Re: many worlds interpretation

From: Wei Dai <weidai.domain.name.hidden>
Date: Fri, 20 Feb 1998 13:29:54 -0800

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

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

Let me try to summarize MWI:

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

2. The UWF can be approximated as many worlds.

3. If physical reality was many worlds, then we would expect to see what
we see.

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

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

> 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
> independently of each other.

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

I know there are some real experts on the MWI on this list. Please let me
know if I'm on the right track.
Received on Fri Feb 20 1998 - 13:31:35 PST