Thank you, Richard, for this opportunity to hear Professor Sheldon Goldstein speak on Bohemian Mechanics & Qutantum. The John Bell Institute looks beautiful off the coast of Croatia. Although I am not a physist, I love listening to amazing minds. In fact, I have listened to this one for hours. 🙏❤️🌍🌿🕊🎵🎶
This was a lovely exploration of beautiful (if still a bit messy) ideas and definitely helped bring me to a new level of appreciation for the origins of Bell's breakthrough. It is also very useful, if also a bit sad, to better understand the "sociological" factors acting like a pilot wave in the background of all our lives. Thank you!
It seems the ontological construct of non locality using a geometric dynamism is a kind of a mirror of true regarding the realization of the physical constants limits to higher dimensions. It is portraited so discrete and elegantly into this discussion.
Loved this one Robinson! Pins sure is a 🐈, but importantly a podcat ! I was , ashamedly, one of the many who judged Bohm solely on the negative vibes given off about him by smart people, who possibly never seriously studied him. . This conversation was a study in showing how we dismiss or conspiratorially “ignore”, in Oppenheimer’s words, someone’s concepts ,on spurious ill informed grounds. Loved Profs explanations and delivery. Thanks from Geeseling Bernardo!
@1:15:00 you should've asked what does he mean by that? (not being clear what "relativistic" means) because to me it is clear. It means absent GR effects, you want a theory to have Lorentz invariance. Simple. Too simple? I think not, fwiw. With gravity you want general covariance. If you do not have Lorentz invariance in the flat space limit, you don't have a rival to orthodox relativistic QFT, hence not a true alternative to orthodox QM.
It is refreshing to see a discussion on Bohmian mechanics for once and not just many-worlds haha, thank you. The Philosophical Survey 2020, indicates: Accept or lean towards collapse: 17.09% (14.75%) Accept or lean towards hidden-variables: 21.94% (18.71%) Accept or lean towards many-worlds: 19.42% (17.09%) Accept or lean towards epistemic: 12.77% (11.33%) Accept an alternative view: 3.78% The question is too unclear to answer: 1.8% There is no fact of the matter: 1.8% Agnostic/Undecided: 24.28% Other: 0.36% N = 556, excluding skipped & insufficiently familiar (558 respondents) Therefore, the hidden-variables view (which will mostly consist of Bohmian mechanics) is thinly the most popular view within philosophical circles, according to this survey.
I think that for many years now Bohmian/ Pilot wave is the most popular among the philosophers ( although there are many fans of MW and GRW also). But among Physicists, the Standard textbook ( Copenhagen -related ) interpretations are still the most popular.
I think what this shows is that most QM interpretations are a result of some sort of philosophical prejudice and/or intuition, and not much more. Philosophers love Bohmian mechanics, physicists hate it.
How is it a "theorem" of Bohmian mechanics that you can't "know" more about the position and momentum of a particle than the wave function tells you? If, as Goldstein says, a good physical theory shouldn't have axioms about such things as "knowledge" or "measurement," and if Bohmian mechanics is a good physical theory, then how does one derive limitations on knowledge from Bohmian mechanics?
I haven't looked at the whole video yet, but he is probably referring to the concept of contextuality. In the Bohmian picture, momentum is contextual and you cannot determine the pre-measurement value of momentum because the measurement itself has an effect on the momentum. This is not the case for position in the Bohmian view. But as I said I haven't seen that part yet of the interview, but that is my guess at this stage. (Edit) : Ok no, Sheldon was talking about uncertainty contained within the initial conditions of a system. My first comment therefore does not apply.
This is easy to answer. Any means of acquiring information about a system requires a physical interaction that reliably conveys that information. The interaction must be such that the interaction between the target system and the probe system takes any of the possible states of the target producted with the probe in its initial state to macroscopically different final states of the probe that are reliably correlated with the initial state of the target. Whether-and to what extent-that can happen depends on the dynamics of the target/probe interaction. Note that the terms "knowledge" and "measurement" do not appear in anything I just wrote. But it should at least be clear that the question posed above can be investigated using the precise form of the possible interactions between the target and the probe. What the theorem shows is that if those interactions are governed by Bohmian mechanics-Schrödinger's equation for the wavefunction and the guidance equation for the particles-there are limitations to the information that can be conveyed by any physical interaction. You might be easily able to see how the unitary nature of Schrödinger evolution can put constraints on this, just as it forms the basis of the standard no-cloning theorem.
@@timmaudlin6997 I don't think you explained anything, actually just begged the question. You didn't say why, or how do those constraints arise, or what's the intuition behind them. You simply repeated a "it can be shown" statement. But that is what Goldstein said already, and what snowpants and others like me are asking about. Besides, if it is a feature particular to Bohmian mechanics and not the usual QM, then it cannot rely *only* on the unitary nature of Schrödinger evolution, otherwise ordinary QM would be just as "respectable". Even if I grant you that you actually give an answer to the question, by Goldstein's statement Bohmian mechanics would be a "bad" physical theory, for as you claim it does put "limitations to the information that can be conveyed by any physical interaction". The information conveyed by interactions is what we mean by knowledge from measurements! Just using synonyms or euphemisms to avoid the "bad" words doesn't do the trick.
Agreed. The point is that since Louis deBroglie’s 1924 work in conjunction with David Bohm’s 1952 work we now have far greater insight than we ever have. DeBroglie and Bohm is at the very heart of Bells theorem without which the quantum information revolution would be quite impossible. It was really deBroglie and Bohm who got the ball rolling on modern quantum information. And no you sure as fuck won’t learn this in high school
@schmetterling4477 If you read Bell you’ll find him talking over and over and over again regarding how deBroglie and Bohm gave him the motivation to formulate his theorem. And we all know that Bell theorem is the heart of quantum information. Evidently we all should take up “religion” if it leads to such a gold mine of further results
And what i mean is this, bell applies to all notions of locality, subliminal and superluminal, but testing that subluminal interactions cannot be responsible is easy, just do any space like separated bell test, but if you want to rule out superluminal interactions now you have a problem, because you can only get a deviation from the result for individual definitions of simultaneity for individual experiments. That is a fact, i wrote a longer explanation, but this is a short clarification. That means that locality is still on the table, but it absolutely has to be invomving faster than light physics to reproduce the results.
What i mean in more detail about the non commuting observables is that when you get an outcome on one side, you change the prediction on the other side, meaning simply something like going from getting annoitcome on particle A of a bellpair in a direction for spin, and then knowing that and not havingnmeasured the other particle, the probability distrobution as a function of the wavefunction plus extra intital conditions is not the same for B, deoending of whether A was measured or not, and if it was measured, that would be essential revealing information about the initial conditions of B but also the initial conditions of the wavefunction, or to have the wavefunction change in accordance with the result on A, such that the expected distribution over initial condition for B that results frlm the wavefunction are different, which gives you the correlations that apear in bells inequality for example. It simply means that after the result on A you change the wavefunction and the initial conditons for B that you know of, the total initial conditions for the whole wavefunction plus particle picture in a case like this implies the spesific interaction, because of the initial conditons on A and B, and so the hidden variables are fine, the change in the wavefunction is fine because it would be a direct consequence of the initial conditons, but the only way you would see the change in the object guiding B would be to have a gods eye view or measure it along the way, which would change it if you didnt already know the initial condition so i hope that is somewhat clear. I am nlt saying anything that contradicts the full complications of the theory, what i am saying is that there is a change there that can be said to be an interaction, and there is some freedom in how to implement that, so it doesn't have to be instantaneous, but can be superluminal instwad potentially. The key takeaway is that the initial conditons plus wavefunction for a and b contains the entire story with three possible versions, either a first b first or ab at the same time, the third can't be explained as a dynamical process, only a jump so to speak, but for the two other cases its plausible the account for it with a completely local interaction. It will be determined by the initial conditions in all 3 cases anyway, its just a question of how, the properties of the wavefunction must be there in some form anyway, but it doesn't need to be in the same form necessarily, it doesnt even have to have the same epistemic limits exactly, but so far i have found versions that are such that constraints on the probabilities with some type of weak measurements, aka probing the initial conditions more precisely than quantum mechanics allows is plausible but with very unforgiving limitations, so the problem in these kinds of theories is building macroscopic structures that can pick up and systematically account for noise and probe the initial conditons that can get yoi better information tham the uncertainty relations say you should get is questionable in practice but not fundamentally, that is to say, it is because you can only build stuff out of atoms that you can't find the state more precisely than the quantum state, whether it is possible to get beyond that in practice is not entirely clear.
