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From: Jeff Bone <jbone.domain.name.hidden>

Date: Thu, 19 Aug 2004 15:47:58 -0500

On Aug 19, 2004, at 2:00 PM, Hal Finney wrote:

*> It's not clear to me that causality and time are inherent properties
*

*> of worlds. I include worlds which can be thought of as n-dimensional
*

*> cells that satisfy some constraints. Among those constraints could be
*

*> ones which induce the effects we identify as causality and time. For
*

*> example, a two-dimensional cell where C[i,j] == C[i-1,j] XOR
*

*> C[i-1,j-1].
*

*> This particular definition has the property that C[i,.] depends only on
*

*> C[i-1,.], which lets us identify i as time, and introduce a notion of
*

*> causality where conditions at time i depend on conditions at time i-1.
*

*>
*

*> But we could just as easily create a cell system where there was no
*

*> natural definition of time, where C[i,j] depended on i+1, i-1, j+1
*

*> and j-1. You could still imaging satisfying this via some constraint
*

*> satisfaction algorithm.
*

+1

I'll have to think about the CA implications --- what is a "cell" in

such a CA, and what is meant by the various "nearness" relationships of

such cells? (I'm still processing Wolfram's book, a couple of years

after reading it the first time. ;-)

I'm just adopting a relatively conventional GR point-of-view here,

where time is just another direction, albeit one in which travel is (in

most circumstances, depending on the local differential geometry and

geometrodynamics) directionally constrained. (I'm ignoring the

thermodynamic interpretation of time's arrow, though when you throw 2LT

into this particular brew things would seem to get rather interesting.

;-)

*> Now these jinni worlds are ones which mostly have these conditions we
*

*> identify as time and causality, but which locally, or perhaps rarely,
*

*> do not satisfy such rules. Seen in this perspective, there is a full
*

*> range of possibilities, from fully causal worlds, to ones which are
*

*> 99.999% causal and only .0001% noncausal, to ones which are 50-50, to
*

*> ones for which no meaningful concept of causality can be defined.
*

We're begging the question re: causality; it was perhaps unfortunate

that I chose to use that word, as it's interpretive rather than

descriptive in itself. The argument Boulware's making appears to be

inherently probabilistic and geometric rather than ontological. That

became less clear in my exposition, my bad.

*> I'll have to look at this. It doesn't sound quite right. If
*

*> probabilities are non-unitary that violates the fundamental rules of
*

*> QM,
*

But do they? This is, I think, perhaps a very interesting and

pertinent question. It certainly appears to throw both the QM

formalism as well as its interpretations into disarray, but I think

perhaps the result is less than fatal. One can certainly do statistics

(and hence QM) with non-unitary probabilities --- the method involves a

kind of normalizing transformation between different probabilistic

measures. (In fact this very issue was dealt with by one of Gott's

grad students; the citation escapes me at the moment, but he found

that you could patch things up by simply supplying a kind of local

correction coefficient. I.e., while this appears prohibitive on the

surface, in fact "fixing it up" isn't all that difficult. The

ontological interpretation of the relationships between these patch

coefficients, OTOH, is IMHO pretty surreal.)

*> I think you're getting awfully speculative here.
*

This is a criticism, in *this* group in particular? ;-) It's

admittedly speculative.

*> It sounds like you are suggesting that it would be simpler to suppose
*

*> that "all universes exist which contain jinn" than "all universes
*

*> exist".
*

Not precisely; I'm suggesting that "simple" is difficult to measure

when speaking about TOEs. There might be some measures of "simple" for

which the above is true; there are others, e.g. the Champernowne

machine and so forth, for which it is certainly not. But Occam's Razor

isn't much help here by itself.

*> That doesn't seem at all plausble to me. My heuristic is that any rule
*

*> of the form "all universes exist except X" is going to be more
*

*> complicated
*

*> than one of the form "all universes exist".
*

On the surface, sure. But consider: the statement "all universes

exist" presupposes a definition of universe that it omits. What is

meant by "universe" requires an exhaustive definition, and the

algorithmic hypotheses make varying assumptions about that definition.

My intuition would be that the most parsimonious definition would be

the preferable one; but we don't have any metrics for "parsimony" on

such definitions. It could be that definitions that statically embed

such jinn might be more parsimonious by some measure than other ones;

the statically-defined jinn might "ground out" the definition and

permit a higher-order / more abstract / terser "universe generation

algorithm." (Think Python vs. its own bytecode.)

