On 24/11/2017 10:15 am, Lawrence Crowell wrote:
On Wednesday, November 22, 2017 at 9:37:48 AM UTC-6, Bruno Marchal wrote:
On 20 Nov 2017, at 23:04, Bruce Kellett wrote:
You clearly have not grasped the implications of my argument. The
idea that "MWI replaces all nonsensical weirdness by one fact
(many histories)" does not work, and is not really an explanation
at all -- you are simply evading the issue.
Without collapse, the apparent correlations are explained by the
linear evolution, and the linear tensor products only. I have not
yet seen one proof that some action at a distance are at play in
quantum mechanics, although I agree that would be the case if the
outcome where unique, as EPER/BELL show convincingly.
Aspect experience was a shock for many, because they find action
at a distance astonishing, but are unaware of the many-worlds, or
just want to dismiss it directly as pure science fiction. But
after Aspect, the choice is really between deterministic and local
QM + many worlds, or one world and 3p indeterminacy and non
locality. Like Maudlin said, choose your poison.
Bruno
Bruce
I am new to this list and have not followed all the arguments here. In
weighing in here I might be making an error of not addressing things
properly.
Consider quantum entanglements, say the entanglements of two spin 1/2
particles. In the singlet state |+>|-> + |->|+> we really do not have
the two spin particles. The entanglement state is all that is
identifiable. The degrees of freedom for the two spins are replaced
with those of the entanglement state. It really makes no sense to talk
about the individual spin particles existing. If the observer makes a
measurement that results in a measurement the entanglement state is
"violently" lost, the entanglement phase is transmitted to the needle
states of the apparatus, and the individual spin degrees of freedom
replace the entanglement.
We have some trouble understanding this, for the decoherence of the
entangled state occurs with that state as a "unit;" it is blind to any
idea there is some "geography" associated with the individual spins.
There in fact really is no such thing as the individual spins. The
loss of the entangled state replaces that with the two spin states.
Since there is no "metric" specifying where the spins are before the
measurement there is no sense to ideas of any causal action that ties
the two resulting spins.
This chaffs our idea of physical causality, but this is because we are
thinking in classical terms. There are two ways of thinking about our
problem with understanding whether quantum mechanics is ontic or
epistemic. It could be that we are a bit like dogs with respect to the
quantum world. I have several dogs and one thing that is clear is they
do not understand spatial relationships well; they get leashes and
chains all tangled up and if they get wrapped up around a pole they
simply can't figure out how to get out of it. In this sense we human
are simply limited in brain power and will never be able to understand
QM in some way that has a completeness with respect to causality,
reality and nonlocality. There is also a far more radical possibility.
It is that a measurement of a quantum system is ultimately a set of
quantum states that are encoding information about quantum states.
This is the a quantum form of Turing's Universal Turing Machine that
emulates other Turing machines, or a sort of Goedel self-referential
process. If this is the case we may be faced with the prospect there
can't ever be a complete understanding of the ontic and epistemic
nature of quantum mechanics. It is in some sense not knowable by any
axiomatic structure.
Hi Lawrence, and welcome to the 'everything' list. I have come here to
avoid the endless politics on the 'avoid' list.
The issue that we have been discussing with EPR pairs is whether many
worlds avoids the implications of Bell's theorem, so that a purely local
understanding of EPR is available in Everettian models. I have argued
that this is not the case -- that non-locality is inherent in the
entangled singlet state, and many worlds does not avoid this
non-locality. I think from what you say above that you might well agree
with this position.
Bruce
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