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From: DAM%MIT-OZ@MIT-MC.ARPA
Newsgroups: net.physics
Subject: Quantum Mechanics
Message-ID: <365@sri-arpa.ARPA>
Date: Tue, 9-Jul-85 14:59:00 EDT
Article-I.D.: sri-arpa.365
Posted: Tue Jul  9 14:59:00 1985
Date-Received: Sat, 13-Jul-85 09:38:15 EDT
Lines: 50


   Date: Monday, 8 July 1985  20:04-EDT
   From: mikes at AMES-NAS.ARPA (Peter Mikes)

   Some people believe that Einstein was right, rather then Bohr. I suggest
   that we do accept the fact that there is indeed a division of opinion
   concerning ... queastion whether QM is paradox free and logicaly
   consistent.  Some people prefer not to see or face the problems
   - that's fine - but lets stop parroting the statement that 'all
   is fine and there is no paradox'.


	I joined this list with the hope of learning some physics
and perhaps discussing some of the philosophical problems with
quantum mechanics.  I have been a little disapointed but maybe I can
initiate the kind of discussion that I had hoped for.

	What bothers me about quantum mechanics is quite simple.
Quantum mechanics is mathematically incomplete: there is no
mathematically complete theory of what constitutes a physical system
and how physical systems change over time.  One approach is to say
that physical systems are wave functions: points in a Hilbert space,
and that the dynamics of such systems are governed by Schodingers
equation.  This is the most mathematically complete statement I have
seen.  However the Schrodinger's cat problem clearly shows that either
this mathematical model is incomplete or we must accept multiple
worlds.  DeWitt, Hugh Everitt, and Wheeler endorse the multiple-worlds
view.  However most physicist seem to reject the idea that Schodingers
equation is a complete model and instead choose to believe in the
Copenhagen interpretation in which wave functions "collapse".  In the
Copenhagen interpretation the act of measurement causes the wave to
change in manner not goverened by Schrodingers equation; the wave
function collapses instantaneously and discontinuously into an
eigenvector of the measured quantity.  The problem with the Copenhagen
interpretation is that there is no MATHEMATICAL theory of what
constitutes a measurement; there is no mathematical theory governing
wave function collapse.

I would enjoy some discussion based on fairly sophisticated knowledge
of the relevant mathematics.  For example, if one accepts the
DeWitt-Everitt-Wheller multiple worlds view then what are the
philosophical consequences of the linearity of the wave function?  The
sum of any two solutions is a solution.  Thus people "living in" one
solution should not be aware of people living in another solution.
Unfortunately the square-amplitute operator governing the probability
distribution of the Copenhagen interpretation is non-linear.  How can
a non-linear effect arise from a linear equation?  The
square-amplitude operator is clearly important for understanding
physical experiments.  This seems to be a flaw in the multiple worlds
view.