Re: Changing the past by forgetting
In "quantum eraser" experiments the erasure is done by making the measured value ambiguous, e.g. by making a different measurement which does not commute with the one to be erased. In terms of MWI this has the effect or recohering (or more accurately, not decohering) the branches rather than cutting one off. After the erasure there is no fact of the matter as to what the value was. Of course in these experiments care must be taken to avoid interaction with the environment so that coherence is not lost before the second measurement. Brent Stephen Paul King wrote: > Hi Brent, > > But does not MWI imply that if we could somehow erase all (retrivable!) > records of a measurement, that we would - in effect - be culling that > branch from the Tree? > > > - Original Message - > From: "Brent Meeker" > To: > Sent: Sunday, March 15, 2009 10:06 PM > Subject: Re: Changing the past by forgetting > > > snip > >> ... Even more telling experiments have already been done in which >> the "measurement" was just the unrecorded IR radiation from buckyballs. >> Buckyballs which were sufficiently cold showed the 2-slit interference >> pattern >> in a Young's slit type experiment. But when they were warm enough to emit >> IR >> radiation that, if detected, could have localized them, the interference >> disappeared. So it is not only a matter of the experimenter not looking >> at the >> result, the rest of the universe has to not look too. >> >> Brent > > It is sad that Einstein was not made aware of this implication of QM. If > he was, his thought about the "moon not being there when I'm not looking at > it" would not have formed. I wish we had a better sense of exactly how > decoherence worked such that we could quantify how there might be "parts" of > a system's wave function that are entagled with its environment and other > parts that are not... > > Onward! > > Stephen > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
On Sun, Mar 15, 2009 at 07:06:06PM -0700, Brent Meeker wrote: > > No need to do it. Even more telling experiments have already been done in > which > the "measurement" was just the unrecorded IR radiation from buckyballs. > Buckyballs which were sufficiently cold showed the 2-slit interference > pattern > in a Young's slit type experiment. But when they were warm enough to emit IR > radiation that, if detected, could have localized them, the interference > disappeared. So it is not only a matter of the experimenter not looking at > the > result, the rest of the universe has to not look too. > > Brent > Interesting! Do you have some citations for this, or even let me know who did the experiment? Cheers -- Prof Russell Standish Phone 0425 253119 (mobile) Mathematics UNSW SYDNEY 2052 hpco...@hpcoders.com.au Australiahttp://www.hpcoders.com.au --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
Hi Brent, But does not MWI imply that if we could somehow erase all (retrivable!) records of a measurement, that we would - in effect - be culling that branch from the Tree? - Original Message - From: "Brent Meeker" To: Sent: Sunday, March 15, 2009 10:06 PM Subject: Re: Changing the past by forgetting snip >... Even more telling experiments have already been done in which > the "measurement" was just the unrecorded IR radiation from buckyballs. > Buckyballs which were sufficiently cold showed the 2-slit interference > pattern > in a Young's slit type experiment. But when they were warm enough to emit > IR > radiation that, if detected, could have localized them, the interference > disappeared. So it is not only a matter of the experimenter not looking > at the > result, the rest of the universe has to not look too. > > Brent It is sad that Einstein was not made aware of this implication of QM. If he was, his thought about the "moon not being there when I'm not looking at it" would not have formed. I wish we had a better sense of exactly how decoherence worked such that we could quantify how there might be "parts" of a system's wave function that are entagled with its environment and other parts that are not... Onward! Stephen --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
russell standish wrote: > On Sun, Mar 15, 2009 at 11:06:42AM -0700, Brent Meeker wrote: >> Saibal Mitra wrote: >>> If we consider measuring the spin of a particle, you could also say that the >>> two possible outcomes just exist and thatthere are two possible future >>> versions of me. There is no meaningful way to associate myself with either >>> of the two outcomes. >>> >>> But then, precisely this implies that after a measurement and forgetting >>> about the result will yield a version of me who is in a similar position as >>> that earlier version of me who had yet to make the measurement. If one could >>> perform measurements in a reversible way, this would be possible to >>> experimentally confirm, as David Deutsch pointed out. You can start with a >>> spin polarized in the x direction. Then you measure the z-component. There >>> then exists a unitary transformation which leads to the observer forgetting >>> about the outcome of the measurement and to the spin to be restored in the >>> original state. The observer does remember having measured the z-component >>> of the spin. >>> >>> Then, measuring the x-component again will yield "spin-up" with 100% >>> probability, confirming that both branches in which the observer measured >>> spin up and spin down have coherently recombined. This then proves that had >>> the observer measured the z-component, the outcome would not be a priori >>> determined, despite the observer having measured it earlier. So, both >>> branches are real. But then this is true in general, also if the quantum >>> state is of the form: >>> >>> |You>[|spin up>|rest of the world knows the spin is up> + |spin down>|rest >>> of the world knows spin is down>] >> You're contemplating reversing three different things: >> >> 1) Your knowledge, by forgetting a measurement result. Something that's >> easy to do. >> >> 2) The spin state of a particle. >> >> 3) The state of what the rest of the world knows. >> >> Because of the entanglement, I don't think you can, in general, reverse the >> spin >> state of the particle without reversing what is known about it by "the rest >> of >> the world". >> If it was a known state (to someone) the particle can easily be put back in >> that >> state. But to do so for a general, unknown state, after a measurement would >> require invoking time-reversal invariance of the state of whole universe (or >> at >> least all of it entangled with the particle spin via the measuring >> apparatus). >> >> Brent Meeker >> > > By contrast, I think this line of reasoning can be used to create an > experiment that tests a couple of different versions of MWI. > > Consider a Stern-Gerlach experiment where a particle is prepared in > the x+ state. Then measure the state of the particle's spin along the > z-axis, but _do not_ record the result. Finally measure the spin along > the x-axis. > > According to Saibal's interpretation (which accords with my own > intuition), the result should be spin up (x+) always. According to the > interpretation you're suggesting Brent (the decoherence of the > environment to contain a memory of whether the spin was z+ or z- - > which I think accords with David Deutch's intuition), the final result > should be x+ or x- with 50% probability. It may be important to send > the result of the intervening measurement to a memory store somewhere > else that the experimenter does not look at. > > This should be a doable experiment, and in fact may already have been > done. It is similar in some respects to a version of the two-slit > experiment performed a couple of years ago that generated a spark of > interest. > > No need to do it. Even more telling experiments have already been done in which the "measurement" was just the unrecorded IR radiation from buckyballs. Buckyballs which were sufficiently cold showed the 2-slit interference pattern in a Young's slit type experiment. But when they were warm enough to emit IR radiation that, if detected, could have localized them, the interference disappeared. So it is not only a matter of the experimenter not looking at the result, the rest of the universe has to not look too. Brent --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
On Sun, Mar 15, 2009 at 11:06:42AM -0700, Brent Meeker wrote: > > Saibal Mitra wrote: > > If we consider measuring the spin of a particle, you could also say that the > > two possible outcomes just exist and thatthere are two possible future > > versions of me. There is no meaningful way to associate myself with either > > of the two outcomes. > > > > But then, precisely this implies that after a measurement and forgetting > > about the result will yield a version of me who is in a similar position as > > that earlier version of me who had yet to make the measurement. If one could > > perform measurements in a reversible way, this would be possible to > > experimentally confirm, as David Deutsch pointed out. You can start with a > > spin polarized in the x direction. Then you measure the z-component. There > > then exists a unitary transformation which leads to the observer forgetting > > about the outcome of the measurement and to the spin to be restored in the > > original state. The observer does remember having measured the z-component > > of the spin. > > > > Then, measuring the x-component again will yield "spin-up" with 100% > > probability, confirming that both branches in which the observer measured > > spin up and spin down have coherently recombined. This then proves that had > > the observer measured the z-component, the outcome would not be a priori > > determined, despite the observer having measured it earlier. So, both > > branches are real. But then this is true in general, also if the quantum > > state is of the form: > > > > |You>[|spin up>|rest of the world knows the spin is up> + |spin down>|rest > > of the world knows spin is down>] > > You're contemplating reversing three different things: > > 1) Your knowledge, by forgetting a measurement result. Something that's easy > to do. > > 2) The spin state of a particle. > > 3) The state of what the rest of the world knows. > > Because of the entanglement, I don't think you can, in general, reverse the > spin > state of the particle without reversing what is known about it by "the rest > of > the world". > If it was a known state (to someone) the particle can easily be put back in > that > state. But to do so for a general, unknown state, after a measurement would > require invoking