Oh, sorry. I though the idea of the inequality was to provide a tool to decide the question that Einstein has put up via an experiment. It's achieving its goal by deciding/settling the problem, no?PeterDonis said:I said nothing whatever about the Kolmogorov axioms. I was responding to your claim about the CHSH inequality. It seems odd to say that that inequality is "achieving its purpose very well" when it makes predictions that are falsified by experiments.
Yes. They're simply constraints on any four binary random variables sharing a common probability space.Killtech said:CHSH and Tsirelson deal with the concept of locality. You cannot take that part away from those and expect them to hold anyway. Or do you actually claim that those have nothing to do with locality?
If you mean that experimentally showing that the CHSH inequality is violated rules out certain types of models, sure, that goal has been achieved. But the claims you are making don't appear to be about ruling out certain types of models. You appear to have some specific type of model in mind that is not ruled out and that somehow "explains" QM without all the problems that other people see. If you do, you should give a specific reference that tells us what that model is, so we have a basis for discussion. For example, if you think some version of "Kolmogorov theory" does the job, give us a reference that explains what that theory is and what predictions it makes.Killtech said:I though the idea of the inequality was to provide a tool to decide the question that Einstein has put up via an experiment. It's achieving its goal by deciding/settling the problem, no?
Oh boy. The whole point of the exercise is the assumption that the quantum systems in Alice and Bobs lab cannot communicate. But if that isolation restriction (which is trying to represent the core property of distance) is lifted, then there is just nothing preventing the violating the inequality by as much as possible, even beyond Tsirelson's bound. If the system in Alice's lab can tell Bob's what it settled for during its measurement and before Bob's system was measured, then of course it can conveniently change itself to whatever it needs to to produce any desired distribution.CelHolo said:Yes. They're simply constraints on any four binary random variables sharing a common probability space.
Break that common probability space into that of a two step stochastic process - i.e. deviate from the assumptions made for CHSH but which is still perfectly fine within Kolmogorovs framework.CelHolo said:I think you just don't know the mathematics, it's quite easy to derive the CHSH inequalities from the assumption of a common probability space. See Streater's Lost Causes in theoretical physics for a full explanation.
As I have already asked you once, please give a reference for the specific model that you have in mind. You can't just wave your hands. Either there is a valid reference describing a specific model with the properties you keep claiming, or there isn't.Killtech said:Break that common probability space into that of a two step stochastic process - i.e. deviate from the assumptions made for CHSH but which is still perfectly fine within Kolmogorovs framework.
Pushed to it's limit, neither the light nor the electron is ontic. They are all "things" we merely theorize from our perceptions. At one time there were different theories explaining those same perceptions, e.g. when the Greeks thought of vision as rays that reached out from one's eye. This seems to point to Quine's concept of ontologies as whatever entities are assumed in one's theory of the world.vanhees71 said:Well, if ontology is about what Kant called "Ding an sich" (I don't know, how to translate Kant into English), then it's something not subject to the natural sciences, because the natural sciences are about nature as can be objectively observed. Objectively means the observations must be reproducible and independent from the individual making the expression.
Take, e.g., classical electrodynamics and the electromagnetic field. Is the classical electromagnetic field ontic, providing an "ontology of light"? I don't know, because if one thinks about it, it's just a mathematical framework describing the phenomena of emission of "light" (e.g., the Sun as a thermal light source) and its registration at some distant place. We never directly observe the field but just its action on some matter. Usually it's the photoelectric effect which provides a signal in a detector (photoplate, CCD cam, the retina of our eyes etc). So "is light really" the electromagnetic field or is it the photo electron ejected from matter which then leads to a "signal" we can preceive?
I think an answer to this question is pretty irrelevant from the point of view of the natural sciences. It's simply easier to talk about the electromagnetic field about some "thing" with a kinematics and dynamics in its own right as if it were something like a substance though for a substance it doesn't have a typical "substance-like" (charge-like) conserved quantity. It basically has been introduced by Faraday (based on his experience with experiments and observations) and then brought in a mathematical form by Maxwell to have a concise way to talk about these electromagnetic phenomena.
First, for me the observation overrides any theoretical concern. If it is not there, how can you measure a phase shift? Second, does not the path integral method effectively give the least action result? If so, the same action determines the phase shift of the wave, does it not?meekerdb said:If it's real how do you explain that the same result can be obtained by Feynmann's path integral method?
When orthodox QM is presented in instrumental form, just as a set of practical rules for computing probabilities of measurement outcomes, it's perfectly consistent. But I see inconsistencies when the orthodox guys start to make a philosophy out of it, i.e. when they try to explain what those rules mean at a deeper level. (The very first inconsistency that many of them commit is that they use philosophy to argue that one should not do philosophy.) Anyway, if some of my demands are too excessive, I would like to know what those demands are.PeroK said:This leaves us with two possibilities:
1) QM is manifestly incomplete - and anyone who believes in orthodox QM must lack something in terms of the intellectual capability to think logically. I.e. they embrace an obvious contradiction.
