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Loren Booda
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Theoretically, if one had all of the classical information in the universe, could one predict quantum mechanical events? I believe this is a very basic and significant question that physicists need to confront.
Perhaps Loren, you could phrase your question in more detail (for example what do you mean by quantum cosmology?). Nevertheless I can add at this moment that Inha's answer has a strong dependence on his interpretation of the measurement problem (it is not for sure at all that true random generators exist in nature - although they do exist in theory if we take QM as it stands now).inha said:No. For example take all probabilistic phenomena. Question confronted, what's next?
Loren Booda said:Theoretically, if one had all of the classical information in the universe, could one predict quantum mechanical events? I believe this is a very basic and significant question that physicists need to confront.
Loren Booda said:Theoretically, if one had all of the classical information in the universe, could one predict quantum mechanical events? I believe this is a very basic and significant question that physicists need to confront.
Careful said:I invite Masudr to consult an elementary GR textbook
Careful said:DrChinese said: I think it is acknowledged by most that it is NOT POSSIBLE, in principle, to know all of the state information about all of the particles in the universe. This would be true regardless of what theory you think is applicable; because it would take an even bigger universe to store that much knowledge.
Nah, it is merely stated so without any profound comments
That is outrageously false: QM contains many more degrees of freedom than CM does (as an easy excercise proves it to be). If QM would contain LESS degrees of freedom, then I would be all ears
Careful said:...it is a bold (and probably mistaken) assumption that you can exclude GR in the description of elementary particle physics...
Just because you might have missed something: I am one of these crazy persons who says you should not quantize gravity at all. Until further notice, I remain convinced that QM (when applied to the correct distance scales) *is* a statistical description of a classical gravito/electromagnetic process (that is why I insist so much that Bell test results are treated with the correct egards.). In such a programme, there is NO need for a new mathematical machinery, but there IS a huge demand for realistic matter models of elementary particles. Such particle models ARE already partially available (for the electron say) and guess what?? The nonlinear corrections due to Einstein Maxwell theory on the Compton scale (vis a vis flat Minkowski electromagnetism) are immense (and gravitation is extremely important in this regard).masudr said:It is, on the contrary, very bold to assume you can include GR on any issue regarding QM, until we have a satisfactory mathematical formalism to do so.
Careful said:You don't seem to have understood that I was merely making fun of your use of the verb ``to THINK´´.
Again, you should take a look at this paper concerning Occam's raisor (just a friendly remark - I promised to behave until the end of the year )
Careful said:I am one of these crazy persons who says you should not quantize gravity at all.
But (1) does not the Ehrenfest theorem show that a form of QM wave equation leads to Newton's equations of motion on the average (see Bohm, 1951, Quantum Theory), and (2) does not the Wentzel-Kramers-Brillouin (WKB) approximation allow for wave functions which, as stated by Bohm (1951) on page 268, is "the same as the classical probability distribution function". So, from the above it does appear that at least some aspects of classical dynamics are well known to be derived from QM--at least according to Bohm. But I no expert at all in this field, so I look forward to your correction of my errors.Careful said:**** Is it not true that we can derive classical dynamics at macroscopic scale from QM, **No, that is not known yet Cheers,Careful
No, I am not saying that at all. In quantum gravity, one of the main (unadressed so far) puzzles (I refuse to accept the MWI interpretation as a credible theory - what is the probability that you are in one universe (P = 0)? and what do you need these other universes for (Occam's razor)? and what makes that you are just in one universe and not in another (consciousness and zombie copies)?) is how to avoid (more or less equal weighted) superpositions of cats (to use Schroedingers example). Another problem is how to deal with the measurement: surely one would like to have ONE dynamics for the microworld and on long distance scales R is not compatible with the local physics we are used to in the macroworld.DrChinese said:That doesn't seem weird to me at all. I wake up at least 4 days a week with that view.
But I am not sure I follow the other part of what you said about electro/gravito interactions. Surely you are not saying that electromagnetism and gravity should be unified... are you?
