A. Neumaier
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No. I misunderstood your intentions. Forget it.Am I misunderstanding the English word "asset"?
No. I misunderstood your intentions. Forget it.Am I misunderstanding the English word "asset"?
This only shifts the problem. Given a prior for the Stokes vector, how is it updated when a new measurement comes in?regardless of the example the state update rules are just those used in quantum tomography in practice.
In this case, if I have the example right, it's the usual measurements to determine the Stokes parameters, just reinterpreted. If I have your example wrong can you say what is the typical way this is done I can check.
The only thing I think about probability theory, successfully applied in statistics as well as theoretical physics for about 150+/- years, is that it works. That's all I need to justify the use of any specific mathematical concept in the natural sciences.Well I don't know if it's a "strange idea" simply because it mightn't be useful in modern quantum theory. However it is, since it's just an alternate motivation for statistical tools that you can use regardless of what you think of probability theory. Such an application is here:
Experimental adaptive quantum tomography of two-qubit states
We report an experimental realization of adaptive Bayesian quantum state tomography for two-qubit states. Our implementation is based on the adaptive experimental design strategy proposed in the work by Husz\'ar and Houlsby [F. Husz\'ar and N. M. T. Houlsby, Phys. Rev. A 85, 052120 (2012).] and...journals.aps.org
Yes, and my very point is that it doesn't make sense to introduce more and more abstruse and esoterical "concepts" to clarify the meaning of Q(F)T.Well, we are discussing here (in the whole thread) various interpretations of quantum mechanics, and some of them are based on subjective probability. I find it strange, too, but one cannot usually discuss other interpretations by casting them in ones own differing interpretation without losing important features - one must use the language in which they describe themselves.
Well, we are discussing here (in the whole thread) various interpretations of quantum mechanics, and some of them are based on subjective probability.
Subjective probability is discussed even in theoretical books about probability theory, such as the one by Whittle (who primarily gives an exposition of the frequentist view), and is discussed at length in quite a number of books on Bayesian statistics, relevant for real data processing, even in physics.This is a science forum (at least that's what I thought) and not about philosophy (even not about philosophy of science).
This thread is explicitly about ''the deeper meaning of quantum mechanics'', so you shouldn't complain in this thread.Particularly even threads where a student asks some scientific question about introductory QM
This split is as ill-defined as the Heisenberg cut - different people place it differently. Like everywhere in discussion forums, the controversial issues take the most space, but are for most readers and contributors also the most interesting ones.one should split the QM section into a strictly scientific part, where standard QM is discussed and another philosophy-of-science part
I disagree that anyone is being abstruse or esoterical. And I disagree with your labeling of discussions as "philosophical". I think that the discussions are physics, not philosophy.Yes, and my very point is that it doesn't make sense to introduce more and more abstruse and esoterical "concepts" to clarify the meaning of Q(F)T.
What's the problem discussing this simply in another subforum?Without these foundational discussions I'd have little incentive to spend time on PF, and would also not contribute to other quantum physics topics.
The professional statisticians, even very applied ones, fall about half/half into objective (primarily frequentist) and subjective (primarily Bayesian) schools, using and recommending different analysis procedures based on the differences in the underlying understanding of probability.Probability is a clear defined mathematical concept with clear applications in terms of statistics
I mainly discuss to learn, not to contribute. Probably I would look only very rarely at the quantum physics forum (as I do now with the other forums) and hence not contribute my knowledge there.What's the problem discussing this simply in another subforum?
Another problem is that there is no clear demarcation line, and different contributors (and especially newcomers) will have quite varied views as to what belongs where. Who decides what belongs where? For each thread a majority vote among the mentors?What's the problem discussing this simply in another subforum?
This is almost blatantly an assumption, with little to no foundational support, especially when speaking about QT.The only thing I think about probability theory, successfully applied in statistics as well as theoretical physics for about 150+/- years, is that it works. That's all I need to justify the use of any specific mathematical concept in the natural sciences.
The problems at the edge of knowledge are actually the only problems really worth worrying about. In this case they are distinctly physical problems, which can only become abundantly clear - i.e. to foundations skeptics such as yourself - once a new theory has actually been developed which manages to supersede the old one in some aspects. The production of any new theory which contains QM as a limit and is falsifiable is one of the major contemporary goals of theoretical physics.where all these speculations about apparent problems, which are in fact pseudo-problems, are discussed without confusing people interested in science rather than cargo cult
This might surprise you, but actually no, it isn't as clear cut as it seems as pointed out by many experts. There are several conceptually different notions related to probability, which in the exact sciences are usually immediately interpreted as being probability as described by the standard theory and therefore reduced to standard probability; a few of these concepts are vagueness, uncertainty, likelyhood, possibility and propensity.Probability is a clear defined mathematical concept with clear applications in terms of statistics. Completed by information theory and QT it provides objective assignments of probability distributions of real-world systems.
Why not, it can be heard and understood. However, others may legitimately want to go further for their intellectual satisfaction.That's all I need to justify the use of any specific mathematical concept in the natural sciences.
Fully agree with this. I think the main value of this forums is to see how other think and reason about open, difficult foundational problems.The problems at the edge of knowledge are actually the only problems really worth worrying about. In this case they are distinctly physical problems, which can only become abundantly clear - i.e. to foundations skeptics such as yourself - once a new theory has actually been developed which manages to supersede the old one in some aspects. The production of any new theory which contains QM as a limit and is falsifiable is one of the major contemporary goals of theoretical physics.
