On 8/4/2011 4:43 PM, Stephen P. King wrote:
Hi Brent,

On 8/4/2011 4:38 PM, meekerdb wrote:
On 8/4/2011 12:10 PM, Stephen P. King wrote:
Hi Brent,

On 8/4/2011 1:44 PM, meekerdb wrote:
On 8/4/2011 9:41 AM, David Nyman wrote:
Hi Stephen

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. that quasi-classical "reality", as ordinarily experienced, is consequent on
the selection of particular "best-fit" or "most fruitful"
interpretations of functional or structural features of the underlying
micro-physical state-of-affairs.

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.

Brent


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.

Again, what is the motivation of the quasi-classical approach? More simple calculations? More intuitive models?

Predicting what is actually observed.

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.

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 evolution.

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 the amplitudes. 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 probabilities." 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.

Brent


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