On 13-05-2022 21:59, Brent Meeker wrote:
On 5/13/2022 12:32 PM, smitra wrote:
On 12-05-2022 22:27, Brent Meeker wrote:
On 5/12/2022 11:42 AM, smitra wrote:
All that the experiments demonstrate is that the wave function
evolves
unitarily between state preparation and measurement. This is most
easily accounted for by assuming that the wave function is a
purely
epistemic vehicle for the time evolution of probabilities. Since
it is
purely epistemic, collapse is not a problem since it is not a
physical
event. One does not have to go the whole way to QBism -- the wave
function can still be objective (inter-subjectively agreed).
That's possible but that means that QM is not a complete fundamental
theory of reality. Anything that explains these probabilities is
then possible, including the existence of a multiverse.
Which is about as explanatory as "God did it." Explaining the values
of the probabilities isn't the problem with MWI, it's explaining
that
there ARE probabilities even though nothing happens, and when and
where the probabilities arise.
I agree with what John Clark said in his reply.
To add to that, the "God did it" thing applies far more to the CI,
because there one postulates the collapse without explaining the
mechanism for it. In the MWI one assumes that the appearance of
collapse can be explained from the known dynamics.
Right CI doesn't explain the collapse and MWI doesn't explain the
collapse either but assumes it can be explained without new physics.
I hypothesize (not assume) that CI+ <non-zero minimum probability> can
explain the collapse. I don't see any big advantage for MWI here.
The big advantage is that decoherence is a well researched area of
(mathematical) physics, results like the density matrix becoming
approximately diagonal, and relations between decoherence to entropy
increase making it effectively irreversible are all rigorous results
that are uncontroversial. People may still have objections against the
MWI, but they'll still accept these results on decoherence.
Non-zero minimum probability on its own, however, does not cause a
system to evolve in a non-unitary way. Bruce is omitting something here,
perhaps some limits in which the time evolution operator becomes
degenerate or something like that. But a product of two unitary
transforms is a unitary transform, so the nth power of a unitary
transform is also a unitary transform. There is no ay you can get
anything non-unitary out of this, unless possibly in the limit of n to
infinity.
My
attitude toward interpretations is that they are unimportant in
themselves, but they are useful in pointing to new, more comprehensive
and accurate theories. That's one reason I'm not impressed by MWI
since it seems to ex hypothesi put any emprical testing out of reach.
But that's because MWI amounts to omitting something from a theory
that's not needed. It's like what would have happened if Einstein had
formulated his theory of special relativity but he had kept the ether to
serve as the medium with strange properties such that you still have the
equivalence of inertial frames. If you then had formulated your
alternative version of special relativity by saying that the ether
doesn't exist, then people who would have stuck to the idea what an
ether must exist could have argued in the same way, i.e. that you are
not adding anything that can be tested experimentally.
Saibal
Brent
Those explanations may not be satisfactory as of yet, but that's
typical for most of science. There are phenomena that as of yet are
not well explained, but that does not (necessarily) lead us to
postulate new physics all the time. Doing so would make us like
creationists who tend to invoke a "God of the gaps".
Saibal
Brent
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