The discussion centers on the effective dynamics of open quantum systems, particularly contrasting stochastic and unitary models. Participants explore how quantum dynamics can be described when a system is not isolated but coupled to a detector, and how this affects the representation of state vectors over time.
Participants do not reach consensus on whether the effective dynamics implies a collapse or if it is merely an effective description. There are competing views on the interpretation of stochastic processes and their relationship to traditional quantum mechanics.
There are unresolved questions regarding the assumptions underlying the stochastic processes discussed, particularly concerning the nature of approximations in the context of open quantum systems.
Since Weinberg has been mentioned in the wave function/collapse debate I thought it worthwhile to mention his 2014 offering here.atyy said:Landay and Lifshitz were perfectly aware that one can get classical behaviour in certain limits from quantum behaviour. They explicitly comment that that does not negate the need for a classical/quantum cut. Again this is all wrt to the orthodox or Copenhagen or minimal interpretation.
There are of course well respected approaches like Many-Worlds, Bohmian Mechanics or Consistent Histories which attempt to solve the measurement problem of Copenhagen. All of these have to add in assumptions (eg. multple outcomes, hidden variables, weaker reality) for the ones they remove (classical/quantum cut and/or observer-dependent collapse). The minimal interpretation without the cut and collapse that seem to be advocated by Ballentine and Peres are not consistent with the vast majority of physics textbooks from Landau and Lifshitz through Cohen-Tannoudji, Diu and Laloe through Nielsen and Chuang through Weinberg. Of course correctness is not based on mainstream physics, so the reader will have to decide for himself whether the opponents of mainstream physics like Ballentine and Peres are correct.
This has already been mentioned and discussed here. One remarkable fact I mentioned there is that in interacting quantum field theory, the notion of a pure state loses its meaning.Mentz114 said:Since Weinberg has been mentioned in the wave function/collapse debate I thought it worthwhile to mention his 2014 offering here.
He seems to be advocating the density matrix formalism and dropping wave function reality. Hooray.
A. Neumaier said:This has already been mentioned and discussed here. One remarkable fact I mentioned there is that in interacting quantum field theory, the notion of a pure state loses its meaning.