Another attack against de Broglie-Bohm theory by Lumo - Printable Version +- Hidden Variables (https://ilja-schmelzer.de/hidden-variables) +-- Forum: Foundations of Quantum Theory (https://ilja-schmelzer.de/hidden-variables/forumdisplay.php?fid=3) +--- Forum: de Broglie-Bohm theory (Bohmian mechanics) and other Hidden Variable Theories (https://ilja-schmelzer.de/hidden-variables/forumdisplay.php?fid=6) +--- Thread: Another attack against de Broglie-Bohm theory by Lumo (/showthread.php?tid=34) Another attack against de Broglie-Bohm theory by Lumo - Schmelzer - 05-11-2016 Lubos Motl (lumo) claims on his "Reference frame" that Bohmian mechanics is incompatible with loop corrections. If one reads lumo, one has to ignore low level polemics which are inappropriate in a scientific discussion. They would not be allowed here, and to answer them here seems useless too. Nonetheless, even such presentations may contain valid arguments which are worth to be discussed. Recovering relativistic symmetry   A first one is the general problem how a theory which is not Lorentz-covariant can give, in some approximation or some limit, a theory which is Lorentz-covariant in its observable predictions.   Quote:The correct way to argue is that the generic theory in the Bohmian class contains infinitely many Lorentz-violating effects and they have no reason to vanish. So the probability that all of them cancel and produce the prediction of Lorentz-invariant phenomena – which are observed – is $$1/\infty^\infty$$. It is zero for all actual purposes. So, the question is what are the reasons to vanish for the Lorentz-violating effects.   The first one is that in dBB theory there is a quantum equilibrium.  An equilibrium is, plausibly, a state with higher symmetry than the general state.  So, while dBB theory outside quantum equilibrium allows superluminal information transfer, dBB theory in quantum equilibrium is equivalent to quantum theory, and, in particular, no longer allows superluminal information transfer.  What is the mechanism which suppresses the non-equilibrium states? It is a variant of the usual mechanism which leads to the usual equilibrium in thermodynamics. This has been shown by Valentini in his "sub-quantum H-theorem", which is works analogical to Boltzmann's H-theorem. Once the quantum equilibrium has been reached, the predictions of dBB theory are already equivalent to those of the corresponding quantum theory, and mainly defined by the symmetries of the corresponding classical theory.   The next important reason for Lorentz-violating effects to vanish is large distance universality.  Assume we have a microscopic theory, say, some complex atomic model of some crystal.  The problem is to derive the approximation of this theory for large distances.  What has been intuitively understood already long ago is much better understood now after Wilson has improved our understanding of renormalization and effective field theories.  Namely, most of the microscopic details have essentially no effect at all for large distances.  Essentially, what matters for large distances are only the lowest order terms - higher order terms become suppressed for large distance by much higher suppression factors.  What remains are, essentially, only renormalizable terms.  So, very different microscopic theories may end up with very similar, and in the limit identical, large distance approximations.  The whole infinity of variants simply vanishes, is reduced to a few parameters of a few renormalizable theories.  Other, non-renormalizable theories have a chance to remain observable only if there are no similar renormalizable terms - as in the case of gravity.  But even in this case, they will be highly suppressed.  Which is the Wilsonian explanation why gravity is so weak in comparison with the other forces.   In some cases, this is already sufficient to establish relativistic symmetry.  For example, if we have a microscopic theory which is described by a single field, say the density, and the equation which remains in the large distance limit is the standard wave equation for sound waves: $(\partial_t^2 - c^2(\partial_x^2+\partial_y^2+\partial_z^2)) \phi(x,y,z,t) = 0.$ with some constant $$c$$, the speed of sound in this medium. Now, what is the symmetry group of this wave equation?  It is the symmetry group of special relativity, the Poincare group.  But even if not, the situation is already much less problematic - we have no longer an infinity, but only a few terms, distinguished by such remarkable properties like renormalizability.   And now some particular properties of the particular model may become important. It may contain some symmetry by construction, or some property of the model may allow to use some other symmetry to prove relativistic symmetry.  