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Now it becomes totally bizzare. If the collapse is not caused by the interaction between the measured system and the measurement device, by what is it caused then?
vanhees71 said:Now it becomes totally bizzare. If the collapse is not caused by the interaction between the measured system and the measurement device, by what is it caused then?
I wouldn't say it's important, since it just makes precise what was already consensus (QM is compatible with locality). However, I like it a lot, since it forces locality deniers to point out an error in the proof, which of course doesn't exist. I also wouldn't call it an interpretation. All interpretations of QM must predict the same probabilities and that papers just shows that they can arise from a classical probabilistic model that happens to be local.Shayan.J said:That seems to be an important paper. Can we call it an interpretation of QM?
I'm not asking for a mathematically rigorous presentation. Also a physicist understands compatibility with relativity to mean the implementation of the Poincare group, possibly at a non-rigorous level (as in QCD). I would already be satisfied if you could show me a non-rigorous implementation of the Poincare group that includes collapse. Show me one textbook that explicitly claims that collapse is compatible with relativity.atyy said:My claim is at the physics level of rigour - in the same way that QED is said to be compatible with relativity. In fact, my claim is found in the standard textbooks.
The overwhelming majority of physicists interprets Bell's result in favour of locality and in disfavour of hidden variables. Only a die-hard minority of Bohmians advocates non-locality. Both groups agree that Bell can be interpreted in both ways. Moreover, the paper that I quoted proves unambiguously that QM is at least compatible with locality. So my view is in accordance with standard science.It's you that it is not accepting standard science.
If you read the paper, you will see that he says that quantum probabilities can be interpreted as conditional probabilities that are embedded in a classical Kolmogorov model. They cannot be interpreted as absolute probabilities. However, the classical model, in which the quantum probabilities are embedded, is fully local. All of that is contained in section 8 of the paper. (In analogy to the situation in geometry: There exist non-Euclidean geometries, but they can be embedded in higher dimensional Euclidean spaces).ddd123 said:Rubi, why do you say "classical probabilistic model that happens to be local", when the abstract of the paper says "violation of Bell's inequality implies the impossibility to apply the classical probability model of Kolmogorov (1933) to quantum phenomena"?
rubi said:Show me one textbook that explicitly claims that collapse is compatible with relativity.
Ok. where does he claim it?atyy said:Weinberg.
rubi said:Ok. where does he claim it?
(I note that you refuse to address my questions.)
In his QFT book, he only states the Born rule. The collapse isn't even mentioned in the list of axioms. As stevendaryl wrote earlier: The Born rule is not the same thing as collapse. Moreover, I have asked for an explicit statement that the collapse is compatible with relativity, not just a statement of the collapse.atyy said:He states the axioms for QM in his QFT book, and that includes collapse. The axioms for QM carry through to QFT.
I pretty much know all the literature and I'm not aware of a single book that explains the compatibility of collapse with the Poincare group. That's why I'm asking. Your first attempt apparently failed already.atyy said:@rubi, also you can look up the literature yourself. It is absolutely standard.
rubi said:In his QFT book, he only states the Born rule. The collapse isn't even mentioned in the list of axioms. As stevendaryl wrote earlier: The Born rule is not the same thing as collapse. Moreover, I have asked for an explicit statement that the collapse is compatible with relativity, not just a statement of the collapse.
But please respond to the following question: How can the non-commutativity of collapse be compatible with relativity, when in relativity, two time evolutions always commute?I pretty much know all the literature and I'm not aware of a single book that explains the compatibility of collapse with the Poincare group. That's why I'm asking. Your first attempt apparently failed already.
atyy said:For example, Peres uses the collapse in his discussion of relativistic QM.
ddd123 said:If you mean his quantum theory book, he only uses collapse for a reductio, to criticize the idea that at each instant an EPR pair has a definite wave function.
atyy said:Yes, that's right. I love Peres's book, but it is deeply flawed. However in this article, he takes a more standard position: http://arxiv.org/abs/quant-ph/9906034
ddd123 said:Do you think that reductio is flawed, and if so, why?
