On 3/4/2020 4:48 PM, Bruce Kellett wrote:
On Thu, Mar 5, 2020 at 10:50 AM 'Brent Meeker' via Everything List
<[email protected]
<mailto:[email protected]>> wrote:
On 3/4/2020 2:43 PM, Bruce Kellett wrote:
On Thu, Mar 5, 2020 at 9:15 AM 'Brent Meeker' via Everything List
<[email protected]
<mailto:[email protected]>> wrote:
Whether MWI is a satisfactory interpretation or not; do you
have a preferred proposal for getting rid of the unobserved
macroscopic states that are predicted by the formalism with a
collapse postulate, e.g. gravitationally induced collapse,
transactional interpretation, or what?
I do not think the problem is solved at the moment. Penrose's
gravitational induced collapse still lacks a dynamical mechanism
for the collapse when the gravitational superposition become
unwieldy.
Have you looked at Laloe's paper which fills this in using some
Bohmian ideas. arXiv:1905.12047v3 [quant-ph] 6 Sep 2019
Cramer's (Kastner's) transactional interpretation introduces a
whole new "possibility world", and relies on the failed absorber
theory of radiation.
I think the function of the possibility space is to avoid the
problems of the absorber theory. The absorbtion is "transacted"
in possibility space. I'm note sure how it handles free radiation
(e.g. the CMB) since nothing happens except by an exchange of
energy/information between an emitter and absorber.
No-go there. Bohm is the preferred option of many philosophers of
QM, but I think Flash-GRW is growing in plausibility. At least it
does give an underlying stochastic dynamics, so doesn't suffer
the problems of introducing probability that other approaches have.
It is still an open question, as far as I can see. The clear
thing is that Everett plainly fails to make any sense of
probability when all outcomes occur for any measurement.
I don't see that as particularly damning. I just means you need
another postulate of the form "And /this/ is a probability measure."
But that does not get around the problem that the set of possible
results from N trials on the state
|psi> = a|0> and b|1>
for non-zero coefficients a and b, is independent of the coefficients
a and b. So any experimental test of any probability idea, whether
imposed by hand or not, is going to show that the probabilities are
not related to the coefficients or branch weights.
For example, if you take Zurek's quantum Darwinism to provide an
objective pointer basis then you can say, in this basis,
off-diagonal terms in the reduced density matrix that are so small
they will never be observed can be set to zero and then the
diagonal terms are just the probability of the (one) world that
will be actual.
That is still a probabilistic assertion. And no derivation of
probabilities for cases in which all outcomes occur is going to be
successful.
That's not what I'm arguing. I arguing that there is a way to make
sense of a and b as "weights" whose square magnitudes give
probabilities. The significance of Zurek's quantum Darwinism is that it
provides and objective pointer basis. Without that one can always says,
no matter how small the off diagonal terms are, there's another equally
valid basis in which they aren't small.
The arguments for probability assignments given by Zurek (and Carroll
and Wallace, among others) all rely, at some point, on the "intuition"
that equal amplitudes equate to equal probabilities. It is that
assumption that I have shown to be false.
If you make it an axiom it ain't false.
Brent
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