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 With an actual outcome the probabilities are no longer applicable due to there being only one outcome.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 -- 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/ee388ec8-49fa-42e2-858e-a5d179c6ac44n%40googlegroups.com.
