On 15-05-2022 05:11, Brent Meeker wrote:
On 5/14/2022 3:55 PM, 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.
But it is more than "effectively" irreversible because decohering
information spreads at the speed of light, and in an expanding
universe cannot be captured and reversed. This why I think there is
some relation between the holographic principle, expansion of the
universe, Hawking-Bekenstien entropy, and a non-zero minimum
probability.
It's still only effectively irreversible because nothing stops one from
reflecting all the escaping photons back. If we use mirrors that are
cooled to almost absolute zero, then the leakage of information from the
interior that results from having carried out a spin measurement there
can be made arbitrarily small, so the probability that the information
escapes from the confined region can be made arbitrarily small. There is
no connection between our ability to observe something and the processes
involved in making sure the photons don't escape, so whether or not
there are actually these supercool mirrors reflecting all the photons
back to recreate the initial state cannot be relevant.
Saibal
Brent
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
Bruce is omitting something here,
perhaps some limits in which the time evolution operator becomes
degenerate or something like that. But a product of two unitary
transforms is a unitary transform, so the nth power of a unitary
transform is also a unitary transform. There is no ay you can get
anything non-unitary out of this, unless possibly in the limit of
n to
infinity.
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