On 12/12/2017 10:55 pm, Bruno Marchal wrote:
On 12 Dec 2017, at 11:14, Bruce Kellett wrote:
On 12/12/2017 8:26 pm, Bruno Marchal wrote:
On 12 Dec 2017, at 02:02, Bruce Kellett wrote:
On 12/12/2017 11:44 am, smitra wrote:
On 11-12-2017 23:15, Bruce Kellett wrote:
On 12/12/2017 1:12 am, Bruno Marchal wrote:
On 10 Dec 2017, at 23:38, Bruce Kellett wrote:
On 11/12/2017 2:19 am, Bruno Marchal wrote:
On 09 Dec 2017, at 00:03, Bruce Kellett wrote:
On 9/12/2017 4:21 am, Bruno Marchal wrote:
Similarly, a shroedinger car, once alive + dead, will never
become a pure alive, or dead cat. It will only seems so for
anyone looking at the cat, in the {alive, dead} base/apparatus.
Superposition never disappear, and a coin moree or less with a
precise position, is always a superposition of a coin with more
or less precise momenta. The relation is given by the Fourier
transforms, which gives the relative accessible states/worlds.
I pointed out that for a macroscopic object such as a coin, the
uncertainty relations give uncertainties in positions and/or
momentum far below any level of possible detection.
Of possible practical detection. That is good FAPP, but
irrelevant
for theoretical consideration.
This is a purely rhetorical objection, Bruno. And when you trot
this out, as you do regularly, I know that your purpose is to
obfuscate, and hide the fact that you have no rational argument to
offer.
You confuse physics and metaphysics. The difference is not
rhetorical, but fundamental in this thread.
Rubbish. The central point of contention on this thread is whether a
coin toss can be regarded as a classical event, with probabilities
given by ignorance of the initial conditions, or as a quantum event
with probabilities given by purely quantum uncertainties.
This is a straightforward question of physics, and has nothing to do
with metaphysics. As usual, you introduce the term 'metaphysics'
merely to obfuscate, because you have no intelligent response to the
clear physics of the situation.
That the probabilities are given by classical physics does not imply
that there is no branching due to the coin toss.
It does, because there is no superposition of head/tails -- no
possibility of interference between heads and tails.
You are begging the question. The point was that without collapse,
the shaking of the dice or coin can make the superposition of the
positions (inherent in the Heisenberg uncertainty) can add up to
make the coin behaving sufficiently differently to obtain a
superposition of the head+tail or 1+2+...+6 superposition.
No, shaking the coin cannot make non-coherent uncertainties add up to
anything. The physics is against you here, Bruno. There is no
superposition, and no splitting of worlds on the toss. If you think
different, prove it.
Just to be sure, do you agree that without collapse, the schroedinger
cat remains in the state alive+dead, even after observation, and we
see it alive OR dead, just by the first-person mechanist indeterminacy
(or something akin to it) ?
The superposition exists in the original quantum state -- essentially
the radioactive nucleus which is a quantum system in a superposition of
decayed/not-decayed. Because of the experimental set up, this
superposition is amplified so that it becomes entangled with the
environment, including the cat and us. So:
|nucleus>|box>|cat>|observer>|rest of the world> --> (by unitary
evolution)
{|decayed>|poison spilt>|cat dead>|see dead cat>|rest of world
confirms dead cat> +
|not decayed>|poison bottle intact>|cat alive>|see live cat>|rest of
world confirms live cat>}
And the decoherence of the quantum phases into the |rest of the world>
environmental states diagonalizes the density matrix FAPP. If you
insist, the superposition is intact in the bird view, but such a
superposition can never recohere, and there are NO consequences of the
existence of other branches, practical or otherwise. Maintaining their
existence might satisfy your existential angst, but it has nothing to do
with physics or experience.
Also, how could the quantum uncertainties becoming non-coherent?
Decoherence, without collapse is something relative to the environment
when its get itself entangled with the superposition of the object
observed. The splitting of worlds is not due to the toss, but to the
fact that the position of the coin diffuse, which means get different
in the multiverse. Instead of shaking the box, waiting long enough
would work as well.
The coin case is different in an essential way -- it does not start from
a single quantum state that can be expanded into {|heads> + |tails>} by
any single quantum event. The system starts off decohered and
non-coherent. So just as you can never bring the two branches of the cat
back together, you can never take an initially decohered state and
reconstruct some imagined coherent superposition, unitary evolution and
the laws of thermodynamics forbid it. There is no part of the multiverse
in which such a superposed {|heads> + |tails>} state exists, it never
did and it never will.
Bruce
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