From: Damien Broderick (thespike@earthlink.net)
Date: Thu Feb 13 2003 - 15:24:37 MST
Serafino says:
[Me trimming desperately:]
> Yes, maybe there are many different MWI.
>
> I.e. there is one MWI assuming that quantum objects, detectors,
> observers, etc., are simply *split* between the various branches.
> There is another MWI assuming that particles, observers, and instruments,
> are *multiplied*.
> > Tegmark argues that universes join as well as branch. We may have
> > multiple pasts as well as multiple futures.
>
> Yes, this seems similar to Feynman paths.
Around this point my brain usually makes a clicking sound and reboots. I
*think* I can see what's going on (yes, like everyone here I've read
*Q.E.D.*) until I try to correlate it all. Just to take one simple point:
The Feynman account of least action is (so to speak) that every action
occurs multiply and simultaneously, with destructive and constructive
interference obliterating the less likely or more energy-hungry trajectories
and reinforcing the least-energy path.
I've never understood what exactly is meant to be doing all this
interference (the wave aspect of the quantum universe, apparently, whatever
that means), or virtual particles, or handwaving in Hilbert space, but once
we move to a MWI *there's no way the superposed alternatives can all be
REAL*.
In olde worlde quantum physics, they weren't kinda really real to start
with; what is real, what is concretized and instantiated, is their
compounded and mutual interaction. (Right?) In Copenhagen, there is only one
Real World; the many worlds blur together like many photographs of faces to
form the One Common True Bland Face of Reality. In Deutschean MW, `shadow'
particles from all the adjacent worlds somehow mess with trajectories of
measurable, detectable particles.
But wait! Here's this great swathe of possible paths, all of them taken,
each of them the trajectory native to its own idiosyncratic world--but what
*we* *here* experience is (almost) always that one goddam minimal action
path. This looks wildly inconsistent with MW to me. (Of course it might be
that in the MW manifold there is an a priori high p value for the least
action path, so any observer is almost always in such a world--but that just
establishes by fiat what is meant to be explained.
Any takers?
Damien Broderick
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