What i meant was not that they are really non commuting, only that they are when they are considered to be in a quantum mechanical description. For example having measured A the wavefunction for B changes before B is measured in a bell pair, of you had a sort of gods eye view. I think in some cases you can because of the previously mentioned arguments about locality, have a concrete interaction that means one observable outcome simply means the other one has to have its distribution of outcomes changed. And i dont think its incoherent to say the wavefunction is a function in space, part of it is, part of it is in momentum space and so on and so forth. For whatever variable you could have a detector with a sort of "location" or " sensitivity " or whatever and in some quantum phase space the wavefunction simoly leads to an expectation for measuring a certain observable depending on the setup, nothing mysterious, but for simple position measurments it is a function over space so when talking about examples where that is essential what matters and you are measuring position at the end of the day, then yeah the effect of the wavefunction with or without interference between sources is just a probability distribution over time andnspace for a position measurement. After doing the math to find the born rule probability, the magnitude only has meaning at detectors but its still fine talking about the probability distortion of outcomes in position space while waving of the hands is going on. That you don't even have to know quantum mechanics to know, you just habe tl know what a position measurment outcome is, on some screen or whatever it is.
But what if we flip a coin and it lands on it's side just on one atom that is about to decay (or not). Depending on the decay the coin would fall to the left or the right ? We cannot predict that decay ? So we cannot determine on what side that particular coin lands ?
The point being, if there is an interaction, such that measurkng A changes B, that can still be contained in the wavefunction plus initial conditons at the outset, but in what way the interaction actually functions in practice leaves some room for different theories, with different predictions, for example when it comes to breakinf lorentz symmetry or not, quantum mechanics gives you the version where it is not broken naturally, because the "influence" or correlation, or interaction is already encoded in the wavefunction plus initial conditions andnthe ordering of a or b doesn't matter, but for the lorentz symmetry breaking version is different but isn't well probed. As i explained bellow in mynfirst two comments
So for bohemian mechanics, you have some bell pair, and the wavefunction changes either instantaneously when the first is measured, or just at some speed much faster than light, andnwe haven't tested that, and we can't test thw differences, other thannin one exact way, which is to refute the instantaneous version, which means discovering that the instantaneous version gives the wrong result for some simultaneous measurment according to some definition of simultaneity. That is the correct state of knowledge and what can be done and not done to improve our understanding of the situation. We have not, and cannot fully rule out some form of superluminal locality, and that is a theorem. What we can do is that if some superluminal locality is real we can refute the instantaneous version. There is no mistake, i promise you, and if you doubt it, i will provide a technical argument with maths and fancy fonts and all, but the argument is quite simple and cannot really be denied if understood. I promise you that it really is a theorem.
Instantaneous nearfield electromagnetic fields are real and have been demonstrated both theoretically using Maxwell equations and experimentally. We present a paper below that shows that information in these fields propagate instantaneously. See links below for more information. This phenomena can also be explained using using the Pilot Wave interpretation quantum mechanics and the Heisenberg uncertainty principle (HUP). In this interpretation HUP is: Δx Δp = h, where Δx and Δp correspond to average values. So in HUP: Δx Δp = h, where Δp=mΔv, thus HUP becomes: Δx Δv = h/m, where m is an effective mass due to momentum. In the nearfield, where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. But according to the Copenhagen interpretation, the above argument does not make sense, since Δv corresponds to uncertainties in their values. In addition to the Pilot Wave interpretation, only the Ensemble Interpretation of Quantum Mechanics also interprets the Heisenberg uncertainty principle (HUP) in terms of averages. But the Ensemble Interpretation does not support instantaneous propagation of information, whereas Pilot Wave theory does. Therefore, other than Pilot Wave theory, no other interpretation of Quantum Mechanics supports instantaneous propagation of information as demonstrated in our experiment, and interprets the Heisenberg uncertainty principle in terms of averages. It should be noted that this argument can be used to argue that all fields should be instantaneous in the nearfield and speed c in the farfield, including the graviton, and this can explain the non-locality observed in quantum entanglement. *Electromagnetic pulse experiment paper showing information propagates instantaneously: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1 *TH-cam presentation of above arguments: th-cam.com/video/sePdJ7vSQvQ/w-d-xo.html *More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145 Dr. William Walker - PhD Physics, ETH Zurich, 1997
Any interactions at the speed of causality -- the speed of light or slower -- are local. Anything significantly faster than C would be unmeasurable and therefore non-local.
The result of a quantum calculation is a probability distribution over some observables, because the mathematical machinery is obtuse and difficult to get physical intuition from, people say a bunch of incoherent sentences and then they calculate some more expectations for whatever it is they end up with in some experiment. As you said the non locality is built into the wavefunction without any obvious tell, outside the results, i doubt that people would call it non local if we didn't do any experiments, because it is when you make some measurment or preform some unitary operation on some bunch of stuff that you find out that it gives predictions that are non local in a certain sense, it is not until you consider tje different possible reductions from measurement, or equivalently the trajectories in bohm that you find out that there are non local properties, precisely because the wavefunction prior to any reductions is transparently just a function that evolves it contains non local information but who cares, i only care that the predictions contain correlations that are only possible when there is some classical interaction that makes it so, or when you have reductions when actually measuring or interacting with something.
And so its notnso much about bell that the destinction between subliminal and superluminal is important, bells theorem applies in the same way for all speeds, but the way relativity works and foliations work in the context of some feature of reality breaking lorentz symmetry, that is why the difference is there and what i wrote is actually an explanation of a theorem.
Prediction for what happens next are a probability distribution, or a spesific outcome, i don't know what it would even mean to say something else. The mathematics that gives you the right probability distrobution in a certain situation is more complicated than that bu the final prediction can't be, its not possible logically. Interference doesn't happen at the level of the prediction, whether there is or not shows up there but the prediction is just some ordinarily function for some observable that is evolving with time of the wavefunction and or additional variables.
With so few Standard Model particles, I just never understood why empty space couldn't provide the wavefunction -- the pilot wave -- for each and every particle? How is one to separate the multiple waves (and gravity!) from space in the first place? There is one, and only one, empty space. Every particle responds to the virtual particles in empty space (ie, the quantum foam) differently. Every particle "sees" empty space differently. But it is the same empty space. There will never be a filter small enough to separate the electron field (pilot wave) from the anti charm quark field (pilot wave) in empty space.
The terms "realism" and "anti-realism" are so misleading. In general, in philosophy, "realism" means "belief that an objective reality independent of the observer exists," which nothing in quantum mechanics even is relevant to this question. In the specifics, "realism" tends to mean "belief that this specific thing has ontological reality." For example, if you are realist _about_ something it means you believe it is an _entity._ A wave function function realist is someone who believes the wave function is a real _object_ in the natural world. A moral realist is someone who believes morality is something objectively part of the natural world. The ironic thing is that if you apply this understanding of realism, then it was Einstein who was the nonrealist. It's unclear to me how the term "realism" even came into physics, my best guess it it's borrowed from the "criterion for reality" in the EPR paper, but anyone who reads that paper knows that it was not a "criterion for whether or not reality exists," but a "criterion for whether or not a theory is a complete description of reality." In other words, it was a criterion for completeness, not for realism. My problem with this abuse of the term "realism" by physicists is that by using the word so bizarrely, they aren't consistent with it. They might use "realism" in reference to completeness in one paper, but then flip-flop and use it in the philosophical sense in another. It's how you end up with academic papers claiming somehow Bell's theorem proves objective reality doesn't exist. PhD physicists lost in quantum woo due to word games! I tend to agree with Maudlin that we should probably should just drop the term "realism" when talking physics. It has no place in the discussion.
34:55 "Non locality is here to stay": The basic problem for Bohmian mechanics, though, is that it's not "weakly" non local, as the interpretations of unmodified QM are, but "strongly" non local, breaking Lorentz invariance, requiring absolute reference frames, like the old (obsolete) days of Larmor et al (the pre-relativistic days of ether and the like...). So, no QFT, no General Relativity for Bohmians...
If you think you can write down a clear and exact theory that violates Bell's Inequality and does not break Lorentz Invariance, give it a try. The standard theory-which uses collapse of the wavefunction but does not exactly specify how it happens in a Relativistic setting-cannot. And putting in a preferred foliation does not conflict with a curved Lorentzian manifold or GR explanations or anything in QFT. Obviously, adding a foliation cannot eliminate any explanatory power. If you don't need the foliation for some purpose, then just ignore it for that purpose. A curved Lorentian manifold with a foliation is not a classical space-time.