It may be compatible with relativistic causality, but saying that it is compatible with relativity is different. A relativistic theory must implement the Poincare group and time evolution is just one special Poincare transformation. I think this is a consensus definition of a relativistic theory among physicists. If collapse is a form of time evolution, then it must be a Poincare transformation. This is a deeply physical requirement and not just unnecessary rigor. Physicists do care about this. Weinberg's QFT book for example puts a lot of emphasis on the implementation of the Poincare group, even though it is not a rigorous text. However, it doesn't address the issue, whether collapse is a Poincare transformation or not. I'm not aware of any physics textbook that addresses this issue.atyy said:I did not attempt to answer your question, as I said, I don't know where that is shown. But certainly collapse is standard in QM, and in all special cases studied, it is consistent with relativity. So yes, it is absolutely standard to say that collapse is consistent with relativity at the physics level of rigour.
My edition of Weinberg's book "The Quantum Theory of Fields, Vol. 1" makes no mention of the collapse postulate. It just states the Born rule and nothing more. I even interpret this omission to be deliberate.And no, you are wrong - the Weinberg book does state collapse.
The paper just explains the compatibility with relativistic causality. I know that this works, but it doesn't address the issue of the compatibility with the Poincare group. This is not an instance of the mathematicians/physicists battle about the right amount of rigor in physical theories. Anyway, I would be really interested in the paper you mentioned. As I said, I don't claim that collapse is incompatible with relativity. I'm just saying your arguments don't guarantee compatibility.See the post above for relevant literature.
BTW, I did once see a paper addressing the question you ask, but can't remember where it is - in the meantime, see the Peres paper above.
There is a problem with your request and I don't know why atyy doesn't point it out!rubi said:It may be compatible with relativistic causality, but saying that it is compatible with relativity is different. A relativistic theory must implement the Poincare group and time evolution is just one special Poincare transformation. I think this is a consensus definition of a relativistic theory among physicists. If collapse is a form of time evolution, then it must be a Poincare transformation. This is a deeply physical requirement and not just unnecessary rigor. Physicists do care about this. Weinberg's QFT book for example puts a lot of emphasis on the implementation of the Poincare group, even though it is not a rigorous text. However, it doesn't address the issue, whether collapse is a Poincare transformation or not. I'm not aware of any physics textbook that addresses this issue.My edition of Weinberg's book "The Quantum Theory of Fields, Vol. 1" makes no mention of the collapse postulate. It just states the Born rule and nothing more. I even interpret this omission to be deliberate.The paper just explains the compatibility with relativistic causality. I know that this works, but it doesn't address the issue of the compatibility with the Poincare group. This is not an instance of the mathematicians/physicists battle about the right amount of rigor in physical theories. Anyway, I would be really interested in the paper you mentioned. As I said, I don't claim that collapse is incompatible with relativity. I'm just saying your arguments don't guarantee compatibility.
I agree fully with this view. Collapse is an effective process that arises from a fully Poincare invariant theory with only unitary evolution. But that only means that the collapse is not part of a fundamental relativistic theory, but rather emerges from such a theory! Think of the following analogy: The quantum harmonic oscillator ##H=p^2+q^2## is not Galilei invariant, but we can embedd it into a larger theory ##H=P^2 + p^2 + (Q-q)^2## which is fully Galilei invariant. The QHO just emerges as the center of mass part of this larger system. In the same way, a theory with collapse emerges from a larger theory without collapse, in which only Poincare transformations are allowed.Shayan.J said:There is a problem with your request and I don't know why atyy doesn't point it out!
Collapse is not supposed to be a time evolution in the same sense as the unitary evolution you're talking about. Its not supposed to be a fundamental evolution besides the unitary evolution. Its not even supposed to be in a fundamental theory!
The crucial point was clearly explained by @stevendaryl but looks like it was ignored. When considering an open quantum system, an effective evolution seems to emerge for the (open) system. We're still unable to completely derive this effective evolution from the fundamental unitary evolution of the larger closed system. That's why we just consider its input and output and treat it as a blackbox and call it by such a mysterious name as collapse. When this blackbox is explained, we all expect to retain all the unitary evolution that is compatible with Poincare group.
