On Wednesday, May 23, 2018 at 12:44:06 AM UTC, Brent wrote: > > > > On 5/22/2018 3:46 PM, [email protected] <javascript:> 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. So quantum measurements are irreversible FAPP, not irreversible in principle. AG > > I still don't get it -- why you and Bruce keep resorting to the MWI to > deny reversible FAPP, when both of you have huge disrespect for the MWI. AG > > > I have huge disrespect for Donald Trump. Theories of physics I regard > with relative equanimity. > You fooled me. You don't seem in any way favorable to the MWI except when you're desperate, at which point you invoke it, say to deny irreversible FAPP when analyzing a quantum experiment.. 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.
