On Wed, Aug 1, 2018 at 1:39 PM Brent Meeker <[email protected]> wrote:
> > > On 8/1/2018 3:51 AM, Bruno Marchal wrote: > > > On 31 Jul 2018, at 21:46, Brent Meeker <[email protected]> wrote: > > > > On 7/31/2018 9:11 AM, Bruno Marchal wrote: > > > On 30 Jul 2018, at 22:27, Brent Meeker <[email protected]> wrote: > > > > On 7/30/2018 9:58 AM, John Clark wrote: > > >> > >> *Forget collapse.* > > Many, perhaps most, physicists do exactly that because they believe in the > "Shut Up And Calculate" quantum interpretation and are only interested in > predicting how far to the right a indicator needle on a meter moves in a > particular experiment. But for some of us that feels unsatisfying and would > like to have a deeper understanding about what's going on at the quantum > level and wonder why there is nothing in the mathematics that says anything > about a wave collapsing. > > > That's not true. "The mathematics" originally included the Born rule as > part of the axiomatic structure of QM. > > > In the usual QM, yes. But this use a vague notion of observer, and a > seemingly forbidden process, a projection (a Kestrel!), I mean forbidden if > we apply the wave to the couple observer-particle. > > > > > Most of all they want to know what exactly is a "measurement" and why it > so mysterious. > > > The problem with the Born rule was that its application was ambiguous: > > > Ah! Exactly. > > > > Where was the Heisenberg cut? Why was "the needle basis" preferred? But > decoherence theory has given answers (at least partially) to those > questions. Given those answers, one can just replace "collapse" with > "discard", i.e. discard all the predicted possible results except the one > observed. Is there really any difference between saying those other > predictions of the wf are in orthogonal, inaccessible "worlds" and saying > they just didn't happen. That seems to be Omnes approach. He writes, > "Quantum mechanics is a probabilistic theory, so it only predicts > probabilities.” > > > > OK, but the honest, and perhaps naive inquirer would like to have an idea > about what are those probabilities about, and where they come from. > > > That was the source of resistance to Born's paper. Physicists assumed > that probability could only arise from ignorance of an ensemble. Since > there was no ensemble in Heisenberg's (or Schroedinger's) QM they resisted > the idea. Lots of attempts were made to reintroduce ensembles, or at least > virtual ensembles, so that they could feel comfortable with having a > probabilistic theory. Omnes' is just saying "Get over it!"; probabilities > are fundamental. > > > > Yes, but he said all this after defending Everett (or its own better > version of Everett). Then, this introduces a notion of ensemble (the set of > all consistent histories), and, at least in some book, just ask us to be > irrational and to dismiss the ensemble at make probability fundamental, > only to make the “other worlds” disappear. In one book he lakes clear that > such a decision is irrational, and that he makes it because he dislike of > find shocking the idea that all quantum possible outcome are realised. It > is a bit like a christian who understand the evolution theory, but add that > it makes just God having invented evolution instead of Adam. > > > > There's nothing irrational about discarding that which is not observed and > keeping that which is observed. > It is irrational if it results in a significantly more complex, ad hoc, or nonsensical theory. Jason > That's what probability means: somethings happen and some don't. The idea > that all the possibilities happen is what has made MWI incoherent. > Gleason's theorem supports the use of the Born rule to define a probability > measure; but the problem is the metaphysical one of whether there is any > meaning to "probability" when everything happens. > > > > > > Everett's MWI is appealing to the same intuition...that probabilities must > refer to ensembles. > > > Wich in my opinion is the only way to make sense of any notion of > probabilities. You need a space or set of events too which the > probabilities applies. > > > But it must be an ensemble from which somethings happen and some don't. > > > > > So the ensemble will be multiple-worlds. But that didn't really work > because Schroedinger's equation didn't predict multiple worlds with the > right ratios, it just gave real number probabilities. So people like Bohm > and Bruno invented infinite ensembles to explain the probability numbers. > Which is OK, but one should recognize that they are *not *just > explicating Schroedinger's equation. > > > There is no probabilities at all in the schroedinger equation. But then > that equation describes also a vast set of relative state describing > indexical probabilities. > > > No, it doesn't describe "indexical probabilities". That's why Born had to > come up with an interpretative rule in order that there be a relation > between the wf and observations. > > It is really similar to the WM-duplication. From the 3p perspective, there > is no probabilities at all, but the duplication (and mechanism) explains > entirely why all first person concerned (having done the self-duplication) > encounter probabilities. Somehow, Shannon entropy, or Botzmann, use > something similar. > > > Or QBism. > > 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. > -- 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.