2) You place excessive demands on a fundamental theorem of nature that, from a matter purely of logical consistency, are not required. I.e. there is no inconsistency, only your perception that this particular fundamental theory of nature is deficient.
My understanding of this thread in broad terms is that orthodox QM does not demand that all measurables have well-defined values at all times and that you believe that this makes QM incomplete and inevitably leads to philosophical inconsistencies.Demystifier said:Anyway, if some of my demands are too excessive, I would like to know what those demands are.
I can well understand that. It's impossible to be totally aphilosophical (since, as you point out, even arguing to keep philosophy out of physics is a philosophy in itself). From my point of view, the whole debate about ontology is a quagmire from which it may be impossible to emerge. I would say - and this is more than "shut up and calculate" - that even if the philosophical questions that QM raises are unanswerable, then this could equally be seen as a warning against expecting too much from a philosophical analysis of natural science.Demystifier said:But I see inconsistencies when the orthodox guys start to make a philosophy out of it, i.e. when they try to explain what those rules mean at a deeper level. (The very first inconsistency that many of them commit is that they use philosophy to argue that one should not do philosophy.)
This was dealt with long ago by Bill Unruh and others. It's impossible to directly measure the quantum state, just as it is impossible to directly measure any set of probability distributions, what they actually do is measure a POVM with postselection.Ian J Miller said:then how do you account for the following paper: Lundeen, J. S., Sutherland, B., Patel, A., Stewart, C., Bamber, C. 2011. Direct measurement of the quantum wavefunction
One must be more careful to formulate things right. It is an indication that we don't do this properly, because we always start from scratch. I come more and more to the conclusion that there's no way to make progress, but here's one more try:Demystifier said:So you are saying that the state always exists, while values of the observables exist only when they are measured, is that right? But it creates a lot of additional questions:
The quantum formalism is the result of many observations and experimental facts. There is no sensible way to answer such "why questions" in the natural sciences, which figure out as precisely as possible how Nature behaves but never can answer why she behaves the way she does. Discussions concerning this quesions touch the realm of religion and are not subject of the natural sciences.Demystifier said:1. Why do values not exist before measurement?
Measurements are interactions between the measurement device and the measured object. The dynamics is described by quantum (statistical) theory.Demystifier said:2. How the values know that there is a measurement out there?
It's given by a concrete measurment apparatus.Demystifier said:3. What's the precise definition of measurement?
The construction of measurment devices is based on the known natural laws as any technical development. The "primitive concepts" behind this constructions thus are the corresponding theories describing them.Demystifier said:4. Can measurement be derived from something more fundamental, or is measurement a primitive concept?
Of course the state of the measured system changes due to the interaction with the measurement device. Whether or not the system persists to exist, i.e., can be in a meaningful way separated from the measurement device an/or "the environment" depends on the specifics of the measurement device. Thus this is a question to be answered theoretically using the theory but it cannot be answered by inventing some new fundamental postulate of the theory.Demystifier said:5. Does a value (randomly created in a measurement) have influence on the state?
A closed system's dynamics is described by unitary time evolution. Attempts to extend QT beyond this standard formulation so far failed (or there are even counterarguments, e.g., by Susskind et al concerning the use of Lindblad equations generalizing the unitary time evolution of the standard theory).Demystifier said:6. If the answer to 5. is "yes", does this influence violate unitarity, linearity, locality and/or the Schrodinger equation?
likewise, why don't they take, any possible value, for example up and up.Demystifier said:So you are saying that the state always exists, while values of the observables exist only when they are measured, is that right? But it creates a lot of additional questions:
1. Why do values not exist before measurement?
2. How the values know that there is a measurement out there?
3. What's the precise definition of measurement?
4. Can measurement be derived from something more fundamental, or is measurement a primitive concept?
5. Does a value (randomly created in a measurement) have influence on the state?
6. If the answer to 5. is "yes", does this influence violate unitarity, linearity, locality and/or the Schrodinger equation
Demystifier said:But I see inconsistencies when the orthodox guys start to make a philosophy out of it, i.e. when they try to explain what those rules mean at a deeper level. (The very first inconsistency that many of them commit is that they use philosophy to argue that one should not do philosophy.)
