On 5/2/2018 4:48 AM, agrayson2...@gmail.com wrote:
On Monday, April 30, 2018 at 3:33:23 AM UTC, agrays...@gmail.com wrote:
Implied by standard QM insofar as the theory is inherently
irreversible, that is, irreversible in principle at the quantum
level since the wf cannot be recovered by time reversal. AG
I argued this conclusion on the Entanglement thread. Here I will add
some additional considerations. When you think of time reversibility,
say for an electron being measured by SG device, you naturally think
of passing the measured electron backward along the same path, trying
to recover the original wf by running time backward. Of course you
can't run time backward during or even after a measurement because QM
doesn't provide any time dependent equations for the measurement
process. But even if you could do the thought experiment, according to
QM, if the measurement was, say, spin UP, it remains spin UP by virtue
of the measurement postulates of QM. Further, This MUST be the
backward in time measurement result if you simply accept time
symmetry, and not appeal to the measurement postulates of QM. Thus, it
seems highly plausible that the original wf, a superposition, cannot
be recovered after the measurement, and that QM is a time IRREVERSIBLE
theory. AG
In MWI the is both a spin UP and a spin DOWN, as projections on
orthogonal subspaces. The theory is mathematically reversible in the
sense that if you reversed the evolution of the state vector it would
reverse the projection in both subspaces.
Brent
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