time-reversal invariance of the state of whole universe (or > at > least all of it entangled with the particle spin via the measuring apparatus). > > Brent Meeker > By contrast, I think this line of reasoning can be used to create an experiment that tests a couple of different versions of MWI. Consider a Stern-Gerlach experiment where a particle is prepared in the x+ state. Then measure the state of the particle's spin along the z-axis, but _do not_ record the result. Finally measure the spin along the x-axis. According to Saibal's interpretation (which accords with my own intuition), the result should be spin up (x+) always. According to the interpretation you're suggesting Brent (the decoherence of the environment to contain a memory of whether the spin was z+ or z- - which I think accords with David Deutch's intuition), the final result should be x+ or x- with 50% probability. It may be important to send the result of the intervening measurement to a memory store somewhere else that the experimenter does not look at. This should be a doable experiment, and in fact may already have been done. It is similar in some respects to a version of the two-slit experiment performed a couple of years ago that generated a spark of interest. -- Prof Russell Standish Phone 0425 253119 (mobile) Mathematics UNSW SYDNEY 2052 hpco...@hpcoders.com.au Australiahttp://www.hpcoders.com.au --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
At 06:20 PM 3/15/2009, George Levy wrote: >I agree with Anna. In addition, it all depends on where you define >the boundary of the self. Just the brain? Brain + body? Brain + body >+ immediate surrounding (prescription glasses being worn, automobile >being driven, binoculars or computer being used) ? Brain + body + >Whole causally connected universe (CCU)? > >There are good arguable reasons for including the CCU as part of the >self. Forgetting would then mean resetting the CCU to the last >"remembered" state. In this case we have an identity relationship >between the self and the universe it inhabits. Resetting the self is >the same as resetting the universe. No more problem or paradox >associated with forgetting! > >George Helmut Schmidt's "retrocausation" (actually a sophisticated delayed choice) experiments suggested that causation might be associated with many-worlds---that is, it might be possible to choose a past that will lead to a present state of a Causally Connected Universe. If different pasts can be associated with equivalent behavioral sets in the present then it would be impossible to differentiate the specific world lines that led to the present behavioral set. If one's present behavioral state is a sum of histories over time, then one could focus on a particular history (say, one without dinosaurs) to subtly alter the present CCU, but if the difference can't be consciously detected, then (a la Copenhagen theory) then it would be irrelevent. As for memory being reconstructive, the fact is we really don't know much about it at all. If time doesn't exist except as a bundle of world lines, memory might involve "sampling" a section of the preceding bundle. In that view we create our own particular CCU. Wrong about past events? Maybe you sampled the wrong world line. R. Miller >A. Wolf wrote: >>> >>>Thanks! This is like undoing historical events. If you forget about the >>>fact that dinosaurs ever lived on Earth and there is an alternative >>>history >>>that led to your existence in the multiverse, and you do the memory >>>erasure >>>also in sectors were dinosaurs never lived, you have some nonzero >>>probability of finding yourself on an Earth were the dinosaurs never >>>lived. >>> >> >> >>The problem I'm having with this line of reasoning is that "memory" isn't a >>fixed physical object. Memory is reconstructive, and depends upon emotional >>triggers both at the time when the memory was encoded and at the time when >>it re-examined in the conscious mind. No memories are particularly >>accurate. >> >>Most of the time, I'm not aware that dinosaurs existed because I'm not >>thinking about it, or any other part of Earth's history, for that >>matter...but I don't seem to have the experience that my environment is >>impoverished of history altogether just because I hadn't been thinking hard >>enough about it. As another example, people who have false recovered >>memories through psychotherapy invariably end up unable to confirm them when >>they look for facts to back up their new memories, and that happens in my >>universe even though I personally don't have any information to confirm or >>deny their memories. >> >>In other words, I don't see why forgetting something is any more likely to >>change events than simply being wrong about having the memory in the first >>place, the latter of which happens constantly. If you want to argue about >>what nonzero probability implies, you'd have a hard time showing that >>anything non-contradictory at all has a nonzero probability of being true. >>:) >> >> >>> >>>Because of the entanglement, I don't think you can, in general, reverse >>>the spin >>>state of the particle without reversing what is known about it by "the >>>rest of >>>the world". >>> >> >> >>The rest of the world? What's that? >> >>Anna >> >> >> >> >> > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
