On 5/9/2013 1:40 PM, Jason Resch wrote:

On Thu, May 9, 2013 at 3:14 PM, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    On 5/9/2013 12:40 PM, Jason Resch wrote:

    On Thu, May 9, 2013 at 2:08 PM, meekerdb <meeke...@verizon.net
    <mailto:meeke...@verizon.net>> wrote:

        On 5/9/2013 11:28 AM, Jason Resch wrote:

        On Thu, May 9, 2013 at 1:11 PM, meekerdb <meeke...@verizon.net
        <mailto:meeke...@verizon.net>> wrote:

            On 5/9/2013 10:02 AM, Jason Resch wrote:
            Von Neumann thought the extra baggage was required to make the model
            match our observations, but Everett later showed that step was
            unnecessary.  The model (free of additional baggage) predicts the 
            observations as the model with it.

            He showed that IF the wave function separates into orthogonal 
            (an irreversible process) then FPI explains the observations.  But 
            model says it never does that; it only approximates that, in 
certain bases.

        Could you explain this?  I don't understand in what sense the 
        equation can only approximate itself?

        If you include the observer and the system observed then when the 
        interacts with system in superposition the observers state becomes a 

    I follow you so far.  To confirm we are on the same page, so you think 
    are special in any physical way from any other "non observer" in a physical 

        in the same basis.  The cross-terms in the superposition are not zero.

    Do they need to be, what if they are not zero?  How does a single-universe
    interpretation avoid this issue?

        They can be shown to become approximately zero if you  include 
interaction with
        an environment that has a large number of degrees of freedom and you 
trace over
        the environment variables.  But that last step isn't part of the 
        equation, it's a separate assumption comparable to Boltzmann's 
assumption of
        molecular chaos.

    Earlier you said it can be shown, so how is it an assumption?  Or do you 
mean it is
    an assumption that the environment has a large number of degrees of freedom?

    That and that the interaction is such that it diagonalizes in the 
variable(s) of

            Decoherence theory tries to fill in the process by which this 
occurs give
            a statistical mechanics type account of irreversibility.

        It gives an account of the appearance of an "irreversible wave-function
        collapse" without their having to be one.  It is derived entirely from 
        theory of QM and is not an extra postulate.

        It depends on the choice of basis.  In general there's other some basis 
        which state is pure.  Decoherence says the density of the subsystem is
        approximately diagonal in a particular basis.  This involves 
assumptions about
        the environment and is not part of the wave function.

    It doesn't matter which/whose basis you use though, does it?

    It's not "whose" but "which".  Most measurements are modeled as position
measurements but you can invent ones that are measurements in momentum space too. But in general you can't create a measurement to determine the pure state which
    includes the environment.

              But you could also take the epistemological interpretation of 
Peres and
            Fuchs instead of inventing other worlds just to save the 
determinism of an

        The other worlds are a required element of the theory, unless you deny 
        reality of superposition.  I think Everett's thought experiment 
explains the
        situation the best:

        Imagine a box with an observe in it who will be measuring the state of a
        particle and writing the result in a notebook.  This box is entirely 
        off from the external world such that the internal result of the 
        remains in a superposition until it is opened.  Now a second, external
        observer models the entire evolution of this box over time, including 
        and after the observer inside measures the state of the particle and 
        the result in a notebook.  He determines the superposition of all the 
        handwritings of all the possible results in the notebook.  Is the 
        observer not conscious in each of the various superpositions resulting 
        the measurement?

        Depends on what you mean by THE internal observer.  There is a 
superposition of
        states that represents the external observers theory of the internal 

    Okay, then from the view point of the external observers, shouldn't the 
    internal observers who remain in a super position, include observers each 
with a
    memories of recording one of the results in the log book, and in their 
brain?  What
    happens to these memories (and presumably the experiences) when the external
    observer opens the room and collapses the superposition?  Are we to believe 
all the
    memories and experiences that internal observer had are retroactively 
erased from
    existence and in fact, never happened at all?

