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?


>
>
>
>
>>   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?


>
>
>
>>   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?


>
>
>
>  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.  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."


>
>
>
>
>
>>   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?



> 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?

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.

Jason

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