Can the laws of quantum mechanics be derived from a more fundamental theory?

Question

String theory takes quantum mechanics and tries to make it compatible with gravity. If it turns out to be a theory of everything then would it explain why our world is described by the laws of quantum mechanics?

I want to understand if the laws of quantum mechanics are the only logical possibility for a low-energy theory potentially derivable from a better understanding of string theory. The other possibility is that they are just strange laws that are discovered through experiments that can't be reached by pure theoretical reasoning.

Which of the two possibilities is more reasonable from a physics point of view and why?

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user bill

Comments

Yes, quantum mechanics is the foundation of all of modern physics - condensed matter physics, nuclear physics, atomic physics, optics, molecular physics, particle physics, quantum gravity, string theory - and it is the only logically possible framework aside from classical physics (which is ruled out) that is worth mentioning. The fact that QM can't be any different has lots of aspects, see e.g. motls.blogspot.com/2013/04/… One may perhaps explain the connections of QM to other things but postulates of QM won't change again. Ever.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Luboš Motl

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Well , the basic assumption is that quantum states are normalizable vectors living in a hilbert space . quantum follows from the linearity and the methods of calculating probabilities .What I really ask is that if it's possible to map quantum mechanics to another theory mathematically so quantum mechanics could actually have richer structure than we know .So,Quantum mechanics could be absolutely correct but there may be a missing part of the story

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user bill

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Related: What are the reasons to expect that gravity should be quantized? and links therein.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Qmechanic

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I do not understand your question.Quantum Mechanics is a theory that uses least number of assumptions.By Occam's razor it should be the most consistent among other theories.If one can discover a theory with less number of assumptions than QM and prove all the things QM has proven then probably that particular theory will be acceptable.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user WInterfell

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I am not sure if you are looking for something along the lines of contextuality? In quantum information theory, quantum states are simply states with a higher degree of correlation than possible within classical theories. There is, however, the possibility of theories where there are even stronger correlations. These would include quantum mechanics, but be distinct from it. I think (I am not sure though), there are certain experimentally verifiable bounds and correlations, but so far no experiment has, to my knowledge, broken them.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user S. Gammelmark

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This doesn't seem to be a question with a concrete answer, but rather a request for discussion. In that sense it is a good questions, but a poor fit for the Q&A format.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user dmckee

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@dmckee I have edited the formulation of this question to make it more to the point. I think asking if the laws of quantum mechanics can be derived from a more fundamental theory is a legitimate fundamental physics question. It can be answered in accordance with the actual point of view hold by theoretical physicists, as Lubos Motls has shown in his comment or in more detail in his blog article he linkes too. So can the question now be reopend? (I think people who do not properly understand the questions discussing too much nonsense in the comments does not invalidate the question itself)

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Dilaton

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The question asks if there is a more fundamental theory behind quantum mechanics(QM). This is a huge subject starting with e.g. hidden variable theories, Bohm's pilot wave theory, 't Hooft's deterministic models, etc.; and continuing with the latest ideas of quantum gravity. Perhaps it would be more constructive if OP would ask about a concrete proposal that extends QM? Related: The reference frame, this and this posts.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Qmechanic

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@Qmechanic as I understood the first version of the question, the OP is mainly interested in the question if the laws of quantum mechanics can be explained from (a deeper understanding of) string theory. Maybe the title should be edited again to reflect this? It would be best if the OP clarifies the issue further but I could edit the title once again too ...

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Dilaton

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Conventional string theory assumes quantum mechanical axioms from the very beginning.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Qmechanic

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@Qmechanic yes I know ... :-). So saying that it is rather the other way round together with Lumo's comment and article about why QM can not be different would make a good correct answer I think.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Dilaton

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I think this question should get reopend to obtain a nice and clear answer which clears all misconceptions up once and for all.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Dilaton

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Just like any physical theory, quantum theory can be wrong, and will almost certainly be proven to be wrong by future experiments. In fact, the combination of quantum theory and general relativity suggests that any theory formulated in terms of real numbers are wrong, which include quantum theory and general relativity. This is because if quantum theory and general relativity are correct, then real number cannot exist, since real number can never be measured. So quantum theory and general relativity are not self consistent. One of them must be wrong. Most likely, both of them are wrong.

This post imported from StackExchange Physics at 2014-04-05 04:41 (UCT), posted by SE-user Xiao-Gang Wen

Answer 1

It was Einstein's dream that nature would arise from his unified field theory, and that QM would describe it at the statistical level. 't Hooft arrived at a similar view. From the analysis of models for ideal quantum measurement, it has become clear the QM indeed leaves open the possibility that it derives from a hidden variables theory. Forget Bell inequalities, they cannot escape the contextuality loophole, and thus cannot have any say on physics. Also forget string theory for this, that is a form of QM.