On 8/4/2011 8:40 PM, meekerdb wrote:
On 8/4/2011 4:43 PM, Stephen P. King wrote:
On 8/4/2011 4:38 PM, meekerdb wrote:
Again, what is the motivation of the quasi-classical approach?
More simple calculations? More intuitive models?
On 8/4/2011 12:10 PM, Stephen P. King wrote:
On 8/4/2011 1:44 PM, meekerdb wrote:
On 8/4/2011 9:41 AM, David Nyman wrote:
Thanks for the link - very enjoyable talk. As far as I could follow
it, he seemed to be saying that the differentiation of decoherent
"worlds" is in the final analysis a "psychological" matter - i.e.
quasi-classical "reality", as ordinarily experienced, is
the selection of particular "best-fit" or "most fruitful"
interpretations of functional or structural features of the
I don't see how life (including us) could exist except at a
quasi-classical level. Evolution needs reliable replication to
work with. Given that we evolved as quasi-classical beings, it
follows that our perception, psychology, and interaction with the
world must be quasi-classical.
Exactly what does the 'quasi-classical" property imply and what
does it bring to the table that is not in the quantum realm? Is it
persistence of structure? How does the unitary evolution of the
wave function not provide that?
It doesn't. Although decoherence theory is suggestive; it has not
yet been able to uniquely define "quasi-classical" within the
framework of QM without additional assumptions about pointer bases.
Predicting what is actually observed.
And what we observe is not framed and molded by our expectations?
Come on! There is no much evidence that people see things only within
the bounds of prior experience or not at all.
I am asking about the motivation to maintain a paradigm that has long
lapsed into obsolescence! The universe is not a giant clock work of
isolatable and separable parts as the scientists of the 18th and 19th
century believed. We have sufficient evidence to see this clearly, so
why the romantic attachment with this vision?
Strawman. I carefully wrote *quasi-classicality*, not classicality.
WHAT DOES QUASI-CLASSICALLY MEAN? Please define this term.
The assumptions about pointer bases is a throwback to Copenhagen,
where Borh, that great champion of QM desperately tried to get the
emerging experimental evidence to get along with the classical
vision. Few people still how up the Copenhagen interpretation as
viable, with its strange duality of classical measuring devices
interacting with quantum systems. Most people have adopted the
Everetian vision of a purely quantum universe, and yet that pesky
basis problem persists! What I am investigating is an attempt to
solve that problem by considering how the interactions between many
systems tends to induce global behaviors that are selective,
selective in the same sense as what we need to solve the basis problem.
I hope you succeed. There have been
Consider what happens when a large number of people communicate
with each other. Even if they start off speaking their own unique
language eventually, because of the way that communications in the
real world occurs, there will emerge a single language that
prodominates. In a similar way, I believe that a basis set emerges
out of the interactions between a large number of QM systems, a basis
that represents the maximally consistent set of observables for that
collection. This is a very crude sketch of the idea, but to explore
it I must jettison all of the classical ideas that so far have been
poisoning the well of thought on this problem.
But if you succeed you must ultimately recover the classical
appearance of the world and the Born rule, at least as approximations.
In fact, the quantum realm seems to even be over-determinative in
the sense that no only is one 'actual' real state of affairs of a
world non-contradictorily exists in the amplitudes of the wave
function but all possible versions of it.
A popular myth. QM does not provide that "everything happens". For
example eigenstates of an operator remain eigenstates in the unitary
Popular and mythological to whom? How does the persistence of
eigenstates under unitary evolution contradict what I wrote? Is it
incorrectly claimed that a quantum state is equivalent to *all
possible statements" that can be made of a system?
While it is true that we seem to observe only one Boolean logic
representable slice of the totality of what is coded in the
amplitudes, it can easily be shown
It isn't "shown" at all. It's hypothesized in one model.
Which model and what are the alternatives?
In Everett's interpretation. In, for example Asher Peres
interpretation, the wave function just encodes what we know about an
ensemble of state preparations.
that this is just something like one subset of the set of all of
the Boolean representable 'possible worlds' that we see coded in
I simply do not comprehend this emotional clinging to a
classical vision of the world; especially given the fact that it is
demonstrably false! It seems to me that your argumentation is just
an attempt to preserve your apparent belief in naive realism.
It seems to me that your reification of the wave function is an over
reaching extension of what we know from our classical observation
driven by a distaste for randomness.
Is it that I have a distaste for randomness or is it that you
have an irrational affection for randomness? What does randomness
give you that you cannot live without?
The Born rule and testable predictions. As Omnes says, "Quantum
mechanics is a probabilistic theory, so naturally it predicts
See for example: arXiv:0905.0624v2 , 0808.2415v1 , 0810.2657v1
and 0312058v3. Of course you may consider these physicists as mere
romantics emotionally attached to mathematical logic.
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