I remember some issue surrounding this. I do not remember the way it was resolved, but I do recall that Hobson was considered wrong.
LC On Saturday, October 29, 2022 at 8:04:35 PM UTC-5 [email protected] wrote: > > > On 10/29/2022 6:29 AM, Lawrence Crowell wrote: > > On Friday, October 28, 2022 at 10:55:50 PM UTC-5 Bruce wrote: > >> On Sat, Oct 29, 2022 at 1:42 PM Brent Meeker <[email protected]> wrote: >> >>> >>> On 10/28/2022 6:43 PM, Bruce Kellett wrote: >>> >>> Look, "ad hoc" is frequently bandied about as a fatal flaw in any >>> theory. Just as Putin waves about the nuclear threat: this is just to >>> intimidate the opposition, it doesn't mean anything more. Any theory has ad >>> hoc elements, or else it would not be of any value in explaining our >>> experience. There is always a theoretical part, and then a collection of >>> elements that serve to relate the theory to observation. Everything is >>> ultimately ad hoc, because it is for the particular purpose of explaining >>> observation. >>> >>> >>> I think you've stretched it's meaning beyond recognition. If every >>> theory that is devised to match experiment is ad hoc then indeed all >>> science is ad hoc...and the better for it. But there is real ad hockery >>> that is deserving of criticism. >>> >>> The real question on the table is what would you take to be not ad hoc; >>> what would be better than "... measurement is then not treated in terms of >>> the fundamental dynamics of the theory." Do you see MWI doing this? >>> >> >> No. MWI takes unitary dynamics of the Schrodinger equation to be >> fundamental. But unitary dynamics and the SE are deterministic, and >> incompatible with a probabilistic interpretation. So MWI is not going to be >> able to give a completely satisfactory account of measurement since the >> outcomes of measurement are inherently probabilistic. So whatever you do in >> MWI, measurement is not treated in terms of the fundamental dynamics of the >> theory; there is always some ad hoc element required to make contact with >> experiment. In that context MWI, is simply engaging in a double standard >> when it criticizes collapse theories as ad hoc. >> >> Bruce >> > > Quantum mechanics deals with the evolution of probability amplitudes a_i > and probabilities are p_i = |a_i|^2. The probabilities are the trace of the > density matrix and the density matrix by the Schrodinger equation is dρ/dt > = [H, ρ], and this describes the evolution of probabilities. With an actual > outcome the probabilities are no longer applicable due to there being only > one outcome. > > LC > > > Art Hobson has a series of papers on the "measurement problem" in which he > argues that past analyses, by von Neumann and others, incorrectly ignore > non-local entanglement in going from the density matrix of the > system+instrument to the diagonalized system+instrument representing a > mixture. And when this is correctly accounted for he says the non-local > entanglement causes the measured value (which is random per Born) to be a > unique realization of the eigenvector...no multiple worlds. > > SUMMARY AND CONCLUSION > Using only the standard principles of quantum physics, but minus the > collapse postulate, we have shown that quantum state collapse occurs as a > consequence of the entanglement that occurs upon measurement as described > in > 1932 by von Neumann (Equation (4)). The entangled "measurement state" of a > quantum system and its detector is the collapsed state: It incorporates > the required > perfect correlations between the system and its detector, it predicts > precisely one > definite outcome, and it incorporates the nonlocal properties--the > instantaneous > collapse across all branches of the superposition--that Einstein showed to > be > required in quantum measurements > > See attached. > > 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/22de4eaa-94a7-4d2a-99f0-a09cba1634cbn%40googlegroups.com.
