Effective Dynamics of Open Quantum Systems: Stochastic vs Unitary Models

[Mentz114]

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.

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]

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.

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]

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.

Thanks, I missed the discussion altogether. Very edifying as always ( and feeding my own inclinations ).