On 28 Apr 2011, at 20:32, meekerdb wrote:
On 4/28/2011 4:07 AM, Bruno Marchal wrote:
On 27 Apr 2011, at 22:48, meekerdb wrote:
On 4/27/2011 12:16 PM, Evgenii Rudnyi wrote:
Recently I have seen interpretation of quantum mechanics in terms
of quantum decoherence, for example Decoherence and the
Transition from Quantum to Classical by Wojciech H. Zurek. What
is an attitude in general to this? Is this good? Is there a good
text for a layman about such an approach?
There's a good review paper by Max Schlosshauer
He later expanded it into a book. Decoherence is a real, observed
physical process predicted by QM. Interest in it is due to it's
role in explaining the appearance of the classical world. It
explains the diagonalization of the reduced density matrix (the
density matrix after averaging over the unknown environment). But
it doesn't explain the realization of just one of the diagonal
values with probabilities according to the Born rule. Omnes and
some others point out that QM is a probabilistic theory and so
probabilities are all you can expect from it.
There is also a problem in explaining the basis in which the
density matrix is diagonalized; this is know as the einselection
problem. Decoherence theory suggests some possible solutions to
the einselection problem but none are really worked out yet.
Yes. Decoherence is real, and can be explained entirely in the QM
without collapse. It is a key ingredient of the Many-World
Interpretation, and that is why those who dislike the MWI try to
still add something to the decoherence effect. Basically
decoherence comes from the contagion of the superposition state to
the environment, which is a consequence of the linearity of tensor
products and of the linear wave equation.
I am not sure there is a "basis problem". Basis are selected by
universal-machine-tropic choice, and Zurek did provide explanation
why the position basis in favored by our type of branch. Quantum
states are relative states, and consciousness can find itself only
on the branches which support stable self-reflexive machine
I think more than "support" is needed - else you might find yourself
the the sole stable consciousness in a world full of quantum
superpositions. Steven Weinstein has shown this to be the generic
Damned! I will have to look at this one.
Hmm... he made a lot of hypotheses which I can hardly judge (not being
a physicist). May be it will be shorter to stick with the comp body
Comp predicts that at some point physics must go wrong, unless they
explicitly take into account the self-reference logics. Remember that
comp entails that deriving physical laws from observation is already a
risky enterprise !
It is an open problem for me if other type of basis (than position)
can play that role.
Max Schlosshauer points out that small systems (e.g. atoms) are
stable in energy-momentum eigenstates, not position eigenstates.
This might explain, with my remark just above, why life and mind does
not seem to appear on such small scale.
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