Stathis Papaioannou wrote:
>
>
> Brent Meeker writes:
>
>>>>> If you died today and just by accident a possible next
>>>>> moment of consciousness was generated by a computer a trillion years in the
>>>>> future, then ipso facto you would find yourself a trillion years in the future.
>>>> That's the whole problem. I could just as easily find myself in an HP
>>>> universe. But I never do.
>>> Not "just as easily". If you are destructively scanned and a moment from now 2 copies
>>> of you are created in Moscow and 1 copy created in Washington, you have a 2/3 chance
>>> of finding yourself in Moscow and a 1/3 chance of finding yourself in Washington. It is a
>>> real problem to explain why the HP universes are less likely to be experienced than the
>>> orderly ones (see chapter 4.2 of Russell Standish' book for a summary of some of the
>>> debates on this issue), but it is not any more of a problem for a mathematical as opposed
>>> to a physical multiverse.
>> I'm not sure what a mathematical MV is: if you mean the Tegmark idea of the set of all mathematically consistent universes then I think you're wrong. There is no measure defined over that set (and I doubt it's possible to define one). But the physical universe obeys the laws of QM and it appears that eigenselection, as proposed by Zeh, Joos, and others, may provide a natural measure favoring order.
>
> What if the set of all mathematically consistent universes were actually, physically instatiated?
> My point is that physical instantiation per se does not solve the HP problem, unless we say that
> only the non-HP universes are instantiated, making "multiverse" narrower than "all mathematically
> consistent universes". I gather that Tegmark's grand ensembles are not mainstream physics, even
> among those who accept the MWI.
The MWI posits multiple worlds in which every evolution of the world consistent with quantum physics is realized - it's really just one Hilbert space and the "multiple" arises only because macroscopically different worlds are projected onto orthogonal subspaces. But it is assumed that evolution in this Hilbert space is due to one Hamiltonian with specific values of coupling constants etc. Tegmark's "all mathematically consistent" universes would seem to include a Newtonian universe, an Aristotelean universe, a Biblical universe, and in fact any universe that didn't include a flat contradiction, X and not-X.
Brent Meeker
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Received on Wed Oct 25 2006 - 12:41:14 PDT