@@timmaudlin6997 One can choose arbitrarily a foliation, there's no problem with that. But if you need a preferred foliation for fundamental reasons, it's a different story. You cannot explain kinematically the usual relativistic effects ( time dilation, length contraction) for example, you need some contrived "mechanism" that mimics/ reproduces these effects with dynamics... You need new physics! Fitzgerald, Lorentz et al tried to do that before Einstein but failed. There's no causal order between space-like separated events in Relativity and a boosted observer could see a different temporal order between such events, depending on which direction she moves etc. Lorentz invariance is basic for all modern physics. It's not written in stone of course, but all the evidence so far indicates that it's a characteristic of our world. And it's the basis for both GR and QFTs, so I respectfully disagree with the point of view that " it doesn't matter if the relativistic axiom that the laws of physics are the same in every reference frame has to be abandoned". From the Bohmian perspective it's crucial to introduce preferred foliations. Objective collapse theories have similar issues, but their proponents are trying to make their models compatible with Relativity, they're not willing to just accept it, perhaps because they are more concerned with the implications of their theories- that are testable , so they have some things to worry about - for the rest of the Physics. But from other points of view ( that consider the observables as more fundamental) the quantum mechanical non locality is "mild", because the "collapse of the Wavefunction" is not an objective effect, it's relative ( so if Alice thinks that her measurement "collapses" the Wavefunction in an EPR setting, Bob thinks the same for his ...). There's no FTL communication of any kind between them, nobody collapses "first," the Wavefunction, because there's no definite temporal order. The issue about non locality is arguably subtle and interesting. Most probably suggests that there are some things that aren't known yet... Ψ-ontic theories that modify the mathematical structure (like Bohm / Pilot wave or physical collapse/GRW ) are respected nowadays. Personally I'm a bit sceptical about them( and MWI also, for different reasons...). It seems to me that thinking the State Vector as "The" ( or " one of The.." in the case of Bohm) fundamental element of reality is like a "Category Error"... Isn't it a Vector in an abstract mathematical space after all? It *describes* the physical world, yes, it gives is the amplitudes/ the probabilities via the Born Rule, but there are other options for realism in physics : After all, we don't observe the Wavefunction, so interactions/ observables ( a kind of Structural Realism) is preferable (?). But I digress...
No, that's just not right, for the reasons I gave. Just because you may use the foliation for some fundamental purposes, you need not mention it for all purposes. If there is an effect that doesn't depend on it-that can be accounted for just using the curved Lorentzian metric-then simple don't refer to it. It is not possible to *lose* explanatory power by *adding* a foliation, because you are free to ignore it when you don't need it. When do you need it? In the standard non-relativistic theory you need it for two purposes. One is just to define what counts as a "configuration" of a system (as Shelly says) because the wavefunction is presented as a complex function on configuration space. So you need configurations to get off the ground, and you need a foliation to define configurations. Second, in the standard theory you have instantaneous collapses of the wavefunction, and you need a foliation to define "instantaneous". IN the pilot wave theory, you have no collapses, but you use the foliation to write down the guiding equation. So the situation with pilot wave and the standard theory is exactly the same. And nothing changes in that respect going to field theory. Collapse is not "relative" in the standard theory: it is a fundamental part of the objective dynamics of the wavefunction (see von Neumann) and is required exactly because the wavefunction is supposed to be complete. If the practical inability to send signals is enough to make a theory Relativistic, then pilot wave theory is already Relativsitic. And if you assert that Relativity requires more than no signaling (which is correct), then you have no argument that the standard theory is Relativistic.@@dimitrispapadimitriou5622
@@timmaudlin6997 Either the laws of physics are the same in all foliations ( choosing "nice" space-like hypersurfaces ) or they are not! We can't have double criteria especially in fundamental physics. Otherwise the theory is not "Realist" in the first place... because the chosen foliation is crucial for the consistency of the theory! Moreover, that "preferred foliation" needs a physical reasoning. It's similar like saying that in GR only a specific coordinate system gives consistent physics! Contrary to the most basic premise of the theory! I understand that this is perhaps the main disagreement about Bohmian mechanics. The other issues ( the difficulties with QFT for example) have their roots in this.
Please read what I wrote. There is nothing wrong with having some equations (say the analog of Schrödinger's equation) that use only a Lorentzian metric and others (say the guidance equation or collapse equation) that use the foliation. That can be completely realist. Further, as I said, the standard approach uses collapses. So try to write down the theory precisely without a foliation. Good luck. My own view is that Relativity is probably emergent from a deeper geometrical structure, but just adding a foliation to a Relativistic metric is both consistent and realist. You add it because you need it, not least to account for violations of Bell's Inequality. Everyone has to do that because it is an observed physical fact.@@dimitrispapadimitriou5622
Bell proved that epr is kind of wrong, but only in the sense that independent non interacting pre-existing elements of reality is not enough. Bells theorem meams you can test whether you need a faster than light interaction to account for entanglement in a classical way. The definition of locality beyond sub light physics is ambigous if you don't have a foliation, but it is absolutely not true that the bell tests we have done so far has ruled out finite but superluminal interactions accounting for the difference between what epr said and what reality demands. You can prove that there is no way to absolutley prove that there is no deviation from the results in some foliation where you do a simultaneous bell test at space like separation. That is to say, the notion that bell tests are lorentz symmetric has not been shown, and connot be fully proven by experiment. And if shelly wants i can prove it to him in a simple and rigours way, i am 100% sure it is mathematically rigours to say so. In fact it is just a simple extension of bells argument to arbitrary velocities, the statement that the space like seperated bell test is not lorentz invariant is one result you can get in exactly the same way an ordinary bell test is done, but to probe all possible time coordinates is not feasible, so the notion of superluminal but not instantaneous locality can only be constrained in a sertain spesific sense, or with a positive result be proven by finding out that simultaneous measurments given some cone of definitions of simultaneity infact do not give the same results and don't violate the inequality or violates it less and less towards the center of the cone, which in that case would serve as a measurment of absolute local simultaneity. What bell proves is that given the inequality being broken, any local description without interactions between the two sides is impossible, and if you do the experiment with any space like separation you like you rule out that this interaction is subluminal in character, and this is already proven, not published formally, but i will bet you the lives of every member of my family because it is quite a simple proof. It is easy for me to imagine a bunch of reasons why people wouldn't not believe it, but it is true and rather easy to prove actually. The first kind of reason is to say "well superluminal physics breaks causality" and that is just wrong. The second kind "well bells theorem has nothing to do with the speed of light" which is also wrong. The first one i don't want to gratify with an answer because people who think that are just confused about something they never really checked. The second one is easy, but understandable, and its wrong because if the interaction in question can not be there or be there, which os the premise of the result motivating experiments in the first place, that is to say if the inequality holds then no interaction is needed to make everything local independently of spacetime interval, if the inequality is broken you have some non local change depending of what happens on the other end, this is indeed independent of the speed the interaction needs. But testing it for subluminal physics just requires one test and it is done, whole for superluminal interactions you need to check each possible definition of simultaneity, because if some subset of definitions are different with respect to the outcome of the result then if is not lorentz symmetric and the universality of frames of reference has nothing to do with anything, so each time coordinate must be checked individually. If you want a technical paper and proof i can produce it for you, but i hope shelly gets the idea, maybe you can forward it to him if you would be so kind, and he doesn't read comments :).
It is of course problematic to talk in loose terms about these things without a shared language, but i hope you get what i mean. The simple things yoj can say about quantum mechanics can be misconstrued in a lot of ways and people are very good at understanding how to misconstrue. Anyway, i enjoyed the pod, i like shelly, he is stubborn and doesn't take half way answers for granted, which is nice, because the first rule of fight club is to never talk yourself into unsupported conclusions.
@1:02:00 he's misleading. You absolutely do *_not_* expect the function describing phase space to be non-local. He got a bit mad hatter there. What you "expect" instead is that Nature aught not allow smooth transitions between pure states (determined eigenvalues). Classical mechanics is such a class of theory. Quantum mechanics is not, QM allows smooth transitions, and simply by "state preparation" (filters and mixers and whatnot) which is highly counter-intuitive. The more modern approaches are not to _interpret_ QM but to _reconstruct_ QM from generalized probability models. QM is amazingly the unique GPM theory that has reversible *_and_* continuous transitions between pure states. In CM the allowed transitions are only reversible, not smooth, which is what gives Kolmogorov probabilities for classical systems. So if you find a "real" ontology that has that class of GPM then chances are good you've got a "correct" physics, at some level of description anyway.
What if the universe is actually non-deterministic, and non-local? What if you cannot predict the future evolution of "things" because a little tiny fluctuation in the initial conditions makes all the difference? What if chaos theory is correct?
Ignore schmett he's a troll. Anyways, chaos theory is still deterministic in the Laplacian sense, which is what most people mean when they talk about determinism. Yes, in practice it is impossible to predict a chaotic system, but in principle its final state is still absolutely determined by its initial state without any other possible outcome. What you're proposing is a nonlocal but deterministic theory where the apparent randomness is due to something chaotic, which there are definitely models like that in the literature. There's a few that treat the very act of measurement as a chaotic process that randomizes some sort of internal state of a system. These models have to effectively be nonlocal because they have to violate the PBR theorem's assumption of preparation independence, which is basically identical to rejecting locality.
