If we assume that there are distinct universes which branch, then the Born rule isn't going to be satisfied (at least, not without some sort of contrived epicycles) in any situation where the probabilities aren't in some integer ratio, e.g. if they're irrational. If on the other hand we assume that there is a continuum of identical universes that is partitioned by a measurement (as David Deutsch suggests in "The Fabric of Reality") then the partitioning can be as finely divided as you like. However, continua are possibly problematic in actual physical systems, like infinities, that is to say, not realistic (because they effectively involve dividing by (uncountable?) infinity). The idea that spacetime can't be infinitely warped - that singularities are unphysical - is related to the idea that continua can't exist. I assume a theory of quantum gravity would not allow either.
In the absence of continua the Born rule can only be satisfied in a multiverse if all measurements split the universes into some integer ratio. This seems rather arbitrary - a measurement with a 1% chance of result X and 99% of result Y produces 100 branches (99 indistinguishable from each other), while a measurement with a 50-50 chance produces 2. A multiverse has philosophical appeal - the string landscape answers the question "why these laws of physics?" while the quantum multiverse answers the question "why this history?" However as far as I know there is no strong scientific (testable, refutable, etc) evidence for either. On Monday, 13 October 2025 at 14:56:05 UTC+13 Alan Grayson wrote: > Correct me if I'm mistaken, but as far as I know the wf has never been > observed; only the observations of the system it represents. This being the > case, in a large number of trials. Born's rulle will be satisfied > regardless of which interpretation an observer affirms; either the MWI with > no collapse of the wf, or Copenhagen with collapse of the wf. That is, > since we can only observe the statistical results of an experiment from a > this-world perspective, and we see that Born's rule is satisfied, so I > don't see how it can be argued that the rule fails to be satisfied if the > MWI is assumed. I think the same can be said about the other worlds assumed > by the MWI, namely, that IF we could measure their results, the rule would > likewise be satisfied.AG -- 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 visit https://groups.google.com/d/msgid/everything-list/06dade74-6bdc-460f-91d5-ff38a8b26e94n%40googlegroups.com.
