On 28 Apr 2011, at 20:32, meekerdb wrote:

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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 termsof quantum decoherence, for example Decoherence and theTransition from Quantum to Classical by Wojciech H. Zurek. Whatis an attitude in general to this? Is this good? Is there a goodtext for a layman about such an approach?EvgeniiThere's a good review paper by Max Schlosshauer http://arxiv.org/abs/quant-ph/0312059He later expanded it into a book. Decoherence is a real, observedphysical process predicted by QM. Interest in it is due to it'srole in explaining the appearance of the classical world. Itexplains the diagonalization of the reduced density matrix (thedensity matrix after averaging over the unknown environment). Butit doesn't explain the realization of just one of the diagonalvalues with probabilities according to the Born rule. Omnes andsome others point out that QM is a probabilistic theory and soprobabilities are all you can expect from it.There is also a problem in explaining the basis in which thedensity matrix is diagonalized; this is know as the einselectionproblem. Decoherence theory suggests some possible solutions tothe einselection problem but none are really worked out yet.Yes. Decoherence is real, and can be explained entirely in the QMwithout collapse. It is a key ingredient of the Many-WorldInterpretation, and that is why those who dislike the MWI try tostill add something to the decoherence effect. Basicallydecoherence comes from the contagion of the superposition state tothe environment, which is a consequence of the linearity of tensorproducts and of the linear wave equation.I am not sure there is a "basis problem". Basis are selected byuniversal-machine-tropic choice, and Zurek did provide explanationwhy the position basis in favored by our type of branch. Quantumstates are relative states, and consciousness can find itself onlyon the branches which support stable self-reflexive machineabilities.I think more than "support" is needed - else you might find yourselfthe the sole stable consciousness in a world full of quantumsuperpositions. Steven Weinstein has shown this to be the genericcase. http://arxiv.org/abs/0807.3376v1

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`

`problem.`

`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) arestable 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.`

Bruno http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.