Dear Aurelien and Reinhard,
to me, your answers indicate the possible foundational incompleteness of BM.
When i teach my students why such a strange theory like QM has ever appeared, i have to prove nonstability of the Rutehrford’s model of the hydrogen atom. Like every mastery, physics requires different tools — classical mechanics and electrodynamics in this case.
Now, if the analogous analysis in the context of BM leads to nowhere… I don’t understand how could we ever believe in ontic reality of quantum particles.
On the other hand, the standard open systems theory clearly accounts for all the constituent ‘systems’ and fields and clearly says what’s been known from the outset, that all [nonrelativistic] quantum systems are open, including all the atomic species.
Finally, Reinhard, thank you very much for mentioning different partitions of the hydrogen atom. As much as i can see [and have seen in the last 15 years with my collaborators] quantum mechanics equally, and equally successfully, regards arbitrary decompositions into subsystems (including ‘virtual particles’). Just to be fair, here i note the following link: http://physics.kg.ac.rs/fizika/pages/quantumStructures/ .