Hi Saibal, Le 27-mai-05, à 14:29, Saibal Mitra a écrit :

----- Oorspronkelijk bericht ----- Van: "Stathis Papaioannou" <[EMAIL PROTECTED]> Aan: <[EMAIL PROTECTED]> CC: <[EMAIL PROTECTED]>; <everything-list@eskimo.com> Verzonden: Friday, May 27, 2005 01:44 AM Onderwerp: Re: Many Pasts? Not according to QM...Saibal Mitra wrote:Quoting Stathis Papaioannou <[EMAIL PROTECTED]>:On 25th May 2005 Saibal Mitra wrote:One of the arguments in favor of the observer moment picture isthatitsolves Tegmark's quantum suicide paradox. If you start with a setofallpossible observer moments on which a measure is defined (which canbecalculated in principle using the laws of physics), then theparadoxneverarises. At any moment you can think of yourself as being randomlydrawnfromthe set of all possible observer moments. The observer moment whohassurvived the suicide experiment time after time after time has averyveryvery low measure.I'm not sure what you mean by "the paradox never arises" here. Youhavesaid in the past that although you initially believed in QTI, you laterrealisedthat it could not possibly be true (sorry if I am misquoting you,thisisfrom memory). Or are you distinguishing between QTI and QS?That's correct. In both QTI and QS one assumes conditionalprobabilities.You justthrow away the branches in which you don't survive and then youconcludethat youcontinue to survive into the infinitely far future (or afterperforminganarbitrary large number of suicide experiments) with probability 1.But if you use the a priori probability distribution then you seethatyouthe measure of versions of you that survive into the far future is almost zero.What does "the measure of versions of you that survive into the farfutureis almost zero" actually mean? The measure of this particular versionofmetyping this email is practically zero, considering all the otherversionsofme and all the other objects in the multiverse. Another way oflooking atitis that I am dead in a lot more places and times than I am alive. Andyetundeniably, here I am! Reality trumps probability every time.You have to consider the huge number of alternative states you couldbe in.1) Consider an observer moment that has experienced a lot of things.Theseexperiences are encoded by n bits. Suppose that these experiences weremoreor less random. Then we can conclude that there are 2^n OMs that allhave aprobability proportional to 2^(-n). The probability that you are one of these OMs isn't small at all! 2) Considering perforing n suicide experiments, each with 50% survivalprobability. The n bits have registered the fact that you havesurvived then suicide experiments. The probability of experiencing that is 2^(-n).The2^(n) -1 alternate states are all unconscious.So, even though each of the states in 1 is as likely as the singlestate in2, the probability that you'll find yourself alive in 1 is vastly morelikely than in 2. This is actually similar to why you never see amixture oftwo gases spontaneously unmix. Even though all states are equallylikely,there are far fewer unmixed states than mixed ones. Saibal

`I agree in the case I could imagine all the "observer moments" in some`

`complete third person way, where the notion of "dying" can be given`

`some third person sense.`

`But the compi and the qti, relies, it seems to me, on the fact that we`

`cannot experience not being there. So that in both case the first`

`person probabilities are one, from first person points of view. They`

`are one, *almost* by definition, the very notion of "probabilitiy"`

`presupposes the ability to test the outcome of a (random) *experiment*`

`(this is still more plausible for an "observer-moment" first person`

`*experience*).`

Do you see what I try to say? That's why we need some "no cul-de-sac" hypothesis.

`[For those who knows the (Godel Lob Solovay) provability logics (G and`

`G*) : you can go from a provability logic Bp (= G; with cul-de-sac`

`accessible from all transitory obsever momente) to a probability logic`

`(without cul-de-sac) by *imposing* consistency: Bp ==> Bp & -B-p. (-B-p`

`= 'Consistent p' remember the dual of Bp is -B-p, and with Bp read as`

`'Provable p', ('Beweisbar p', in German), -B-p is 'Consistent p'. And`

`if you remind Kripke Semantics, Con p, means there is at least one`

`observer moment (with p true) accessible from you current observer`

`moment.`

`Of course G* proves Bp <-> (Bp & -B-p), But G* proves also -B(Bp <->`

`(Bp & -B-p)), so that from the machine point point of view, it will`

`change the provability logic, indeed, it changes it into a probability`

`logic.]`

`In my 1988 paper, I argue that the qti is a confirmation of the compi.`

`(Given that the uda shows comp entails the no cul-de-sac hypothesis).`

Or you are (still) with the ASSA ? Or do I miss what you try to explain? Bruno http://iridia.ulb.ac.be/~marchal/