I agree with Anna. In addition, it all depends on where you define the boundary of the self. Just the brain? Brain + body? Brain + body + immediate surrounding (prescription glasses being worn, automobile being driven, binoculars or computer being used) ? Brain + body + Whole causally connected universe (CCU)? There are good arguable reasons for including the CCU as part of the self. Forgetting would then mean resetting the CCU to the last "remembered" state. In this case we have an identity relationship between the self and the universe it inhabits. Resetting the self is the same as resetting the universe. No more problem or paradox associated with forgetting! George A. Wolf wrote: >> Thanks! This is like undoing historical events. If you forget about the >> fact that dinosaurs ever lived on Earth and there is an alternative >> history >> that led to your existence in the multiverse, and you do the memory >> erasure >> also in sectors were dinosaurs never lived, you have some nonzero >> probability of finding yourself on an Earth were the dinosaurs never >> lived. >> > > The problem I'm having with this line of reasoning is that "memory" isn't a > fixed physical object. Memory is reconstructive, and depends upon emotional > triggers both at the time when the memory was encoded and at the time when > it re-examined in the conscious mind. No memories are particularly > accurate. > > Most of the time, I'm not aware that dinosaurs existed because I'm not > thinking about it, or any other part of Earth's history, for that > matter...but I don't seem to have the experience that my environment is > impoverished of history altogether just because I hadn't been thinking hard > enough about it. As another example, people who have false recovered > memories through psychotherapy invariably end up unable to confirm them when > they look for facts to back up their new memories, and that happens in my > universe even though I personally don't have any information to confirm or > deny their memories. > > In other words, I don't see why forgetting something is any more likely to > change events than simply being wrong about having the memory in the first > place, the latter of which happens constantly. If you want to argue about > what nonzero probability implies, you'd have a hard time showing that > anything non-contradictory at all has a nonzero probability of being true. > :) > > >> Because of the entanglement, I don't think you can, in general, reverse >> the spin >> state of the particle without reversing what is known about it by "the >> rest of >> the world". >> > > The rest of the world? What's that? > > Anna > > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
I agree with Anna. In addition, it all depends on where you define the boundary of the self. Just the brain? Brain + body? Brain + body + immediate surrounding (prescription glasses being worn, automobile being driven, binoculars or computer being used) ? Brain + body + Whole causally connected universe (CCU)? There are good arguable reasons for including the CCU as part of the self. Forgetting would then mean resetting the CCU to the last "remembered" state. In this case we have an identity relationship between the self and the universe it inhabits. Resetting the self is the same as resetting the universe. No more problem or paradox associated with forgetting! George A. Wolf wrote: >> Thanks! This is like undoing historical events. If you forget about the >> fact that dinosaurs ever lived on Earth and there is an alternative >> history >> that led to your existence in the multiverse, and you do the memory >> erasure >> also in sectors were dinosaurs never lived, you have some nonzero >> probability of finding yourself on an Earth were the dinosaurs never >> lived. >> > > The problem I'm having with this line of reasoning is that "memory" isn't a > fixed physical object. Memory is reconstructive, and depends upon emotional > triggers both at the time when the memory was encoded and at the time when > it re-examined in the conscious mind. No memories are particularly > accurate. > > Most of the time, I'm not aware that dinosaurs existed because I'm not > thinking about it, or any other part of Earth's history, for that > matter...but I don't seem to have the experience that my environment is > impoverished of history altogether just because I hadn't been thinking hard > enough about it. As another example, people who have false recovered > memories through psychotherapy invariably end up unable to confirm them when > they look for facts to back up their new memories, and that happens in my > universe even though I personally don't have any information to confirm or > deny their memories. > > In other words, I don't see why forgetting something is any more likely to > change events than simply being wrong about having the memory in the first > place, the latter of which happens constantly. If you want to argue about > what nonzero probability implies, you'd have a hard time showing that > anything non-contradictory at all has a nonzero probability of being true. > :) > > >> Because of the entanglement, I don't think you can, in general, reverse >> the spin >> state of the particle without reversing what is known about it by "the >> rest of >> the world". >> > > The rest of the world? What's that? > > Anna > > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
