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?

>   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.

>   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?

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.

>   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?


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