The speed of light is not a constant speed as once thought, and this has now been proved by Electrodynamic theory and by Experiments done by many independent researchers. The results clearly show that light propagates instantaneously when it is created by a source, and reduces to approximately the speed of light in the farfield, about one wavelength from the source, and never becomes equal to exactly c. This corresponds the phase speed, group speed, and information speed. Any theory assuming the speed of light is a constant, such as Special Relativity and General Relativity are wrong, and it has implications to Quantum theories as well. So this fact about the speed of light affects all of Modern Physics. Often it is stated that Relativity has been verified by so many experiments, how can it be wrong. Well no experiment can prove a theory, and can only provide evidence that a theory is correct. But one experiment can absolutely disprove a theory, and the new speed of light experiments proving the speed of light is not a constant is such a proof. So what does it mean? Well a derivation of Relativity using instantaneous nearfield light yields Galilean Relativity. This can easily seen by inserting c=infinity into the Lorentz Transform, yielding the GalileanTransform, where time is the same in all inertial frames. So a moving object observed with instantaneous nearfield light will yield no Relativistic effects, whereas by changing the frequency of the light such that farfield light is used will observe Relativistic effects. But since time and space are real and independent of the frequency of light used to measure its effects, then one must conclude the effects of Relativity are just an optical illusion. Since General Relativity is based on Special Relativity, then it has the same problem. A better theory of Gravity is Gravitoelectromagnetism which assumes gravity can be mathematically described by 4 Maxwell equations, similar to to those of electromagnetic theory. It is well known that General Relativity reduces to Gravitoelectromagnetism for weak fields, which is all that we observe. Using this theory, analysis of an oscillating mass yields a wave equation set equal to a source term. Analysis of this equation shows that the phase speed, group speed, and information speed are instantaneous in the nearfield and reduce to the speed of light in the farfield. This theory then accounts for all the observed gravitational effects including instantaneous nearfield and the speed of light farfield. The main difference is that this theory is a field theory, and not a geometrical theory like General Relativity. Because it is a field theory, Gravity can be then be quantized as the Graviton. Lastly it should be mentioned that this research shows that the Pilot Wave interpretation of Quantum Mechanics can no longer be criticized for requiring instantaneous interaction of the pilot wave, thereby violating Relativity. It should also be noted that nearfield electromagnetic fields can be explained by quantum mechanics using the Pilot Wave interpretation of quantum mechanics and the Heisenberg uncertainty principle (HUP), where Δx and Δp are interpreted as averages, and not the uncertainty in the values as in other interpretations of quantum mechanics. So in HUP: Δx Δp = h, where Δp=mΔv, and m is an effective mass due to momentum, thus HUP becomes: Δx Δv = h/m. In the nearfield where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. Consequently the Pilot wave interpretation should become the preferred interpretation of Quantum Mechanics. It should also be noted that this argument can be applied to all fields, including the graviton. Hence all fields should exhibit instantaneous nearfield and speed c farfield behavior, and this can explain the non-local effects observed in quantum entangled particles. *TH-cam presentation of above arguments: th-cam.com/video/sePdJ7vSQvQ/w-d-xo.html *More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145 *Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1 Dr. William Walker - PhD in physics from ETH Zurich, 1997
These are not fundamentally non commuting quantities, no that is not what i mean, i just means that in a certain sense they should be seen as not beign independent events. What people usually say is that quantum mechanics is local because spacelike separated events are commuting and there is no interaction between them, which is just teutological bs in my opinion, i just think they habe no clue what a wavefunction is and how the non locality works, and how it is related to other kinds of respesentation. Not saying they don't understand what a tensor product is or what a wavefunction is, i just think nobody really understands them properly, i think you and bell and people that are ready ti admit that they contain non local information are closer to the truth, but i basically just think the non locality is analogous to distrobutions of various different possible interactions that go faster than light or instantaneous, that can in principle describe any non local property that consists of a dependence of one distribution of outcomes on another, which is all we get to consider anyway, we are never going to measure and not measure things at the same time, or make spaghetti out of air, actually that last one is essentially the only way we make spaghetti, but i digress :').
The “many worlds theory” is wonderful if you’re expanding the Marvel Comic book storylines, or countless other sci-fi plot devices. Otherwise it is the literal definition of a theory that can never actually be “tested” by any understanding of test and measurement. If The Copenhagen paradigm is Atheistic, The “multiverse” is Metaphorical Magical incantation; it surely fits Dr. Strange but not so much Dr. Albert Einstein.
@@rv706 I have. MWI was never mentioned. If, however, you took an undergrad level class and you did pay attention and you did happen to read Everett's thesis, then you would have noticed that his second sentence is already wrong and that his argument never recovers from that error. ;-)
@@rv706 Doesn't even matter. You only need to understand the very basics of quantum mechanics in order to grasp these philosophical questions. A lot of it revolves around Bell's theorem, for example, which is trivial, especially the simplified version in the form of the CHSH theorem can be explained to a middle-schooler. People who pretend like you need a PhD in quantum mechanics to have some understanding of these philosophical problems are usually just quantum woo mystics trying to distract from people questioning their mysticism. The majority of a PhD is on more specific applications of quantum mechanics. Take, for example, the orbits of an electron, which is a specific derivation from quantum mechanics, yet is entirely irrelevant to the more broad philosophical and you do not need to know it. The philosophical questions only require an introductory level understanding of quantum information science, which by its very nature abstracts out most of the specifics you learn in a PhD course and you can get an idea of from reading a single book on the subject and experimenting with the mathematics in things like IBM's cloud quantum computer, allowing even regular people to get hands-on experience with these things. You would only actually need a PhD if you're trying to modify the theory, as that of course would require a very deep level of understanding of its specifics.
There are so many people working in this ugly and unnatural interpretation of QM. The need to cling to a basically classical picture of the world is strong...
The worst problem with Bohmian/ pilot wave theories is that they are not compatible with special relativity. They need an absolute reference frame for their theory to make sense, so a simple kinematic explanation ( as in SR) of the usual well confirmed effects like time dilation/ length contraction has to be replaced by contrived Larmor - style mechanisms , reminiscent of the old Ether days... It's not a big surprise that they have serious problems with the generalisation to relativistic QFT.
You should grow up and do something for yourselves. The worst problem with the arguments you are makingnis that you habe no idea what it means. And so the uglyness is a consequence of your ignorance not rigour. Get gud
You know what the equations of motions in an absolute frame of reference is that reproduces the same dynamics? Its the same equations. There is no destinction, you habe just confused about representation theory and that is that, if you knew what you were talking about then you would say something about the motivation for taking an absolute simultaneity innterms of changing the physics, not the convention, but you will learn eventually 🍻™️
again the same mistake in the intro as u make on all these QM episodes. When u say QM must be non-local, then u are assuming statistical independence. Please educate yourself about this so u stop making this embarassing mistake every time. It's getting really annoying
@@dimitrispapadimitriou5622u must be a regular viewer of this channel. But no. Check out Sabine's physics channel here on youtube for an easy to understand explanation of why u can't assume statistical independence
@@rv706" superdeterminism", aka: " we don't like what experiments reveal about the Physical world, so we try to find desperately some loophole, no matter how implausible or contrived it is"...
@@rv706 the 2 proposed ways to get reality from the results of the bell equalities experiments are either with non-locality or with superdeterminism. Being satisfied with non-locality by ignoring the other possibility is not good science.
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This is one of the best interviews I have ever seen on QM. I love his approach to the subject. Very no-nonsense.
Thank you, Richard, for this opportunity to hear Professor Sheldon Goldstein speak on Bohemian Mechanics & Qutantum.
The John Bell Institute looks beautiful off the coast of Croatia.
Although I am not a physist, I love listening to amazing minds. In fact, I have listened to this one for hours. 🙏❤️🌍🌿🕊🎵🎶
Top notch guests all around, very cool!
This was a lovely exploration of beautiful (if still a bit messy) ideas and definitely helped bring me to a new level of appreciation for the origins of Bell's breakthrough. It is also very useful, if also a bit sad, to better understand the "sociological" factors acting like a pilot wave in the background of all our lives. Thank you!
It seems the ontological construct of non locality using a geometric dynamism is a kind of a mirror of true regarding the realization of the physical constants limits to higher dimensions. It is portraited so discrete and elegantly into this discussion.
Loved this one Robinson! Pins sure is a 🐈, but importantly a podcat ! I was , ashamedly, one of the many who judged Bohm solely on the negative vibes given off about him by smart people, who possibly never seriously studied him. . This conversation was a study in showing how we dismiss or conspiratorially “ignore”, in Oppenheimer’s words, someone’s concepts ,on spurious ill informed grounds. Loved Profs explanations and delivery. Thanks from Geeseling Bernardo!
@1:15:00 you should've asked what does he mean by that? (not being clear what "relativistic" means) because to me it is clear. It means absent GR effects, you want a theory to have Lorentz invariance. Simple. Too simple? I think not, fwiw. With gravity you want general covariance. If you do not have Lorentz invariance in the flat space limit, you don't have a rival to orthodox relativistic QFT, hence not a true alternative to orthodox QM.
It is refreshing to see a discussion on Bohmian mechanics for once and not just many-worlds haha, thank you.