> what nonzero probability implies, you'd have a hard time showing that > anything non-contradictory at all has a nonzero probability of being true. Er, I typed too quickly. I mean you'd have a hard time of showing that anything non-contradictory has zero probability. Anything that isn't mathematically contradictory has a nonzero probability, as far as I'm concerned. Anna --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
> Thanks! This is like undoing historical events. If you forget about the > fact that dinosaurs ever lived on Earth and there is an alternative > history > that led to your existence in the multiverse, and you do the memory > erasure > also in sectors were dinosaurs never lived, you have some nonzero > probability of finding yourself on an Earth were the dinosaurs never > lived. The problem I'm having with this line of reasoning is that "memory" isn't a fixed physical object. Memory is reconstructive, and depends upon emotional triggers both at the time when the memory was encoded and at the time when it re-examined in the conscious mind. No memories are particularly accurate. Most of the time, I'm not aware that dinosaurs existed because I'm not thinking about it, or any other part of Earth's history, for that matter...but I don't seem to have the experience that my environment is impoverished of history altogether just because I hadn't been thinking hard enough about it. As another example, people who have false recovered memories through psychotherapy invariably end up unable to confirm them when they look for facts to back up their new memories, and that happens in my universe even though I personally don't have any information to confirm or deny their memories. In other words, I don't see why forgetting something is any more likely to change events than simply being wrong about having the memory in the first place, the latter of which happens constantly. If you want to argue about what nonzero probability implies, you'd have a hard time showing that anything non-contradictory at all has a nonzero probability of being true. :) > Because of the entanglement, I don't think you can, in general, reverse > the spin > state of the particle without reversing what is known about it by "the > rest of > the world". The rest of the world? What's that? Anna --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: [Fwd: NDPR David Shoemaker, Personal Identity and Ethics: A Brief Introduction]
Hi Günther, > > Hi Bruno, > > thanks for your interesting answer, I have some questions though. > >> course, as I said, this will depend of what you mean by "you". In >> case >> you accept the idea of surviving with amnesia, you can even get to a >> state where you "know" you are immortal, because your immortality >> is a >> "past event". > > > I would equate total amnesia with death (we've been through this > before, > Stathis has written about this, if I remember correctly). I remember Quentin identifying himself with his memory, and very logically, identifying total amnesia with death. It is a complex matter. Total amnesia concern only some form of declarative knowledge, you cannot loss your "procedural memory", because it is part of ... arithmetic, and common to all elementary knowers. > > > I agree with you that you can't have a universal machine stopping > relatively to all others from it's POV; but I don't see why we can't > think of it having total amnesia. So, for the time being, let us take > surviving as meaning to keep (at least large parts) of one's memory. All right. Comp leads also to that form of immortality, at least for awhile (if I can say). The problem of death is intrinsically difficult, because you will survive with amnesia or not according of the level of substitution, which we cannot know, but only bet on (or perhaps even choose in some circumstances?). Total amnesia seems to lead to the remembering of you being the universal person, plausibly Plotinus "Soul-Universe", or the arithmetical S4Grz (the third hypostase). Total amnesia is complete fusing. We "remember" we are all the same person. We can lost that memory only by differentiating oneself again. > > >> facts, like the continuum of many-worlds. If Loop Gravity is 100% >> correct, and if the big bang has a finitely describable origin then >> comp is false! > > Could you elaborate? I don't see why LG should be bad news for comp? > You mean because LG proposes a fundamental spacetime quantization? > I don't see how it would falsify comp? It is obviously an open problem. But taking literally the UDA, and making abstraction of some still possible (logically) conspiration of the numbers, it seems clear that comp predict that an electron, for going from A to B, with respect to you, will be supported by a continuum of computational histories. I have no clue how to select a finite or countable infinity of subcomputations. But if that is the case, the UDA shows that such a conclusion (like LG) has to be derived from arithmetic. Otherwise, it would be treachery. > > > And why the finitely describable Big Bang? It seems you have a problem > when there are some finite limits (outside of the effective > computation > of mind). Is this because you need the continuum in the AUDA to get > Quantum logic or something