On Wednesday, February 12, 2020 at 5:09:45 AM UTC-7, Alan Grayson wrote: > > > > On Wednesday, February 12, 2020 at 3:49:53 AM UTC-7, Bruce wrote: >> >> On Wed, Feb 12, 2020 at 9:32 PM Alan Grayson <[email protected]> wrote: >> >>> On Tuesday, February 11, 2020 at 12:44:38 PM UTC-7, Brent wrote: >>>> >>>> >>>> >>>> I think decoherence theory is a big step forward in describing the >>>> quantum->classical emergence. It was also a step forward in solving the >>>> measurment problem. But it has still left gaps. It shows how the density >>>> matrix becomes diagonalized in a measurement process. BUT only FAPP. And >>>> it doesn't explain why only one diagonal value is realized (MWI wants to >>>> keep them all) or the Born rule. I'm presently reading Ruth Kastner's >>>> book >>>> on the "Possibilist Transactional Interpretation" which is her version of >>>> Cramer's TI. Her basic idea, which could be applied to MW as well as TI, >>>> is that all the mathematical evolution takes place in possibility space, >>>> which is just as real as Hilbert space or wave-functions...but not as real >>>> as spacetime, and then one result, at random (and she justifies the Born >>>> rule) is actualized (which is a step better than realized). >>>> Metaphysically >>>> it is like MWI in practice, you calculate what happens in the many worlds >>>> and then you throw all but one away. The main difference is PTI depends >>>> on >>>> the idea of absorbers to define when a measurement is completed. The >>>> absorbers in a measurement are like the environment in decoherence, but >>>> there are also particle level absorbers...which I haven't finished reading >>>> about yet. >>>> >>>> Brent >>>> >>> >>> You (and Bruce) are on the same page wrt unitary time evolution for the >>> measurement process; namely, that it's violated. OTOH, you (and Bruce) like >>> decoherence theory. According to Wiki, when the environment is included in >>> the measurement process, the total process satisfies unitary time >>> evolution, whereas the total process excluding the environment creates just >>> the appearance of violating unitary time evolution. Is this your >>> assessment; that unitary time evolution in the measurement process is >>> satisfied when the environment is taken into account? TIA, AG >>> >> >> Decoherence is unitary interaction with the environment. That is not the >> problem. The thing is that that isn't a complete solution of the >> measurement problem. >> > > Right. Decoherence theory doesn't tell us what will be measured, which I > assume is the complete solution of the measurement problem. AG >
If the complete solution to the measurement problem is what I stated above, this would transform a probabilistic theory into a deterministic one. I vaguely recall that this has an implication, making it impossible. I can't recall what the issue is -- maybe a violation of the HUP, or the existence of a hidden variable, or something devastating. To best of your knowledge, is my vague recollection correct? TIA, AG > >> The difficulty I am pointing to is somewhat different. It is clear that >> unitary evolution based on the Schrodinger equation cannot account for >> scientific observations. Unitarity is not really the problem. The problem >> is that unitary evolution can give only one brach or world for each basis >> state in the superposition. This rules out any application of the Born rule. >> > > ISTM, that the only way we know that Born's rule is valid, is to take an > ensemble of outcomes and compare them with the predictions of the rule. Why > can't we do this in the context of many branches; just create an ensemble > of measurements in this world, and see that the result is what Born's rule > predicts? I mean just ignore the hypothetical measurements in the other > branches, which we cannot in principle observe anyway. AG > >> >> Bruce >> > -- 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/7a0f9410-963a-4282-b2d9-33a35de5f106%40googlegroups.com.