Indeed. What those who complain about threads like these don't seem to understand is that problems in the foundations of physics are always open problems! @vanhees71 such open problems are where contemporary physics simply has no clear answers and they are always with us - usually carefully tucked far away from more practical physics where higher levels of certainty often reign freely.Fully agree with this. I think the main value of this forums is to see how other think and reason about open, difficult foundational problems.
I fully agree with this. The long form somewhat personal discussion format of physicsforums - IMO even moreso than on stackexchange and far more than Twitter - offers an open platform of free speech, to those interested at all levels and from all walks of life.If I have a basic question about something standard, that can be found in textbooks i would go consult the books, not ask people on internet to explain to this me and consider it an authorative answer. So for me, physicsforums is all about exchanging ideas and ways of reasoning and understanding foundations of physics and science.
Feynman said:The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn’t know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty darn sure of what the result is going to be, he is still in some doubt. We have found it of paramount importance that in order to progress we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty — some most unsure, some nearly sure, but none absolutely certain.
Now, we scientists are used to this, and we take it for granted that it is perfectly consistent to be unsure, that it is possible to live and not know. But I don’t know whether everyone realizes this is true. Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle: permit us to question — to doubt — to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.
In a way i feel that foundational QM questions (this is explicitly so in my personal perspective) often belongs to BTSM because some aspire not to be "interpretations" but rather proper reconstructions that impact the whole standardmodel.I agree with @vanhees71 in his view that maybe a subforum "quantum foundation" can be created, however, I think that might complicate many questions that could be borderline between standard and foundation.
The problem is that even when I try this, also threads starting about "normal" quantum theory turns rapidly into a discussion about "interpretation" and philosophy. See, e.g., the thread about picture dependence, which has nothing to do whatsoever with interpretational (pseudo-)issues but rapidly was turned into a discussion about it and about non-scientific questions concerning subjective and objective meanings or probabilities!What's your problem with simply ignoring threads about foundations (i.e., what you label philosophy)?
I don't see where the thread 'Interpretation of QM in the Heisenberg Picture' degenerated in this way.The problem is that even when I try this, also threads starting about "normal" quantum theory turns rapidly into a discussion about "interpretation" and philosophy. See, e.g., the thread about picture dependence, which has nothing to do whatsoever with interpretational (pseudo-)issues but rapidly was turned into a discussion about it and about non-scientific questions concerning subjective and objective meanings or probabilities!
I agree. I myself have few times indicated such thoughts that a good theory should really be all encompassing. But you know the academic pressures moto, slowly does it, and its dangerous for them to go all out. Then on the other end of the spectrum you have people that seem highly missguided or mentally disturbed at worst, and whatever comes in between is lost and brushed off very quickly and not taken seriously to be examined carefully and further developed. That is just the way it is.I personally never quite understood the pure interpretation discussion which aim to make no difference to open issues.
Vanheez71. I've been thinking of the above statement of yours for 3 weeks. It is the gist of your aguments why you believed the minimal interpretation was enough. Hope you can put it as part of your profile to summarize your bottom line.My problem is to see the necessity for "completions", as long as there are no observations hinting at an incompleteness of QT. The problem I have with understanding, why some people are so obsessed with purely philosophical issues that they think the QT is somehow incomplete. The only incompleteness I'm aware of is the pressing issue of the missing quantum theory of gravity (and, in view common of the geometrical interpretation of GR, probably also spacetime).
I want to show you there are strong indications of incompleteness in QT. If I go to Germany. Will you meet me (perhaps at the university coffee cafe) so I can show you? You don't have private messages on so let me ask here.Your problem seems precisely to be that there's no problem. I can't say, which phenomena would indicate an incompleteness of QT since there are none known today.
Concerning the incompleteness of QT with regard of describing the gravitational interaction (or spacetime geometry) the problem is that the only hint are the singularities of GR (black holes, big bang/crunch etc.), where obviously something is wrong, but whether this is cured by some future quantum formulation or not I can't say. As far as I know there are no hints about phenomena related to quantum features of gravity either.
Concerning supersymmetry, it's a purely theoretical construct which in some sense look mathematically natural and predicts some interesting features like the coupling constants of the SM merging in a closer region (maybe 1 point) hinting at some unification of all known forces. It also may provide dark-matter candidates. The trouble here is that it's with today technology impossible to look for the entire SUSY-extension landscape of the SM. Only the minimal extensions are under test at the LHC and so far it hints at more and more regions of the landscape of the minimal extension are ruled out.
It seems that you do not shy away from philosophical statements when you want to heighten importance of QFT.This is a science forum (at least that's what I thought) and not about philosophy (even not about philosophy of science). However the QM-section more and more is deformed to a discussion forum about this off-topic subject, and I find this a pity. Particularly even threads where a student asks some scientific question about introductory QM it's soon turned to discussions about some quibbles with the standard minimal interpretation.
I still think, and I hope finally the mentors here agree, that one should split the QM section into a strictly scientific part, where standard QM is discussed and another philosophy-of-science part, where all these speculations about apparent problems, which are in fact pseudo-problems, are discussed without confusing people interested in science rather than cargo cult!
Ironically for photons you come very far with just thinking about them not as classical particles (which is far from their true nature which is only describable in QED) but as classical electromagnetic waves.