On 5/15/2022 12:11 AM, smitra wrote:
On 15-05-2022 00:55, Bruce Kellett wrote:
On Sun, May 15, 2022 at 1:17 AM smitra <smi...@zonnet.nl> wrote:
On 13-05-2022 21:59, Brent Meeker wrote:
Right CI doesn't explain the collapse and MWI doesn't explain the
collapse either but assumes it can be explained without new
physics.
I hypothesize (not assume) that CI+ <non-zero minimum probability>
can
explain the collapse. I don't see any big advantage for MWI here.
The big advantage is that decoherence is a well researched area of
(mathematical) physics, results like the density matrix becoming
approximately diagonal, and relations between decoherence to entropy
increase making it effectively irreversible are all rigorous results
that are uncontroversial. People may still have objections against
the
MWI, but they'll still accept these results on decoherence.
Yes. And decoherence says that with time, the off-diagonal elements of
the density matrix become arbitrarily small. If there is a smallest
non-zero probability, then eventually these off-diagonal elements
become zero. This reduces the pure state to a mixture. Which is to say
that there is a collapse; unitary evolution ceases, and we have
reached a classical world.
Non-zero minimum probability on its own, however, does not cause a
system to evolve in a non-unitary way.
It does when decoherence is taken into account. See the above
explanation. Bruce has not omitted anything.
Bruce
I see, but these sorts of models can already be ruled out. There are
plenty of simple systems where one can make extremely accurate
measurements on which can be kept totally isolated and quantum
coherent for long enough where such effects would have become visible.
If it's isolated the probability amplitudes are not changing so a
non-zero minimum probability would have no consequence. You're thinking
of experiments to refute spontaneous collapse theories; but I don't know
that any have been done. GRW chose the parameters so the system has to
be quite big in order to observe spontaneous collapse in reasonable
isolation period.
Brent
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