In  this derivation of the Einstein Equivalence Principle the symmetry which is used is the "action equals reaction" symmetry, which one gets for free together with the Langrange formalism. What is necessary to transform the "action equals reaction" symmetry to the EEP is a particular property of the ether model - its universality: The ether does not interact with anything else, so that all the fields we observe have to be fields which describe properties of the ether itself. Is there an equivalence proof? Lumo suggests, that there cannot be an equivalence between dBB theory and quantum theory, with the following remark: Quote:In Hardy's paradox, any local realist theory predicts the probability of a certain combined outcome to be P=0 while experiments and quantum mechanics say P=1/16. Could you please show us the calculation in Bohmian mechanics that reproduces P=1/16P=1/16? This point of Hardy's paradox is a good argument against "local" (better: Einstein-causal) realist theories.  But dBB theory is not "local".  And if one wants to compute the result in dBB theory, there is a simple way:  One uses the equivalence theorem between dBB theory and quantum theory, and, then, uses standard quantum computations.   Unfortunately, lumo thinks that the equivalence theorems are simply wrong. The equivalence has been proven in a peer-reviewed widely cited paper (Bohm, D: A suggested interpretation of the quantum theory in terms of "hidden" variables, Phys. Rev. 85, 166-193, 1952). If it contains errors, one would expect also a published refutation. But a request for a published refutation lumo answers with   Quote:There are almost certainly no professional physics journal articles about comparisons of QFT with a Bohm theory because Bohm theories don't belong to professional particle physics (and they don't belong to professional condensed matter physics and similar things, either!). and, instead, refers to his personal website for such a proof.  Hm ...   Ok, I will not start to characterize what this type of behavior remembers, the discussion in this forum should be restricted to the scientific content.  One could ignore such  non-peer-reviewed arguments completely, and some of them will be, indeed, not considered here (like the one presented in his posting "All realistic "interpretations" falsified by low heat capacities". If two theories are proven to be equivalent on the microscopic level, and someone claims to see different results in macroscopic variants, ....).   How quantum field theory fits into dBB theory On the other hand, let's consider here the main point made in the post itself.  It is claimed that dBB theory Quote:... actually has a serious problem with all conceptually new effects by which quantum field theory differs from non-relativistic quantum mechanics. It isn't compatible with the particle creation and annihilation. The calculations of renormalization can't be embedded into Bohmian mechanics in any way. Of course, the equivalence proof, even if it is quite simple, works only if there is a dBB theory. So, one first has to construct one.  This is not always trivial.  The simple, standard way to construct a dBB-like theory works only for a general but fixed configuration space Q and a Hamiltonian which is quadratic in the momentum variables, $$H = p^2+V(q)$$. So, at a first look, lumo seems to have a point if he considers quantum field theory, with variable particle numbers, and a relativistic energy of the particle which is not quadratic in the momentum variables.  Unfortunately for this argument, pilot wave theoreticians are not obliged to choose particles as the configuration space. In principle, they can try any maximal algebra of commuting observables as the configuration space of their dBB proposal.  And, instead of the particles, which vary in their numbers, there is a much better candidate for defining the dBB configuration - the field itself.  Let's look at the simplest example of a relativistic quantum field theory, a simple scalar field.  Here we have the Lagrangian $S = \int \frac12 \eta^{\mu\nu}\partial_\mu \varphi \partial_\nu \varphi -\frac12 m^2\varphi^2 d^4x$ which gives the momentum variables $$\pi(x) = \partial_t \varphi(x)$$ and the Hamiltonian $H = \int \frac12 \pi^2 + \frac12 (\nabla\varphi)^2 + \frac12 m^2\varphi^2 d^3 x$ which is of the required form quadratic in the momentum variables.  Of course, this would be a field theory, which shares with quantum field theory all the problems related with an infinite number of the degrees of freedom.  What to do?  The same as what is done in QFT, namely one regularizes the theory.  A simple way to do this is lattice regularization.  So, we approximate the field by the field values at lattice points at some distance h,  with a large enough number of lattice nodes and some periodic boundary conditions so that their number remains finite.  