I stipulate that nearly anything can be a consequence of MWI, but not with equal probability.
Note that MWI postulates unitary evolution of the wave function, and in unitary evolution there are no probabilities, everything is completely deterministic, no exceptions. None. Let it sink in:
NO PROBABILITIES. PURE DETERMINISM OF THE WAVE FUNCTION EVOLUTION
There have been numerous attempts to saddle this unitary evolution with something extra that would give us the empirically observed probabilities. Everett suggested some in his PhD, many others did, with marginal success. The only statement nearly everyone is on board with is that, if we were to look for a way to assign probabilities, the Born rule is the only sensible one. In that sense, the Born rule is not an arbitrary one, but a unique way to map wave function to probability. The need to get probabilities from the unitary evolution of the wave function is not built into the MWI, but is grafted on it by the need to connect this theory with observations, exactly like the Born rule in the Copenhagen interpretation was.
That said, we might be on the cusp of something super mega extra interesting observed in the next few years, much more so than the recent black hole doughnut seen by the EHT: Measuring gravitational field from Schrodinger cat-like objects. There are no definite predictions on what we will see in this case, because QM and general relativity currently do not mix, and this is what makes it so exciting. I have mentioned it in a blog post discussing how MWI emerges from unitary evolution:
I’m still not entirely clear what you mean by “MWI proves too much”.
If I try to translate this into simpler terms, I get something like: MWI only matches our observations if we apply the Born rule, but it doesn’t motivate the Born rule. So there are many sets of observations that would be compatible with MWI, which means P(data | MWI) is low and that in turn means we can’t update very much on P(MWI | data).
Is that approximately what you’re getting at?
(That would be a nonstandard usage of the phrase, especially given that you linked to the wikipedia article when using it. But it kind of fits the name, and I can’t think of a way for the standard usage to fit.)
It seems like we are talking about something similar. If you interpret MWI as “anything can happen with some probability, and, given that we are here observing it, the posterior probability is obviously high enough”, then you can use it to explain anything. I agree that my usage was not quite standard, but it fits somewhat, because you can use MWI to justify any conclusion, including an absurd one.
Note that MWI postulates unitary evolution of the wave function, and in unitary evolution there are no probabilities, everything is completely deterministic, no exceptions. None. Let it sink in:
NO PROBABILITIES. PURE DETERMINISM OF THE WAVE FUNCTION EVOLUTION
There have been numerous attempts to saddle this unitary evolution with something extra that would give us the empirically observed probabilities. Everett suggested some in his PhD, many others did, with marginal success. The only statement nearly everyone is on board with is that, if we were to look for a way to assign probabilities, the Born rule is the only sensible one. In that sense, the Born rule is not an arbitrary one, but a unique way to map wave function to probability. The need to get probabilities from the unitary evolution of the wave function is not built into the MWI, but is grafted on it by the need to connect this theory with observations, exactly like the Born rule in the Copenhagen interpretation was.
That said, we might be on the cusp of something super mega extra interesting observed in the next few years, much more so than the recent black hole doughnut seen by the EHT: Measuring gravitational field from Schrodinger cat-like objects. There are no definite predictions on what we will see in this case, because QM and general relativity currently do not mix, and this is what makes it so exciting. I have mentioned it in a blog post discussing how MWI emerges from unitary evolution:
https://edgeofgravity.wordpress.com/2019/01/19/entanglement-many-worlds-and-general-relativity/
There is some discussion of this issue online, and I have mused about it on my blog some time ago:
https://edgeofgravity.wordpress.com/2019/02/25/schrodingers-cattraction/
I’m still not entirely clear what you mean by “MWI proves too much”.
If I try to translate this into simpler terms, I get something like: MWI only matches our observations if we apply the Born rule, but it doesn’t motivate the Born rule. So there are many sets of observations that would be compatible with MWI, which means P(data | MWI) is low and that in turn means we can’t update very much on P(MWI | data).
Is that approximately what you’re getting at?
(That would be a nonstandard usage of the phrase, especially given that you linked to the wikipedia article when using it. But it kind of fits the name, and I can’t think of a way for the standard usage to fit.)
It seems like we are talking about something similar. If you interpret MWI as “anything can happen with some probability, and, given that we are here observing it, the posterior probability is obviously high enough”, then you can use it to explain anything. I agree that my usage was not quite standard, but it fits somewhat, because you can use MWI to justify any conclusion, including an absurd one.