On 02 Jun 2017, at 04:06, Bruce Kellett wrote:
<snip> (answered in my previous post).
In quantum mechanics, this change is brought about by the unitary
processes of decoherence,
As Everett explains well, and suggest already this makes any
influence at a distance only apparent, but never real. Einstein can
sleep well.
and the non-unitary trace over the environmental degrees of freedom.
Which reflects only, in the MWI, the contagion of the superposition
to the environment.
This is an essential difference between classical and quantum
physics, and the necessity for this non-unitary reduction of the
pure state to a mixture is ultimately why MWI is actually no
better at explaining quantum measurement than are the collapse
models.
Only if you interpret the decoherence as a physical phenomenon, but
then we get non unitary evolution in Nature, and -quantum mechanics-
without collapse is false.
Are you suggesting that decoherence is *not* a physical phenomenon?
I am saying that the first person seeing mixed states is a first
person valid seeing from its "personal branch" perspective, but there
is no definite outcome in the third person view we can have on the
wave or the formalism.
Decoherence and the pure-to-mixed transition do indeed say that MWI
is strictly false -- you need non-unitary additions.
?
Only the collapse, if real, needs to falsify the unitarity of the
evolution.
The question is, what determined (from the 3p view) that the
universe followed that particular path and not any of the others?
Why do you reject out of hand that the universe might be
probabilistic? It is possible 'nothing' determined which path
from the possibilities was actually followed. All that is known
are the probabilities for each path. We do not know that the
other paths are followed, either 1p or 3p.
In QM, we do have evidences that many path are taken all
together. if only the two slits.
That is not really a relevant comment. Quantum mechanics is
characterized by the presence of superpositions -- that is what
makes the theory work, and why it is so different from classical
physics. Superpositions generally represent pure states, and these
must be reduced to mixed states by the measurement process.
Without collapse, that never happens.
So your non-collapse theory is immediately falsified by every
quantum experiment ever performed.
It is falsified only if you take a definite outcome as being absolute
and not branch relative.
Bruno
http://iridia.ulb.ac.be/~marchal/
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