like that? Not at all. That would be treachery too. If the continuum was not possibly emerging from AUDA, I would take this as an evidence that comp is false. The reason comes really from computer science and the (enumerable) redundancy of the computational states, and the non enumerable redundancy of the "1-pov" infinite stories. > > >> Our bodies can be considered programmed to stop (by sex and death), >> our soul just cannot, there is always a consistent continuation (even >> without amnesia > > Why do you believe that latter? Consider someone who dies, relatively to you. Well, La Palisse was found of "tautology": after he died, someone said" 5 minutes avant sa mort, Monsieur de La Paice vivait encore". "Fives minutes before he died, Sir de La Palice was still alive". Now, from the point of view of the dying person, the UD generates 2^aleph_zero histories going through that state "where he is is still alive", and which are below its computational relevant substitution level. Even with just QM, you can see stories which will "repair anything wrong with whatever needed to generate a short consistent computation. At his substitution level he is finite, and finite machine can always be fixed, and that is all the soul need to survive an instant. But this is true for all instants, by exactly the repetition of the argument. Perhaps some Gods can be mortal, but no souls, as supported by finite entities. That would be like my mechanics: "no, you car is definitely broken". It is a lie, or a simplification, what it means is "it would be more expensive to fix it than to buy a new one". In the ud, the first person has unbound-able resources. I think, and Quentin disagrees, that, would I be dying, I would feel myself surviving more probably in the "amnesic stories", probably because I tend to believe (those days) that, if comp is true, my substitution level could probably be rather high. So I would survive in those "normal world" with a "lesser brain". But if Quentin is right and all my memory are necessary for being me, I will
Re: Changing the past by forgetting
Saibal Mitra wrote: > If we consider measuring the spin of a particle, you could also say that the > two possible outcomes just exist and thatthere are two possible future > versions of me. There is no meaningful way to associate myself with either > of the two outcomes. > > But then, precisely this implies that after a measurement and forgetting > about the result will yield a version of me who is in a similar position as > that earlier version of me who had yet to make the measurement. If one could > perform measurements in a reversible way, this would be possible to > experimentally confirm, as David Deutsch pointed out. You can start with a > spin polarized in the x direction. Then you measure the z-component. There > then exists a unitary transformation which leads to the observer forgetting > about the outcome of the measurement and to the spin to be restored in the > original state. The observer does remember having measured the z-component > of the spin. > > Then, measuring the x-component again will yield "spin-up" with 100% > probability, confirming that both branches in which the observer measured > spin up and spin down have coherently recombined. This then proves that had > the observer measured the z-component, the outcome would not be a priori > determined, despite the observer having measured it earlier. So, both > branches are real. But then this is true in general, also if the quantum > state is of the form: > > |You>[|spin up>|rest of the world knows the spin is up> + |spin down>|rest > of the world knows spin is down>] You're contemplating reversing three different things: 1) Your knowledge, by forgetting a measurement result. Something that's easy to do. 2) The spin state of a particle. 3) The state of what the rest of the world knows. Because of the entanglement, I don't think you can, in general, reverse the spin state of the particle without reversing what is known about it by "the rest of the world". If it was a known state (to someone) the particle can easily be put back in that state. But to do so for a general, unknown state, after a measurement would require invoking time-reversal invariance of the state of whole universe (or at least all of it entangled with the particle spin via the measuring apparatus). Brent Meeker > > although you cannot directly verify it here. But that means that you cannot > rule out an alternative theory in which only one of the branches is real > when performing a measurement in this case. But if the reality of both > branches is accepted, then each time you make a measurement and you don't > know the outcome, the outcome is not fixed (proovided, of course, there is > indeed more than one branch). > > > - Original Message - > From: "Jack Mallah" > To: > Sent: Thursday, March 12, 2009 03:47 AM > Subject: Re: Changing the past by forgetting > > > > > --- On Tue, 3/10/09, Saibal Mitra wrote: >> http://arxiv.org/abs/0902.3825 >> >> I've written up a small article about the idea that you could end up in a > different sector of the multiverse by selective memory erasure. I had > written about that possibility a long time ago on this list, but now I've > made the argument more rigorous. > > Saibal, I have to say that I disagree. As you acknowledge, erasing memory > doesn't recohere the branches. There is no meaningful sense in which you > could end up in a different branch due to memory erasure. > > You admit the 'effect' has no observable consequences. But it has no > unobservable meaning either. > > In fact, other than what I call 'causal differentiation', which clearly will > track the already-decohered branches (so you don't get to reshuffle the > deck), there is no meaningful sense in which "you" will end up in one > particular future branch at all. Other than causal differentiation > tracking, either 'you' are all of your future branches, or 'you' are just > here for the moment and are none of them. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
