Re: Travelling to a different universe
Charles Goodwin wrote: From: Bruno Marchal [EMAIL PROTECTED] I ask first the biological version: which way do you feel having ending up? or more simply are you the biological or the digital? Bio-Charles makes at this point some medical observation on itself and discovers he is the biological: so for him it was just false to say that he has end up as both. Let us ask the same question are you the biological or the digital? to the digital Techno-Charles. As expected, Techno-Charles makes some medical observation on itself and discovers he is the digital one. So for him too, it was just false to say that he should have end up as both. That is what I meant when I said that our notion of 'I' was incorrect. Charles did, in fact, end up as both. Obviously neither of the versions of Charles which *now* exist feel as though they ended up as both, because THEY didn't end up as both. Only the original version of Charles ended up as both, and he's no longer around to ask. This would mean the original version of Charles died in the process. But in *that* sense the original version of Charles dies every instant. Why are you saying the use of I was incorrect. The term I is an indexical: its *meaning* remains the same although its *reference* can change according to the locutor using it. (Similar things happens for different indexical terms like now, modern, current, artificial, ...) Now, both with MWI or even just comp, we learn that I, actually any Is, differentiate(s) all the time. This does not change the meaning of I but entails the possibility of multiplying its references. That's hardly new, amoeba does that since a long (earth) time. There exists computer science tools for defining self and making precise the meaning of I by finitely describable entities, including their possible contextually dependent references. Such tools relies on diagonalisation. Perhaps you can look at http://www.cis.udel.edu/~case/self-ref.html (or wait patiently for diagonalisation 2 on the parallel list!). Bruno
Re: Travelling to a different universe
George Levy This is interesting. Is it possible to transmit information from the future to the past? If yes, how would this information be restricted? This is a very difficult issue, as you can see (example below). A single particle [the example is discussed in references 4, 2, 1] at time t_0 is (preselected) in the state |psi_0 = 3 ^ (-1/2) ( |a + |b + |c ) and at a later time t_f is (postselected) in the state |psi_f = 3 ^ (-1/2) ( |a + |b - |c ) where |a, |b and |c correspond to the particle being found in 3 boxes: A, B and C, respectively. (The N boxes case is discussed in reference 3.) At the intermediate time t_i, where t_0 t_i t_f, a measurement is performed on the system. The ABL rule [see reference 5] states that if a measurement is performed, at time t_i, on this system, with the above preselection and postselection of states, the probability for an outcome of either a or b (eigenvalues corresponding to find the particle in box A or in box B, respectively) is 100%. That is to say, the intermediate _measurement_ cannot project the initial state |psi_0 onto the state 2 ^ (-1/2) ( |b + |c ) -- particle not found in A -- or onto the state 2 ^ (-1/2) ( |a + |c ) -- particle not found in B --. That's because both states are othogonal to the final state |psi_f. Both states are then impossible. As long as we keep the QM formalism and the ABL rule, in each case any particles (which end up postselected) are ones which could not have been in any box except the one which was opened, be it A or B. Possible solutions? There are some. In example 1. QM formalism is right. There is no paradox. That's real. 2. QM formalism is right. That's not real. QM does not speak of reality. 3. Counterfactuals. To make a claim about the elements of reality of an individual system we have to consider the *physical* situation involved in an individual run of the experiment. But here, in each run, we have to make a *choice* to measure A or B. If we choose A, all postselected particles had to be found in box A. If we choose B, all postselected particles had to be found in box B. But the property of being, with certainty, in any one of those 2 boxes (depending on wich one is opened) cannot apply to the *same* *individual* particle in *any* given run of the experiment. 4. We cannot use the ABL rule here [see reference 6], because of the counterfactuals. Regards, -s. [1] David Z. Albert, Yakir Aharonov, Susan D'Amato, Physical Review Letters, vol. 54, pages 5 - 7, (1985) [2] David Z. Albert, Yakir Aharonov, Susan D'Amato, Physical Review Letters, vol. 56, p. 2457, (1986) [3] Yakir Aharonov, Lev Vaidman J. Phys, A-24, pages 2315 - 2328, (1991) [4] Lev Vaidman Foundations of Physics, 26, pages 895 - 906, (1996) [5] Yakir Aharonov, P.G. Begmann, J.L. Lebowitz, Physical Review, 134-B, pages 1410 - 1416, (1964) [6] R. E. Kastner Foundations of Physics, 29, pages 851 - 863, (1999)
Re: Travelling to a different universe