Rade said:But (1) does not the Ehrenfest theorem show that a form of QM wave equation leads to Newton's equations of motion on the average (see Bohm, 1951, Quantum Theory), and (2) does not the Wentzel-Kramers-Brillouin (WKB) approximation allow for wave functions which, as stated by Bohm (1951) on page 268, is "the same as the classical probability distribution function". So, from the above it does appear that at least some aspects of classical dynamics are well known to be derived from QM--at least according to Bohm. But I no expert at all in this field, so I look forward to your correction of my errors.
Careful said:Not quite, his Occam's razor principle is a balancing act between theory complexity and accuracy of prediction as it should be. It kills off oversimplified theories which make bad predictions as well as too complex theories which do make accurate fits. The ideal theory is the one which makes a particular experimental outcome very likely and is not more complex than it should be (of course it is a subject of debate how to define theory complexity ). For this Occam's razor principle to apply, it is of ultimate importance that we have detailed information about Bell test setups as well as the RAW (unprocessed) data at hand.
Well, objectively, it seems to me that the theory which is known to have the broader range and the higher accuracy is always preferred. However, I do admit that the relation between Newtonian Mechanics and GR is much more subtle that the one with QM since NM is actually a simpler theory and still does a wonderful job at the scales of everyday life. Therefore, in the right circumstances, it is more profitable to use NM in practice.DrChinese said:Ideal=his ideal. Theories with different inputs and different output precisions can all be good. Newtonian gravity - as a theory - is absolutely useful, even in the presence of Einstein's GR. I would not agree that one is objectively better than the other in all cases.
Careful said:Perhaps Loren, you could phrase your question in more detail (for example what do you mean by quantum cosmology?). Nevertheless I can add at this moment that Inha's answer has a strong dependence on his interpretation of the measurement problem (it is not for sure at all that true random generators exist in nature - although they do exist in theory if we take QM as it stands now).
Nah, I bet you are pleased with copenhagen ... but if you want to explain your point of view, go ahead.inha said:The only measurement problem I have first hand experience with is a scintillator detector dying on me. Wanna guess my philosophical stance on QM?
Rade said:But (1) does not the Ehrenfest theorem show that a form of QM wave equation leads to Newton's equations of motion on the average (see Bohm, 1951, Quantum Theory),
and (2) does not the Wentzel-Kramers-Brillouin (WKB) approximation allow for wave functions which, as stated by Bohm (1951) on page 268, is "the same as the classical probability distribution function".
Locrian said:No, the idea that you can get classical mechanics from quantum mechanics is a myth perpetuated by poor textbooks. In textbooks they create imaginary situations where QM and CM end up with similar results over many measurements, but in reality these situations rarely occur; more often, trying to use QM to produce classical equations for a situation is either impossible or a failure. Nevermind the fact that "proof" by example is no proof at all! There is no mathematical proof that shows that classical mechanics can really be produced from quantum mechanics, and in practice it is a miserable waste of time to try. This idea fails in both philosophy and practice.
Careful said:(a) did you waste too much time in trying this ?
(b) what is the conclusion you draw ?
Deterministic quantum mechanics is a branch of quantum mechanics that describes the behavior of physical systems using deterministic equations. It suggests that the state of a system can be precisely determined at any given time, and that there is no element of chance or randomness involved in the system's evolution.
Traditional quantum mechanics, also known as probabilistic quantum mechanics, is based on the principle of indeterminacy, which suggests that it is impossible to precisely determine the state of a physical system. In contrast, deterministic quantum mechanics rejects the notion of randomness and instead proposes that the state of a system can be determined with certainty.
Some key concepts in deterministic quantum mechanics include determinism, measurement problem, superposition, and entanglement. These concepts are used to describe the behavior and properties of physical systems at the quantum level.
The implications of deterministic quantum mechanics are still a topic of debate among scientists. Some argue that it challenges the traditional understanding of quantum mechanics and could potentially lead to a more complete and deterministic theory of nature. Others argue that it is merely an alternative interpretation of the existing quantum theories.
Currently, there is no conclusive evidence to support deterministic quantum mechanics. While some experiments have shown results that are consistent with a deterministic interpretation, others have shown results that are more in line with traditional quantum mechanics. Further research and experimentation are needed to fully understand the implications and validity of deterministic quantum mechanics.