.

In this video, it was not clear to me what position Lev defends, it looked like some vague heuristic standard textbook QM to me. It seems to me that he was trying to say: Tim, there is nothing wrong with your perspective, it makes perfect sense, but other people have different perspectives and their perspectives make perfect sense too.

In other discussions, Lev is quite eclectic about quantum interpretations: sometimes he defends standard QM, sometimes many worlds, sometimes Bohmian trajectories, and sometimes his weak values and the two-state interpretation.

 

[vanhees71]

In other words as many "interpreters" he confuses the subject rather than clarifying it. That's against the scientific goal of making "things as simple as possible, but not simpler".

 

[Fra]

P. A. M. Dirac in “The Evolution of the Physicist’s Picture of Nature” (Scientific American Vol. 208, No. 5 (1963)):

“….. That is how quantum mechanics was discovered. It led to a drastic change in the physicist’s picture of the world, perhaps the biggest that has yet taken place. This change comes from our having to give up the deterministic picture we had always taken for granted. We are led to a theory that does not predict with certainty what is going to happen in the future but gives us information only about the probability of occurrence of various events. This giving up of determinacy has been a very controversial subject, and some people do not like it at all. Einstein in particular never liked it.”

Unfortinately the revolution is not complete from the perspective of inference as we still have the exact same deterministic picture (newtonian paradigm); with

timeless statespace
timeless evolution rules (hamiltonian)

The difference is that we went from (q,p) to the quantum state.

But both "ontologies" are given, rather than explained/inferred.

So we still hang onto a deterministic picture of dynamical law. Here QM is not one bit more satisfactory than classical mechanics. Its just that its more annoying in QM, because I have much higher expectations on QM than I ever had on classical mechanics, so the fact that its half baked is annoying. The bigger part of the revolution is still ahead I am sure!

/Fredrik

 

[Demystifier]

In other words as many "interpreters" he confuses the subject rather than clarifying it. That's against the scientific goal of making "things as simple as possible, but not simpler".

In your opinion, did Einstein himself followed his rule of explaining "things as simple as possible, but not simpler"?

 

[vanhees71]

I think so. His papers are examples of clarity and masterful scientific prose.

 

[martinbn]

In this video, it was not clear to me what position Lev defends, it looked like some vague heuristic standard textbook QM to me. It seems to me that he was trying to say: Tim, there is nothing wrong with your perspective, it makes perfect sense, but other people have different perspectives and their perspectives make perfect sense too.

In other discussions, Lev is quite eclectic about quantum interpretations: sometimes he defends standard QM, sometimes many worlds, sometimes Bohmian trajectories, and sometimes his weak values and the two-state interpretation.

I haven't seen the whole debate, but my impression was that Lev didn't exactly know what Tim meant by a beable and was saying that you don't need it, all the information is already in the wave function.

 

[martinbn]

In your opinion, did Einstein himself followed his rule of explaining "things as simple as possible, but not simpler"?

Do you think otherwise? Any examples?

 

[Fra]

I sometimes wonder if Einsteins objections to QM is misinterpreted or have more components? The lack of determinism etc may be a bit simplistic, I guess where was more to it! Especially his quest for a unified field theory?

It's a pity we can't listen to Einstens view of the ideas of holography and dualities between theories of different topologies etc.

Even if SR and GR is not at all a theory of "measurements" - like QM, Einstens seems to make forceful use of thinking tools with gedanken observers, what was "inside the system". And then adding the idea of observer equivalence. And somehow, the construction of SR is the purest example of constructing a theory by enforcing observer equivalence (+ invariant sup speed limit)!! Then when he widened the class of "observer" there was quite a challenge to find the equivalence relations, but via some not as pretty turns he made something up.

But conicidently this is exactly the problem with QM, as alot centeres around the "problem of the observer", and this was as far as I understand, the key constructingprinciple of Relativity as well. But the gedanken observer in QFT, really isn't inside the system, they are at scattering distance. This is a headache, that I would presume Einstein - giving the central use of obserer equivalence and gedankend observers - that would bother him with QM. This way of seeing it, has little todo with "dice" issues, its something much harder to grasp.

/Fredrik

 

[Demystifier]

Do you think otherwise? Any examples?

Many of his papers are quite philosophical (EPR for instance), so I thought @vanhees71 might not think that these papers are very clear.

 

[Demystifier]

I haven't seen the whole debate, but my impression was that Lev didn't exactly know what Tim meant by a beable and was saying that you don't need it, all the information is already in the wave function.

Maybe Lev had a bad day. It looked as if he didn't even understood that a particle entangled with other particles does not have a wave function of the form $\psi(x,y,z)$.

 

[Structure seeker]

That's the point of my argument. There were strong attempts to somehow circumvent the conclusion that Nature behaves irreducibly random from the very beginning of Born's probability interpretation, and all these attempts failed.

