>From: Brent Meeker <meekerdb.domain.name.hidden>
> > Of course, if we already had a theory of quantum gravity, and if the
>math calculation already yielded the prediction that p=x, then p(o|1) (if
>you like, p(x|1)) would be 1 - based on that math, not on the fact that we
>do see x.
>
>That's exactly what I took Candidate #1 to be - we have a theory that
>mathematically constrains all parameters either to particular values or to
>ranges which are consistent with SAS's. If that was not what you meant by
>Candidate #1 (and apparently it wasn't), why didn't you consider that as
>Candidate #4; after all it's what most physicist hope and work for.
The whole point is that right now, we don't have such a theory! And
what my analysis seems to point to is that there isn't one.
If, on the other hand, we had a theory that exactly specified (up to
many decimal places) each physical constant, and it predicted the values we
see, then that theory would have a huge probability advantage over #2 (which
only constrains the values to a range, albeit a narrow one). We don't.
(I said "seems to" because my example assumed there was only one set of
physical laws. It didn't take into account other possibilities such as some
of the stuff discussed on the everything-list. Thus, even if there is only
one possible theory of quantum gravity, other types of physical laws could
also exist as weighted by complexity. The point being that QM + SM +
gravity is already too complex to be the only physical reality, and as much
of an anthropic constraint as the parameters. The advantage will always
belong to *some* type of ensemble theory, erasing the anthropic
"coincidence".
Ensemble #2 easily beats non-ensemble #1, but "apparent ensemble #2 with
Tegmark ensemble" is not necessarily any more likely than such an "apparent
non-ensemble #1 with Tegmark ensemble". Tricky! (And similar to the effect
of the MWI on "god's coin toss".)
But important to point it out now, lest physicists should come up with a
unique consistent set of physical constants, and then try to use that as
evidence against the MWI way of thinking about physical laws! It wouldn't
be.)
> > I do mention consistent histories briefly on my historical
> > interpretations page. As for decoherence, that is a common feature of
>all interpretations because it's just part of QM, not an interpretation.
>As for more parsimonious, you are wrong. The MWI just states (regarding
>physics) that the wavefunction evolves normally and doesn't collapse.
>There is no simpler interpretation possible in principle. Of course to get
>predictions from any mathematical model, even classical mechanics (if you
>don't cheat by leaving out the observers from the math), you need a theory
>of mind such as
> > computationalism.
>
>The reason I consider the MWI less parsimonious is that either (depending
>on which version you have in mind) 1) requires that there be some special
>property of minds which causes the universe to branch when a mind becomes
>aware of something OR 2) it requires that the branching be a continuous
>process generated by every interaction that leaves a classical record. I
>think the consistent histories approach may also require a special property
>of minds - namely that brains have evolved such that the minds they
>implement only perceive via certain operators which correspond to classical
>variables. This would be explained by evolutionary selection. Of course
>this still leaves a stochastic element, which the MWI 'explains' by saying
>'they all happen', but I
>don't find this explanation any better than just saying 'one of them
>happens at random, in accordance with psi*psi.
You still don't seem to understand what the MWI says. In both 1) and 2)
you seem to assume branching is some special physical process beyond normal
Shrodinger evolution. You probably have seen a lot of books characterize
the MWI that way. Believing those books is like letting John Rocker be your
tour guide in NYC.
As I said, in both my version of the MWI and Everett's, "branching" is
just a manner of speaking about the typical behavior in Shrodinger evolution
where decoherence occurs. A theory of mind is needed by *any* theory to
generate *any* prediction about observations. I attempt to formulate one in
my CWIA.
Finally, it's obvious to me that a stochastic theory, which says that
the Kolmogorov complexity of the physical world increases with every event,
continuously violates Occam's razor.
- - - - - - -
Jacques Mallah (jackmallah.domain.name.hidden)
Physicist / Many Worlder / Devil's Advocate
"I know what no one else knows" - 'Runaway Train', Soul Asylum
My URL:
http://hammer.prohosting.com/~mathmind/
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Received on Mon Jul 03 2000 - 14:31:20 PDT