On 2/13/2012 3:43 PM, Joseph Knight wrote:

On Mon, Feb 13, 2012 at 11:47 AM, Stephen P. King <stephe...@charter.net <mailto:stephe...@charter.net>> wrote:

    On 2/13/2012 12:11 PM, Joseph Knight wrote:
    I think you should probably read Maudlin's paper
    <http://www.finney.org/%7Ehal/maudlin.pdf> for specifics. I don't
    think thermodynamics will have much to do with the conclusions,
    whatever they may be (and I don't think it's obvious what
    /exactly /Maudlin showed).

    Hi Joseph,

        Thank you for the new link to Maudlin''s paper. I was having a
    hard time finding my copy... As to your comment: Would you
    consider exactly what a "computational structure" means in a
    universe that allows for perpetual motion

You should be aware that our universe allows for perpetual motion.

    (We are going to run a reductio argument

        One thing that I see is that in such a universe we would have
    a huge White Rabbit problem because all brains in it would only be
    those of the Boltzmann type
    <http://en.wikipedia.org/wiki/Boltzmann_brain>. There could not be
    any invariant form of sequencing that we could run a UD on. How
    so? Becasue in a universe without thermodynamics

A Big universe "with thermodynamics" will still admit perpetual motion machines (in fact, our Universe is such a universe). Are you aware that, in the 19th century, classical thermodynamics was transformed into a statistical theory? You made a huge (and incorrect) leap from "admits a perpetual motion machine" to "no thermodynamics".

Hi Joseph,

Yes, you are correct, but notice that we can have perpetual motion in the sense of closed-time-like loops in GR but we can never extract more energy from them than it takes to construct the mechanism to interface with the devious little bastards!

If you can have Boltzmann Brains you can have Universal Dovetailers run for arbitrary (even infinite) amounts of time.

No, that would violate the definition of Boltzmann brains as they can only be connected and chained up into a UD after the fact of their actualization. Otherwise we are in a situation where noise is indistinguishable from a signal as the minds implemented by such Boltzmann brains. Think about it, Boltzmann brains are stochastic and to define a continuation of them we have to simultaneously embed at least two into a preorder to get a sequence for a UD. One cannot claim to operate on an entity before it even exists.

At any rate, the notion of a "sufficiently robust universe" is a provisional premise that is dropped later in the UDA, so it's not important.

That is a red Herring. One can always set the bar of what a measurement is so that it is too high to overcome by current means. This is a fallacy that is prevalent all over the place in physics, sadly. :-(



    there is no such a thing as a sequence of events that is invariant
    with respect to transitions from one observer to another, i.e.
    there would be no such thing as time definable in a 'dimensional'
    sense. All sequences would be at best Markov
    <http://en.wikipedia.org/wiki/Markov_property>. With such a
    restriction to Markov processes, how to you define a UD? Without a
    UD, how do we get COMP to work?

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