🚀 go-pugleaf

Hi everyone...glad to see there are people interested in discussing these
topics...:

John and Stephen both emphasize the conditional probability interpretation
given to the density matrix or decohereing histories formulation of
quantum cosmology. However, in QM the density matrix contains not only our
ignorance of the details of the ensembe but also the QM uncertainty. Even,
if we can enumerate completely the position and momentum of every particle of
the tea and cup and surrounding enviroment to the limit imposed by the 
uncertainty principle we still cannot proceed deterministically... can we?
Also...when Steve admits a final and initial density matrix in the ADH what
exactly is fixed uniquely? Is it that collection of 
quasi-classical coarse grained histories which maximize the information 
content (ie. most finely grained histories compatible with quasi-classisity).
If this collection is not unique then we do not have complete prediction
of these histories. Also.. these histories presumably refer to suitably gross
collective coordinates ie. the path of a football through the air... if I
decide to ask ADH about the evolution of coordinates of a molecule of leather
in this football then ADH looses a degree of predictive power as we may be
going beyond that above mentioned  quasi-classically-optimised graining.


Jason

---------------------------------------------------------------------------
Jason Twamley                            | "WHY must I treat the measuring
Univ. of Adelaide Math. Physics          | device classically??  What will
GPO Box 498, Adelaide                    | happen to me if I don't??"
South Australia 5001                     |       -- Eugene Wigner
jtwamley@physics.adelaide.edu.au