I'm not sure what you mean by a larger theory, but I expect that collapse emerges from the same QM we already have, when applied to an open system.rubi said:I think atyy doesn't point this out, because he doesn't agree that collapse can emerge from a larger theory.
Yes, that's what I mean too. However, this is a controversial topic. Many physicists (like me) believe that this works out and others don't. I'd say the issue isn't settled completely.Shayan.J said:I'm not sure what you mean by a larger theory, but I expect that collapse emerges from the same QM we already have, when applied to an open system.
rubi said:It may be compatible with relativistic causality, but saying that it is compatible with relativity is different. A relativistic theory must implement the Poincare group and time evolution is just one special Poincare transformation. I think this is a consensus definition of a relativistic theory among physicists. If collapse is a form of time evolution, then it must be a Poincare transformation. This is a deeply physical requirement and not just unnecessary rigor. Physicists do care about this. Weinberg's QFT book for example puts a lot of emphasis on the implementation of the Poincare group, even though it is not a rigorous text. However, it doesn't address the issue, whether collapse is a Poincare transformation or not. I'm not aware of any physics textbook that addresses this issue.
rubi said:My edition of Weinberg's book "The Quantum Theory of Fields, Vol. 1" makes no mention of the collapse postulate. It just states the Born rule and nothing more. I even interpret this omission to be deliberate.
rubi said:The paper just explains the compatibility with relativistic causality. I know that this works, but it doesn't address the issue of the compatibility with the Poincare group. This is not an instance of the mathematicians/physicists battle about the right amount of rigor in physical theories. Anyway, I would be really interested in the paper you mentioned. As I said, I don't claim that collapse is incompatible with relativity. I'm just saying your arguments don't guarantee compatibility.
Shayan.J said:There is a problem with your request and I don't know why atyy doesn't point it out!
Collapse is not supposed to be a time evolution in the same sense as the unitary evolution you're talking about. Its not supposed to be a fundamental evolution besides the unitary evolution. Its not even supposed to be in a fundamental theory!
The crucial point was clearly explained by @stevendaryl but looks like it was ignored. When considering an open quantum system, an effective evolution seems to emerge for the (open) system. We're still unable to completely derive this effective evolution from the fundamental unitary evolution of the larger closed system. That's why we just consider its input and output and treat it as a blackbox and call it by such a mysterious name as collapse. When this blackbox is explained, we all expect to retain the unitary evolution that is compatible with Poincare group. So even if there is an incompatibility with the Poincare group, its because we're considering an effective evolution and ignoring part of the system.
Now it seems to me that the only point of disagreement here, can be whether that effective evolution actually emerges or not.
rubi said:I think atyy doesn't point this out, because he doesn't agree that collapse can emerge from a larger theory.
What's wrong with a universe that evolves unitarily?atyy said:I don't discuss this because if all you have is unitary evolution, you will end up with unitary evolution of the universe with all the problems of interpretation including MWI etc.
As I said, it seems to me the only thing that can be a matter of disagreement here is that whether collapse happens for an open quantum system or not(whether its emergent as I say, or fundamental as you say, we should first establish that it happens because vanhees71 doesn't think that it does!). Can you give a reference that it does? I mean, experimentally. Something like this!(I'm not saying its a good example, just an example!)atyy said:My aim in this thread is to defend the minimal interpretation or shut up and calculate because it works. Vanhees71 claims to support shut up and calculate or the minimal interpretation, but if you notice, it is he that is always bringing up issues of interpretation by objecting to collapse.
This paper https://arxiv.org/abs/1412.6987 is not published in peer reviewed journal so as I understand you leave it up to me to point out the flaws in this local model. Fine.rubi said:There is of course no counterexample to a proven theorem. Using frequencies instead of probabilities doesn't change that. The existence of a local probabilistic model that predicts the QM probabilities proves beyond doubt that these probabilities are compatible with locality. What's wrong with your counterexample? Frequency proofs of Bell's theorem make the same assumptions, they are just less obvious, because nobody is used to the frequency formulation. The choice of subsequences in the frequency formulation of probability is dual to the choice of a conditional probabilities in the measure formulation.