This is interesting. Is it possible to transmit information from the future to the past? If yes, how would this information be restricted? George scerir wrote: Saibal Mitra Now there exists a class of universes, with a very low measure, in which the laws of physics are such that I am guaranteed to win. There is also the interesting class of TSQT. Quantum theory is time symmetric as long as it can be described by the evolution of a state vector according to the Schroedinger equation. But as soon as measurement and wave function collapse are involved, the symmetry breaks down. But in the Time Symmetrized Quantum Theory (TSQT) it is argued that information propagating in a time reversed direction from future measurements can provide information about appropriately selected systems (!!!). Ensembles of such sustems are referred to as pre-selected and post-selected. The basic claim of TSQT is that a fundamental time symmetry applies to the interval between two ideal measurements. According to TSQT the quantum state of a system, between two measurements occurring at times t1 and t2, contains information based not only on the initial measurement (pre-selection) but also on the final measurement (post-selection). Aharonov, Bergman and Lebowitz (ABL) invented the well-known time symmetric formalism for describing quantum systems between two complete measurements. Does TSQT ensures or forbids your win? Regards, -s.
Re: Travelling to a different universe
Saibal Mitra Now there exists a class of universes, with a very low measure, in which the laws of physics are such that I am guaranteed to win. There is also the interesting class of TSQT. Quantum theory is time symmetric as long as it can be described by the evolution of a state vector according to the Schroedinger equation. But as soon as measurement and wave function collapse are involved, the symmetry breaks down. But in the Time Symmetrized Quantum Theory (TSQT) it is argued that information propagating in a time reversed direction from future measurements can provide information about appropriately selected systems (!!!). Ensembles of such sustems are referred to as pre-selected and post-selected. The basic claim of TSQT is that a fundamental time symmetry applies to the interval between two ideal measurements. According to TSQT the quantum state of a system, between two measurements occurring at times t1 and t2, contains information based not only on the initial measurement (pre-selection) but also on the final measurement (post-selection). Aharonov, Bergman and Lebowitz (ABL) invented the well-known time symmetric formalism for describing quantum systems between two complete measurements. Does TSQT ensures or forbids your win? Regards, -s.
Re: Travelling to a different universe
Saibal wrote: There is a selection effect by the very use of the suicide machine. In the usual WM experiment this doesn't occur, so let's modify it slightly. First I measure the z-component of a spin ½ particle is measured 1000 times in succesion. Provided I don't find 1000 times spin up I will perform the usual WM experiment, otherwise I will only make copies that end up in Washington. Suppose you use the suicide machine to select W ten thousand times in a row, what would the probability be that I had found 1000 times spin up? Near zero. (A priori the W selection should not interfere with the spin measurements unless you change the goal with the suicide machine). Perhaps you are linking the experience by testing me on the WM after linking your decision on the spin measurements. In that case I would say the probability you found 1000 times spin up would be great, but only by pure Bayesian reasoning (not linked to the duplication indeterminacy). Bruno
Re: Travelling to a different universe
Saibal Mitra wrote: Now there exists a class of universes, with a very low measure, in which the laws of physics are such that I am guaranteed to win. The probability that I find myself in such a universe will have increased substantially after each experiment. After a few years I will be sure to live in such a universe. It would be easy to check, all I would have to do is to buy a ticket and see if I have won without using the suicide machine. Just do the computation. At each suicide you will survive in the nearer world from the one you left. That is: the more normal world relatively to you. Of course you will be sure that you live in such a universe, but you will be wrong. If you stop to use the suicide machine you will stop winning (unless you are using explicitely the suicide machine for filtering just a world where you win without suicide machine, but then that is an another experiment). Look at the iteration 64 times of simple self-duplication WM. Among the 2^64 resulting person, one will believe ending up always at W, but if you iterate *again* 32 times you know that this one will have 2^32 - 1 descendant knowing that the expection was wrong, and only one believing (more and more) having been magically linked to Washington. Bruno
Re: Travelling to a different universe
