On 5/20/2018 3:47 AM, [email protected] wrote:
On Sunday, May 20, 2018 at 6:52:41 AM UTC, Brent wrote: On 5/19/2018 8:19 PM, [email protected] <javascript:> wrote:On Saturday, May 19, 2018 at 3:59:03 PM UTC, Brent wrote: On 5/18/2018 10:53 PM, [email protected] wrote:On Saturday, May 19, 2018 at 5:29:33 AM UTC, Brent wrote: On 5/18/2018 10:14 PM, [email protected] wrote:*So why don't you draw the obvious inference? If those other worlds don't exist -- which if I can read English has been your passionate position all along -- then quantum measurements in this world, the only world, are statistical and hence NOT reversible in principle. AG* but it is different in each branch of the wave function, so reversing this branch does nothing for the others, and does not restore the original superposition. Thus the process is irreversible in principle (nomologically irreversible -- to reverse violates the laws of physics). *But if those other worlds don't exist, it makes no sense whatever to rely on them to establish irreversible in principle in this world (as distinguished from statistically irreversible or irreversible FAPP). It seems you want to have it both ways; that many worlds really don't exist. but quantum measurements in this world are irreversible in principle due the existence of many worlds. AG*You don't handle uncertainty well, do you. Brent You know, it's not a perfect analogy, but I don't believe that when I pull the one arm bandit with 64 million possible outcomes, that 64 million (minus one) worlds are created, each with an identical copy of me, getting those other outcomes. What do you believe? AGI believe I'll wait for a better theory. One that includes gravity and spacetime and consciousness. Brent I see. But you seem too ready to defend the MWI when it appears to imply irreversible in principle. Or do you accept Bruce's claim that the projection operator implies irreversible in principle? AGEither of them implies irreversiblity. Whether it is "in principle" depends on what principle you invoke, mathematics, practice, ...? MWI puts information in orthogonal subspaces where we exist in copies such that each copy can act only in one subspace and hence cannot put together the information from other subspaces. A projection operator is just a mathematical model of this confinement to one subspace. BrentPlease; no evasive games. We can forget about the MWI, given its absurdity. Does, or does not the projection operator imply irreversibility in principle as Bruce claims? AG
Sure, a projection operator throws away information so its action is irreversible. If I project a star onto the celestial sphere I preserve its longitude and latitude, but it doesn't show how far away it is. That's why the MWI advocates say projection conflicts with all the rest of fundamental physics which is described by evolution that is at least reversible in the mathematical sense.
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