On 12-11-2017 11:21, Bruce Kellett wrote:
On 12/11/2017 9:14 pm, smitra wrote:
On 12-11-2017 07:57, Bruce Kellett wrote:
On 12/11/2017 5:39 pm, Brent Meeker wrote:
In Bruno's model the "influence at a distance" is determing which
world you're in.
If that means anything at all, it is still non-local because Bruno
has to rule out the worlds in which angular momentum is not
conserved;
he has not shown how he can do this. If it is simply that you cannot
find yourself in a world in which AM is not conserved, then that is
just an unabashed appeal to magic, since such worlds have not been
shown not to exist.
Bruce
There are two correlated copies of Alice and Bob induced by the
correlated spins, there is nothing nonlocal about that in the MWI.
There is only a non- locality problem here if you assume a collapse
interpretation of QM. In the MWI the correlation arises via an
originally local common cause.
There is no collapse assumption in anything that I have written about
this scenario. What is the local common cause in MWI? Is that a local
hidden variable? Such would work in the time-like case, but not in
general -- that is Bell's result.
But you have still not answered the fundamental question as to what
causes Bob to necessarily measure spin down when Alice joins him with
a spin-up result? What turns Bob's particle from an unpolarized to a
polarized state so that the probabilities change from 50/50 to 100%
for spin down?
Bruce
Bob's particle never changed due to anything Alice did in the MWI. All
that happened was that Alice got entangled with her particle (and not
just Alice, her entire environment gets entangled with the state of her
particle), which in turn was entangled with Bob's particle. So, Bob has
the same probabilities for finding spin up or down, except that he can
now measure the state of his particle by performing a measurement on
Alice, by asking her what she found for her spin.
It's not true that before Bob knows what Alice has found that only one
of the two version's of Alice has arrived and that the information of
her spin state is then already present in Bob's sector. This is not true
in the MWI, decoherence simple means that you can't demonstrate the
existence of the two versions of Alice via an interference experiment.
But the inability to do so, doesn't by itself imply that only one
version really exists.
Saibal
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