Then, for each lattice node n, we have a field value $$\varphi_n$$, which defines the configuration, and the corresponding momentum $$\pi_n = \partial_t \varphi_n$$, and the energy is defined by $H = \sum_n \frac12 \pi_n^2 + V(\varphi)$   where $$V(.)$$ depends only on the configuration variables $$\varphi_n$$.  This already fits completely into the classical case of a fixed finite number of degrees of freedom with an energy quadratic in the momentum variables. So, the standard equivalence proof works, and the resulting dBB theory is equivalent to the correspondent quantum lattice theory.  Of course, this does not mean that a relativistic multi-particle theory with variable particle number has to fail.  For such a theory, the configuration space Q has to contain parts with different particle numbers.  Some proponents of dBB theory develop these directions.  I don't think this is a good idea - but this is my personal opinion. About renormalization What about the claim that calculations for renormalization cannot be done?  We have already done the most important first step - to define a regularization, one where we have a well-defined, in any sense, theory.  And for this regularization, we have constructed the corresponding dBB theory, in a way that its equivalence to the quantum lattice theory is a triviality.   One can object that we have considered here only one regularization scheme - lattice regularization.  Other regularization schemes may have some advantages, in particular, it may be much easier to compute some integrals, say, using dimensional regularization.  But can one make an argument against dBB theory what it has not yet provided a dBB variant for quantum theory in a $$4-\varepsilon$$ dimensional space?  I doubt.  If renormalization is reasonable method, the results should not depend on the particular regularization scheme used. So, for the renormalization in dBB context it seems sufficient to have equivalent dBB theories for one variant of a regularization of QFT. Lumo has also raised another problem - that of fermion fields.  This is, indeed, a difficult problem - but, nonetheless, already solved.  But the solution will be left to a separate post. RE: Another attack against de Broglie-Bohm theory by Lumo - Schmelzer - 05-12-2016 Let's look at another argument from the same  Bohmian mechanics is incompatible with loop corrections post: Quote:But the new Bohmian theory is only ready for a measurement of the value of the fields $$F_{\mu\nu}(\vec{x})$$. It's no good because the measurement of the locations of quanta can in no way be reduced to a measurement of $$F_{\mu\nu}(\vec{x})$$. If you want to guarantee that the theory will observe a photon at one particular place, you will need a collapse, anyway. You will need to borrow parts of the "standard quantum mechanics" because no value of the location of the photon $$\vec{x}$$ is "ready" before the measurement. So the very reason why Bohmian mechanics was constructed in the first place breaks down. The new Bohmian theory won't be capable of producing sharp results for the most usual experiments. Before you measure the location of a high-energy photon, no "beable" seems to know what result you should get. It's clear that the "right result" can be neither a function of the guiding functional, nor the classical values of the fields . So the Bohmian theory just can't possibly be able to predict what happens in the position measurement. While this is formulated as a seemingly new, independent argument against dBB field theories, it is essentially only a variant of the old argument that dBB theory would be unable to recover the predictions of quantum theory for measurements different from position measurements.  This problem was solved already by Bohm in his original 1952 paper.  Let's explain how.   Once the system and the measurement device are independent before the measurement, the wave function is assumed to be the product of the wave functions of system and measurement device: $\psi(q_{sys},q_{dev},t_0) = \psi_{sys}(q_{sys},t_0)\psi_{dev}(q_{dev},t_0) = (\sum_a f_a \psi^a_{sys}(q_{sys},t_0)) \psi_{dev}(q_{dev},t_0)$ The Schrödinger equation gives, then, the result of the measurement as a superposition of states: $\psi(q_{sys},q_{dev},t_1) = \sum_a f_a \psi^a_{sys}(q_{sys},t_1)\psi^a_{dev}(q_{dev},t_1),$ where the $$\psi^a_{sys}$$ are the eigenstates with eigenvalue $$a$$ of the system for the measured operator $$A$$, and $$\psi^a_{dev}$$ the wave functions of the pointer of the measurement device if the value $$a$$ is measured. The measurement is finished if these states no longer overlap for different values of $$a$$. An important point is that the operator $$A$$ is completely arbitrary - it can be any quantum operator, in no way only a position measurement operator - as well as the interaction operator which leads to the Schrödinger evolution - we use here nothing but the standard evolution of the wave