If we consider measuring the spin of a particle, you could also say that the two possible outcomes just exist and thatthere are two possible future versions of me. There is no meaningful way to associate myself with either of the two outcomes. But then, precisely this implies that after a measurement and forgetting about the result will yield a version of me who is in a similar position as that earlier version of me who had yet to make the measurement. If one could perform measurements in a reversible way, this would be possible to experimentally confirm, as David Deutsch pointed out. You can start with a spin polarized in the x direction. Then you measure the z-component. There then exists a unitary transformation which leads to the observer forgetting about the outcome of the measurement and to the spin to be restored in the original state. The observer does remember having measured the z-component of the spin. Then, measuring the x-component again will yield "spin-up" with 100% probability, confirming that both branches in which the observer measured spin up and spin down have coherently recombined. This then proves that had the observer measured the z-component, the outcome would not be a priori determined, despite the observer having measured it earlier. So, both branches are real. But then this is true in general, also if the quantum state is of the form: |You>[|spin up>|rest of the world knows the spin is up> + |spin down>|rest of the world knows spin is down>] although you cannot directly verify it here. But that means that you cannot rule out an alternative theory in which only one of the branches is real when performing a measurement in this case. But if the reality of both branches is accepted, then each time you make a measurement and you don't know the outcome, the outcome is not fixed (proovided, of course, there is indeed more than one branch). - Original Message - From: "Jack Mallah" To: Sent: Thursday, March 12, 2009 03:47 AM Subject: Re: Changing the past by forgetting --- On Tue, 3/10/09, Saibal Mitra wrote: > http://arxiv.org/abs/0902.3825 > > I've written up a small article about the idea that you could end up in a different sector of the multiverse by selective memory erasure. I had written about that possibility a long time ago on this list, but now I've made the argument more rigorous. Saibal, I have to say that I disagree. As you acknowledge, erasing memory doesn't recohere the branches. There is no meaningful sense in which you could end up in a different branch due to memory erasure. You admit the 'effect' has no observable consequences. But it has no unobservable meaning either. In fact, other than what I call 'causal differentiation', which clearly will track the already-decohered branches (so you don't get to reshuffle the deck), there is no meaningful sense in which "you" will end up in one particular future branch at all. Other than causal differentiation tracking, either 'you' are all of your future branches, or 'you' are just here for the moment and are none of them. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Changing the past by forgetting
Thanks! This is like undoing historical events. If you forget about the fact that dinosaurs ever lived on Earth and there is an alternative history that led to your existence in the multiverse, and you do the memory erasure also in sectors were dinosaurs never lived, you have some nonzero probability of finding yourself on an Earth were the dinosaurs never lived. - Original Message - From: "Bruno Marchal" To: Sent: Wednesday, March 11, 2009 06:54 PM Subject: Re: Changing the past by forgetting > > Nice! I did refer often to the Saibal Mitra backtracking procedure (in > immortality discussions). I will take a further look on your paper. > If valid, it should work in the comp frame. Amnesia could lead you to > the "original singularity", which could be a kind of blind spot of > "universal consciousness", except that with comp such a singularity > should looks like a "little Mandelbrot" set, at first sight, I mean > something like a compact view of a universal dovetailing. > > Bruno > > On 10 Mar 2009, at 19:55, Saibal Mitra wrote: > > > > > http://arxiv.org/abs/0902.3825 > > > > I've written up a small article about the idea that you could end up > > in a > > different sector of the multiverse by selective memory erasure. I had > > written about that possibility a long time ago on this list, but now > > I've > > made the argument more rigorous. > > > > > > > > > http://iridia.ulb.ac.be/~marchal/ > > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
