Forgiveness for any typos. I'm in a hurry here. I was going to reply to Miller's message directly, but I see where I can kill two birds with one stone:
----- Original Message -----
From: "Patrick Leahy"
To: rmiller
Subject: Re: Sociological approach
Date: Mon, 23 May 2005 11:04:53 +0100 (BST)
>
>
> On Sun, 22 May 2005, rmiller wrote:
>
> >
> >
> > I'm approaching this as a sociologist with some physics
> > background so I'm focusing on what the behavior system perceives
> > ("measures"). If all possible worlds exist in a superpositional
> > state, then the behavior system should likewise exist in a
> > superpositional state.
If the behavior system is the things that measures, the yes it could be said to exist in a superpositional state.
>
> First, it looks like you are confusing the multiverse of QM with
> the plenitude of "all theories" or all UTM programs (Level 3 with
> Level 4 multiverse in Tegmark's terminology). Different level 4
> worlds do not superpose, they don't relate to each other in any
> way, by definition.
>
I'm glad that Patrick pointed this out. The UTM programs or Level 3 and 4 from Tegmark's theory I can do without. I think they lie in the realm of pure speculation and have little bearing on what we could actually hope to experience. This is what I meant by the mathematical models that Tegmark had and my being able to tolerate them, but not really needing them at all. I think Miller's comment above is fine for QM models.
> Second, in QM you need to distinguish between two kinds of
> superposition: those which cause interference effects (e.g. 2-slit
> experiment), and those which don't (because the wave functions of
> the superposed "worlds" don't overlap or are incoherent).
There are physicists who would disagree with the idea that they never overlap. It's a feature from E/W that's been changing over the years. I think also, from the way that Patrick states that "superposed worlds don't overlap", it could be said that if the worlds are "superposed" they are part of the same wave function. After all, what does a wave function describe besides the possible states that the thing that it describes could be in?
> "Behaviour systems" are complicated enough that it is a
> mathematical certainty that they fall in the second class. In which
> case there is no way to detect that the superposition is happening;
> for all practical purposes each world goes its own sweet way.
>
I would tend to agree with this. The behavior system being in a superpositional state really has to do with measurement and observation. In the Schroedinger Cat example, taken to the extreme, it has been said that the experimenter, who will make the observation of the state of the cat, is in a superpositional state for the person outside the lab until the experimenter opens the door to announce which state the cat was found in, and for those outside the building, the person who was waiting outside the lab is in a superpositional state until...
> > If there are say, 10 possible "worlds" available to the
> > behavioral state (percipient) but each world differs from the
> > other by elements that are not observed by the percipient, then
> > the behavior system is under the assumption that interaction is
> > taking place with a single, unified environment.
> >
Exactly. The question though is what does Patrick mean by "available". Taken literally, I would interpret it as the 10 worlds form a superpositional state from which the percipient may observe one of the 10, thus "the behavior system is under the assumption that interaction is taking place with a single, unified enviroment." I think, "unified" can be left out of it, because it leads one to possible think that the 10 worlds are then merged into one at that point, when that's not what the case would be. The other 9 would exist in decoherence and be unavailable to the percipient, under normal conditions.
> > Recalling the Copenhagen interpretation: does Chicago exist if
> > you happen to be by yourself in a hotel room in Des Plaines, IL?
> > The answer is irrelevant until the behavior system begins to
> > experience some aspect of Chicago.
I'm not sure that "the answer is irrelevant" until the behavior system begins to experience some aspect of Chicago. Afterall, if the answer is "No, Chicago doesn't exist", then there would be no aspect of Chicago to experience. I would say that from the point of view of a person by their self in a hotel romm in Des Plaines, IL the answer would be "probably", but as we know from recent history, for a person from New York on a vacation in the heart of the Amazon and cut-off from any media, you could ask them on 9-11, "hey you're here in the heart of the Amazon. Do you think the World Trade Center still exists?" and they'd probably say, "Sure. Why wouldn't it?". It's the realistic version of that stupid philosophical question, "Does a tree make a noise when it falls in a forest, if there's no one around to hear it?" The answer of course is "yes", due to normal, everyday, macroscopic physics. But if the question were, "does any arbitrary tree exist in the forest if you aren't there to see it?", then the answer would be "no".
>
> The superposition properties depend on the information available in
> the whole system (e.g. your hotel room), not just the mind of the
> observer. The world is constantly in close touch with itself. For
> instance, if Chicago vanished in a large quantum fluctuation,
> photons which would otherwise have been reflected from its streets
> to the clouds would be different. Hence photons leaving the clouds
> that land in fields 40 miles away would be different and so on.
> Very soon (within microseconds) the photons comint through your
> hotel window are affected, and you become 100% correlated with the
> state of Chicago. From your point of view, Chicago is either there
> or not.
