tag:blogger.com,1999:blog-8148573551417578681.post3560729184380212018..comments2024-07-30T16:59:56.776-07:00Comments on Dark Buzz: Superdeterminism does not Save LocalityRogerhttp://www.blogger.com/profile/03474078324293158376noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-8148573551417578681.post-41954208586552738472022-09-23T04:47:25.200-07:002022-09-23T04:47:25.200-07:00Ajit,
Roger is correct here to state that QM is l...Ajit,<br /><br />Roger is correct here to state that QM is local. The "nonlocality" of quantum states that you mention is simply that they contain correlations. One could similarly call classical probability distributions "nonlocal" when they are non-separable due to the presence of correlations.Curiousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-70009901297084221502022-09-14T10:39:44.608-07:002022-09-14T10:39:44.608-07:00Dear Roger,
> "Local quantum is what ever...Dear Roger,<br /><br />> "Local quantum is what everybody believes, and what the textbooks say. You only get nonlocality if you insist on pre-1925 classical mechanics."<br /><br />Well, see: https://physics.stackexchange.com/questions/367378/locality-in-qft-vs-non-local-in-qm <br /><br />States in QM are nonlocal. In the non-relativistic QM, evolution of states too is nonlocal --- the Hamiltonian operator used in the Schroedinger equation is nonlocal. However, in the relativistic QM (RQM), while states remain nonlocal, the Hamiltonian is local in the same sense in which the propagation of changes in the fields is a local process in the EM theory. <br /><br />As to the pre-QM theories, as I noted in my paper, the Fourier theory is nonlocal, and so is Newtonian gravity. However, interactions between particles of Newtonian mechanics are local, and so are the propagation of changes in the EM fields. There is no single, overarching, "classical" ontology to speak of. If you insist on using the word "classical" as if there were a single ontology to it all, you run into errors.<br /><br />In general, when it comes to RQM, the notion of locality has to be taken in a more technical / advanced sense --- it refers to measurement events, not to states. Further, though neither commenter at the above URL (Dr. Motl included) touched upon it, one must remember that states remain normalized even in RQM; the evolution has to be unitary; and this constraint has implications for the sense in which we can take the word "locality" in RQM. The notion of locality used in RQM (including in QFT) is not quite the same simple notion as that with which we can describe the interactions (the forces of the direct contact) in the Newtonian mechanics of particles.<br /><br />Hope this helps.<br /><br />Best,<br />--Ajit<br />Ajit R. Jadhavhttps://AjitJadhav.wordpress.comnoreply@blogger.com