function defined by standard quantum theory for the same measurement. The Copenhagen interpretation tells us that it is the result of the measurement - as observed in the classical part - which defines the resulting wave function of the system. Pilot wave theory contains, with the configuration of the measurement device $$q_{dev}(t)$$, the measurement result, and the rule how to define an effective wave function of the subsystem $$\psi_{sys}(q_{sys},t)$$ given the global wave function $$\psi(q_{sys},q_{dev},t)$$ and the measurement result $$q_{dev}(t)$$ is straightforward: $\psi(q_{dev},q_{sys},t) \to \psi(q_{dev}(t),q_{sys},t) = \psi^{eff}_{sys}(q_{sys},t)$ This formula makes the difference between the purely quantum description of the subsystem, which becomes a mixed state, and the pilot wave description, where the effective wave function of the subsytem is a pure state. And it leads to the effective reduction of the wave function by the measurement to the eigenstate defined by the measured eigenvalue. So, lumo is in some sense correct that dBB theory "needs" a collapse.  But it is not a problem, because it has a collapse - not of the whole wave function, which includes even the macroscopic measurement devices, but of the effective wave function, which describes only the quantum subsystem. And it is the trajectory of the measurement device $$q_{dev}(t)$$ which allows to define the state after the measurement.  If what is measured is $$a$$, it means that for all the $$a'\neq a$$ we have $$\psi^{a'}_{dev}(q_{dev},t_1) \sim 0$$, and, therefore, the $$\psi^{eff}_{sys}(q_{sys},t_1) \sim \psi^a_{sys} (q_{sys})$$. RE: Another attack against de Broglie-Bohm theory by Lumo - Schmelzer - 05-13-2016 Lumo has banned me on his blog. Here his justification:  Quote:Because you are just repeating lies that contradict facts and proofs, with no desire to behave honestly or constructively (in fact, a clear promise *not* to ever do any quantitative calculation), I banned you. Let's see what I have written there and what was the reason for this accusation: Quote:Why should one repeat things already done? One has to show the equivalence of dBB theory to QT and, then, can rely on normal QT. So, I have proposed a simple way, which allows to reuse standard QFT calculations in dBB theory:  To use an equivalence theorem between some dBB theory and the corresponding quantum theory.  If this is successful, one can simply copy-paste the QFT calculations, and will, by construction, obtain the same results as in the corresponding quantum theory.   So, this is not at all a refusal to do calculations, instead, a concrete proposal how to do these calculation - by establishing that the standard QFT methods how to do this can be used in dBB theory too. And, to be clear:  If there would be no such equivalence theorem, if dBB theory would appear to be a different theory even in the quantum equilibrium case, this would be a good argument against dBB theory. In this case, I would have to reevaluate my relation to this theory. That means, or I would give up dBB completely, or I would continue to support it for new, completely different reasons.   And repeating lies?  I'm repeating only claims made in peer-reviewed literature.  No doubt, even peer-reviewed literature may be false, and I'm open to argue about this.  And Bohm's original article is peer-reviewed literature.  It contains a measurement theory which shows that not only position measurements, but all measurements give the same result in dBB theory and in quantum theory.  And it already contains a proposal for a dBB theory for the EM field.  Some other accusation: Quote:These claims of yours about the equivalence are completely wrong but they seem also immoral in some sense. On one hand, your movement claims that you have some theory that is "better" which means that it must be different - and it obviously *is* different. On the other hand, you seem to claim that everything that works in any other theory must automatically work in yours - without even any need to show it. As one can see here, I personally rely only on a quite restrictive variant:  that a dBB theory can be constructed for every quantum theory with a finite number of degrees of freedom and a Hamiltonian of type $$H= (p,p) + V(q)$$,  where the energy depends on momentum variables in a quadratic form.  Which is trivially sufficient for a lattice regularization of a scalar relativistic field theory.  So, first, I see a need to show equivalence - the only difference is that I think it has been shown.  Then, what I think has been shown is that the testable predictions of the two theories are equivalent.  But this is not everything.   Quantum theory in the Copenhagen interpretation contains two parts - the classical part, and the quantum part.  Above parts are important and necessary.  