On 10/26/2013 10:21 AM, Jason Resch wrote:
Section 3b of ( http://arxiv.org/pdf/quant-ph/9709032v1.pdf ) seems to also answer some
of the questions you posed recently regarding superposition in MWI:
B. “It doesn’t explain why we don’t perceive weird
That’s right! The Everett postulate doesn’t! Since the
state corresponding to a superposition of a pencil lying
in two macroscopically different positions on a table-top
is a perfectly permissible quantum state in the MWI,
why do we never perceive such states?
inability to answer this question was originally a serious
weakness of the MWI, which can equivalently be phrased
as follows: why is the position representation so special?
Why do we perceive macroscopic objects in approximate
eigenstates of the position operator r and the momentum
operator p but never in approximate eigenstates of
other Hermitian operators such as r + p? The answer
to this important question was provided by the realization
that environment-induced decoherence rapidly destroys
macrosuperpositions as far as the inside view is
concerned, but this was explicitly pointed out only in
the 70’s  and 80’s , more than a decade after Everett’s
original work. This elegant mechanism is now
well-understood and rather uncontroversial , and the
interested reader is referred to  and a recent book
on decoherence  for details. Essentially, the position
basis gets singled out by the dynamics because the field
equations of physics are local in this basis, not in any
If you do not find this answer satisfying, I would be interested to know why.
I'm familiar with that answer. It's the same one Schlosshauer considers in his review
paper. But he also notes that atoms, for example, are found in energy eigenstates - not
position eigenstates (in spite of the EM field also be "local"). More generally the basis
is supposedly "ein-selected" by being the basis whose interaction Hamiltonian with the
environment is robust against perturbations.
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