On 11 Oct 2013, at 13:09, Pierz wrote:

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On Friday, October 11, 2013 12:25:45 PM UTC+11, Brent wrote:So there are infinitely many identical universes preceding ameasurement. How are these universes distinct from one another?They aren't 'distinct'. The hypothesis is that every universe branchcontains an *uncountable* infinity of fungible (identical andinterchangeable) universes. While this seems extravagant, itactually kind of makes more sense than the idea of a universe"splitting" into two (where did the second universe come from?).Instead, uncountable infinities of universes are differentiated fromone another. Quantum interference patterns arise because of thepossibility of universes merging back into one another again.

`With comp too, it is best to see one consciousness differentiating`

`than actual splitting of "universes".`

Do they divide into two infinite subsets on a binary measurement, ordo infinitely many come into existence in order that some branch-counting measure produces the right proportion? Do you not see anyproblems with assigning a measure to infinite countable subsets (arethere more even numbers that square numbers?).The former. Deutsch goes into the problem of infinite countable setsin great detail and shows how this is *not* a problem for theseuncountable infinities (as Russell points out)), whereas it may be aproblem for Bruno's computations - a point I've tried to argue withBruno, but he bamboozles my sophomoric maths with his replies. To meit seems you can't count computations that go through a state,because for every function f that computes a certain function, thereis also some function f1 that also computes f such that f1 = f + 1 -1. But maybe that can be solved by counting only the functions withthe least number of steps (?).

`You have to take all the programs, and all computations. Your relative`

`1-indeterminacy bears on all computations going through your state.`

Using little programs would beg the 1-p/3-p problem.

`There is an uncountable set of such computations, as they dovetail on`

`the reals. Just keep in mind that the UD is enough dumb to implement`

`the infinite iterated self-duplication, which leads to uncountably`

`many histories.`

`(Having said that, there are many ways to put probability and measure`

`on any set, finite, enumerable, non enumerable, etc. Sometimes people`

`just relinquish the "sigma-additivity" condition, and still get`

`something very close to a measure).`

And why should we prefer this model to simply saying the Born rulederives from a Bayesian epistemic view of QM as argued by, forexample, Chris Fuchs?I don't know about Chris Fuchs, although isn't that just Copenhagen?It's clear that one would need strong reasons to favour MWI with itscrazy proliferation of entities, which at first blush seems to runagainst Occam's razor. However Deutsch makes a damn good fist ofexplaining why we in fact have those reasons. For instance, when aquantum computer calculates a function based on a superposition ofstates, MWI can explain where these calculations are occurring - inother universes. The computer is exploiting the possibility ofmassive parallelism inherent in that infinity of universes. It isentirely unclear how these calculations occur in the standardinterpretation. MWI also solves the problem of what happens to non-realized measurement states once a system decoheres. And of courseit gets around the intractable difficulties of non-computable wave"collapse". So it's a case of choose your poison: infinite universesor conceptual incoherence. I'll take the former, even though in someways I'd "like" the universe (or the multiverse) better if it wasn'tthat way.Max Born was my great grandfather. I wonder what he would have madeof Everett if he'd been a bit younger. When he died in 1970, it wasstill probably too out there for him to have seriously considered.

`That would have been nice to know. I really love the correspondence`

`between Max Born and Albert Einstein. I think both would have accepted`

`Everett, even if with some grimaces, like François Englert and many`

`quantum cosmologists.`

`I disagree with the idea that Everett propose a new interpretation of`

`QM. Everett proposes a new theory, which is just Copenhagen without`

`the collapse. Everett himself talk about a new formulation of QM, not`

`a new interpretation. that is not so important, except when we begin`

`to use logic, which forces to be precise on what is a theory, and what`

`is an interpretation of a theory.`

And Everett QM obeys Occam in the sense that he used less hypotheses. Bruno

Brent On 10/10/2013 6:11 PM, Pierz wrote:I'm puzzled by the controversy over this issue - although giventhat I'm not a physicist and my understanding comes from popularrenditions of MWI by Deutsch and others, it may be me who's missingthe point. But in my understanding of Deutsch's version of MWI,the reason for Born probabilities lies in the fact that there is nosuch thing as a "single branch". Every branch of the multiversecontains an infinity of identical, fungible universes. When aquantum event occurs, that set of infinite universes dividesproportionally according to Schroedinger's equation. The appearanceof probability arises, as in Bruno's comp, from multiplication ofthe observer in those infinite branches. 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 Everettianquantum mechanics persists. British Jour. Philosophy of ScienceIN PRESS.ABSTRACT. Everettian quantum mechanics (EQM) results in ‘multiple,emergent, branching quasi-classical realities’ (Wallace [2012]).The possible outcomes of measurement as per ‘orthodox’ quantummechanics are, in EQM, all instantiated. Given this metaphysics,Everettians face the ‘probability problem’—how to make senseof probabilities, and recover the Born Rule. To solve theprobability problem, Wallace, following Deutsch ([1999]), hasderived a quantum representation theorem. I argue that Wallace’ssolution to the probability problem is unsuccessful, as follows.First, I examine one of the axioms of rationality used to derivethe theorem, Branching Indifference (BI). I argue that Wallace isnot successful in showing that BI is rational. While I think it iscorrect to put the burden of proof on Wallace to motivate BI as anaxiom of rationality, it does not follow from his failing to do sothat BI is not rational. Thus, second, I show that there is analternative strategy for setting one’s credences in the face ofbranching which is rational, and which violates BI. This is BranchCounting (BC). Wallace is aware of BC, and has proffered variousarguments against it. However, third, I argue that Wallace’sarguments against BC are unpersuasive. I conclude that theprobability problem in EQM persists.http://www.foaddb.com/FDBCV.pdfPublications (a Ph.D. in Philosophy, London School of Economics,May 2012)‘The Probability Problem in Everettian Quantum MechanicsPersists’, 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. Alsoavailable in:‘Why I am not an Everettian’, in D. Dieks and V. Karakostas(eds): Recent Progress in Philosophy of Science: Perspectives andFoundational Problems, 2013, (The Third European Philosophy ofScience Association Proceedings), Dordrecht: SpringerI think this list needs another discussion of the possible MWIprobability problem although it has been covered here and elsewhereby members of this list. Previous discussions have not beenpersonally convincing.Richard --You received this message because you are subscribed to the GoogleGroups "Everything List" group.To unsubscribe from this group and stop receiving emails from it,send an email to everything-li...@googlegroups.com.To post to this group, send email to everyth...@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.comVersion: 2014.0.4158 / Virus Database: 3609/6739 - Release Date:10/10/13--You received this message because you are subscribed to the GoogleGroups "Everything List" group.To unsubscribe from this group and stop receiving emails from it,send an email to everything-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.

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