At least I think so, looking at the result of the attempt to get rid of the classical part completely - the many worlds interpretation.  For all practical purposes, a subdivision of the world into a classical and a quantum part is, of course, sufficient. So, for a rabid positivist, everything with Copenhagen may be fine.  But I'm not a positivist, and I think that an interpretation which splits the world artificially into a classical and a quantum part is conceptually not satisfactory.  The additional value of dBB is that it solves this problem - it is a unified theory.  It describes the classical and the quantum part in the same way.  And it reaches this without giving up anything which is really important from the Copenhagen interpretation.   Quote:I am really saying a very simple general thing - the ways in which states get mixed to interesting and observable superpositions are so general that no theory with any "preferred observables" or "preferred measurements" (i.e. "beables") can never reproduce QM. This argument fails because choosing some particular configuration space Q in no way restricts the superpositions which are allowed.  In dBB theory, reality is described by the wave function $$\psi(q)\in \mathcal{L}^2(Q)$$ and the actual configuration $$q \in Q$$.   The$$\mathcal{L}^2(Q)$$ is the same as in quantum theory, and the Schrödinger equation which describes the evolution of the wave function is also the same as in quantum theory.  No difference at all.  That the beables are defined by the configuration, and not the momentum or something different, prefers one of the valid representations of quantum mechanics.  But each representation is, from point of view of quantum theory, equivalent (as long as it is correctly identified, via the classical part of Copenhagen, which operator measures which observable).   And there is also no preferred measurement.  All the measurements allowed by quantum theory are allowed in dBB theory too.  The only place where we really need the configuration is in the classical part - where we have to identify the result of the measurement, as the one defined by the configuration $$q(t)$$ of the measurement device.  And in the classical part, it does not really matter what is preferred as the "configuration" - anyway, they are all well-defined, and all of them are sufficient to identify the measurement result correctly.   Quote:... the spin is absent from the "beables" and its measurements are reduced to measurement of positions etc. This means that the Bohmian logic "the measured value is prepared before the measurement" doesn't apply to the spin, and one has to rely on a later stage of the measurement that will measure something else. The main problem here is that  "the measured value is prepared before the measurement" is not a "Bohmian logic".  A measurement is a particular interpretation for an interaction with some quantum system, and does not even play a special role in whatever can be named "Bohmian logic".  Bell has written a paper titled "Against Measurement", which is, of course, not directed against the idea to measure something, but against interpreting an experiment, an interaction, as a "measurement", which wrongly  suggests that what is "measured" is something which already exists before the "measurement".   Quote:But the Bohmian theory doesn't contain any discrete beables. It means that the value of these beables have to be decided at some moment by the usual "quantum methods" - randomness plus collapse - anyway. dBB theory is deterministic. But this does not mean that there are no random elements. In fact, the measurement result depends, in an essential way, not only on the initial value of the quantum system, but also on the initial value of the measurement device.  Thus, the "measurement result" is nothing which depends only on the quantum system, but it depends also on an external variable, which is essentially random (in quantum equilibrium). And there is, of course, a collapse - the collapse of the effective wave function of the measured system. RE: Another attack against de Broglie-Bohm theory by Lumo - secur - 05-13-2016 This stance of lumo's is a surprise to me. I thought dBB was an accepted alternative interpretation in modern physics - today, not just 1952. That's what people at PF say. But lumo says dBB can't mimic the results of Feynman diagrams with loop corrections. He also mentions spin and momentum measurements, and even Lorentz invariance. All of these issues are addressed in Bohm and Hiley, "Undivided Universe", 1993, except the Feynman diagram loops. Maybe it's briefly mentioned somewhere; certainly doesn't go into it in depth. B & H do discuss boson field and interactions, at least. So, does lumo think B & H is wrong? Other physicists (PF) don't. Or, does he say it's superficial, and breaks down in more complex circumstances (like loop corrections)? Perhaps I should