On Wednesday, May 2, 2018 at 6:01:28 PM UTC, Brent wrote: > > > > On 5/2/2018 4:48 AM, [email protected] <javascript:> wrote: > > > > On Monday, April 30, 2018 at 3:33:23 AM UTC, [email protected] 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 >
In MWI and CI we have projection operators, aka in CI as collapse. Aren't they all non unitary regardless of the interpretation, implying IIUC, that they can't be time-reversed. AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
