On Wednesday, May 23, 2018 at 1:45:39 AM UTC, Brent wrote: > > > > On 5/22/2018 5:59 PM, [email protected] <javascript:> 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: >>> >>> >>> >>> On Tuesday, May 22, 2018 at 10:06:39 PM UTC, Brent wrote: >>>> >>>> >>>> >>>> On 5/22/2018 6:39 AM, [email protected] wrote: >>>> >>>> I'm OK with getting rid of the projection operator. Are you now >>>>> claiming information is lost or inaccessible in these orthogonal >>>>> subspaces >>>>> and therefore quantum measurements cannot be reversed? >>>>> >>>>> >>>>> They are inaccessible to the people of any one world of the MWI. >>>>> >>>> >>>> No! Irreversible FAPP! Think heat bath or Bucky Balls. >>>> >>>> https://en.wikipedia.org/wiki/Quantum_decoherence >>>> >>>> Examples of non-unitary modelling of decoherence Decoherence >>>> <https://en.wikipedia.org/wiki/Decoherence> can be modelled as a non- >>>> unitary <https://en.wikipedia.org/wiki/Unitary_operator> process by >>>> which a system couples with its environment (although the combined system >>>> plus environment evolves in a unitary fashion).[4] >>>> <https://en.wikipedia.org/wiki/Quantum_decoherence#cite_note-Lidar_and_Whaley-4> >>>> >>>> Thus the dynamics of the system alone, treated in isolation, are >>>> non-unitary and, as such, are represented by irreversible >>>> transformations <https://en.wikipedia.org/wiki/Irreversibility> acting >>>> on the system's Hilbert space >>>> <https://en.wikipedia.org/wiki/Hilbert_space>, H {\displaystyle >>>> {\mathcal {H}}} [image: {\mathcal {H}}]. Since the system's dynamics >>>> are represented by irreversible representations, then any information >>>> present in the quantum system can be lost to the environment or heat >>>> bath <https://en.wikipedia.org/wiki/Heat_bath>. Alternatively, the >>>> decay of quantum information caused by the coupling of the system to the >>>> environment is referred to as decoherence.[3] >>>> <https://en.wikipedia.org/wiki/Quantum_decoherence#cite_note-Bacon-3> >>>> Thus decoherence is the process by which information of a quantum system >>>> is >>>> altered by the system's interaction with its environment (which form a >>>> closed system), hence creating an entanglement >>>> <https://en.wikipedia.org/wiki/Quantum_entanglement> between the >>>> system and heat bath (environment). As such, since the system is entangled >>>> with its environment in some unknown way, a description of the system by >>>> itself cannot be made without also referring to the environment (i.e. >>>> without also describing the state of the environment). >>>> >>>> >>>> Notice that this doesn't explain how one gets to a single result. >>>> >>> >> 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 > > Brent > -- 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.