Now about your objections to my counterexample. There is no need to use frequencies in my counterexample. This counterexample boils down to the statement that there is no set of possible detections sequences that satisfy QM predictions (exactly) and locality conditions. If you are unsure about provided argument you can take some limit for detection sequences and test all possible combinations using brute-force search but as I see, the argument why it is not possible is rather trivial and does not require such a test to see the point.rubi said:There is of course no counterexample to a proven theorem. Using frequencies instead of probabilities doesn't change that. The existence of a local probabilistic model that predicts the QM probabilities proves beyond doubt that these probabilities are compatible with locality. What's wrong with your counterexample? Frequency proofs of Bell's theorem make the same assumptions, they are just less obvious, because nobody is used to the frequency formulation. The choice of subsequences in the frequency formulation of probability is dual to the choice of a conditional probabilities in the measure formulation.
http://www.worldscientific.com/doi/10.1142/S1230161216500086zonde said:This paper https://arxiv.org/abs/1412.6987 is not published in peer reviewed journal
Forum guidelines contains a link where one can check acceptable sources http://ip-science.thomsonreuters.com/mjl/Shayan.J said:
Come on, if you say there is a collapse, it can only be caused by the interaction of the particle with the measurement apparatus. If you say there is no interaction, you cannot measure anything.atyy said:The minimal interpretation is agnostic about "cause". "Local interactions" are properties of Hamiltonians. The collapse does not even affect the Hamiltonian, so how can the collapse be related to interactions?
World Scientific is not a journal, but a publisher. The journal itself is Open Systems & Information Dynamics, and it's impact factor for 2015 is 1.3.zonde said:Forum guidelines contains a link where one can check acceptable sources http://ip-science.thomsonreuters.com/mjl/
I can not find WorldScientific there.
The model in the paper was published in a reputable journal in the reference [12] of that paper. The paper is just a cooked down version of that reference.zonde said:This paper https://arxiv.org/abs/1412.6987 is not published in peer reviewed journal so as I understand you leave it up to me to point out the flaws in this local model. Fine.
The model considers all detections, so it doesn't exploit the detection loophole. Moreover, the model uses a different method to embedd the probabilities into a Kolmogorov space. It doesn't use marginals, but rather conditionals.Statement that QM probability space is embedded in larger classical probability space means that model exploits detection loophole.
The model doesn't exploit the superdeterminism loophole, because it is not deterministic. Only a deterministic theory can be superdeterministic. The model however is purely stochastic. The non-local variables occur in the conditional probabilities and that is natural, since the quantum probabilities depend on the angles of both Alice and Bob, so we must condition on a non-local pair of angles to obtain the quantum probabilities. The author shows that despite of this, one obtains a local stochastic model.The statement in bold clearly says that this model is exploiting superdeterminism loophole and that is not acceptable in scientific model.
As I said, the use of subsequences in frequency versions of the inequality amounts exactly to the use conditionals in the probability setting. You can't just select a subsequence and expect it to be distributed in the same way as the original sequence. This assumption must be made in all proofs of the inequality. The inequality can't be proved without this assumption.zonde said:Now about your objections to my counterexample. There is no need to use frequencies in my counterexample. This counterexample boils down to the statement that there is no set of possible detections sequences that satisfy QM predictions (exactly) and locality conditions. If you are unsure about provided argument you can take some limit for detection sequences and test all possible combinations using brute-force search but as I see, the argument why it is not possible is rather trivial and does not require such a test to see the point.
If you rely on authority more than checking the arguments yourself there is Eberhard's paper http://link.aps.org/doi/10.1103/PhysRevA.47.R747. In this paper Eberhard has included Bell type inequality proof that takes similar approach as in the counterexample I gave.
This discussion is a mess, and I'm sorry that I got involved into it again. The physics is very clear, and there is no problem.ddd123 said:On my part, I don't know what to think. On one hand, the long-range correlations are there because of measurement, and avoiding collapse doesn't practically account for compound measurements (you have to believe it would work if you could do the practically impossible calculation of treating the whole measurement device quantum mechanically). On the other hand, collapse is frame-dependent, although the consequences are the same whatever frame you choose in the end, so it seems to beg for a deeper explanation.