>
The only problem I have with that is the complete improbability of being conscious that any of that had taken place. Especially while he's probably watching HBO and raiding the snack fridge.
> >
> > What if Deutsch is incorrect about contact between the various worlds?
>
> i.e., what if quantum theory is wrong and a different theory applies?
> But the only reason we have to believe this stuff is the evidence
> in favour of QM (which is pretty overwhelming).
>
I'd agree here, for sure.
> > Suppose the behavior system normally exists across a manifold of
> > closely-linked probabilities, with the similarities forming a
> > central tendency and the differences existing at each edge of the
> > distribution?
>
If the behavior system is the same as the "percipient" here, then it does exist "across a manifold", but I would be careful about using language like "a central tendency". Tendency toward what? If the similarities were to form the hump in the wave function and the differences appearing at the sloping extremes, then I could go along with that.
> Again, QM makes definitive (but difficult-to-understand)
> predictions about this. Yes there is a manifold of possibilities,
> in fact an infinite number of them, for instance "configuration
> space" which is the manifold of all particle positions (3N
> dimensional for N particles), or "momentum space", the manifold of
> all particle momenta (also 3N dim). According to QM, the
> probability distributions in these manifolds are not independent,
> e.g. config and momentum wave functions are related by a Fourier
> transform.
>
> Your "central tendency" is just the wave function, which is peaked
> around some configuration of particles in any given branch. What
> people generally don't factor into this is just how *BIG* 3N
> dimensional spaces are, when N is macroscopic. Even apparently
> minor differences, such as the presence or absence of a speck of
> dust, correspond to enormously large separations in configuration
> space. Although technically there is some (usually infinitesimal)
> amplitude for all configurations, the only way you can get a useful
> amplitude for two macroscopically different "worlds" is to amplify
> some quantum behaviour, in which case the wave function splits into
> 2 or more branches, each of which behaves more or less according to
> classical physics. The "width" of the distribution for a single
> branch corresponds to ordinary microscopic quantum fuzziness. Hence
> the branches don't overlap in configuration space (or in the space
> of any other macroscopic variable), and so can't communicate.
>
Yeah, well said. The devil is in the details. However, I might add that there are possibilities for information to "tunnel" from one world to another, but that would probably be a different topic.
> > If the behavior system can perceive only a small chunk of
> > information at a time, then it may be possible that each
> > percipient really does live in his or her own little world---a
> > small island of similar probabilities made"real" from the larger
> > cloud of probabilities.
>
> We are all in our own little worlds, but in an objective sense; the
> same is true for "non-behavior" systems, e.g. rocks.
>
I agree here as well.
> >
> > If we quantify a behavior system in terms of elements and
> > interactions between elements, we arrive at a complex, but
> > definable state. If that behavior system exists across multiple
> > worlds that differ in minute details (i.e. a unobserved kitchen
> > saucer moved an inch to the side) then the behavior systems would
> > exist as identical entities (or, as my friend Giu P. would say,
> > *shadows*) across the similar "sections." Employing a little
> > math, the behavior system could exist as an object in Z
> > space--not too different than a fibre bundle in topology.
> > Differences among the realized probabilities among these "shadow
> > worlds" might show up at each end of the normal distribution, but
> > may be still be perceived by the behavior system as guesses or
> > hunches, depending upon where the primary centre of the
> > behavioral bundle is at the time. Psychology experiments in the
> > 1980s suggest (to me anyway) that a psychological mechanism has
> > evolved that helps the behavioral system "negotiate" this
> > territory.
>
Actually, here I am strongly with Miller, as "guesses or hunches" translates quite easily for me into "dreams" and "deja vu", etc.
> If this has anything to do with the basic laws of physics we have
> to replace QM.
No, actually we don't. E/W is evolving, as does everything else. When we got relativity, we didn't have to throw out Newtonian physics, did we?
> Personally it sounds to me like great SF and very
> duff science.
Then again, I don't recall cognitive technology and quantum psychology being listed as part of Patrick's department. Just an observation.
> >
> > Bottom line, it may be useful to take a step back and challenge
> > some of our primary assumptions---namely, that we exist in a
> > discrete world in the multiverse and that we can never "step"
> > into the one next door. That is, we may be wondering why we
> > can't visit the next room, when in fact, we inhabit the entire
> > neighborhood.
>
Here Miller asks the right questions. If we in fact, inhabit the entire "neighborhood" as he put it, I'd say that the "we's" are still separate. The real question is can one "we" visit any of the others. Depending on the possible sh*t rain of indignation that this conversation may instigate, I would invite Mr. Miller to email me personally, if he likes. I think we have a lot to talk about.
> This is not so much an assumption as a fact. Schrodinger's cat is
> either alive or dead and once the experiment is done we can't
> change the outcome.
>
> Paddy Leahy
True. But the question is can we vistit the alternate outcome?
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