Thanks for your reply. It seems to me you are from the perspective of classical reality wording what quantum physics tells, which is kind of logical from science history perspective. But I think with quantum physics we have a deeper level of understanding physics, so I try to look at classical "reality" (your definition of realism) to point out what about the underlying quantum physics (or reality, that is mostly the same to me) it hides. So the "reality" of measured observables are a foundation of classical physics, but in fact they don't give the entire truth (that is quantum physical).

That does not amount to hidden variables: those try to re-establish classical "reality" and determinism. It is instead about considering classical reality as just the only way quanta can be represented in the macro world, while in fact they are in the micro world wavefunctions or whatever QM tells, and governed by the (deterministic) Schrodinger equation. It's nice if for now all we know about it can be described in probabilistic terms.

 

[Demystifier]

I think so. His papers are examples of clarity and masterful scientific prose.

Would you say so also for the EPR paper?

 

[gentzen]

In other discussions, Lev is quite eclectic about quantum interpretations: sometimes he defends standard QM, sometimes many worlds, sometimes Bohmian trajectories, and sometimes his weak values and the two-state interpretation.

In other words as many "interpreters" he confuses the subject rather than clarifying it. That's against the scientific goal of making "things as simple as possible, but not simpler".

I have a very high opinion of Lev Vaidman, and I adore his courage to tell other MWI supporters when they are wrong or "cheat". I didn't hear of "his weak values and the two-state interpretation" before, and have not yet tried to look it up. From my point of view, Lev is certainly somebody who tries to clarify the subject. In the debate, Lev's behavior feels more appropriate than Tim's to me, but I don't know who is right.

I don't understand why vanhees71 is currently so eager to bash philosophers or Lev, or ... I thought of quoting one of the many nasty passages from René Thom/Paraboles et catastrophes (1980), in French ... ("Les remarques de René Thom ne sont pas de nature à lui faire beaucoup d'amis dans les milieux scientifiques.") But then I decided instead to quote from my reply to a very friendly email by S. Goldstein:

You might also be interested in "On the Role of Density Matrices in Bohmian Mechanics"

I will definitely read this one. Also because it is "just" 16 pages. I will be more careful with the two papers with >70 pages. I know from past experience with myself that I invariably fail to read such papers from start to finish, even if the topic really interests me. But hopefully I will already learn more by selective reading and merely browsing them.

The papers in question were

• Quantum Equilibrium and the Origin of Absolute Uncertainty, by D. Dürr, S. Goldstein and N. Zanghì, Journal of Statistical Physics 67, 843-907 (1992), quant-ph/0308039
• Quantum Equilibrium and the Role of Operators as Observables in Quantum Theory, by D. Dürr, S. Goldstein and N. Zanghì, Journal of Statistical Physics 116, 959-1055 (2004), quant-ph/0308038
• On the Role of Density Matrices in Bohmian Mechanics, by D. Dürr, S. Goldstein, R. Tumulka, and N. Zanghì, Foundations of Physics 35, 449-467 (2005), quant-ph/0311127

In the meantime, I did read those 16 pages, and also tried to read and browse the two papers with >70 pages. I enormously enjoyed the short paper (and learned a lot), but on reflection what I learned from the long papers, there was nothing. Really nothing! And that is why I could never have become a philosopher, because they need that ability to read overly wordy and long texts, and draw something substantial from them. And I guess vanhess71 has the same problem, but instead of admitting it, he prefers to bash philosophers.

 

[Demystifier]

I have a very high opinion of Lev Vaidman, and I adore his courage to tell other MWI supporters when they are wrong or "cheat".

Can you be more specific, what did he criticize about MWI?

 

[gentzen]

Can you be more specific, what did he criticize about MWI?

In section "IX. What might be the reasons for the MWI not being in a consensus?" of "Why the Many-Worlds Interpretation?" (https://arxiv.org/abs/2208.04618) he writes:

Negative publicity for the MWI comes from the controversial claims about advantages of the MWI relative to other interpretations, e.g., that the Born Rule can be derived instead of postulated [30]. The claim is natural, because it is not simple to postulate the Born Rule in the MWI, but I believe it is false. In any case, the difficulties of this program reflect negatively on the MWI.
Another source of negative publicity is the controversy generated by presenting MWI as a theory of the universal wave function on configuration space [27], obscuring the connection between ontology and our experience. Avoiding non-separability by moving to configuration space [31], is hardly helpful.
In my view, similar damage comes from an attempt to present MWI in the Heisenberg picture with a controversial claim of bringing separability into quantum mechanics [32]. ...

 

[Fra]

See for example this discussion between Tim Maudlin (a philosopher) and Lev Vaidman (a physicist):

The debate starts at 36:20 and gets stopped at 44:33 (by a moderator). My link above starts at 39:00, where the debate gets hot. In this debate, Tim Maudlin defends more or less Demystifier's position, while Lev Vaidman defends an idea that I personally first learned about from A. Neumaier's book.

