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From: Mitchell Porter <mitch.domain.name.hidden>

Date: Sat, 21 Feb 1998 18:33:32 +1000 (EST)

WD:

*> On Fri, Feb 20, 1998 at 09:16:12PM +1000, Mitchell Porter wrote:
*

*> > But in that case 'world' can't be a fundamental concept, in the way
*

*> > that many-worlds would have it. The essence of many-worlds, I thought,
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*> > was that *there are many worlds*, and we-here exist in one of them;
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*> > and the substance of the theory should lie in making these concepts
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*> > precise. But if the concept of world can't be given a crisp,
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*> > nonapproximate (i.e. nonarbitrary) definition, then I can't see
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*> > what use it has in this context.
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*>
*

*> No, I think the essence of many-worlds is that there is no collapse, and
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*> that the UWF can be approximated as many worlds. The use, again, is as an
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*> intuition and computation aid. The problem with no collapse seems to be
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*> that the UWF quickly becomes very complex as it evolves. It's easier to
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*> think of it as a many independent, non-interfering worlds, even though
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*> that is only an approximation. In theory we don't really need the "world"
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*> concept. If we had enough computational resources we should be able to
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*> make predictions directly from the UWF without reference to worlds.
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*>
*

*> Let me try to summarize MWI:
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*>
*

*> 1. Physical reality is the UWF evolving according to the Schroedinger
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*> equation with no collapse.
*

*>
*

*> 2. The UWF can be approximated as many worlds.
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*>
*

*> 3. If physical reality was many worlds, then we would expect to see what
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*> we see.
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*>
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*> 4. If physical reality was the UWF, then we would also expect to see what
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*> we see (because of 2 and 3).
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*>
*

*> The reason we need "worlds" is to be able to derive 4, even though 1 and 4
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*> are what really matters, and they don't mention "worlds".
*

Aren't we-here supposed to be part of a world? But how can we

be part of an approximation? Is there no *exact* concept of 'world' about

which one can say, not just 'it's an approximation', but 'it's real'?

*> > In that case, they won't affect each other at all, thanks to the
*

*> > linearity of the Schroedinger equation. c_0 and c_1 will evolve
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*> > independently of each other.
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*>
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*> Yes, they evolve independently, but they still "affect" each other in the
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*> sense that they interfere (minimally) with each other. (BTW, I think you
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*> mean PSI_0 and PSI_1, since c_0 and c_1 are fixed coefficients.)
*

Yes, my last statement was a silly one, although true - they will "evolve"

by not changing! But in the specific case we are discussing, I don't see

how you can defend the claim that they affect each other. Your

mathematical criterion may possibly measure some form of correlation,

but that's a non-causal relation between worlds, and one having no

impact at all on their individual evolutions.

*> I know there are some real experts on the MWI on this list. Please let me
*

*> know if I'm on the right track.
*

-mitch

http://www.thehub.com.au/~mitch

Received on Sat Feb 21 1998 - 00:34:04 PST

Date: Sat, 21 Feb 1998 18:33:32 +1000 (EST)

WD:

Aren't we-here supposed to be part of a world? But how can we

be part of an approximation? Is there no *exact* concept of 'world' about

which one can say, not just 'it's an approximation', but 'it's real'?

Yes, my last statement was a silly one, although true - they will "evolve"

by not changing! But in the specific case we are discussing, I don't see

how you can defend the claim that they affect each other. Your

mathematical criterion may possibly measure some form of correlation,

but that's a non-causal relation between worlds, and one having no

impact at all on their individual evolutions.

-mitch

http://www.thehub.com.au/~mitch

Received on Sat Feb 21 1998 - 00:34:04 PST

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