[Dean's World] Dave Price: Decoherence, Incoherence, Elucidation

[notify at powerblogs.com]

Posted by Dave Price:
Decoherence, Incoherence, Elucidation
http://www.deanesmay.com/posts/1190834578.shtml


   A [1]flurry of poorly-written [2]news briefs, replete with claims of
   time travel made possible and proof of parallel universes, have been
   spawned by the announcement by Oxford scientists that a mathematical
   model of the [3]Many Worlds Interpretation is more robust than
   thought. Predictably, perhaps the best explanation of what MWI means
   [4]comes from a Slashdot commenter:

     The remaining issue in a theory of quantum + decoherence is that
     the classical states have the right probabilities, but there is
     still nothing to explain why we observe a particular classical
     state (photon measured spin-up instead of spin-down). However the
     (ad-hoc) postulate of wavefunction collapse, no longer being
     necessary to explain how the probabilities arise, can in fact be
     entirely removed if we allow that the global superposition never
     collapses.
     Thus, a local observer (e.g. an instrument or a human) perceives a
     single outcome only because they are a participant in this "global
     superposition" (the superposition of the entire universe). The
     wavefunction of the universe as a whole evolves deterministically.

   It's odd to think of the Universe we experience as a superposition,
   but that does seem to be the implication of our current understanding
   of quantum mechanics.

References

   1. http://news.google.com/news?hl=en&q=oxford+parallell+universe&um=1&ie=UTF-8&sa=N&tab=wn
   2. http://www.breitbart.com/article.php?id=paUniverse_sun14_parallel_universes&show_article=1&cat=0
   3. http://en.wikipedia.org/wiki/Many_worlds
   4. http://science.slashdot.org/comments.pl?sid=306735&cid=20733021