Bruno wrote: Saibal Mitra wrote: Now there exists a class of universes, with a very low measure, in which the laws of physics are such that I am guaranteed to win. The probability that I find myself in such a universe will have increased substantially after each experiment. After a few years I will be sure to live in such a universe. It would be easy to check, all I would have to do is to buy a ticket and see if I have won without using the suicide machine. Just do the computation. At each suicide you will survive in the nearer world from the one you left. That is: the more normal world relatively to you. Of course you will be sure that you live in such a universe, but you will be wrong. If you stop to use the suicide machine you will stop winning (unless you are using explicitely the suicide machine for filtering just a world where you win without suicide machine, but then that is an another experiment). Look at the iteration 64 times of simple self-duplication WM. Among the 2^64 resulting person, one will believe ending up always at W, but if you iterate *again* 32 times you know that this one will have 2^32 - 1 descendant knowing that the expection was wrong, and only one believing (more and more) having been magically linked to Washington. There is a selection effect by the very use of the suicide machine. In the usual WM experiment this doesn't occur, so let's modify it slightly. First I measure the z-component of a spin ½ particle is measured 1000 times in succesion. Provided I don't find 1000 times spin up I will perform the usual WM experiment, otherwise I will only make copies that end up in Washington. Suppose you use the suicide machine to select W ten thousand times in a row, what would the probability be that I had found 1000 times spin up? Saibal
Re: Travelling to a different universe
Brent meeker wrote: On 25-Dec-01, Saibal Mitra wrote: Charles Goodwin wrote: Or are you claiming that repeated quantum suicide attempts increase the chances that you are a computer simulation? Yes that is what I claim. That would only occur if there was some sort of cul-de-sac (assuming you *start* from a physical instantiation, at least). If you are physically instantiated at some point in time, all physical instantiations must end in a cul-de-sac before you can 'travel' to a universe in which you are a computer simulation. Why? If your brain were replaced by a digital one, you would still be the same person. If I made a digital version of you and let the biological version of you live on, then there would be a 50% chance you would end up as the digital person. [Brent Meeker]I'm not sure what to make of such statements. It seems to me there's a 100% chance Charles would end up as both. Are you positing a supernatural soul that's *really* Charles and can only be in one of the two physical 'brains'? Suppose you are right and that there is a 100% chance Charles end up at both. So, let us ask both Charles after the construction of the digital version was done. I ask first the biological version: which way do you feel having ending up? or more simply are you the biological or the digital? Bio-Charles makes at this point some medical observation on itself and discovers he is the biological: so for him it was just false to say that he has end up as both. Let us ask the same question are you the biological or the digital? to the digital Techno-Charles. As expected, Techno-Charles makes some medical observation on itself and discovers he is the digital one. So for him too, it was just false to say that he should have end up as both. The indeterminacy here is the first person indeterminacy. Note that each Charles get one bit of information after they have completed the medical observation. And this follows from NOT positing supernatural soul to Charles but just simple memory retrieval ability and the ability of reading his medical observation report ... (Of course from a third person perspective everything remains deterministic here and Charles end up as both, but prediction can be verified and aknowledged only from a first person point of view with or without quantum or comp suicide). Bruno
Re: Travelling to a different universe
On 25-Dec-01, Saibal Mitra wrote: Brent Meeker wrote: On 25-Dec-01, Saibal Mitra wrote: Charles Goodwin wrote: Or are you claiming that repeated quantum suicide attempts increase the chances that you are a computer simulation? Yes that is what I claim. That would only occur if there was some sort of cul-de-sac (assuming you *start* from a physical instantiation, at least). If you are physically instantiated at some point in time, all physical instantiations must end in a cul-de-sac before you can 'travel' to a universe in which you are a computer simulation. Why? If your brain were replaced by a digital one, you would still be the same person. If I made a digital version of you and let the biological version of you live on, then there would be a 50% chance you would end up as the digital person. I'm not sure what to make of such statements. It seems to me there's a 100% chance Charles would end up as both. Are you positing a supernatural soul that's *really* Charles and can only be in one of the two physical 'brains'? Not at all. There are two identical ``souls´´. Of course there is a 100% chance that you would be in either the real world or the simulation. I am saying that if Charles could perform an experiment to find out whether he was in the simulation or in the real world, there would be a 50% chance for him to be in the simulation. I guess I still find the question slightly incoherent. ...whether he was in the simulation... invites the question, To whom does 'he' refer? Brent Meeker