The Philosophical Survey 2020, indicates:
Accept or lean towards collapse: 17.09% (14.75%)
Accept or lean towards hidden-variables: 21.94% (18.71%)
Accept or lean towards many-worlds: 19.42% (17.09%)
Accept or lean towards epistemic: 12.77% (11.33%)
Accept an alternative view: 3.78%
The question is too unclear to answer: 1.8%
There is no fact of the matter: 1.8%
Agnostic/Undecided: 24.28%
Other: 0.36%
N = 556, excluding skipped & insufficiently familiar (558 respondents)
Therefore, the hidden-variables view (which will mostly consist of Bohmian mechanics) is thinly the most popular view within philosophical circles, according to this survey.
I think that for many years now Bohmian/ Pilot wave is the most popular among the philosophers ( although there are many fans of MW and GRW also).
But among Physicists, the Standard textbook ( Copenhagen -related ) interpretations are still the most popular.
Oxfors mafia using name recognition.
I think what this shows is that most QM interpretations are a result of some sort of philosophical prejudice and/or intuition, and not much more. Philosophers love Bohmian mechanics, physicists hate it.
@@Al-ji4gd Bohmian mechanics has this issue with Lorentz Invariance.
@@dimitrispapadimitriou5622 Yeah, I know it has issues, most interpretations do. Just making an observation.
"All the romantic ideas concerning quantum mechanics." The absolutely best line
How is it a "theorem" of Bohmian mechanics that you can't "know" more about the position and momentum of a particle than the wave function tells you? If, as Goldstein says, a good physical theory shouldn't have axioms about such things as "knowledge" or "measurement," and if Bohmian mechanics is a good physical theory, then how does one derive limitations on knowledge from Bohmian mechanics?
I thought exactly the same. Not sure what is his answer
I haven't looked at the whole video yet, but he is probably referring to the concept of contextuality. In the Bohmian picture, momentum is contextual and you cannot determine the pre-measurement value of momentum because the measurement itself has an effect on the momentum. This is not the case for position in the Bohmian view. But as I said I haven't seen that part yet of the interview, but that is my guess at this stage.
(Edit) : Ok no, Sheldon was talking about uncertainty contained within the initial conditions of a system. My first comment therefore does not apply.
Mhmmm
This is easy to answer. Any means of acquiring information about a system requires a physical interaction that reliably conveys that information. The interaction must be such that the interaction between the target system and the probe system takes any of the possible states of the target producted with the probe in its initial state to macroscopically different final states of the probe that are reliably correlated with the initial state of the target. Whether-and to what extent-that can happen depends on the dynamics of the target/probe interaction. Note that the terms "knowledge" and "measurement" do not appear in anything I just wrote. But it should at least be clear that the question posed above can be investigated using the precise form of the possible interactions between the target and the probe. What the theorem shows is that if those interactions are governed by Bohmian mechanics-Schrödinger's equation for the wavefunction and the guidance equation for the particles-there are limitations to the information that can be conveyed by any physical interaction. You might be easily able to see how the unitary nature of Schrödinger evolution can put constraints on this, just as it forms the basis of the standard no-cloning theorem.
@@timmaudlin6997 I don't think you explained anything, actually just begged the question. You didn't say why, or how do those constraints arise, or what's the intuition behind them. You simply repeated a "it can be shown" statement. But that is what Goldstein said already, and what snowpants and others like me are asking about. Besides, if it is a feature particular to Bohmian mechanics and not the usual QM, then it cannot rely *only* on the unitary nature of Schrödinger evolution, otherwise ordinary QM would be just as "respectable".
Even if I grant you that you actually give an answer to the question, by Goldstein's statement Bohmian mechanics would be a "bad" physical theory, for as you claim it does put "limitations to the information that can be conveyed by any physical interaction". The information conveyed by interactions is what we mean by knowledge from measurements! Just using synonyms or euphemisms to avoid the "bad" words doesn't do the trick.
the central question of "why anything" is where attention must be drawn to establish a fundamental framework to work from
Refreshingly honest admissions of what we don’t know.
We have known how this really works since 1927, kid. You are almost 100 years late confessing that you weren't paying attention in high school. ;-)
Agreed. The point is that since Louis deBroglie’s 1924 work in conjunction with David Bohm’s 1952 work we now have far greater insight than we ever have. DeBroglie and Bohm is at the very heart of Bells theorem without which the quantum information revolution would be quite impossible. It was really deBroglie and Bohm who got the ball rolling on modern quantum information. And no you sure as fuck won’t learn this in high school
@@equivariance You were so close and then you picked religious nonsense. ;-)
@schmetterling4477 If you read Bell you’ll find him talking over and over and over again regarding how deBroglie and Bohm gave him the motivation to formulate his theorem. And we all know that Bell theorem is the heart of quantum information. Evidently we all should take up “religion” if it leads to such a gold mine of further results
@@equivariance In your next life? Are you waiting to be reborn in the multiverse? ;-)
Fabulous guest, thanks!
My thesis was on Bohemian mechanics and the Pilot Wave model.
Good man. But did you ever get to meet Goldstein in person? He is an absolute delight to speak with
And what i mean is this, bell applies to all notions of locality, subliminal and superluminal, but testing that subluminal interactions cannot be responsible is easy, just do any space like separated bell test, but if you want to rule out superluminal interactions now you have a problem, because you can only get a deviation from the result for individual definitions of simultaneity for individual experiments. That is a fact, i wrote a longer explanation, but this is a short clarification. That means that locality is still on the table, but it absolutely has to be invomving faster than light physics to reproduce the results.
What i mean in more detail about the non commuting observables is that when you get an outcome on one side, you change the prediction on the other side, meaning simply something like going from getting annoitcome on particle A of a bellpair in a direction for spin, and then knowing that and not havingnmeasured the other particle, the probability distrobution as a function of the wavefunction plus extra intital conditions is not the same for B, deoending of whether A was measured or not, and if it was measured, that would be essential revealing information about the initial conditions of B but also the initial conditions of the wavefunction, or to have the wavefunction change in accordance with the result on A, such that the expected distribution over initial condition for B that results frlm the wavefunction are different, which gives you the correlations that apear in bells inequality for example. It simply means that after the result on A you change the wavefunction and the initial conditons for B that you know of, the total initial conditions for the whole wavefunction plus particle picture in a case like this implies the spesific interaction, because of the initial conditons on A and B, and so the hidden variables are fine, the change in the wavefunction is fine because it would be a direct consequence of the initial conditons, but the only way you would see the change in the object guiding B would be to have a gods eye view or measure it along the way, which would change it if you didnt already know the initial condition so i hope that is somewhat clear. I am nlt saying anything that contradicts the full complications of the theory, what i am saying is that there is a change there that can be said to be an interaction, and there is some freedom in how to implement that, so it doesn't have to be instantaneous, but can be superluminal instwad potentially. The key takeaway is that the initial conditons plus wavefunction for a and b contains the entire story with three possible versions, either a first b first or ab at the same time, the third can't be explained as a dynamical process, only a jump so to speak, but for the two other cases its plausible the account for it with a completely local interaction. It will be determined by the initial conditions in all 3 cases anyway, its just a question of how, the properties of the wavefunction must be there in some form anyway, but it doesn't need to be in the same form necessarily, it doesnt even have to have the same epistemic limits exactly, but so far i have found versions that are such that constraints on the probabilities with some type of weak measurements, aka probing the initial conditions more precisely than quantum mechanics allows is plausible but with very unforgiving limitations, so the problem in these kinds of theories is building macroscopic structures that can pick up and systematically account for noise and probe the initial conditons that can get yoi better information tham the uncertainty relations say you should get is questionable in practice but not fundamentally, that is to say, it is because you can only build stuff out of atoms that you can't find the state more precisely than the quantum state, whether it is possible to get beyond that in practice is not entirely clear.
Jesus how long does this thing take to get started
What i meant was not that they are really non commuting, only that they are when they are considered to be in a quantum mechanical description. For example having measured A the wavefunction for B changes before B is measured in a bell pair, of you had a sort of gods eye view. I think in some cases you can because of the previously mentioned arguments about locality, have a concrete interaction that means one observable outcome simply means the other one has to have its distribution of outcomes changed. And i dont think its incoherent to say the wavefunction is a function in space, part of it is, part of it is in momentum space and so on and so forth. For whatever variable you could have a detector with a sort of "location" or " sensitivity " or whatever and in some quantum phase space the wavefunction simoly leads to an expectation for measuring a certain observable depending on the setup, nothing mysterious, but for simple position measurments it is a function over space so when talking about examples where that is essential what matters and you are measuring position at the end of the day, then yeah the effect of the wavefunction with or without interference between sources is just a probability distribution over time andnspace for a position measurement. After doing the math to find the born rule probability, the magnitude only has meaning at detectors but its still fine talking about the probability distortion of outcomes in position space while waving of the hands is going on. That you don't even have to know quantum mechanics to know, you just habe tl know what a position measurment outcome is, on some screen or whatever it is.