Yeah I find this an odd question. To make scientific progress we had to realize that often most/all observables do not have a well-defined value. To me it would be like having a problem with GR because nobody has told you "why" spacetime is curved. Isn't QM a success because it correctly captures these new fascinating aspects of nature?vanhees71 said:The quantum formalism is the result of many observations and experimental facts. There is no sensible way to answer such "why questions" in the natural sciences, which figure out as precisely as possible how Nature behaves but never can answer why she behaves the way she does
Not exactly. I can accept a theory in which some values are not always defined, as far as the theory clearly specifies sufficient and necessary conditions for the values to become defined. The usual condition that it happens when those are "measured" is just not clear enough, unless one also makes a clear definition of measurement. It is this typical lack of clarity that makes it incomplete, which does not necessarily make it inconsistent. The inconsistencies usually appear in the second step, when people who are well trained in physics and math try to do philosophy.PeroK said:My understanding of this thread in broad terms is that orthodox QM does not demand that all measurables have well-defined values at all times and that you believe that this makes QM incomplete and inevitably leads to philosophical inconsistencies.
EPR started from the same postulate and, by assuming also locality, derived that QM is incomplete. I know that you disagree with EPR, but I don't see any consistent way to disagree with them given those two premises.vanhees71 said:An observable has a determined value, if with 100% probability a measurement of this observable results in this value.
But they said clearly what they mean by incomplete. In that sense QM is incomplete no question about it. Was that a useful definition?Demystifier said:EPR started from the same postulate and, by assuming also locality, derived that QM is incomplete. I know that you disagree with EPR, but I don't see any consistent way to disagree with them given those two premises.
I disagree with EPR, because local relativistic QFT is a model, where locality and indeterminism is fully consistently discribed. For me EPR is completely refuted by the demonstration of the violation of Bell's inequalities.Demystifier said:EPR started from the same postulate and, by assuming also locality, derived that QM is incomplete. I know that you disagree with EPR, but I don't see any consistent way to disagree with them given those two premises.
I don't understand in which part you disagree with EPR?vanhees71 said:I disagree with EPR, because local relativistic QFT is a model, where locality and indeterminism is fully consistently discribed. For me EPR is completely refuted by the demonstration of the violation of Bell's inequalities.
To be honest given the near century we've had of not needing such a theory while increasing our understanding of nature while remaining in the "EPR-incomplete" theory and all the no-go theorems against the EPR style theories, it's fruitless to keep seeking an EPR theory.vanhees71 said:Whether there is a then indeed necessarily nonlocal EPR-complete theory as "complete" in describing Nature as relativistic local QFT or not, I don't know
That's an utter nonsense. To agree with EPR means to agree that their assumptions logically imply their conclusions. No experiment can refute a validity of a logical argument. A logical argument can only be refuted by another logical argument. The logical assumptions of EPR are QM and locality, which you accept. Their logical conclusion is incompleteness, which is not refuted by experimental violation of Bell's inequalities.vanhees71 said:I disagree with EPR, because local relativistic QFT is a model, where locality and indeterminism is fully consistently discribed. For me EPR is completely refuted by the demonstration of the violation of Bell's inequalities.
Yes it was. When combined with the Bell's result, now we know that if we want to complete QM in this sense, we must abandon locality (in the EPR-Bell sense).martinbn said:But they said clearly what they mean by incomplete. In that sense QM is incomplete no question about it. Was that a useful definition?
How is that useful?Demystifier said:Yes it was. When combined with the Bell's result, now we know that if we want to complete QM in this sense, we must abandon locality (in the EPR-Bell sense).
There is one more ingredient to EPR, the definition of incompleteness. He (vanhees71) can disagree with that definition.Demystifier said:That's an utter nonsense. To agree with EPR means to agree that their assumptions logically imply their conclusions. No experiment can refute a validity of a logical argument. A logical argument can only be refuted by another logical argument. The logical assumptions of EPR are QM and locality, which you accept. Their logical conclusion is incompleteness, which is not refuted by experimental violation of Bell's inequalities.
So, hypothetically, we get E, P & R back; show them Bell's inequality; show them a modern experimental set-up of Bell's inequality (I think they'd be very excited at this point); run the experiment; and:Demystifier said:That's an utter nonsense. To agree with EPR means to agree that their assumptions logically imply their conclusions. No experiment can refute a validity of a logical argument. A logical argument can only be refuted by another logical argument. The logical assumptions of EPR are QM and locality, which you accept. Their logical conclusion is incompleteness, which is not refuted by experimental violation of Bell's inequalities.
I think that none of them will say "Oh, nature is non-local, relativity is wrong, we must adopt a preferred frame theory."PeroK said:So, hypothetically, we get E, P & R back; show them Bell's inequality; show them a modern experimental set-up of Bell's inequality (I think they'd be very excited at this point); run the experiment; and:
@vanhees thinks they'd go away disappointed
You think they'd say "I told you so"?
It's like usefulness of the impossibility of perpetuum mobile. We don't longer waste time on thinking about the impossible.martinbn said:How is that useful?