scerir wrote: > Bruno Marchal: > > > In Bohm's theory there is no collapse of the wave. > > No collapse of the wave-function takes place upon measurement. > One must obtain, nevertheless, the "reduced" wave-function of the > system. Once a specific result has been obtained in a measurement, > only that term (of the global, universal superposition) counts. > This is a sort of "effective" or, better, "pragmatic" collapse.
This not quite the case. In the Bohmian interpretation the "collapse" is, in fact, determined by the non-local quantum potential pretty much as the outcome of a critical phase transition which suppresses all the branches of the superposition but the one that matches the measured outcome. This is indeed "effective" but hardly pragramatic. > > > So it is indeed as deterministic as Everett formulation of QM. > > Are they both non-local, at least in principle? I'm asking this > because, usually, I read that MWI is local, and that seems to me > very very strange, just because of the "split". I also read that > the Bohmian theory is non-local (though this original non-locality > is almost, but not entirely, suppressed by the general quantum > "equilibrium" condition). > The Bohmian Int. (in the post-51 version) is decidedly non-local and amounts to an alternative (hidden variable) theory with the same phenomenology as QM. The Everett Interpretation is just as non-local as QM with the peculiar distinction that it accommodates non-locality in its peculiar way, where the unconnected "locales" are made relative to the different branches of the wave function. It should perhaps be pointed out that a good number of advocates of Everett (David Albert anong them) are keen in not using the "Many-Worlds" ontology and insist on Everett's original "Relative Interpretation of the Wave Function" which makes a lot more sense in my opinion, as an interpretation of entanglement. > > Regards, > > s. Best -Joao -- Joao Pedro Leao ::: [EMAIL PROTECTED] Harvard-Smithsonian Center for Astrophysics 1815 Massachussetts Av. , Cambridge MA 02140 Work Phone: (617)-496-7990 extension 124 VoIP Phone: (617)=384-6679 Cell-Phone: (617)-817-1800 ---------------------------------------------- "All generalizations are abusive (specially this one!)" -------------------------------------------------------