The links to the book and SG's site are broken...
Love your channel! New huge fan, but not like one you’d find at an off-shore wind farm 😊✨🦋
But what if we flip a coin and it lands on it's side just on one atom that is about to decay (or not). Depending on the decay the coin would fall to the left or the right ? We cannot predict that decay ? So we cannot determine on what side that particular coin lands ?
@21:49 where do I find his version of it? I’m curious
The point being, if there is an interaction, such that measurkng A changes B, that can still be contained in the wavefunction plus initial conditons at the outset, but in what way the interaction actually functions in practice leaves some room for different theories, with different predictions, for example when it comes to breakinf lorentz symmetry or not, quantum mechanics gives you the version where it is not broken naturally, because the "influence" or correlation, or interaction is already encoded in the wavefunction plus initial conditions andnthe ordering of a or b doesn't matter, but for the lorentz symmetry breaking version is different but isn't well probed. As i explained bellow in mynfirst two comments
So for bohemian mechanics, you have some bell pair, and the wavefunction changes either instantaneously when the first is measured, or just at some speed much faster than light, andnwe haven't tested that, and we can't test thw differences, other thannin one exact way, which is to refute the instantaneous version, which means discovering that the instantaneous version gives the wrong result for some simultaneous measurment according to some definition of simultaneity. That is the correct state of knowledge and what can be done and not done to improve our understanding of the situation. We have not, and cannot fully rule out some form of superluminal locality, and that is a theorem. What we can do is that if some superluminal locality is real we can refute the instantaneous version. There is no mistake, i promise you, and if you doubt it, i will provide a technical argument with maths and fancy fonts and all, but the argument is quite simple and cannot really be denied if understood. I promise you that it really is a theorem.
Instantaneous nearfield electromagnetic fields are real and have been demonstrated both theoretically using Maxwell equations and experimentally. We present a paper below that shows that information in these fields propagate instantaneously. See links below for more information. This phenomena can also be explained using using the Pilot Wave interpretation quantum mechanics and the Heisenberg uncertainty principle (HUP).
In this interpretation HUP is: Δx Δp = h, where Δx and Δp correspond to average values. So in HUP: Δx Δp = h, where Δp=mΔv, thus HUP becomes: Δx Δv = h/m, where m is an effective mass due to momentum. In the nearfield, where the field is created, Δx=0, therefore Δv=infinity.
In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c.
So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. But according to the Copenhagen interpretation, the above argument does not make sense, since Δv corresponds to uncertainties in their values.
In addition to the Pilot Wave interpretation, only the Ensemble Interpretation of Quantum Mechanics also interprets the Heisenberg uncertainty principle (HUP) in terms of averages. But the Ensemble Interpretation does not support instantaneous propagation of information, whereas Pilot Wave theory does. Therefore, other than Pilot Wave theory, no other interpretation of Quantum Mechanics supports instantaneous propagation of information as demonstrated in our experiment, and interprets the Heisenberg uncertainty principle in terms of averages.
It should be noted that this argument can be used to argue that all fields should be instantaneous in the nearfield and speed c in the farfield, including the graviton, and this can explain the non-locality observed in quantum entanglement.
*Electromagnetic pulse experiment paper showing information propagates instantaneously:
www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1
*TH-cam presentation of above arguments:
th-cam.com/video/sePdJ7vSQvQ/w-d-xo.html
*More extensive paper for the above arguments:
William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023:
vixra.org/abs/2309.0145
Dr. William Walker - PhD Physics, ETH Zurich, 1997
Any interactions at the speed of causality -- the speed of light or slower -- are local. Anything significantly faster than C would be unmeasurable and therefore non-local.
The result of a quantum calculation is a probability distribution over some observables, because the mathematical machinery is obtuse and difficult to get physical intuition from, people say a bunch of incoherent sentences and then they calculate some more expectations for whatever it is they end up with in some experiment. As you said the non locality is built into the wavefunction without any obvious tell, outside the results, i doubt that people would call it non local if we didn't do any experiments, because it is when you make some measurment or preform some unitary operation on some bunch of stuff that you find out that it gives predictions that are non local in a certain sense, it is not until you consider tje different possible reductions from measurement, or equivalently the trajectories in bohm that you find out that there are non local properties, precisely because the wavefunction prior to any reductions is transparently just a function that evolves it contains non local information but who cares, i only care that the predictions contain correlations that are only possible when there is some classical interaction that makes it so, or when you have reductions when actually measuring or interacting with something.
And so its notnso much about bell that the destinction between subliminal and superluminal is important, bells theorem applies in the same way for all speeds, but the way relativity works and foliations work in the context of some feature of reality breaking lorentz symmetry, that is why the difference is there and what i wrote is actually an explanation of a theorem.
Prediction for what happens next are a probability distribution, or a spesific outcome, i don't know what it would even mean to say something else. The mathematics that gives you the right probability distrobution in a certain situation is more complicated than that bu the final prediction can't be, its not possible logically. Interference doesn't happen at the level of the prediction, whether there is or not shows up there but the prediction is just some ordinarily function for some observable that is evolving with time of the wavefunction and or additional variables.
With so few Standard Model particles, I just never understood why empty space couldn't provide the wavefunction -- the pilot wave -- for each and every particle? How is one to separate the multiple waves (and gravity!) from space in the first place? There is one, and only one, empty space. Every particle responds to the virtual particles in empty space (ie, the quantum foam) differently. Every particle "sees" empty space differently. But it is the same empty space. There will never be a filter small enough to separate the electron field (pilot wave) from the anti charm quark field (pilot wave) in empty space.
You can separate Johannes Brahms' Symphony No. 3 in F major into separate sine waves. But you can't remove one of them and get the same audio.
Wintergreen never mentioned pilot wave theory,l took his course
The terms "realism" and "anti-realism" are so misleading. In general, in philosophy, "realism" means "belief that an objective reality independent of the observer exists," which nothing in quantum mechanics even is relevant to this question. In the specifics, "realism" tends to mean "belief that this specific thing has ontological reality." For example, if you are realist _about_ something it means you believe it is an _entity._ A wave function function realist is someone who believes the wave function is a real _object_ in the natural world. A moral realist is someone who believes morality is something objectively part of the natural world. The ironic thing is that if you apply this understanding of realism, then it was Einstein who was the nonrealist. It's unclear to me how the term "realism" even came into physics, my best guess it it's borrowed from the "criterion for reality" in the EPR paper, but anyone who reads that paper knows that it was not a "criterion for whether or not reality exists," but a "criterion for whether or not a theory is a complete description of reality." In other words, it was a criterion for completeness, not for realism. My problem with this abuse of the term "realism" by physicists is that by using the word so bizarrely, they aren't consistent with it. They might use "realism" in reference to completeness in one paper, but then flip-flop and use it in the philosophical sense in another. It's how you end up with academic papers claiming somehow Bell's theorem proves objective reality doesn't exist. PhD physicists lost in quantum woo due to word games! I tend to agree with Maudlin that we should probably should just drop the term "realism" when talking physics. It has no place in the discussion.
I don't think Bohmian Mechanics is perfect (feel free to ask me why), but this was cool, thanks. Especially @27:00 lol.
I'll ask why but in trepidation I won't understand any of it. ;)
34:55 "Non locality is here to stay":
The basic problem for Bohmian mechanics, though, is that it's not "weakly" non local, as the interpretations of unmodified QM are, but "strongly" non local, breaking Lorentz invariance, requiring absolute reference frames, like the old (obsolete) days of Larmor et al (the pre-relativistic days of ether and the like...).
So, no QFT, no General Relativity for Bohmians...
If you think you can write down a clear and exact theory that violates Bell's Inequality and does not break Lorentz Invariance, give it a try. The standard theory-which uses collapse of the wavefunction but does not exactly specify how it happens in a Relativistic setting-cannot. And putting in a preferred foliation does not conflict with a curved Lorentzian manifold or GR explanations or anything in QFT. Obviously, adding a foliation cannot eliminate any explanatory power. If you don't need the foliation for some purpose, then just ignore it for that purpose. A curved Lorentian manifold with a foliation is not a classical space-time.
@@timmaudlin6997 One can choose arbitrarily a foliation, there's no problem with that.
But if you need a preferred foliation for fundamental reasons, it's a different story.
You cannot explain kinematically the usual relativistic effects ( time dilation, length contraction) for example, you need some contrived "mechanism" that mimics/ reproduces these effects with dynamics... You need new physics!
Fitzgerald, Lorentz et al tried to do that before Einstein but failed.
There's no causal order between space-like separated events in Relativity and a boosted observer could see a different temporal order between such events, depending on which direction she moves etc.
Lorentz invariance is basic for all modern physics.
It's not written in stone of course, but all the evidence so far indicates that it's a characteristic of our world.
