On 19 Oct 2013, at 01:09, meekerdb wrote:

On 10/18/2013 1:45 PM, Jason Resch wrote:On Fri, Oct 18, 2013 at 11:37 AM, meekerdb <meeke...@verizon.net>wrote:On 10/18/2013 12:42 AM, Jason Resch wrote:But that's not compatible with Bruno's idea of eliminating thephysical - at least not unless he can solve the basis problem.Could you do me a favor and explain what the basis problem is in away that a 6th grader could understand? I've found all kinds ofthings said on it, and they all seem to be asking different things.For physicists, it's part of the problem of explaining theemergence of the classical world from the quantum world.Decoherence can diagonalize (approximately) a reduced densitymatrix IN SOME BASIS.Is this the same basis as in "momentum basis" and "position basis",or is it some other usage of the term?Forgive my ignorance, but what does it mean to "diagonalize areduced density matrix"?It means to take an average over all the other variables exceptthose of interest (i.e. the ones you measure). If you do this in aparticular basis we think it makes the submatrix corresponding tothose variables diagonal. Then it can be interpreted as theprobabilities of the different values. Note that it is amathematical operation that depends on choosing a basis, not aphysical process. The MWI view is that this is a physical process- which it could be IF the basis was not an arbitrary choice but wassomehow dictated by the physics. But so far there are only handwaving arguments that "it must be that way".

`The whole picture does not depend on the basis. Everett made this very`

`clear, in my opinion.`

`The choice of the base happened in the earlier apparition of life. As`

`I said, the first amoeba did it.`

Being diagonal in one basis means it's superposition in someother basis. So for physicists the problem is saying whatprivileges or picks out the particular bases we see inexperiments. Why do our instruments have needlesthat are in eigen states of position, while some other things (e.g.atoms) are in eigen states of energy or eigen states of momentum.For physicists there are some suggestive, but not fully worked outanswers to these questions, e.g. you get position eigenstatesbecause the interaction term of the Hamiltonian is a function ofposition. But those answers assume the physics. If you want toreconstruct physics from experiences, you can't borrow the physicalexplanation to say why your experiences are classical.I think the assumption that experiences are classical comes fromthe classicality of Turing machines (which are the supposedmechanism by which experiences are manifest).I don't think there's anything either classical or quantum aboutTuring machines. They are just mathematical abstractions.

`Those mathematical abstraction relies on the fact that such machine`

`can distinguish some classical, well defined, states. The tape`

`contains bits, not qubits, for all practical evolutionnary purpose. Of`

`course, in their physical implementation, those are qubit, and that is`

`why the state of the machines differentiate into quasi-classical`

`world. Why nature did not evolve quantum brain might be explained by`

`the fact that evolution has favorised classical macroscopic mind, for`

`reason comparable of why nature did not evolve any wheels.`

`If you want, the base has been selected by the first macroscopic`

`organism, or the first Turing universal system. The theory of`

`decoherence explains well why macroscopic objects leads to classical`

`states. It is probably as difficult for nature than for humans to`

`isolate a quantum macroscopic universal system. We are classical`

`because our bodies contains many atoms entangling quickly their states`

`with their neighborhood. It is a good thing as this explains how the`

`quantum reality defined a first person *plural*, duplicating us`

`together.`

Bruno

And assuming they read and write qubits instead of bits doesn'tchange the range of things they can compute.Brent --You received this message because you are subscribed to the GoogleGroups "Everything List" group.To unsubscribe from this group and stop receiving emails from it,send an email to everything-list+unsubscr...@googlegroups.com.To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.

http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.