`So there are infinitely many identical universes preceding a measurement. How are these`

`universes distinct from one another? Do they divide into two infinite subsets on a`

`binary measurement, or do infinitely many come into existence in order that some`

`branch-counting measure produces the right proportion? Do you not see any problems with`

`assigning a measure to infinite countable subsets (are there more even numbers that square`

`numbers?).`

`And why should we prefer this model to simply saying the Born rule derives from a Bayesian`

`epistemic view of QM as argued by, for example, Chris Fuchs?`

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Brent On 10/10/2013 6:11 PM, Pierz wrote:

I'm puzzled by the controversy over this issue - although given that I'm not a physicistand my understanding comes from popular renditions of MWI by Deutsch and others, it maybe me who's missing the point. But in my understanding of Deutsch's version of MWI, thereason for Born probabilities lies in the fact that there is no such thing as a "singlebranch". Every branch of the multiverse contains an infinity of identical, fungibleuniverses. When a quantum event occurs, that set of infinite universes dividesproportionally according to Schroedinger's equation. The appearance of probabilityarises, as in Bruno's comp, from multiplication of the observer in those infinitebranches. Why is this problematic?On Saturday, October 5, 2013 2:27:18 AM UTC+10, yanniru wrote: Foad Dizadji-Bahmani, 2013. The probability problem in Everettian quantum mechanics persists. British Jour. Philosophy of Science IN PRESS. ABSTRACT. Everettian quantum mechanics (EQM) results in ‘multiple, emergent, branching quasi-classical realities’ (Wallace [2012]). The possible outcomes of measurement as per ‘orthodox’ quantum mechanics are, in EQM, all instantiated. Given this metaphysics, Everettians face the ‘probability problem’—how to make sense of probabilities, and recover the Born Rule. To solve the probability problem, Wallace, following Deutsch ([1999]), has derived a quantum representation theorem. I argue that Wallace’s solution to the probability problem is unsuccessful, as follows. First, I examine one of the axioms of rationality used to derive the theorem, Branching Indifference (BI). I argue that Wallace is not successful in showing that BI is rational. While I think it is correct to put the burden of proof on Wallace to motivate BI as an axiom of rationality, it does not follow from his failing to do so that BI is not rational. Thus, second, I show that there is an alternative strategy for setting one’s credences in the face of branching which is rational, and which violates BI. This is Branch Counting (BC). Wallace is aware of BC, and has proffered various arguments against it. However, third, I argue that Wallace’s arguments against BC are unpersuasive. I conclude that the probability problem in EQM persists. http://www.foaddb.com/FDBCV.pdf <http://www.foaddb.com/FDBCV.pdf> Publications (a Ph.D. in Philosophy, London School of Economics, May 2012) ‘The Probability Problem in Everettian Quantum Mechanics Persists’, British Journal for Philosophy of Science, forthcoming ‘The Aharanov Approach to Equilibrium’, Philosophy of Science, 2011 78(5): 976-988 ‘Who is Afraid of Nagelian Reduction?’, Erkenntnis, 2010 73: 393-412, (with R. Frigg and S. Hartmann) ‘Conﬁrmation and Reduction: A Bayesian Account’, Synthese, 2011 179(2): 321-338, (with R. Frigg and S. Hartmann) His paper may be an interesting read once it comes out. Also available in: ‘Why I am not an Everettian’, in D. Dieks and V. Karakostas (eds): Recent Progress in Philosophy of Science: Perspectives and Foundational Problems, 2013, (The Third European Philosophy of Science Association Proceedings), Dordrecht: Springer I think this list needs another discussion of the possible MWI probability problem although it has been covered here and elsewhere by members of this list. Previous discussions have not been personally convincing. Richard --You received this message because you are subscribed to the Google Groups "EverythingList" group.To unsubscribe from this group and stop receiving emails from it, send an email toeverything-list+unsubscr...@googlegroups.com.To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out. No virus found in this message. Checked by AVG - www.avg.com <http://www.avg.com> Version: 2014.0.4158 / Virus Database: 3609/6739 - Release Date: 10/10/13

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