On Thu, May 9, 2013 at 4:21 PM, meekerdb <meeke...@verizon.net> wrote:

>  On 5/9/2013 1:40 PM, Jason Resch wrote:
>
>
>
>
> On Thu, May 9, 2013 at 3:14 PM, meekerdb <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> wrote:
>>
>>>  On 5/9/2013 11:28 AM, Jason Resch wrote:
>>>
>>>
>>>
>>>
>>> On Thu, May 9, 2013 at 1:11 PM, meekerdb <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 same
>>>> observations as the model with it.
>>>>
>>>>
>>>>  He showed that IF the wave function separates into orthogonal
>>>> components (an irreversible process) then FPI explains the observations.
>>>> But the 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
>>> Schrodinger equation can only approximate itself?
>>>
>>>
>>>  If you include the observer and the system observed then when the
>>> observer interacts with system in superposition the observers state becomes
>>> a superposition
>>>
>>
>>  I follow you so far.  To confirm we are on the same page, so you think
>> observers are special in any physical way from any other "non observer" in
>> a physical system?
>>
>>
>>>  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 Schrodinger 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 interest.
>>
>>
>>
>>
>>>
>>>
>>>
>>>
>>>>   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 the theory of QM and is not an extra postulate.
>>>
>>>
>>>  It depends on the choice of basis.  In general there's other some basis
>>> in 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 equation.
>>>>
>>>
>>>  The other worlds are a required element of the theory, unless you deny
>>> the 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
>>> sealed off from the external world such that the internal result of the
>>> experiment remains in a superposition until it is opened.  Now a second,
>>> external observer models the entire evolution of this box over time,
>>> including before and after the observer inside measures the state of the
>>> particle and records the result in a notebook.  He determines the
>>> superposition of all the possible handwritings of all the possible results
>>> in the notebook.  Is the internal observer not conscious in each of the
>>> various superpositions resulting from 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 observer.
>>>
>>
>>  Okay, then from the view point of the external observers, shouldn't the
>> various 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
>>> reality at all, aside from what we can see and learn, which to me seems
>>> like a dead 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 models 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 as silly as any theory of inflation which said: "Once
>> a galaxy crosses beyond our 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.
>

Okay, lets use atoms then.  It is a little harder to see atoms on the far
sides of the Hubble volume, but it doesn't change the point I made.  We
make models of reality, and update, extend, or simplify those models as new
evidence or reasoning permit.


>
> 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.
>

Cool, we are in agreement on this.


>   But I don't see that saving determinism in an undetectable way makes for
> a superior theory.
>

I agree, it is the fewer postulates that I think make QM (read literally) a
superior theory.  And unlike epistemological interpretations, it purports
to model some reality that is really out there, independent of us or our
observations.



>
>
>
>
>
>>
>>
>>
>>
>>>
>>>
>>>
>>>
>>>
>>>>   I like MWI and Bruno's FPI idea, but without some testable prediction
>>>> (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.
>

Okay, I understand that position.  However, I think right now we are in a
state similar to that time when heliocentrism and geocentrism were debated,
but before either was proven by observations of parallax.  Neither theory
has suffered a fatal blow, but there is a theory that is a little simpler.
Would the creation of a working quantum computer that can factor thousand
digit numbers (which not even an Earth-sized classical computer could) be a
parallax moment for you?



>
>
>
>
>
>>
>>
>>
>>
>>>  What do you find compelling about the idea that the unity of your
>>> consciousness is an illusion.
>>>
>>>
>>
>>  Is this the real source of your resistance to MWI, that you do not feel
>> yourself 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
>> predict something.
>>
>>
>
>  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.
>
>
Yes that could be.


>
>
>  (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.
>

I don't think MWI must be true, but I have offered reasons for why I think
Everett's model is preferred.  I prefer it for the same reason one might
prefer heliocentrism (even before any conclusive experiment is performed):
it is more elegant.

Jason

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