And it's the basis for both GR and QFTs, so I respectfully disagree with the point of view that " it doesn't matter if the relativistic axiom that the laws of physics are the same in every reference frame has to be abandoned".
From the Bohmian perspective it's crucial to introduce preferred foliations.
Objective collapse theories have similar issues, but their proponents are trying to make their models compatible with Relativity, they're not willing to just accept it, perhaps because they are more concerned with the implications of their theories- that are testable , so they have some things to worry about - for the rest of the Physics.
But from other points of view ( that consider the observables as more fundamental) the quantum mechanical non locality is "mild", because the "collapse of the Wavefunction" is not an objective effect, it's relative ( so if Alice thinks that her measurement "collapses" the Wavefunction in an EPR setting, Bob thinks the same for his ...).
There's no FTL communication of any kind between them, nobody collapses "first," the Wavefunction, because there's no definite temporal order.
The issue about non locality is arguably subtle and interesting.
Most probably suggests that there are some things that aren't known yet...
Ψ-ontic theories that modify the mathematical structure (like Bohm / Pilot wave or physical collapse/GRW ) are respected nowadays.
Personally I'm a bit sceptical about them( and MWI also, for different reasons...).
It seems to me that thinking the State Vector as "The" ( or " one of The.." in the case of Bohm) fundamental element of reality is like a "Category Error"...
Isn't it a Vector in an abstract mathematical space after all?
It *describes* the physical world, yes, it gives is the amplitudes/ the probabilities via the Born Rule, but there are other options for realism in physics :
After all, we don't observe the Wavefunction, so interactions/ observables ( a kind of Structural Realism) is preferable (?).
But I digress...
No, that's just not right, for the reasons I gave. Just because you may use the foliation for some fundamental purposes, you need not mention it for all purposes. If there is an effect that doesn't depend on it-that can be accounted for just using the curved Lorentzian metric-then simple don't refer to it. It is not possible to *lose* explanatory power by *adding* a foliation, because you are free to ignore it when you don't need it.
When do you need it? In the standard non-relativistic theory you need it for two purposes. One is just to define what counts as a "configuration" of a system (as Shelly says) because the wavefunction is presented as a complex function on configuration space. So you need configurations to get off the ground, and you need a foliation to define configurations. Second, in the standard theory you have instantaneous collapses of the wavefunction, and you need a foliation to define "instantaneous". IN the pilot wave theory, you have no collapses, but you use the foliation to write down the guiding equation. So the situation with pilot wave and the standard theory is exactly the same. And nothing changes in that respect going to field theory.
Collapse is not "relative" in the standard theory: it is a fundamental part of the objective dynamics of the wavefunction (see von Neumann) and is required exactly because the wavefunction is supposed to be complete. If the practical inability to send signals is enough to make a theory Relativistic, then pilot wave theory is already Relativsitic. And if you assert that Relativity requires more than no signaling (which is correct), then you have no argument that the standard theory is Relativistic.@@dimitrispapadimitriou5622
@@timmaudlin6997 Either the laws of physics are the same in all foliations ( choosing "nice" space-like hypersurfaces ) or they are not!
We can't have double criteria especially in fundamental physics.
Otherwise the theory is not "Realist" in the first place... because the chosen foliation is crucial for the consistency of the theory!
Moreover, that "preferred foliation" needs a physical reasoning.
It's similar like saying that in GR only a specific coordinate system gives consistent physics!
Contrary to the most basic premise of the theory!
I understand that this is perhaps the main disagreement about Bohmian mechanics. The other issues ( the difficulties with QFT for example) have their roots in this.
Please read what I wrote. There is nothing wrong with having some equations (say the analog of Schrödinger's equation) that use only a Lorentzian metric and others (say the guidance equation or collapse equation) that use the foliation. That can be completely realist.
Further, as I said, the standard approach uses collapses. So try to write down the theory precisely without a foliation. Good luck.
My own view is that Relativity is probably emergent from a deeper geometrical structure, but just adding a foliation to a Relativistic metric is both consistent and realist. You add it because you need it, not least to account for violations of Bell's Inequality. Everyone has to do that because it is an observed physical fact.@@dimitrispapadimitriou5622
Bell proved that epr is kind of wrong, but only in the sense that independent non interacting pre-existing elements of reality is not enough. Bells theorem meams you can test whether you need a faster than light interaction to account for entanglement in a classical way. The definition of locality beyond sub light physics is ambigous if you don't have a foliation, but it is absolutely not true that the bell tests we have done so far has ruled out finite but superluminal interactions accounting for the difference between what epr said and what reality demands. You can prove that there is no way to absolutley prove that there is no deviation from the results in some foliation where you do a simultaneous bell test at space like separation. That is to say, the notion that bell tests are lorentz symmetric has not been shown, and connot be fully proven by experiment. And if shelly wants i can prove it to him in a simple and rigours way, i am 100% sure it is mathematically rigours to say so. In fact it is just a simple extension of bells argument to arbitrary velocities, the statement that the space like seperated bell test is not lorentz invariant is one result you can get in exactly the same way an ordinary bell test is done, but to probe all possible time coordinates is not feasible, so the notion of superluminal but not instantaneous locality can only be constrained in a sertain spesific sense, or with a positive result be proven by finding out that simultaneous measurments given some cone of definitions of simultaneity infact do not give the same results and don't violate the inequality or violates it less and less towards the center of the cone, which in that case would serve as a measurment of absolute local simultaneity. What bell proves is that given the inequality being broken, any local description without interactions between the two sides is impossible, and if you do the experiment with any space like separation you like you rule out that this interaction is subluminal in character, and this is already proven, not published formally, but i will bet you the lives of every member of my family because it is quite a simple proof. It is easy for me to imagine a bunch of reasons why people wouldn't not believe it, but it is true and rather easy to prove actually. The first kind of reason is to say "well superluminal physics breaks causality" and that is just wrong. The second kind "well bells theorem has nothing to do with the speed of light" which is also wrong. The first one i don't want to gratify with an answer because people who think that are just confused about something they never really checked. The second one is easy, but understandable, and its wrong because if the interaction in question can not be there or be there, which os the premise of the result motivating experiments in the first place, that is to say if the inequality holds then no interaction is needed to make everything local independently of spacetime interval, if the inequality is broken you have some non local change depending of what happens on the other end, this is indeed independent of the speed the interaction needs. But testing it for subluminal physics just requires one test and it is done, whole for superluminal interactions you need to check each possible definition of simultaneity, because if some subset of definitions are different with respect to the outcome of the result then if is not lorentz symmetric and the universality of frames of reference has nothing to do with anything, so each time coordinate must be checked individually. If you want a technical paper and proof i can produce it for you, but i hope shelly gets the idea, maybe you can forward it to him if you would be so kind, and he doesn't read comments :).
It is of course problematic to talk in loose terms about these things without a shared language, but i hope you get what i mean. The simple things yoj can say about quantum mechanics can be misconstrued in a lot of ways and people are very good at understanding how to misconstrue. Anyway, i enjoyed the pod, i like shelly, he is stubborn and doesn't take half way answers for granted, which is nice, because the first rule of fight club is to never talk yourself into unsupported conclusions.
@1:02:00 he's misleading. You absolutely do *_not_* expect the function describing phase space to be non-local. He got a bit mad hatter there. What you "expect" instead is that Nature aught not allow smooth transitions between pure states (determined eigenvalues). Classical mechanics is such a class of theory. Quantum mechanics is not, QM allows smooth transitions, and simply by "state preparation" (filters and mixers and whatnot) which is highly counter-intuitive. The more modern approaches are not to _interpret_ QM but to _reconstruct_ QM from generalized probability models. QM is amazingly the unique GPM theory that has reversible *_and_* continuous transitions between pure states. In CM the allowed transitions are only reversible, not smooth, which is what gives Kolmogorov probabilities for classical systems. So if you find a "real" ontology that has that class of GPM then chances are good you've got a "correct" physics, at some level of description anyway.
Generalized probability theories have an epistemic/agentic/operational/interventionist approach, right? (not a rhetorical question)
What if the universe is actually non-deterministic, and non-local? What if you cannot predict the future evolution of "things" because a little tiny fluctuation in the initial conditions makes all the difference? What if chaos theory is correct?
Then you have merely admitted that you didn't pay attention in school. :-)
@@schmetterling4477 no, it means I *did*pay attention
@@ariadne4720 Maybe in creative writing, but certainly not in science class. ;-)
Ignore schmett he's a troll. Anyways, chaos theory is still deterministic in the Laplacian sense, which is what most people mean when they talk about determinism. Yes, in practice it is impossible to predict a chaotic system, but in principle its final state is still absolutely determined by its initial state without any other possible outcome. What you're proposing is a nonlocal but deterministic theory where the apparent randomness is due to something chaotic, which there are definitely models like that in the literature. There's a few that treat the very act of measurement as a chaotic process that randomizes some sort of internal state of a system. These models have to effectively be nonlocal because they have to violate the PBR theorem's assumption of preparation independence, which is basically identical to rejecting locality.
