# Re: Maudlin's argument


Russell Standish wrote:
> On Fri, Oct 13, 2006 at 07:03:18AM -0000, [EMAIL PROTECTED] wrote:
> >
> > Also see my reply to Russell below:
> >
> >
> > >Russell Standish
> > >
> > >The Multiverse is defined as the set of consistent histories described
> > >by the Schroedinger equation. I make the identification that a quantum
> > >state is an observer moment, and the set of consistent quantum
> > >histories is the set of observer histories. As such all observer
> > >moments are in the Multiverse.
> > >
> > >But I appreciate this is not a widely held interpretation...
> >
> >
> > Indeed so.  And there's a good reason why it isn't a widely held
> > interpretation, as J.barbour explained in 'The End Of Time'.  In order
> > to define 'the Multiverse' in terms of QM one needs a *static*
> > wave-function solution for the entire universe (one which doesn't
> > change) , whereas conventional QM solutions to real world problems are
> > *dynamic* wave-function solutions (wave functions which evolve with
> > time).  No one has yet succeeded in demonstrating a static
> > wave-function solution for the entire universe.
> >
>
> I haven't read Barbour's book, but if that is what he is saying, he
> would be wrong. Consider a universe of a single electron living in a
> potential well V(x)=|x|^2, x\in R^3. There is a well defined solution
> \psi(t,x) = \sum_j <\psu_0|j><j| exp(-iE_j t) given the initial
> condition \psi_0.
>
> The function \psi: R x R^3 -> C is a static (time independent)
> mathematical object (I wrote it the mathematicians write to emphasize
> this point). Why wouldn't you identify this with the Multiverse of
> that electron?
>
> Now I am aware that several people (Hawking included I gather) have
> proposed various "wave functions of the universe", which tend to be
> solutions of the Wheeler de Witt equation, which is a time independent
> equation. However, I'm not so interested in following that literature.


Barbour argues the same way you do.  But he does concede that his
argument is not yet proven.  The trouble is that in the case of, for
instance, the electron, in the example you give, there is still an
environment external to the electron, but for the entire universe there
could be nothing external to the wave function of the universe.  And
the wave function of the universe, if the block-universe picture is
right, would have to be a static equation as well, as I mentioned
above.  Apparently, none of the proposals for time-independent
equations of the entire universe have yet been made to work.

>
> > See what I said above.  If the *same* QM state could be associated with
> > *different* observer moments, then observer moments would not be
> > reducible to QM states and the set of consistent quantum histories
> > could not be said to be fully identified with the set of observer
> > histories.
> >
>
> If the same QM state is associated with different observer moments,
> you must be talking about some non-functionalist approach to
> consciousness. The QM state, by definition, contains all information
> that can be extracted from observation.
>
> Cheers
>
>

See above.  As was pointed out, functionalism allows for one-to-many
relationships between conscious experiences and the physical substrates
on which these experiences are instantiated.

What I really mean by 'observer moment' in the fullest sense of the
phrase is 'conscious experience'.  Conventional QM cannot yet explain
how the actual consciously observed reality is supposed to emerge from
the QM wave-function.  As has been pointed out, the observed reality
can only be derived from QM+Additional Assumptions.  There are implicit
theories of consciousness in any account of how the actual observed
reality is supposed to emerge from the QM wave-function and convincing
explanations for how or why these assumptions are supposed to work are
not yet forth-coming.

How does the *observed* (classical) reality emerge from the QM
wave-function?  Not explained!  Coarse graining, decoherence,
consistent histories etc etc don't yet convincingly explain it.

Until these questions are fully resolved, doubt must remain about the
static timeless 'block universe' picture put forward by hard-core
multiverse fans.

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