Re: QM

From: Jacques Mallah <jackmallah.domain.name.hidden>
Date: Sat, 24 Jun 2000 22:01:31 EDT

>From: GSLevy.domain.name.hidden
>jackmallah.domain.name.hidden writes:
> > jackmallah.domain.name.hidden writes:
> > QM is the laws of physics that best explains what we see. I think
>that says it all. I should point out that there is really no summation
>involved, especially not a sum over worlds. There is just -i hbar d/dt psi
>= H psi.
> > Of course, you could write psi as a sum of orthogonal functions and you
>could choose nearly decoherent such functions.
> > In the computationalist view, there is a wavefunction, and it
>implements computations. These implementations may resemble those that
>would be produced by classical mechanics, modified by interference terms
>that may be small.
>
>OK, the Shoedinger equation is -i hbar d/dt psi = H psi, Why? Why does the
>equation have an imaginary form? What is the meaning of Planck's constant
>it the CONTEXT of the MWI? Just saying, as you do, that the SE is what it
>is just because, is adopting the same POSITIVIST attitude as the Copenhagen
>school. I am looking for the INTERPRETATION of this equation in terms of
>the MW. Is it possible to derive this equation from a PURELY
>COMPUTATIONALIST APPROACH?

    If you mean to derive it from the AUH (+ computationalism), I don't
blame you for wanting that. That's the holy grail. It would be one of the
greatest intellectual achievements in all of human history. The Nobel Prize
would be the least of it. Don't hold your breath.
    I wouldn't be mucking around with trying to measure wabbittiness if I
could derive the SE from the AUH. As it is, the best I think is practical
is trying to predicts things like wabbittiness, and to argue that the SE
*could* be what a typical observer-moment in the AUH would see. We expect
the observation to be consistent with apparent laws of physics that are
relatively simple, in a universe that is computationally deep. (See the
discussion Wei Dai and I had soon after I joined this list.) Getting more
specific is hard.
    As for positivism, what you say is false. Even if (as I did *not* say),
the SE is not derivable from the AUH, that's not a positivist statement. A
positivist would say there is really no SE in existance, but we can use the
SE to make predictions.

>You say that psi can be written in terms of orthogonal (decoherent)
>functions. Are those functions equivalent to the individual worlds in the
>MW? If so, then we certainly have the ability to be affected by several
>such worlds simultaneously because of the phenomenon of superposition. What
>does this say about consciousness? Does consciousness have "thickness"
>across the MW? How does this fit with the ideas of Lewis and Kriepke?

    Don't misquote me. I said it could be written in terms of nearly
decoherent functions. On that 'nearly' hangs interference, the basic
property of QM and our main defense against the 'collapse' idea.
    'Individual worlds' - a matter of definition. "Many worlds" is a great
way of describing QM - until the details start to matter, in which case
those words can cause as much confusion as enlightenment.
    I don't know what ideas L&K have.

> > You still don't know what computationalism means? It means that
>certain computations give rise to consciousness. It does not explain
>behavior at all, and does not allow zombies
>
>It seems that you need to be more precise. Computationalism ASSUMES that
>certain computations give rise to consciousness. It does not EXPLAIN
>consciousness. And without a third person/ first person theory you can only
>talk about behaviors as observed from a third person point of view without
>ever describing what it is to be (yourself) conscious.

    You say assumes, I said asserts. Whatever. True, computationalism
makes no claim about *why* computations are conscious. There are two
schools of thought about why: reductionism and dualism. Both are compatible
with computationalism.
    Reductive computationalism is the belief that consciousness is nothing
more than computation. Obviously, if this could be proven, it would not
have to compete with the rival school. That is obvious, isn't it?
    You can certainly talk about consciousness, though. And
computationalism explicitly, and by definition, does talk about it.
    But as for describing what it's like *qualitatively*, that's impossible.
  Language cannot convey that regardless of your ideology.
    Well, I hope you soon see the light (in more ways than one). Get well
soon.

>From: Russell Standish <R.Standish.domain.name.hidden>
>Basically, the i in the equation is to ensure that the Hamiltonian is
>hermitian, which is required by the law of conservation of probability
>(d/dt (psi* psi))=0. This latter law is simply the statement that the
>axiom saying the probability of the certain event is 1, and shall
>remain so for all time.

    As you know Russell, I find your "derivation" of the SE quite wanting.
As far as conservation of probability, it is not obvious that measure should
be conserved as a function of time. In fact, measure is not strictly
conserved.
    The i is there to make the equation simpler to write. Of course one
could write it in terms of real quantities only, such as amplitude and
phase.

>As for the value of hbar, this is to fix a rather arbitrary set of
>units we happened to choose to measure the world in. If we did
>everything in terms of Planck units, hbar=1.

    This one you got right. Of course, one could ask about the
dimensionless 'constants' of physics, and make an anthropic principle
argument.

                         - - - - - - -
               Jacques Mallah (jackmallah.domain.name.hidden)
         Physicist / Many Worlder / Devil's Advocate
"I know what no one else knows" - 'Runaway Train', Soul Asylum
         My URL: http://hammer.prohosting.com/~mathmind/

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Received on Sat Jun 24 2000 - 19:03:24 PDT

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