2009/5/14 ronaldheld <ronaldh...@gmail.com>:
> read Aixiv.org:0905.0624v1 (quant-ph) and see if you agree with it

This part at the end, proposing an empirical method of distinguishing
between MWI and single world interpretations and reminiscent of
quantum suicide experiments, is interesting:

"Finally, suppose, notwithstanding all the arguments above, that we
arrive at an Everettian theory that, while
perhaps ad hoc and unattractive, is coherent – for example, some
version of the many-minds interpretation[15]. It is
generally believed that, without very advanced technology which allows
the re-interference of macroscopically distinct
branches, such a theory will necessarily be empirically
indistinguishable from Copenhagen quantum theory.
The following argument against this conclusion relies on anthropic
reasoning and also on the hypothesis that species
may evolve a consistent preference for or against higher population
expectation over higher survival probability. An-
thropic reasoning is notoriously tricky to justify, and we may anyway
not necessarily have evolved demonstrable
consistent preferences one way or the other, so the argument may not
necessarily have practical application. Nonethe-
less, it does show in principle that evolutionary evidence could make
many-worlds theories more or less plausible.
Consider a simple model of two species A and B, both of which begin
with population P and are offered, each
year, the option of doing something that depends on a quantum event
and carries a 0.5 probability of extinction and
a 0.5 probability of trebling the species population. Suppose that, if
they reject the option, their population remains
constant, as it does in between these decisions. Species A is
risk-averse, and so always declines the option. Species B
is risk-tolerant, and instinctively driven to maximise expected
population, and so always accepts.
Now let N be a large integer. After N years, if one-world quantum
theory is correct, species A will have population
P, and species B will have either population 0 (with probability (1−(
2 )N)) or population 3N (with probability (
2 )N).
In other words, species B will almost surely be extinct. If these are
the only two species, and you are alive in the
N-th year, almost certainly you belong to species A.

If many-worlds quantum theory is correct, species A still has
population P in all branches. Species B has population
0 in branches of total Born weight (1 − ( 1
2 )N), and population 3N in branches of total Born weight ( 1
2 )N. Now, if
anthropic reasoning is justifiable here, and you are alive in the N-th
year, almost certainly you belong to species B.
(There are ( 3
2 )N times as many minds belonging to species B as to A after N years.)
In other words, there is a sense in which long-run evolutionary
success is defined by different measures in one-world
and many-worlds quantum theory. If anthropic reasoning were
justifiable, then one could in principle infer whether
one-world or many-worlds quantum theory is likelier correct by seeing
whether one belongs to a Born-weighted
expected population maximising species or to a risk-averse species
that seeks to maximise its Born-weighted survival
probability. Readers may thus wish to consider whether their species
has evolved a coherent strategy of either type."

Stathis Papaioannou

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