> Il 22 ottobre 2018 alle 23.20 [email protected] ha scritto: > > > > On Saturday, October 20, 2018 at 5:39:28 PM UTC, [email protected] > wrote: > > > > > > > > On Friday, October 19, 2018 at 9:08:47 PM UTC, Brent wrote: > > > > > > > > > > > > > On 10/19/2018 10:59 AM, [email protected] wrote: > > > > > > > > > > > > > > > > > > On Friday, October 19, 2018 at 5:44:10 PM UTC, Brent > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > On 10/19/2018 12:17 AM, [email protected] wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I can see how recoherence is impossible FAPP, but > > > > > > > after some time elapses the state of the cat could Dead or Alive; > > > > > > > not necessarily the original state, Alive. AG > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > When recoherence is no longer possible that's a real > > > > > > > > physical change. The system has evolved. > > > > > > > > > > > > > > > > > > > > > > > > > > Since decoherence is a unitary process, > > > > > > isn't recoherence always possible, even if not FAPP? AG > > > > > > > > > > > > > > > > > Sure. If you > > > > > > could reverse the outgoing waves and the local universe. > > > > > > > > > > > > > > > > > > Since recoherence is always possible, even if > > > > astronomically unlikely like many physical macro processes, why do you > > > > make the point that there's a real physical change when it's no longer > > > > possible (which is never)? I ask because your comment is confusing. AG > > > > > > > > > > > That's the real physical change. > > > > Outgoing radiation has left at the speed of light out into an expanding > > > > universe; it ain't comin' back. Why is that confusing? > > > > > > > > > > You seem to conflate two concepts; Irreversible FAPP, and > > Irreversible (aka Absolutely Irreversible, aka Irreversible in Principle). > > I tend to believe that every unitary process is either easily reversible, > > or irreversible FAPP (meaning possibly reversible even if hugely > > improbable). In the case of two closed containers attached to each other, > > one in vacuum state and the other filled with gas at some temperature, one > > can imagine all the gas in one container finally equalizing in both > > containers. That would occur in finite time, but is Irreversible FAPP. In > > your example above, one can imagine the outgoing photons bending around > > super dense masses and returning to their original positions or states. So > > I would say this outcome is Irreversible FAPP, but you say it's > > Irreversible, meaning Absolutely Irreversible or Irreversible in Principle. > > So which is it? AG > > > > The more interesting issue is whether the WF in the Cat experiment, > > or for an atom with a half life for decay, evolves in time while the box is > > closed. I say it must evolve because the probability amplitudes are time > > dependent. What say you? AG > > > > > > Seriously; if the wf for a radioactive atom evolves in time, why would > placing it in a box change that (or do I misunderstand what you and Bruce are > claiming)? AG >
The original 'cat' was, of course, Einstein's 'gunpowder' paradox. 'The system is a substance in chemically unstable equilibrium, perhaps a charge of gunpowder that, by means of intrinsic forces, can spontaneously combust, and where the average life span of the whole setup is a year. In principle this can quite easily be represented quantum-mechanically. In the beginning the psi-function characterizes a reasonably well-defined macroscopic state. But, according to your equation [i.e., the Schrödinger equation], after the course of a year this is no longer the case. Rather, the psi-function then describes a sort of blend of not-yet and already-exploded systems. Through no art of interpretation can this psi-function be turned into an adequate description of a real state of affairs; in reality there is no intermediary between exploded and not-exploded.' Letter from Einstein to Schrödinger, dated 8 August 1935. in Fine, A. The Shaky Game: Einstein, Realism, and the Quantum Theory, University of Chicago Press, Chicago (1986). Letter from Einstein to Schrödinger, dated 8 August 1935. > > > > > > > > > > > > > > Brent > > > > > > > > > > > > > > -- > 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] > mailto:[email protected] . > To post to this group, send email to [email protected] > mailto:[email protected] . > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > -- 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.
