Please substitute in my last post: "this does stay in conflict" by "this 
does NOT stay in conflict"!!

Jan Harms schrieb:
> Hello Brent,
> perhaps one remark concerning your understanding of "einselection". 
> Please correct me if I am wrong here, but einselection - which is as you 
> say related to decoherence - is not selecting one state out of a 
> superposition of states, but selecting a certain basis in a Hilbert 
> space. The corresponding basis states are usually what we experience as 
> classical states. So it serves as an explanation why the world appears 
> as it is. However, this does stay in conflict with Everett's 
> relative-state multiverse theory. Instead, einselection is something 
> heavily required to make multiverse theories a serious candidate of QM 
> foundation. The only thing which may eventually undermine the beautiful 
> QM multiverse theory is, that someone discovers a nonlinear effect 
> inherent to the Schrödinger equation, which hasn't been discovered yet, 
> because it acts on an incredible small timescale.
> Jan
> Brent Meeker schrieb:
>> Ronald Held wrote:
>>> I am giving a talk on the Multiverse to Star Trek fans in several
>>> weeks. I would appreciate any advice and suggestions, since as of now,
>>> I have an outline based on Tegmark's four levels.
>> One thing I would avoid is presenting the multiverse (of any level) as the 
>> latest "gee-whiz, science has discovered that..."  It is interesting 
>> speculative metaphysics.  Good fodder for SciFi fans but not yet science. I 
>> cringe when Scientific American or the L.A. Times or some other popular 
>> publication takes scientific speculation and hypes it as though it were a 
>> new revelation of science.  It happens most often in medical stories, but 
>> also in physics and astronomy pieces.  In the end I think it debases 
>> science in the popular mind as just more advertising hype and spin noise.
>> ISTM there were several independent threads that lead to different ideas of 
>> the multiverse:
>> 1) The apparent inherent randomness of QM inconsistent with "hidden 
>> variables" which made the "collapse of the wave function" mysterious and ad 
>> hoc.  The led Everett to argue for a relative-state interpretation which 
>> implied  the QM-multiverse.  However, theories of einselection based on 
>> decoherence and perhaps weak anthropic selection may undermine the 
>> QM-multiverse.  In this theory there is really only one universe but each 
>> of us consists of multiple branches on which different values are projected.
>> 2) Completely independent of (1), development of theories of cosmogony 
>> based on quasi-classical quantum gravity showed the universe could arise 
>> from "nothing".  These theories naturally have the consequence that 
>> arbitrarily many other universes could also have arisen.  Any natural 
>> process is repeatable.  This theory of multiverses allows that universes 
>> exist with different values of those physical constants that seem arbitrary 
>> in our current theories (a set that could change).  These universes all 
>> exist in the same sense this universe exists, they may even have common 
>> points (e.g. in singularities).  Again some anthropic selection principle 
>> must be invoke to explain *this* universe.
>> 3) The extremely abstract nature of physics has led naturally to the 
>> speculation that only the mathematics matters.  We seem to know nothing 
>> about elementary particles and the interior of black holes beyond the 
>> mathematics they satisfy. So perhaps it is only the relational properties 
>> of information coded into the mathematics that is the ur-stuff of the 
>> world.  In that case all possible information structures may be considered 
>> equally "existent".  This also fits with the idea that reality can be 
>> simulated.  If reality consists in the relation of information, it doesn't 
>> matter how that information is embodied or maybe that it is embodied at 
>> all.  Therefore reality may *be* a simulation - as on the holodeck of the 
>> Enterprise.
>> 4) Finally, what seems to have motivated Tegmark and also perhaps Bruno and 
>>   others is Wheeler's question, "What makes them fly?"  Why is one set 
>> equations instantiated in the world and others are not?  Why is there some 
>> special property of "existing" that some possibilities have and others 
>> don't.  Tegmark sidesteps the question by answering that they are all 
>> instantiated; so "to exist" is simply to be the subject of propositions 
>> that form a non-self contradictory set.  Starting from this he then must 
>> try to recover some explanatory power by limiting what we experience by 
>> appealing to some anthropic principle.
>> Brent Meeker
> >

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