go ask him. Obviously since so few work on dBB, it's bound to fall behind in some new areas. That doesn't invalidate it; we must expect it to constantly need more work to justify and extend it. It's very nice of lumo to point out where such work is needed. It would be even nicer if he went ahead and did the work, but no reason he should. But it's not reasonable to reject it on those grounds; he must wait until dBB theorists have a chance to do the work - and then he must read their arguments carefully and without pre-judgment. Bohm's overall strategy was to show dBB equivalence to standard QM within realms tested by current technology. I thought he had successfully done so, as of 1993. But this strategy is vulnerable to future developments, needs to be extended, and may break down at any time. Of course that's good, it means dBB is falsifiable; but it's bad if you are a dBB proponent, means you are vulnerable to attacks like lumo's. Note that MWI and other interpretations don't have this problem: the math is identical to standard QM, so no contradiction can arise. dBB math however is, at the detailed level, different. Unfortunately the best I can do is follow the arguments (including math) on each side; I'm not competent to judge who's right. So for now I can only go on general considerations. That's why I'm happy when all reputable physicists agree on something: I can just agree also! If lumo is the only anti-dBB guy out there, I can safely ignore him and believe Schmelzer and PF. (I think we can agree there are many competent people there, however much we may disagree with their attitudes sometimes!) But if many physicists agree with lumo, I have no opinion until the two sides reach a conclusion. So at this time my main question is: who represents mainstream opinion re. dBB: lumo, or PF? Is lumo's a minority, fringe opinion, or not? Now, here is my only argument against lumo: it's not technical, but philosophical. Clearly he hates dBB and the philosophy it represents. He makes no secret of this. So, prima facie, he's very biased. Does that mean he's wrong? Absolutely not. Maybe one reason he hates dBB is precisely because he knows, correctly, that it's wrong! Still it obviously makes his conclusion less reliable. Remember this is from my point of view: his technical argument's validity has nothing to do with his bias; if I were competent to judge it directly I wouldn't even mention it. But as a layman, looking at the overall situation, clearly this bias reduces his credibility. On the other side, are you, Schmelzer, biased in favor of dBB? You haven't said so (as lumo has), but I suspect dBB philosophy is attractive to you. I'd like to ask, why? Do you (as lumo indicates) see dBB, similar to ether theory, as a way to rid physics of the vague, unsatisfying logical-positivism of the 20th century and return to more of a classical picture, where things intuitively makes sense? If so, I appreciate that desire, but don't care a whole lot which way it comes out. Personally I have no problem with the standard view of QM. As Einstein might put it, God does play dice with the universe. Perhaps the moon really isn't there until a mouse looks at it - so to speak. Fine with me. At the moment, in fact, I fully accept this probabilistic view of reality. If it is proven wrong someday I'll fully accept that proof, and be content with the classical view instead. One way that could happen is that technology finally can test reality down to such a precise level that dBB is proven right, probabilistic view wrong. But I'm quite confident that won't happen in my lifetime. Anyway - this whole issue is annoying! I had pigeon-holed dBB as a viable interpretation, accepted by all real physicists. Since I don't care much about it, that comfortable conclusion allowed me to put it aside and work on other things. If I meet someone like Schmelzer who (as far as I can tell) "believes" it, fine. If someone else doesn't "believe" it, also fine: both are logical and acceptable stances. But if dBB comes into question like this it means I've got to take a closer look at the issue. Once I learn a bit more about dBB's status in modern physics I'll intend to go ask lumo some of these questions. Perhaps first I'll ask PF exactly what they think about it. Meanwhile, Schmelzer, can you tell me: is there a solid mainstream opinion today about dBB, and if so, what is it? RE: Another attack against de Broglie-Bohm theory by Lumo - Schmelzer - 05-14-2016 Lumo has always opposed dBB theory, but it seems he is now more radicalized about this.  