Re: Travelling to a different universe
On 25-Dec-01, Saibal Mitra wrote: Charles Goodwin wrote: Or are you claiming that repeated quantum suicide attempts increase the chances that you are a computer simulation? Yes that is what I claim. That would only occur if there was some sort of cul-de-sac (assuming you *start* from a physical instantiation, at least). If you are physically instantiated at some point in time, all physical instantiations must end in a cul-de-sac before you can 'travel' to a universe in which you are a computer simulation. Why? If your brain were replaced by a digital one, you would still be the same person. If I made a digital version of you and let the biological version of you live on, then there would be a 50% chance you would end up as the digital person. I'm not sure what to make of such statements. It seems to me there's a 100% chance Charles would end up as both. Are you positing a supernatural soul that's *really* Charles and can only be in one of the two physical 'brains'? Brent Meeker
Re: Travelling to a different universe
I don't see why one would want to go back, but there are still copies left in ordinary universes, there are universes in which the probability to win will return to normal after a while. One should thus be able to go back using a suicide machine. Also one could use memory erasure to go back. Saibal John Mikes wrote: OK, Saibal Mitra, you won. Are you happy now? Can you ever go back? John Mikes Suppose that every week I subject myself to a suicide experiment. I usea suicide machineto win that weeks lottery. After a few years I will have won hundreds of times in succession. Now there exists a class of universes, with a very low measure, in which the laws of physics aresuch that I am guaranteed to win. The probability that I find myself in such a universe will have increased substantially aftereach experiment. After a few years I will be sure to live in such a universe. It would be easy to check, all I would have to do is to buy a ticket and see if I have won without using the suicide machine. Saibal
Re: Travelling to a different universe
I had the set of all possible universes in mind. But, as I wrote earlier (in August), the set of all possible universes is contained in the MWI. The reason is that there is a nonzero probability that you are be simulated by a computer. This computer could run any program. Saibal Charles Goodwin wrote: I can't see this. For one thing, you can't 'travel' to other universes with different laws of physics, at least not according to the MWI. More to the point, assuming quantum suicide works, you will find yourself in one of the sheaf of universes which has split off from the one you started in. This is true anyway, according to MWI, but if you also use quantum suicide you limit your existence to a small subset of that sheaf (the subset in which you won the lottery, for example). Since you only experience universes which are physically possible continuers of the universe you started in, you keep the same laws of physics. So - you can't journey to a universe in which the laws of physics are X by using quantum suicide to select versions of yourself for which X is true; you can only limit your existence to universes in which X happens to be true. Always assuming that quantum suicide actually works (as Larry Niven said about the matter transmitter which destroys you at point A and creates a perfect copy at point B, I wouldn't ride in the damn thing). Charles - Original Message - From: Saibal Mitra [EMAIL PROTECTED] To: everything [EMAIL PROTECTED] Cc: FoR [EMAIL PROTECTED] Sent: Monday, December 24, 2001 2:48 AM Subject: Travelling to a different universe Suppose that every week I subject myself to a suicide experiment. I use a suicide machine to win that weeks lottery. After a few years I will have won hundreds of times in succession. Now there exists a class of universes, with a very low measure, in which the laws of physics are such that I am guaranteed to win. The probability that I find myself in such a universe will have increased substantially after each experiment. After a few years I will be sure to live in such a universe. It would be easy to check, all I would have to do is to buy a ticket and see if I have won without using the suicide machine. Saibal [Non-text portions of this message have been removed] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Yahoo! Groups Sponsor -~-- Access Your PC from Anywhere - Full setup in 2 minutes - Free Download http://us.click.yahoo.com/1GUySC/E6eDAA/ySSFAA/pyIolB/TM -~- Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Re: Travelling to a different universe
Dear Saibal, you misunderstood my post. I did not ask about "technicalities" of your sci-fi, I simply suggested that you may not "play" to get from here to there, but are "here" by a play from "over there". Simply humor, nothing else. John I don't see why one would want to go back, but there are still copies left in ordinary universes, there are universes in which the probability to win will return to normal after a while. One should thus be able to go back using a suicide machine. Also one could use memory erasure to go back. Saibal John Mikes wrote: SNIP
