On Sunday, May 20, 2018 at 9:13:42 PM UTC, Brent wrote: > > > > On 5/20/2018 1:44 PM, [email protected] <javascript:> wrote: > > > > On Sunday, May 20, 2018 at 7:29:42 PM UTC, Brent wrote: >> >> >> >> 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] 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? AG >>>> >>>> >>>> I 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? AG >>> >>> >>> Either 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. >>> >>> Brent >>> >> >> Please; 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. >> >> Brent >> > > But how do you know that the projection operator represents an actual > physical process? It could be just a bookkeeping device to describe the > fact that when many possible outcomes are possible, we get a particular > outcome. > > > Exactly. The quantum Bayesian take this view >
How does "Baysian" fit into this picture? Can't one interpret the SWE as a representation of what we know about a system, without being a Baysian? AG > and consider Schroedinger's equation also as a personal book keeping > device of what one knows about a system and then the Born rule and > projection operators fit neatly into the scheme of updating one's personal > knowledge. > I would delete "personal" from your comment. We're referring to the knowledge of any observer. AG > > ISTM, that to argue for "irreversible in principle", it is insufficient to > appeal solely to the properties of the projection operator. AG > > Exactly what led to Everett, MWI, and decoherence theory. But at the > price of having multiple, orthogonal "worlds" to explain the appearance of > randomness. Of course some people hate randomness and are quite happy to > have multiple worlds instead. > Looks like I am in the decoherence camp; namely, that when a quantum measurement occurs, entanglements with reservoir states somehow suppresses all outcomes but one, and the process is statistically irreversible (irreversible FAPP) since all entanglements are reversible (or do they run amok of Bell's theorem?). I can't prove it of course, but it seems like the most sober, conservative assumption given the choices. What I object to about Bruce's approach, is that he simply claims "irreversible in principle" based on the projection operator, and won't admit it's just his opinion, or else make a real effort to argue it. It's like he now sees himself as the *Oracle from Australia*. AG > > 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]. 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.
