On Wednesday, May 23, 2018 at 8:16:07 AM UTC, Bruce wrote: > > From: <[email protected] <javascript:> > > On Wednesday, May 23, 2018 at 7:09:31 AM UTC, Bruce wrote: >> >> From: <[email protected]> >> >> >> On Wednesday, May 23, 2018 at 4:44:30 AM UTC, Brent wrote: >>> >>> >>> On 5/22/2018 9:41 PM, [email protected] wrote: >>> >>> >>> On Wednesday, May 23, 2018 at 4:05:58 AM UTC, Brent wrote: >>>> >>>> >>>> >>>> On 5/22/2018 8:29 PM, [email protected] wrote: >>>> >>>> >>>> >>>> On Wednesday, May 23, 2018 at 2:24:07 AM UTC, Bruce wrote: >>>>> >>>>> From: <[email protected]> >>>>> >>>>> >>>>> On Wednesday, May 23, 2018 at 1:45:39 AM UTC, Brent wrote: >>>>>> >>>>>> >>>>>> >>>>>> On 5/22/2018 5:59 PM, [email protected] wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Wednesday, May 23, 2018 at 12:44:06 AM UTC, Brent wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On 5/22/2018 3:46 PM, [email protected] wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Tuesday, May 22, 2018 at 10:41:11 PM UTC, [email protected] >>>>>>> wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> I did, but you're avoiding the key point; if the theory is on the >>>>>>> right track, and I think it is, quantum measurements are irreversible >>>>>>> FAPP. >>>>>>> The superposition is converted into mixed states, no interference, and >>>>>>> no >>>>>>> need for the MWI. >>>>>>> >>>>>>> >>>>>>> You're still not paying attention to the problem. First, the >>>>>>> superposition is never converted into mixed states. It >>>>>>> *approximates*, FAPP, a mixed state* in some pointer* basis (and >>>>>>> not in others). Second, even when you trace over the environmental >>>>>>> terms >>>>>>> to make the cross terms practically zero (a mathematical, not physical, >>>>>>> process) you are left with different outcomes with different >>>>>>> probabilities. CI then just says one of them happens. But when did it >>>>>>> happen?...when you did the trace operation on the density matrix? >>>>>>> >>>>>> >>>>>> I think the main takeaway from decoherence is that information isn't >>>>>> lost to other worlds, but to the environment in THIS world. >>>>>> >>>>>> >>>>>> But that ignores part of the story. The information that is lost to >>>>>> the environment is different depending on what the result is. So if by >>>>>> some magic you could reverse your world after seeing the result you >>>>>> couldn't get back to the initial state because you could not also >>>>>> reverse >>>>>> the "other worlds". >>>>>> >>>>> >>>>> What "other worlds"? If they don't exist, why should I be concerned >>>>> about them? AG >>>>> >>>>> >>>>> I think you are ignoring the facts of the mathematics of unitary >>>>> evolution of the wave function. Under unitary evolution the wave function >>>>> branches, one branch or each element of the superposition, which is, one >>>>> branch for each possible experimental result. These branches are in the >>>>> mathematics. Now you can take all branches as really existing every much >>>>> as >>>>> the observed result exists -- that is the MWI position. Or you can throw >>>>> them away as not representing your experimental result -- which is the >>>>> collapse position. But in both cases, the evolution of the wave function >>>>> shows that there is information in each mathematical branch. If you >>>>> discard >>>>> the branches (collapse) you throw this information away: if you retain >>>>> the >>>>> branches as other worlds, the information becomes inaccessible by >>>>> decoherence and partial tracing. >>>>> >>>>> The situation is the same in either approach. Brent and I are not >>>>> being inconsistent, devious, or otherwise tricky by referring to both MWI >>>>> and CI approaches -- we are just recognizing the actual mathematics of >>>>> quantum mechanics. The mathematics has to be interpreted, and different >>>>> interpretations are available for the way in which the information in >>>>> other >>>>> branches is treated. >>>>> >>>>> Bruce >>>>> >>>> >>>> Consider this interpretation of the wf, which for simplicity I consider >>>> as a superposition of two eigenfunctions, and based on the probability >>>> amplitudes represents a 50% probability of each outcome at some point in >>>> time. Since the measurement hasn't occurred, where does this information >>>> reside? Presumably it all resides in THIS world. As time evolves the >>>> probability distribution changes, say to 75-25, and later to 90-10, and so >>>> on. All of this information resides in this world since without a >>>> measurement occurring, there are no other worlds, and no collapse. Suppose >>>> at some point in time, the values changed to 100-0, Isn't 100-0 as good as >>>> other pair if they sum to zero? And why would anyone think another world >>>> comes into existence because one of the values evolved to 0? I will now >>>> define, in answer to one of Brent's questions, when the measurement >>>> occurs. >>>> I assert it occurs when one of the pair of values equals 0, All throughout >>>> all information was in this world. Why would another world come into >>>> existence if one of the values happened to be 0? AG >>>> >>>> >>>> First, in the cases of interest there is no mechanism for going from >>>> 50/50 to 100/0 because it goes 0/100 as well, and it's random. You may >>>> hypothesize there is such process, but that's equivalent to assuming a >>>> hidden variable. And then Aspect's experiments show such a hidden >>>> variable >>>> transmits influence faster than light...which then cascades into problems >>>> with special and general relativity and quantum field theory and so on... >>>> >>>> Brent >>>> >>> >>> I was assuming the wf evolves to different probabilities via the SWE. >>> Nothing wrong with going to 0/100 because that just means the other >>> eigenvalue became the final state. AG >>> >>> >>> That's why I wrote "in cases of interest". If it evolves to 0/100 via >>> the SWE no problem...no interest either. >>> >> >> Why no interest? Haven't I described the case of a system evolving >> according to the SWE, then a measurement occurring, and throughout all the >> information is residing in THIS world. >> >> >> Your thought experiment does not correspond to unitary quantum evolution. >> > > Why not? Would different intermediate values correspond to unitary quantum > evolution? AG > > > You describe the evolution of a quantum state to a different state -- you > are not describing a measurement operation. If you measure a different > state, you can expect different results. > > > Why would information be lost to some other world simply because one value >> of the pair of probabilities equals 0? >> >> >> If one of the probabilities is zero, it means that the wave function has >> no corresponding component. If the only other part of the wave function has >> probability 100%, then the outcome is certain, and no information can >> reside anywhere else. >> > > I was trying to describe a situation where the wf collapses, in terms of > probability, to a delta function, where a single outcome is achieved with > 100% probability, and the other does not, so it has probability of 0. AG > > > That is a measurement on a different state, where one would expect > different results. > > IOW, the example is meant to illustrate the fallacy of claiming some >> information is lost when the measurement occurs, and now resides in some >> inaccessible other world. In decoherence, isn't all the lost information >> lost in THIS world, to the environment, like a heat bath? Isn't decoherence >> therefore in conflict with the MWI? AG >> >> >> No. Decoherence occurs independently for each branch of the wave >> function, so information is disseminated into the environment in all >> branches of the wave function independently. >> > > OK, but how does one jump to the assumption of other worlds? Doesn't each > "branch" exist in this world? AG > > > Initially yes. But decoherence diagonalizes the density matrix FAPP, so > the other branches become unreachable. That is what one means by separate > worlds. >
*I am tentatively OK with this conclusion (tentatively until I examine the mathematics and verify it), as long as these separate "worlds" do NOT contain copies of THIS world. It's the copying that I find hugely extravagant, ridiculous, and erroneous! Can decoherence theory be consistent without the "copying" claim? Is this the view you adopt to keep your sanity? TIA, AG* > > Bruce > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
