> On 1 Aug 2018, at 20:39, 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] >>> <mailto:[email protected]>> wrote: >>> >>> >>> >>> On 7/31/2018 9:11 AM, Bruno Marchal wrote: >>>> >>>>> On 30 Jul 2018, at 22:27, Brent Meeker <[email protected] >>>>> <mailto:[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. That's what probability means: somethings > happen and some don't.
I agree. We do that automatically in dreams too. That does not mean that what we observe is the real thing. It can be a shadow of something else, or an hallucination. > The idea that all the possibilities happen is what has made MWI incoherent. The MW does not entail that all possibilities happen. > 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. Even if everything happen, each thing could be weighted differently. QM do predict that if you jump out of the window, there is a high probability you get badly wounded. That is why we have probabilities, and why we are concerned about what the probabilities can be applied. > > >> >> >> >>> 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. Not necessarily. The WM-duplication, like Everett QM, illustrates that sometimes two events can be realised from a third person pod, yet only one event is realised from the observer’s pov, and that brings back a notion of first person indeterminacy, and notions of local probabilities, credibilities, plausibilities, etc. > >> >> >> >>> 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. OK. I should ahem said “amplitude of probability”. But they are related to the indexical probability through the act of measurement. Then Gleason theorem makes this more precise, and unique. > >> 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. Eventually, it is plausibly only 2+2=4, or KKK=K. Necessarily so if mechanism is true. We have plenty evidences for mechanism (from biology, physics, mathematics, etc.). But there is no evidence at all for Matter. Only a discrepancy between physics and machine self-reference would give such an evidence, but there are no discrepancies discovered yet. Matter is a preprogrammed fiction to simplify our choice between preys and predators, but it does not work for the details of the physics of matter especially when taking into account consciousness and the 1p/3p distinction. Physicalism simply does not work when we assume mechanism. Bruno > > 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 > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <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.