Think of it this way: any formal system has its base axioms. In this

context, the "universe generator" is the system in toto; the jinn

could form (at least a part of) its axioms. Or, thinking about it in

nonlinear dynamical terms, the jinn form the attractors which

"condense" permissible universes out of the space of all possible

universes. Or, thinking about programming languages: this works the

same way that e.g. code generation templates for various programming

language compilers (and the associated high-level language primitives

and syntax) define the space of permissible programs. This doesn't

restrict program behavior at a high order, but does prohibit the direct

expression of nonsensical things like 1/0. (Okay, the latter analogy

is stretching things pretty far... ;-)

To be clear about all of this, though: I'm not really proposing any

hypothesis here, more like musing out loud. :-)

jb

Received on Thu Aug 19 2004 - 17:20:56 PDT

Date: Thu, 19 Aug 2004 15:47:58 -0500

On Aug 19, 2004, at 2:00 PM, Hal Finney wrote:

+1

I'll have to think about the CA implications --- what is a "cell" in

such a CA, and what is meant by the various "nearness" relationships of

such cells? (I'm still processing Wolfram's book, a couple of years

after reading it the first time. ;-)

I'm just adopting a relatively conventional GR point-of-view here,

where time is just another direction, albeit one in which travel is (in

most circumstances, depending on the local differential geometry and

geometrodynamics) directionally constrained. (I'm ignoring the

thermodynamic interpretation of time's arrow, though when you throw 2LT

into this particular brew things would seem to get rather interesting.

;-)

We're begging the question re: causality; it was perhaps unfortunate

that I chose to use that word, as it's interpretive rather than

descriptive in itself. The argument Boulware's making appears to be

inherently probabilistic and geometric rather than ontological. That

became less clear in my exposition, my bad.

But do they? This is, I think, perhaps a very interesting and

pertinent question. It certainly appears to throw both the QM

formalism as well as its interpretations into disarray, but I think

perhaps the result is less than fatal. One can certainly do statistics

(and hence QM) with non-unitary probabilities --- the method involves a

kind of normalizing transformation between different probabilistic

measures. (In fact this very issue was dealt with by one of Gott's

grad students; the citation escapes me at the moment, but he found

that you could patch things up by simply supplying a kind of local

correction coefficient. I.e., while this appears prohibitive on the

surface, in fact "fixing it up" isn't all that difficult. The

ontological interpretation of the relationships between these patch

coefficients, OTOH, is IMHO pretty surreal.)

This is a criticism, in *this* group in particular? ;-) It's

admittedly speculative.

Not precisely; I'm suggesting that "simple" is difficult to measure

when speaking about TOEs. There might be some measures of "simple" for

which the above is true; there are others, e.g. the Champernowne

machine and so forth, for which it is certainly not. But Occam's Razor

isn't much help here by itself.

On the surface, sure. But consider: the statement "all universes

exist" presupposes a definition of universe that it omits. What is

meant by "universe" requires an exhaustive definition, and the

algorithmic hypotheses make varying assumptions about that definition.

My intuition would be that the most parsimonious definition would be

the preferable one; but we don't have any metrics for "parsimony" on

such definitions. It could be that definitions that statically embed

such jinn might be more parsimonious by some measure than other ones;

the statically-defined jinn might "ground out" the definition and

permit a higher-order / more abstract / terser "universe generation

algorithm." (Think Python vs. its own bytecode.)

Think of it this way: any formal system has its base axioms. In this

context, the "universe generator" is the system in toto; the jinn

could form (at least a part of) its axioms. Or, thinking about it in

nonlinear dynamical terms, the jinn form the attractors which

"condense" permissible universes out of the space of all possible

universes. Or, thinking about programming languages: this works the

same way that e.g. code generation templates for various programming

language compilers (and the associated high-level language primitives

and syntax) define the space of permissible programs. This doesn't

restrict program behavior at a high order, but does prohibit the direct

expression of nonsensical things like 1/0. (Okay, the latter analogy

is stretching things pretty far... ;-)

To be clear about all of this, though: I'm not really proposing any

hypothesis here, more like musing out loud. :-)

jb

Received on Thu Aug 19 2004 - 17:20:56 PDT

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