On 10/13/2019 9:10 PM, Alan Grayson wrote:
On Sunday, October 13, 2019 at 5:50:35 PM UTC-6, Brent wrote:
On 10/13/2019 1:08 PM, Alan Grayson wrote:
> What are YOU talking about? I just made a GUESS about the
decoherence
> time! Whatever it is, it doesn't change my conclusion. If there's a
> uncertainty in time, are you claiming the cat can be alive and dead
> during any duration? Is this what decoherence theory offers? AG
Yes, part of the cat can be alive and part dead over a period
seconds.
Or looked at another way, there is a transistion period in which
the cat
is both alive and dead.
But the main point is that this time had nothing to do with
Schroedinger's argument (he knew perfectly well the time of death was
vague); his argument was that Bohr's interpretation implied that
the cat
was in a super-position of alive and dead from the time the box was
closed until someone looked in.
Brent
Agreed. Without decoherence, the cat would be in a superposition of
alive and dead from the time the box was closed until someone opened
it. With decoherence, it would be in that superposition for a very short
time, the decoherence time, when it would be in state, |decayed>|dead>
or |undecayed> |alive> before the box was opened, provided it was
opened after the decoherence time. So, as I see it, decoherence just
moves the "collapse" earlier, before the box is opened, and does not
resolve S's problem with superposition.
True, but it resolves the problem about whether conscious observers are
necessary to "collapse" the wave function (or split the world). The idea
of decoherence is that, it not carefully isolated, systems are
continuously "monitored" by the environment and so act classically.
Here's a good analysis which casts the Schroedinger cat story into a
double slit-experiment.
https://arxiv.org/pdf/1405.7612.pdf
The cause of the problem, or
paradox if you will, is the superposition interpretation of the
radioactive
source. AG
Yes, that's the problem. The radioactive nucleus is effectively
isolated until it decays, after which it is not isolated...it has
interacted with the detector. So in the MWI the system is splitting
continuously into the branch were the atom hasn't decayed and the branch
where is has just decayed and interacted with the environment. The atom
is in a superposition of decayed and not decayed with amplitudes varying
in time: psi = sqrt[exp(-at)]|not decayed> +sqrt[1-expt(-at)]|decayed> .
Brent
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