Le 03-nov.-05, à 19:29, Hal Finney a écrit :
> Bruno Marchal writes:
>> And that illustrates the advantage of the comp theory, it gives by
>> construction the correct physics, without any need, for a comp
>> "believer" to verify it. Except, of course, that comp need to be
>> postulated and we must be open it is could be false. With comp, you
>> see, physics is approached in a radically different way. Different
>> from
>> the 2300 years of Aristotelian Naturalism: comp makes us to go back to
>> Plato. Updtated by Godel's discoveries (and Church, Turing, etc.).
>
> Let me see if I understand how you construct the correct physics from
> comp.
>
> You start with the principle of the Universal Dovetailer, which creates
> all possible universes.
OK. But the word "universe" can be misleading here. It is probably less
misleading to say that the Universal Dovetailer generates all
computations. By assuming comp, this generates also all the (first
person) observer-moments (states/worlds/...).
The physical reality will emerge from that, but there is no a priori
reason to believe the UD generates any particular physical reality,
although we have empirical reason that some quantum dovetailer will win
the "measure" battle.
> You then examine those universes for subsystems
> which are consistent with your own first-person conscious experiences.
If that means that my probable future, when I am in a comp state S, is
entirely determined by the collection of computations going through S,
with "intrinsical weight" determined by the UD (and thus by theoretical
computer science alone), then OK.
> You set up some kind of measure over this selected subset of universes.
... of relative states or relative consistent extension. I only
isolate the logic of the "measure 1" from pure comp, and I got a
confirmation by showing it to be quantum-like. I did analyse only the
"propositional physics", but the SOL ° THEAE ° COMP functor gives the
whole of physics when you extend it to the quantified (first order)
generalization of G. Which unfortunately (but expectedly) is a highly
undecidable theory, as the russian logicians have succeed to show (see
Boolos 1993).
> (The Universal Dovetailer perhaps implies the Universal Distribution.)
The universal dovetailer implies a *relative* gaussian distribution,
from which a "quantum-like-distribution" is extracted when we
distinguish the 1 and 3 person point of views.
> And based on this measure you arrive at first-person indeterminacy
> about
> which laws of physics hold for you.
Not really about which laws of physics holds because the "unique
possible laws of physics" emerge from all computations.
Suppose you measure the position of an electron and you find x. And
then You want to evaluate the probability you will find it at y. In QM
you need to take into account all path the electron will (or could) do
for going from x to y. With comp you need to take into account all but
only the computations going from your comp-states when you see the
electron in x to the comp-states when you observe the electron in y.
>
> Is that right, is that the mechanical procedure by which someone
> derives
> their laws of physics from comp?
That was a pretty short description, yes. I would just insist more on
the fact that the physical reality is really a first person (plural)
emergence from the "interference" of all third person describable
computations. comp makes physics unique (Generalisation: each
alpha-comp makes each alpha-physics unique, so that by observation we
can have empirical reasons to bet on some alpha and measure some degree
(alpha) of non computationality).
Bruno
http://iridia.ulb.ac.be/~marchal/
Received on Sat Nov 05 2005 - 08:35:34 PST