On 27 Nov 2017, at 00:07, [email protected] wrote:
On Sunday, November 26, 2017 at 2:29:22 PM UTC, Bruno Marchal wrote:
On 24 Nov 2017, at 15:59, Lawrence Crowell wrote:
On Thursday, November 23, 2017 at 5:53:14 PM UTC-6, Bruce wrote:
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
Of course MWI can do nothing of the sort. MWI suffers from much the
same problem all quantum interpretations suffer from.
I don't see this. the MW theory (that is the WWE without the
collapse axiom) explains the violation of inequality in a way which
avoids any action at a distance, but when we assume one universe,
like Einstein explains very clearly already in 1927, you get a
notion of simultaneousness incompatible with special relativity and
very minimal form of realism.
For me, as a logician, I consider that SWE and SWE+collapse are
different theories. The first is local, deterministic and admits a
local physical realism, the second is not intelligible at all, as
the notion of observer is unclear and dualistic.
Bruno
So you see one observer in one world as unclear and dualistic,
Yes. Even without quantum mechanics, I can explain why this cannot
work, when we assume the Digital Mechanist hypothesis.
but an infinity of worlds with an infinity of observers presents no
problem?
Yes, as it will be line with the natural numbers. Having them all is
more easy that having any finite number of them. "Everything" is
simpler than one thing. That is basically the guiding intuition of the
"everything-list", both for physics and psychology/metaphysics/theology.
As for collapse, it's easily seen in the double slit experiment. The
electron, say, moves through space as a wave -- which explains the
interference effects due to splitting into two waves, each emanating
from one of the slits -- and is ALWAYS observed as localized in
space, aka a PARTICLE. That is, the wave collapses into a particle!
There is no other reasonable interpretation of results of the double
slit experiment, which demonstrates the collapse phenomenon for
those able to see.
The SWE explains why the observer will believe that there is a
collapse, and this without assuming that there is a collapse. No need
to assume something as non linear than the collapse. How would that
non linearity occur?
Then, I am not Aristotelian. They believe in what they see. A
platonist is skeptical about what he sees. he will believe only in
what makes sense, or in what makes more sense. Many universe is not
more astonishing than many water molecules. Nature loves to add and
multiply. But a collapse, which needs to be instantaneous, brings many
conceptual and physical difficulties, if only a precise definition. It
leads to 3p dualism which is really hard to sustain.
Concerning your use of tensor calculus and linearity, the entangled
pair to be measured is assumed as ISOLATED prior to measurement, so
you CANNOT assume it's superposed state is entangled with Alice or
Bob prior to measurement.
Of course. I did not have contested this.
Of course, Alice and Bob can be deleted from the experiment. All you
need is a detector or counter attached to the SG device to record
the results.
I agree that the result would entail action at a distance, in case of
collapse and mono-universe assumption. But not in the pure SWE: there
is no physical action at a distance needed to explain why it looks
like action at a distance occurred. With the SWE, the weirdness is
only an appearance. With Mechanism, even the SWE will be seen as an
appearance. (But that is for later, I guess).
Bruno
AG
With MWI there is a nice idea of the world continuing on as a
complete pure state quantum system, but it has the problem that we
observers have some restriction on our observational domain. This
is because we are thrust into some subset of the Hilbert space of
evolution. It really is a sort of collapse, but rather than of an
epistemic wave function it is within a map on the ontological
domain an observer can access.
LC
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