Date: Tue May 27 2003 - 13:28:32 MDT
Mitchell Porter wrote:
> But an important point is that there is no canonical set of decoherent
> histories associated with a particular wavefunction, not even a
> canonical 'maximal set' (no extra histories or finer graining of
> operators possible). So it's the basis problem again, at a more
> sophisticated level.
Although this is a problem for those versions of Everett that explicitly
point to terms in the state vector as being worlds, and thus build them
directly into the formalism, it is not considered a problem in the more
sophisticated versions of Everett, in which worlds are seen as structures
emerging inside the state vector (as "higher order ontology", much like
waves in water or instants in relativity theory). The basis selected by
decoherence is well-defined For All Practical Purposes, which is enough
in this view.
This interpretation is developed in (for example) the work of Simon
Saunders and David Wallace. I recommend looking at the following papers,
if you haven't already.
http://arxiv.org/abs/quant-ph/0107144 "Everett and Structure"
http://arxiv.org/abs/quant-ph/0103092 "Worlds in the Everett
http://arxiv.org/abs/quant-ph/0210204 "Quantum Computation and Many
I like this interpretation, because it has all the beautiful simplicity
of the Everett interpretation without the problems of other versions. The
problem of probability also seems solvable or solved (in this version and
others such as Deutsch's). It also fits nicely with functionalism and
with the idea that identity over time (of observers and worlds) need not
be exactly well-defined.
This way of thinking may have other flaws that I'm not aware of. However,
the majority of objections usually stated apply only to the (IMO) more
naive and more popularized versions of many-worlds.
-- http://www.fastmail.fm - Or how I learned to stop worrying and love email again
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