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.
> 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
>> 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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