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- TL;DR Summary
- Lee Smolin has a new book out called "Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum". It is a book on the foundations of QM. For a brief review of the first half see: https://www.physicsforums.com/threads/what-are-you-reading-now-stem-only.912884/post-6176357
SPOILER WARNING
What I believe we can directly take away from this book with regard to discussions on QM foundations is I think his classification of interpretations of QM.
SPOILER WARNING: If you don't want to be spoiled about the book, stop reading now!
I just finished the new book. First I would recommend the book to anyone who reads or takes part in discussions on QM foundations. Briefly put, Smolin offers a simple classification of almost all interpretations of QM and their pros and cons with respect to a more fundamental theory than QM or QFT. The classification he gives for the interpretation of QM is realist vs anti-realist, where realism is the view of reality which all scientific theories of physics (except for QM) adhere to, and where anti-realism is essentially the instrumentalist view of QM and science at large as propagated by Bohr and Heisenberg. Suffice to say, the standard textbook operationalist view of QM is also anti-realist.
Realism on the other hand branches off into a few more specific views. The most important of these are what Smolin calls naive realism, magical realism and critical realism. Each of these branches consist of groups of theories which are fundamentally conceptually similar to each other, i.e. they have the same strengths and weaknesses.
Naive realism gives several options about what is real: either both particles and waves are real (pilot wave theory), only waves are real (collapse models) or only particles are real (Nelson's stochastic mechanics).
Magical realism has a few exemplifying interpretations, most importantly Everett's Many Worlds Interpretation. This interpretation is less predictive than QM because it literally predicts everything happens based on deterministic unitary evolution alone and therefore has a problem introducing probabilities.
Critical realism contains again a few exemplifying options: the Oxford interpretation, which can best be summarized as 'decoherence solves the issues with Everett's MWI.' In general, the way in which the problems of the MWI are attempted to be solved do not seem to work for several reasons.
Smolin in the book reviews all of the above interpretations, impartially gives both their merits and drawbacks, and more importantly explains what each of them teaches us about physics and what a successful realist completion of QM would need to be capable of achieving in order to become the theory to dethrone QM, i.e. simultaneously reproducing each of the successes of all of the interpretations while avoiding all of their problems.
Smolin then gives an outline how to achieve such a project based on a first principles approach similar to Lucien Hardy's approach for doing foundational physics. He names and describes a set of principles which a realist completion of QM and therefore a theory beyond QM needs to adhere to. From memory I think this approach is based largely on Einstein's philosophy of physics which clearly illustrates the difference between constitutive theories and principle theories.
The rest of the book illustrates a few specific implementations of research done so far which actually complete QM and go beyond it, i.e. which have actually reproduced all the successes of many of the interpretations so far. These projects are each very impressive in their own right, but - as Smolin describes - while they may reproduce some or all of the successes, they do not necessarily avoid all the problems.
Naturally, anyone who wants clarification should read the book, I'd recommend it to anyone interested in QM, regardless of their level of expertise. Again any further discussion in this thread will necessarily go into more depth than this post and spoil the book even more.
I just finished the new book. First I would recommend the book to anyone who reads or takes part in discussions on QM foundations. Briefly put, Smolin offers a simple classification of almost all interpretations of QM and their pros and cons with respect to a more fundamental theory than QM or QFT. The classification he gives for the interpretation of QM is realist vs anti-realist, where realism is the view of reality which all scientific theories of physics (except for QM) adhere to, and where anti-realism is essentially the instrumentalist view of QM and science at large as propagated by Bohr and Heisenberg. Suffice to say, the standard textbook operationalist view of QM is also anti-realist.
Realism on the other hand branches off into a few more specific views. The most important of these are what Smolin calls naive realism, magical realism and critical realism. Each of these branches consist of groups of theories which are fundamentally conceptually similar to each other, i.e. they have the same strengths and weaknesses.
Naive realism gives several options about what is real: either both particles and waves are real (pilot wave theory), only waves are real (collapse models) or only particles are real (Nelson's stochastic mechanics).
Magical realism has a few exemplifying interpretations, most importantly Everett's Many Worlds Interpretation. This interpretation is less predictive than QM because it literally predicts everything happens based on deterministic unitary evolution alone and therefore has a problem introducing probabilities.
Critical realism contains again a few exemplifying options: the Oxford interpretation, which can best be summarized as 'decoherence solves the issues with Everett's MWI.' In general, the way in which the problems of the MWI are attempted to be solved do not seem to work for several reasons.
Smolin in the book reviews all of the above interpretations, impartially gives both their merits and drawbacks, and more importantly explains what each of them teaches us about physics and what a successful realist completion of QM would need to be capable of achieving in order to become the theory to dethrone QM, i.e. simultaneously reproducing each of the successes of all of the interpretations while avoiding all of their problems.
Smolin then gives an outline how to achieve such a project based on a first principles approach similar to Lucien Hardy's approach for doing foundational physics. He names and describes a set of principles which a realist completion of QM and therefore a theory beyond QM needs to adhere to. From memory I think this approach is based largely on Einstein's philosophy of physics which clearly illustrates the difference between constitutive theories and principle theories.
The rest of the book illustrates a few specific implementations of research done so far which actually complete QM and go beyond it, i.e. which have actually reproduced all the successes of many of the interpretations so far. These projects are each very impressive in their own right, but - as Smolin describes - while they may reproduce some or all of the successes, they do not necessarily avoid all the problems.
Naturally, anyone who wants clarification should read the book, I'd recommend it to anyone interested in QM, regardless of their level of expertise. Again any further discussion in this thread will necessarily go into more depth than this post and spoil the book even more.