In the past  the discussion has been more reasonable. To say what the mainstream thinks is difficult, because the mainstream does not think about dBB theory. Those who care about interpretations at all have been, for a large time, complete outsiders. This seems to change during the last years, but it does not mean that the mainstream already cares about interpretations. My impression is that the mainstream thinks that dBB theory needs a preferred frame, thus, has a problem with relativity. And that it is defined only for non-relativistic particles. Bohmian field theory is essentially simply unknown. But that mainstream scientists think that Bohm's equivalence proof is false I have never heard. A criticism which is widely known is that the Bohmian trajectories are surrealistic - that they do not fit into our classical ideas about trajectories. The MWI proponents have proposed the thesis that dBB theory is "many worlds in denial", in other words, that it is essentially correct, but the trajectory is an unnecessary and unobservable ingredient one should simply omit. The result would be MWI. So, the opinion that dBB theory works only for nonrelativistic particle theory is widespread, but not based on arguments but on simple ignorance, given that the first Bohmian relativistic field theory was already presented by Bohm himself 1952 for the EM field. The claim that there is no equivalence theorem even for non-relativistic particles seems to me, instead, fringe. The probabilistic character is not a problem at all. There are realistic interpretations which use probabilistic equations, like Nelsonian stochastics or Caticha's entropic dynamics. This is something different from giving up realism and causality. Do I have some prejudices in favor of dBB? Actually, I think Caticha's entropic dynamics is the best attempt to interpret QT. Unfortunately, it has a problem with the Wallstrom objection. So, there is yet something to do for a really satisfactory interpretation, but some of the points of Caticha are really nice, so that I think there is something behind them. Then, dBB theory is nothing uniquely defined - dBB needs some additional structure, the configuration space Q, and there may be different choices. But what I have a clear "prejudice" for are realistic and causal interpretations. This is because Bell's theorem shows that a realistic or causal interpretation needs a preferred frame. So, if somebody accepts realism or causality, he has to accept a preferred frame too. But what about the counterargument "realism and causality fail anyway, because of the strangeness of quantum theory"? This counterargument is rejected by good realistic and causal interpretations of QT. So, realistic and causal interpretations implicitly supports my ether theories. And the reverse holds too. There is the objection against interpretations with a preferred frame, that even if one could define them for special relativity, in general relativity this is no longer possible. And my ether theory of gravity gives an answer to this objection. It was never my aim to preserve some classical philosophy, some classical dogma or so. If the world is really strange, so be it. But if I see a possibility for a more classical interpretation, I use it. My rule is much closer to "don't introduce mystics without necessity" than to "preserve classical common sense at any costs". Of course, once I have found that some common sense idea appears compatible with modern physics in my approach, but not in the mainstream approach, I feel free to use this common sense idea as further support for my approach By the way, once I'm banned on his blog I cannot give there a link to my answers here. It would be nice if you could do this. RE: Another attack against de Broglie-Bohm theory by Lumo - secur - 05-16-2016 Schmelzer, I went to Lumo's forum and asked him about dBB. BTW I called myself "algore" which was my old net name for decades. Wasn't allowed on PF - either because it's a famous politician, or already in use, so I became "secur". You can look at the results there if you want. Warning - algore's personality is definitely not up to your standards! Perhaps I was getting somewhere and was about to propose that he reinstate you but he hasn't responded, don't know why. I'll post a link to your page, but only with permission, you understand. Since at the moment you're persona non grata I will tell him whose the link is (if I get that far) and he can decide whether it's Ok. There's no way anyone is going to convince him of anything, IMHO. His mind is made up - stubborn. Doesn't matter; except, of course, one wants to spread one's ideas as far as possible. He's certainly entertaining ... see what happens. Re prejudice - I'm "prejudiced", alright, in favor of open discussion and unbiased appraisal of all ideas. Also, in favor of each person rejecting anything he doesn't like, without interfering with other's freedom. Finally, I'm "prejudiced" in favor of the owner of a given board: he, or she, can do whatever they want with their own turf. As far as I know dBB is reasonable and possible; still haven't seen anything to make me think otherwise - just polemics.