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I'd like to see a clear overview of why the many-world interpretation (WWI) of quantum is wrong, written by someone who believes that.

This would be aimed at a technically aware audience, yet as an overview, would have a broader view than just specific technical details. I'd like it to take on not only on philosopical issues like Ockham's Razor, but mathematical questions like the measurable distinction between entanglement and collapse.

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marked as duplicate by Ben Crowell, Kyle Oman, Kyle Kanos, Ali, Brandon Enright Oct 9 '14 at 0:39

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    $\begingroup$ There is a difference between something being wrong and something being not even wrong in physics. The multiworld interpretation is not even wrong... but it is completely useless, since it can't explain anything new while requiring an infinity potentiated to an infinity of universes to achieve exactly the same thing that can be had for absolutely free without it. As for collapse... there is no such thing. That's just a fudge for the folks who couldn't (or still can't) let go of classical particles. $\endgroup$ – CuriousOne Oct 7 '14 at 9:50
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    $\begingroup$ @CuriousOne: Although there is no such thing as collapse, there is arguably still a measurement problem: why does a single realization of a measurement have a particular outcome. QM cannot predict the cause behind each outcome, however, it can predict the distribution. To me it seems it remains a matter of taste to reject that it is possible to find such a cause. However, I must admit that such a theory would probably be very complicated. $\endgroup$ – Jasper Oct 7 '14 at 10:31
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    $\begingroup$ @Bubble: No really, this is just not correct. You don't need arbitrary accuracy to show that the coin will lie on one of two sides. You just need to be able to increase to sufficient accuracy, which can be rigorously specified. However, in quantum mechanics there seems to be no way to increase the accuracy. Nevertheless, there is no proof that it is impossible. In all other fields of science we do try to find causal relations between events, and it seems to me to be more a failure of imagination to suggest that in microscopic systems you cannot provide such relations. $\endgroup$ – Jasper Oct 7 '14 at 11:32
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    $\begingroup$ @JoshuaFox: There is not much of argument there. Nobody of importance disagrees that interpretation doesn't get you anywhere in physics. "So, if you think MWI is nonsense, could you refer me to a relevant article.": you need to read all the important physicists (e.g. the folks at CERN and in other labs who are doing the real work) who have NOT written a single line about it because they don't care. :-) $\endgroup$ – CuriousOne Oct 7 '14 at 13:55
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    $\begingroup$ From what I understand, MWI is simply the idea that observers of a superposition enter a superposition themselves rather than collapsing the superposition of the observed system. It's plausible and consistent, but it's not clear how it would be useful. Perhaps it could motivate you to increase the probability of agreeable macroscopic states, but you should be motivated to do so anyway, regardless of how many quantum states wind up being real. So I suppose the only real counter-argument is that there's no practical reason to care, which applies equally to all interpretations. $\endgroup$ – Keen Oct 7 '14 at 14:33
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Here are some random references out of the top of my head. I recommend chapter 8 of the book of Schlosshauer - Decoherence and the Quantum-To-Classical Transition. Also in favor of the MWI, see the book by David Wallace - The emergent multiverse, which addresses also open problems and discusses some criticisms. Also see: http://plato.stanford.edu/entries/qm-manyworlds/#6 and references therein. An old article: http://arxiv.org/abs/gr-qc/9703089v1 . Note: I'm not a fan of the MWI.

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  • $\begingroup$ Also see Steven Weinberg's book "Lectures on quantum mechanics" for a short discussion of MWI and its problems. $\endgroup$ – Jasper Oct 7 '14 at 12:57
  • $\begingroup$ @Jaster, thank you. OK, Weinberg is anti-MWI. I am reading Wallace, but he is pro-MWI (though there are two interludes with objections.) I am also aware of the "objections" section in the Stanford encyclopedia, but I'd prefer a focused article against MWI. The arxiv article by Kent is from 1990. I'd prefer an up-to-date overview of the field by a strong advocate. Is Schlosshauer anti-MWI? That's what I'm looking for. $\endgroup$ – Joshua Fox Oct 7 '14 at 13:34
  • $\begingroup$ @Joshua Fox: Schlosshauer is a good author and physicist as he does not lean any way strongly, but he just looks at their merit. The article by Kent should be useful, though, for a critical viewpoint. This might also be useful: journals.aps.org/rmp/abstract/10.1103/RevModPhys.76.1267 $\endgroup$ – Jasper Oct 7 '14 at 13:39
  • $\begingroup$ @JoshuaFox: So what experiment have any of these people done that has found more than one universe? :-) $\endgroup$ – CuriousOne Oct 7 '14 at 13:56
  • $\begingroup$ None ;) But such discussions are more about consistency. The same can be said of the inside of a black hole, but we believe we can describe such a part of the universe by extrapolating from our well-established theories. The interpretation of MW is a matter of extreme extrapolation and you can disagree with the assumptions of the extrapolation. In the end, these kinds of discussions quite often do lead to interesting new insights. $\endgroup$ – Jasper Oct 7 '14 at 15:09
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None of the interpretations are right or wrong, since they are interpretations of the same mathematical formalism which predict the same events. Interpretations are a philosophical adjunct that provides a "what is REALLY happening" view. If an interpretation is tested and shown to be wrong, then it is no longer an interpretation - just wrong physics. Similarly, I am not sure if any interpretation could ever be shown to be the correct one.

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  • $\begingroup$ OK, but this is a topic of serious debate in the academic community. Respected professors have argued both sides. So, could you refer me to a relevant article? $\endgroup$ – Joshua Fox Oct 7 '14 at 12:20
  • $\begingroup$ @JoshuaFox: but this is a topic of serious debate in the academic community That doesn't contradict anything Dirk Bruere said. Interpretations have to do with the philosophy of science. Philosophy is a topic of serious debate, but it doesn't make testable predictions. $\endgroup$ – Ben Crowell Oct 8 '14 at 22:49
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MWI has issues with how the effect of a measurement causes the world (universe) to split into potentially an infinite number of copies of itself, each slightly different. How fast does the influence "rip" (tear?) through the Universe? At the speed of light? No, it would have to be faster otherwise ERP experiments would not work. So, instantaneously? But in whose frame of reference? Also, there would be Universes where every toss of a coin yields a HEAD, but everyone believes in probability theory. MWI is a great devices for constructing Science Fiction stories, but not really viable IMHO. It confuses the sample space with reality.

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    $\begingroup$ It's not true that MWI requires FTL "splitting" to explain EPR correlations--it exploits a loophole in Bell's proof, namely his assumption of unique measurement results at each location. In contrast, the MWI assumes each experimenter measuring one member of an entangled pair splits locally into versions which see different results, the universe need not "decide" which versions of experimenter 1 get matched to which versions of experimenter 2 until there's been time for a signal moving at the speed of light or slower to pass between them. See arxiv.org/abs/quant-ph/9906007 for details. $\endgroup$ – Hypnosifl Oct 8 '14 at 17:37

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