The speed of light is not a constant speed as once thought, and this has now been proved by Electrodynamic theory and by Experiments done by many independent researchers. The results clearly show that light propagates instantaneously when it is created by a source, and reduces to approximately the speed of light in the farfield, about one wavelength from the source, and never becomes equal to exactly c. This corresponds the phase speed, group speed, and information speed. Any theory assuming the speed of light is a constant, such as Special Relativity and General Relativity are wrong, and it has implications to Quantum theories as well. So this fact about the speed of light affects all of Modern Physics. Often it is stated that Relativity has been verified by so many experiments, how can it be wrong. Well no experiment can prove a theory, and can only provide evidence that a theory is correct. But one experiment can absolutely disprove a theory, and the new speed of light experiments proving the speed of light is not a constant is such a proof. So what does it mean? Well a derivation of Relativity using instantaneous nearfield light yields Galilean Relativity. This can easily seen by inserting c=infinity into the Lorentz Transform, yielding the GalileanTransform, where time is the same in all inertial frames. So a moving object observed with instantaneous nearfield light will yield no Relativistic effects, whereas by changing the frequency of the light such that farfield light is used will observe Relativistic effects. But since time and space are real and independent of the frequency of light used to measure its effects, then one must conclude the effects of Relativity are just an optical illusion.
Since General Relativity is based on Special Relativity, then it has the same problem. A better theory of Gravity is Gravitoelectromagnetism which assumes gravity can be mathematically described by 4 Maxwell equations, similar to to those of electromagnetic theory. It is well known that General Relativity reduces to Gravitoelectromagnetism for weak fields, which is all that we observe. Using this theory, analysis of an oscillating mass yields a wave equation set equal to a source term. Analysis of this equation shows that the phase speed, group speed, and information speed are instantaneous in the nearfield and reduce to the speed of light in the farfield. This theory then accounts for all the observed gravitational effects including instantaneous nearfield and the speed of light farfield. The main difference is that this theory is a field theory, and not a geometrical theory like General Relativity. Because it is a field theory, Gravity can be then be quantized as the Graviton.
Lastly it should be mentioned that this research shows that the Pilot Wave interpretation of Quantum Mechanics can no longer be criticized for requiring instantaneous interaction of the pilot wave, thereby violating Relativity. It should also be noted that nearfield electromagnetic fields can be explained by quantum mechanics using the Pilot Wave interpretation of quantum mechanics and the Heisenberg uncertainty principle (HUP), where Δx and Δp are interpreted as averages, and not the uncertainty in the values as in other interpretations of quantum mechanics. So in HUP: Δx Δp = h, where Δp=mΔv, and m is an effective mass due to momentum, thus HUP becomes: Δx Δv = h/m. In the nearfield where the field is created, Δx=0, therefore Δv=infinity. In the farfield, HUP: Δx Δp = h, where p = h/λ. HUP then becomes: Δx h/λ = h, or Δx=λ. Also in the farfield HUP becomes: λmΔv=h, thus Δv=h/(mλ). Since p=h/λ, then Δv=p/m. Also since p=mc, then Δv=c. So in summary, in the nearfield Δv=infinity, and in the farfield Δv=c, where Δv is the average velocity of the photon according to Pilot Wave theory. Consequently the Pilot wave interpretation should become the preferred interpretation of Quantum Mechanics. It should also be noted that this argument can be applied to all fields, including the graviton. Hence all fields should exhibit instantaneous nearfield and speed c farfield behavior, and this can explain the non-local effects observed in quantum entangled particles.
*TH-cam presentation of above arguments: th-cam.com/video/sePdJ7vSQvQ/w-d-xo.html
*More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145
*Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1
Dr. William Walker - PhD in physics from ETH Zurich, 1997
70% of industry as trial inventions are based on QM and only one invention is based relativityGPT.
Involving * sorry i write on my phone, and i have fast and big thumbs and dont proof read my errors or really read while i'm typing.
QM is not really nonlocal. This is a massive misconception.
These are not fundamentally non commuting quantities, no that is not what i mean, i just means that in a certain sense they should be seen as not beign independent events. What people usually say is that quantum mechanics is local because spacelike separated events are commuting and there is no interaction between them, which is just teutological bs in my opinion, i just think they habe no clue what a wavefunction is and how the non locality works, and how it is related to other kinds of respesentation. Not saying they don't understand what a tensor product is or what a wavefunction is, i just think nobody really understands them properly, i think you and bell and people that are ready ti admit that they contain non local information are closer to the truth, but i basically just think the non locality is analogous to distrobutions of various different possible interactions that go faster than light or instantaneous, that can in principle describe any non local property that consists of a dependence of one distribution of outcomes on another, which is all we get to consider anyway, we are never going to measure and not measure things at the same time, or make spaghetti out of air, actually that last one is essentially the only way we make spaghetti, but i digress :').
Bohmian mechanics is certainly interesting, but the so-called quantum potential is too contrived to be plausible.
I know he's a professor of math, etc, but getting yelled at for 1:30 is not much fun.
The “many worlds theory” is wonderful if you’re expanding the Marvel Comic book storylines, or countless other sci-fi plot devices.
Otherwise it is the literal definition of a theory that can never actually be “tested” by any understanding of test and measurement.
If The Copenhagen paradigm is Atheistic, The “multiverse” is Metaphorical Magical incantation; it surely fits Dr. Strange but not so much Dr. Albert Einstein.
Have you taken any university-level courses on basic quantum mechanics?
@@rv706 I have. MWI was never mentioned. If, however, you took an undergrad level class and you did pay attention and you did happen to read Everett's thesis, then you would have noticed that his second sentence is already wrong and that his argument never recovers from that error. ;-)
@@rv706 Doesn't even matter. You only need to understand the very basics of quantum mechanics in order to grasp these philosophical questions. A lot of it revolves around Bell's theorem, for example, which is trivial, especially the simplified version in the form of the CHSH theorem can be explained to a middle-schooler. People who pretend like you need a PhD in quantum mechanics to have some understanding of these philosophical problems are usually just quantum woo mystics trying to distract from people questioning their mysticism. The majority of a PhD is on more specific applications of quantum mechanics. Take, for example, the orbits of an electron, which is a specific derivation from quantum mechanics, yet is entirely irrelevant to the more broad philosophical and you do not need to know it. The philosophical questions only require an introductory level understanding of quantum information science, which by its very nature abstracts out most of the specifics you learn in a PhD course and you can get an idea of from reading a single book on the subject and experimenting with the mathematics in things like IBM's cloud quantum computer, allowing even regular people to get hands-on experience with these things. You would only actually need a PhD if you're trying to modify the theory, as that of course would require a very deep level of understanding of its specifics.
I prefer Bohmian Rhapsody.
There are so many ads your content has become unwatchable. Unsubscribing now.
Meow
There are so many people working in this ugly and unnatural interpretation of QM. The need to cling to a basically classical picture of the world is strong...
The worst problem with Bohmian/ pilot wave theories is that they are not compatible with special relativity.
They need an absolute reference frame for their theory to make sense, so a simple kinematic explanation ( as in SR) of the usual well confirmed effects like time dilation/ length contraction has to be replaced by contrived Larmor - style mechanisms , reminiscent of the old Ether days...
It's not a big surprise that they have serious problems with the generalisation to relativistic QFT.
Yeah go go power fanboys. No you guys are just wrong and should be a bit humble ;).
You should grow up and do something for yourselves. The worst problem with the arguments you are makingnis that you habe no idea what it means. And so the uglyness is a consequence of your ignorance not rigour. Get gud
You know what the equations of motions in an absolute frame of reference is that reproduces the same dynamics? Its the same equations. There is no destinction, you habe just confused about representation theory and that is that, if you knew what you were talking about then you would say something about the motivation for taking an absolute simultaneity innterms of changing the physics, not the convention, but you will learn eventually 🍻™️
@@monkerud2108 ???
again the same mistake in the intro as u make on all these QM episodes. When u say QM must be non-local, then u are assuming statistical independence. Please educate yourself about this so u stop making this embarassing mistake every time. It's getting really annoying
"Statistical independence" is very basic for doing science. Without it you're heading for conspiracy theories...
@@dimitrispapadimitriou5622u must be a regular viewer of this channel. But no. Check out Sabine's physics channel here on youtube for an easy to understand explanation of why u can't assume statistical independence
By "statistical independence", do you mean what Hossenfelder calls "future input dependence"?
@@rv706" superdeterminism", aka: " we don't like what experiments reveal about the Physical world, so we try to find desperately some loophole, no matter how implausible or contrived it is"...
@@rv706 the 2 proposed ways to get reality from the results of the bell equalities experiments are either with non-locality or with superdeterminism. Being satisfied with non-locality by ignoring the other possibility is not good science.