Already, people like Omnes regard it as a non-problem because
decoherence diagonalizes the density matrix FAPP and so it can be
interpreted as being the same as a mixed state, which is how classical
probability is represented in QM. But others say FAPP isn't good enough
because (1) in principle it's reversible and (2) it doesn't answer the
problem of the Heisenberg cut. I think everyone agrees that if, within
QM, it can be shown that the density matrix is strictly diagonalized by
known dynamics - then that solves the measurement problem.
Brent
On 11/9/2017 6:13 PM, Alan Grayson wrote:
How would you define "the measurement problem" to conclude that
strictly diagonalizing the density matrix would be a solution? TIA
On Thu, Nov 9, 2017 at 2:45 PM, Brent Meeker <meeke...@verizon.net
<mailto:meeke...@verizon.net>> wrote:
The "measurement problem" isn't necessarily finding a
deterministic subquantum dynamics. If you could show that the
density matrix becomes strictly diagonal in some non-arbitrary way
(i.e. described by dynamics) and the eigenvalues obey the Born
rule (which I think would follow from Gleason's theorem) then I
think that would be a satisfactory solution. And in fact I think
Zurek has provided most of that except for the details of the
dynamic description. He relies on decoherence which produces
multiple copies of the measurement result in the environment and
he argues that the density matrix must be strictly diagonal in
order that repeating a measurement yields a repeat of the result.
Given that much then you can either suppose this defines the
splitting into multiple worlds OR, following Omnes, you can say
the theory predicts probabilities and one of them is
realized...which is all you can expect of a probabilistic theory.
Brent
On 11/9/2017 12:01 PM, agrayson2...@gmail.com
<mailto:agrayson2...@gmail.com> wrote:
If what you state is correct, then there's no solution to the
measurement problem (if that means discovering a deterministic
outcome for individual trials). Why then is the "measurement
problem" still considered a problem to be solved? What you've
presented is more or less proof that no such solution exists.
On Thursday, November 9, 2017 at 11:27:26 AM UTC-7, Brent wrote:
It would make it possible to use EPR like experiments to send
signals faster than light...which is to say backward in
time. That would pretty much screw up all known
physics...and common sense.
Brent
On 11/9/2017 7:43 AM, agrays...@gmail.com wrote:
If the measurement problem were solved in the sense being
able to predict exact outcomes, thus making QM a
deterministic theory, would that imply an INCONSISTENCY in
the postulates of QM? TIA.
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