On 4/28/2011 4:07 AM, Bruno Marchal wrote:

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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 ofquantum decoherence, for example Decoherence and the Transition fromQuantum to Classical by Wojciech H. Zurek. What is an attitude ingeneral to this? Is this good? Is there a good text for a laymanabout 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's rolein explaining the appearance of the classical world. It explains thediagonalization of the reduced density matrix (the density matrixafter averaging over the unknown environment). But it doesn'texplain the realization of just one of the diagonal values withprobabilities according to the Born rule. Omnes and some otherspoint out that QM is a probabilistic theory and so probabilities areall you can expect from it.There is also a problem in explaining the basis in which the densitymatrix is diagonalized; this is know as the einselection problem.Decoherence theory suggests some possible solutions to theeinselection 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 to stilladd something to the decoherence effect. Basically decoherence comesfrom the contagion of the superposition state to the environment,which is a consequence of the linearity of tensor products and of thelinear wave equation.I am not sure there is a "basis problem". Basis are selected byuniversal-machine-tropic choice, and Zurek did provide explanation whythe position basis in favored by our type of branch. Quantum statesare relative states, and consciousness can find itself only on thebranches which support stable self-reflexive machine abilities.

`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 case.`

`http://arxiv.org/abs/0807.3376v1`

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.`

Brent

Bruno http://iridia.ulb.ac.be/~marchal/

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