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.



>
>
>
>
>>
>>
>>
>>
>>
>>>   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?



>
>
>
>
>>  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.

(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.

Jason

-- 
You received this message because you are subscribed to the Google Groups 
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.


Reply via email to