On 5/24/2018 1:51 PM, [email protected] wrote:
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? AGIt'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. AGIt seems metaphysically problematic to give all subspaces the same existential status, when only one provides the environment for all entanglements for all subspaces. AGI 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. AGNo, 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? AGThat 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. BrentWould 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"?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
Yeah, and it's true equally for each of the "this world" choices.
I am positing a model wherein every outcome is realized, but only one outcome is associated with the lab / instrument;
Every world has lab/insturments which are slightly different because they are entangled with different point results on the instrument. There is no 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
They don't need to be measured by what we would recognize as an instrument we could read, but their IR entangles them with the walls which has the same decohering effect.
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