The discussion centers on the dynamics of open quantum systems, emphasizing the distinction between stochastic and unitary models. It establishes that effective dynamics for a small quantum system, when coupled to a detector, is inherently stochastic and nonunitary, often described by classical processes such as jump processes and diffusion processes. The conversation highlights the importance of the Lindblad equation and its relation to stochastic differential equations, asserting that the effective description of quantum dynamics does not invoke collapse but rather provides a coherent framework for understanding measurement interactions. Key references include Section 7 of the paper at arxiv.org, which discusses continuous monitoring of single atoms.
PREREQUISITESQuantum physicists, researchers in quantum mechanics, and anyone interested in the effective dynamics of open quantum systems and the implications of measurement theory.
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.