On Thursday, May 24, 2018 at 7:33:06 PM UTC, Brent wrote: > > > > On 5/23/2018 11:48 PM, [email protected] <javascript:> wrote: > > > > On Thursday, May 24, 2018 at 6:02:30 AM UTC, Brent wrote: >> >> >> >> On 5/23/2018 10:37 PM, [email protected] wrote: >> >> >> >> On Thursday, May 24, 2018 at 4:53:29 AM UTC, Brent wrote: >>> >>> >>> >>> On 5/23/2018 9:43 PM, [email protected] wrote: >>> >>> >>> >>> On Thursday, May 24, 2018 at 4:28:58 AM UTC, Brent wrote: >>>> >>>> >>>> >>>> On 5/23/2018 9:17 PM, [email protected] wrote: >>>> >>>> In the MWI interpretation there is no reason to preference one over the >>>>> other with the honorific of "exists". They are just projective subspaces >>>>> that are essentially (FAPP) orthogonal to one another. >>>>> >>>> >>>> I can buy that, although tentatively, with difficulty, until I see the >>>> mathematics which demonstrates it. AG >>>> >>>> >>>>> Each one includes copies of the system, the environment, and the >>>>> observer(s) which is necessary so that it constitute a classical "world" >>>>> in >>>>> which everyone agrees on the result. >>>>> >>>> >>>> This I absolutely CANNOT buy, as I have explained numerous times. >>>> Cannot decoherence and the MWI have descriptive value without all of this >>>> COPYING being assumed, which I find outlandish? Would it be fatal to any >>>> of >>>> these concepts to affirm that the entanglements which occur in these >>>> subspaces are equivalent to measurements in these subspaces? AG >>>> >>>>> >>>> It's fine if you just assume the other subspaces vanish as far as doing >>>> physics. Metaphysically it's problematic because you've used a certain >>>> theory up to that point which predicts that all the subspaces are equally >>>> real (and may be more probable than the one you experience) and there are >>>> copies of you and your lab etc which are equally real and now you're going >>>> to stop using that theory which was so amazingly successful...why? >>>> >>>> Brent >>>> >>> >>> The other subspaces don't vanish. They continue to exist and all >>> possible measurements are in fact measured according to my proposal. But >>> the subspace in which the observer exists seems apriori different and more >>> significant in terms of physical reality; it's the environment in which all >>> entanglements of all subspaces come into being. >>> >>> >>> The entanglements coming into being is what makes the subspaces become >>> orthogonal and become separate "worlds". The entanglements are different >>> (in detail) in each different subspace reflecting the fact that they are >>> correlated with a different result. >>> >> >> Yes, I am imagining a different result in each subspace. AG >> >>> >>> It seems metaphysically problematic to give all subspaces the same >>> existential status, when only one provides the environment for all >>> entanglements for all subspaces. AG >>> >>> >>> I don't know what entanglements you're talking about. The system >>> measured has different entanglements with the different environments and >>> observers in the different "worlds". There is no privileged world which >>> provides a privileged environment and observer. >>> >> >> I am imagining a superposition of states, and when the measurement >> occurs, each component of the superposition becomes entangled with the >> environment in this world, the world in which the measuring device exists. >> Then, somehow, the subspaces become orthogonal FAPP. AG >> >> >> No, it's the interaction, the entangling of different results with the >> environment, that makes the subspaces orthogonal. >> > > That's what I assumed; that the entanglement for each subspace causes the > orthogonality (though I can't imagine how that would come about). > > > If you look at the mathematics of the total (system+environment+observer) > density matrix, the off-diagonal terms have products of wf terms from the > system and environment. The environment wf are of course unknown, so one > averages over them by taking the trace over them. This makes the cross > terms for the reduce density matrix (that of the system) go to zero, so now > it is *formally* the same as the probability matrix for a set of > classical states. As Bruce points out this "taking the trace" is a > non-unitary operation that is equivalent to applying a projection operator, > as in the Copenhagen interpretation. Which is why I say decoherence only > gets you part way to solving the measurement problem. It has a mechanism > and a statistical rationale, but it still takes a little jump to get to the > classical definite result. > > Isn't "the environment" the this-world environment, the measuring device > in this world? Isn't it this entanglement that destroys the interference > FAPP with the other components of the superposition in this world, which > might be what the Bucky Ball experiment establishes? What are you objecting > to? AG > > > That there is a unique "this world". I use use "world" (with the scare > quotes) to indicate a coherent, quasi-classical world where observers don't > see superpositions of alive and dead cats. The measuring device and the > environment is in all the "worlds", one for each measurement result. > > I happened across a very good book that discusses these questions well > without mathematics, "Mind, Brain, and the Quantum" by Michael Lockwood. > It's a philosophy book about epistemology and consciousness and discusses a > lot more about the brain and it's function. But is has a couple of chapters > on the quantum measurement problem. It says the same thing Bruce and I > have been saying except Lockwood looks at what I've been calling "worlds" > (per the usual MWI terminology) as macroscopic states which exist in > superposition in one world (which is usually called the universe or > multi-verse), the superpositions just happen to be orthogonal (FAPP) and so > don't interfere. > > Brent > > > The result is in effect encoded all through the subspace, that's why >> different people in that "world" can agree on what happened; that's what >> makes it a (quasi) classical world where people don't see superpositions of >> measurement results. >> >> Brent >> > Would it be consistent with decoherence theory to say that each component of a superposition gets entangled with the environment defined by the lab / instrument in which an experiment is performed -- what I have been calling "this world" -- and the other branches, one for each of the remaining eigenstates -- are mutually orthogonal, and orthogonal to the subspace in "this world"? I am positing a model wherein every outcome is realized, but only one outcome is associated with the lab / instrument; the other outcomes or measurements occur without needing a measuring device -- like those Bucky Balls didn't need to be measured by any device to lose their interference. AG
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