Haha... not knowing their faces, just jumping into the video I thought the physicists was the philosopher, but then i googled them and found out it was the other way around as the physicists seems to be the one confused at first :-)

I seems the physicists questions the purpose of a beable (or ontology to connect to the OT). Like what do we need it for?

It seems to me the physicists stances is mainly to stay descriptive, and to just describe the observables (given the states spaces and hamiltonian) indeed the beable seems to serve no purpose. This is I think close to the traditional conservative paradigm. It's certainly not wrong, but it seems like a narrow view.

I think that the motivation for the "local beable"(or some "local ontology" in general not not restrict to bohmain mechanics) is that it potentially adds explanatory value such as explaining WHY the hamiltonian of a composite system is what it is. If you always have the paradigm where the dynamical evolution operator, and the initial conditions are given (put in by hand or whatever). Such "hidden explanation" seems superflous, and seems esotheric or "philosophical" only. But I think when one starts to think about the unificaiton of forces; which is essentially in part to understand how as very small (or energetic) particles interact, the phenomenology changes as you go into lower energy. So from low energy perspective one could say, that quarks is just esotheric stuff that makes no difference - at least until we get up in energy and our theory breaks down.

Is it "philosophical" to expect a smooth coherent theory instead of a pathwork of effective ones with lots of experimentally fitted parameters, or is it part of foundational physics?

/Fredrik

 

[vanhees71]

I have a very high opinion of Lev Vaidman, and I adore his courage to tell other MWI supporters when they are wrong or "cheat". I didn't hear of "his weak values and the two-state interpretation" before, and have not yet tried to look it up. From my point of view, Lev is certainly somebody who tries to clarify the subject. In the debate, Lev's behavior feels more appropriate than Tim's to me, but I don't know who is right.

I don't understand why vanhees71 is currently so eager to bash philosophers or Lev, or ... I thought of quoting one of the many nasty passages from René Thom/Paraboles et catastrophes (1980), in French ... ("Les remarques de René Thom ne sont pas de nature à lui faire beaucoup d'amis dans les milieux scientifiques.") But then I decided instead to quote from my reply to a very friendly email by S. Goldstein:

The papers in question were

In the meantime, I did read those 16 pages, and also tried to read and browse the two papers with >70 pages. I enormously enjoyed the short paper (and learned a lot), but on reflection what I learned from the long papers, there was nothing. Really nothing! And that is why I could never have become a philosopher, because they need that ability to read overly wordy and long texts, and draw something substantial from them. And I guess vanhess71 has the same problem, but instead of admitting it, he prefers to bash philosophers.

The problem is that they make many words with unprecise meaning. You can read as careful philosophical papers as you wish, you never know, what there words really mean. They also use the same words as physicists with a different meaning (e.g., "local" becomes a totally confused notion, while for physicists it simply states that space-like separated events within relativistic theories cannot be causally connected).

 

[Fra]

The problem is that they make many words with unprecise meaning. You can read as careful philosophical papers as you wish, you never know, what there words really mean.

I agree this is bad. But it is also bad when there is precise meaning, but which are rooted in axioms, that you never know how they are precisely related to reality. A balances seem required, and one shoule be aware of the balance.

Mathematicians can define things, physicists postultes often comes with a idealized correspondence to reality. But even pure mathematics often have a purpose beyond physics, it describes all things in nature, I find in particular the history of probability theory in reasoning interesting. Such writings almost "motivates" mathematical axioms of probability theory, which are ultimately a "arbitrary choice", but if you plan to use this to quantify rational reasoning for example, the postualtes need motivation just like postulates in physics, so one can't get away from the philosophy connection I think?

In our ambition to be very precise we assume the cow is spherical: Everyone is happy, even if we know its wrong. But at least we are precise! You can't have both.

/Fredrik

 

[Demystifier]

(e.g., "local" becomes a totally confused notion, while for physicists it simply states that space-like separated events within relativistic theories cannot be causally connected).

So Bell, who introduced a different notion of locality, is not a physicist?
And Anderson, who discovered Anderson localization in condensed matter, is not a physicist?

 

[vanhees71]

Bell didn't introduce a different notion of locality, as you can read in his famous paper where he introduced the Bell inequality for local realistic theories.

I don't know, what Anderson thought with regard to interpretational issues and whether he ever considered relativistic quantum field theory. As a condensed-matter physicist, I guess he usually dealt with non-relativistic QM and non-relativistic QFT, which a priori is a non-local theory.

 

[Demystifier]

I don't know, what Anderson thought with regard to interpretational issues and whether he ever considered relativistic quantum field theory. As a condensed-matter physicist, I guess he usually dealt with non-relativistic QM and non-relativistic QFT, which a priori is a non-local theory.

The point is that the effect bearing his name is called Anderson localization, which is a non-relativistic effect, showing that your statement about what "local" means for physicists is not universally valid. The l-word has different meanings in different physical contexts, whether you like it or not.