On 8/1/2018 3:46 PM, Jason Resch wrote:
On Wed, Aug 1, 2018 at 1:39 PM Brent Meeker <[email protected] <mailto:[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.It is irrational if it results in a significantly more complex, ad hoc, or nonsensical theory.
So it's irrational if it postulates infinitely many unobservable worlds. Nothing is more sensible than discarding that which is unobservable.
See, I can be just as snarky as you. 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.