    No, we believe the external observer needs to update the wave function he's 
using to
    describe the internal observer, based on his new information.

But what about what happened before the outside observer gets that new information? Or are we just not allowed to talk or think about that?

        Epistemological interpretations seem to deny there is any fundamental 
        at all, aside from what we can see and learn, which to me seems like a 
        end in the search for truth.

        Shifting the truth off to undetectable realms doesn't help much.

    They are implied by the model of reality.

    They are implied by ONE model of reality.

Yes, that is what I meant.

    Just like the galaxies beyond the cosmological horizon are implied by some 
    of inflation.  Why contort a perfectly good and simple theory to make it 
match our
    (known) limited perceptive capacities?  To me, single universe theories are 
    silly as any theory of inflation which said: "Once a galaxy crosses beyond 
    cosmological horizon, it ceases to exist, and any life forms that might 
have been
    in those galaxies cease to be."

    Except there are no galaxies that are observed to cross the Hubble sphere.

Well according to inflation models there are galaxies that are outside the Hubble sphere already (presumably some of them were not always outside that sphere, because they were much closer and interacted leading to a very uniform temperature throughout the universe). So whether or not we have observed such a crossing is outside the point, it is in my opinion, an equally indefensible position for the existence or non-existence of something to hinge on one's ability to see it or interact with it. It's like reverting to state of a someone who hasn't developed object permanence.

Galaxies aren't permanent. And according the concordance model they all formed *after* inflation and so the only crossing of the Hubble sphere would be from the outside to the inside.

I'm perfectly happy to suppose that things exist that I can't interact with, provided that's part of a theory that is superior in other ways. But I don't see that saving determinism in an undetectable way makes for a superior theory.

              I like MWI and Bruno's FPI idea, but without some testable 
            (not retrodiction) I don't find them compelling.

        Why do you find compelling about the idea that all other superpositions
        (except for one) vanish?

        It comports with experiment.

    What experiment even hints that other superpositions vanish?

    "Vanish" = no longer seen.

In this case, I was referring to the third definition: http://dictionary.reference.com/browse/vanish?s=t which is what single-universe theories hold happens to the other parts of the wave function. That they are no longer seen because they no longer exist. MWI explains why they are no longer scene, so why make the leap that they no longer exist?

You keep assuming that because I don't vow allegiance to the MWI faith that I reject it. I said I liked it, I'm just not compelled to accept it so long has it has not empirical advantage.

        What do you find compelling about the idea that the unity of your 
        is an illusion.

    Is this the real source of your resistance to MWI, that you do not feel 
    split when your intuition suggests you should feel it?

    No.  It's that it makes no testable predictions.

So single universe theories are right because they came first?

If MWI had come first, would you reject the single universe theories of QM because they make no testable predictions?

    It's just metaphysics to satisfy a demand for determinism - unless it can 

Again, I repeat this is not about determinism at all, it is about reading the theory for what it is, a model of reality itself, and not adding additional assumptions or postulates which are in no way needed for the model to be consistent with our observations.

But whether it is really consistent, even consistent with the appearance of the classical world, is not clear. The decoherence program may eventually show it to be, but for now there are still problems. It may be that the solution requires a theory of consciousness like Bruno's.

(All this ignores any preference one may have for determinism, locality, linearity, reversibility, which are features of nearly every other known physical principle)

    Don't worry, you don't need to condemn your copies to a superposition with 0
    amplitude to explain why you (in this branch), do not have access to the
    memories/experiences of the other yous (in other branches).

    This is the same error presentism makes: believing we must make all other 
points in
    time non-real to explain why we feel ourselves to be in this single point 
in time.

    So to answer your question, what I find compelling is not contorting a 
theory to
    solve imagined problems.

    I think of non-determinism as an imagined problem.

So be it. I haven't once in this discussion said it is a problem or is not a problem. You, however, have not provided any justification for why we should believe things we cannot see must not exist.

Nor have you shown shown why we should believe Everett's multiple worlds must exist. But as a rule-of-thumb it is better to tentatively assume things we cannot see don't exist.


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