Tracks in cloud chambers (Mott’s problem) and quantum state reduction (collapse) After reading Mott’s paper
https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1929.0205
The wave mechanics of α-ray tracks
Mott N.F., Proc. R. Soc. Lond. A, 126, 79-84, 1929.
my simple question is why this kind of reasoning isn’t sufficient to show that any kind of quantum state reduction (projection postulate, collapse of the wave function) is  unnecessary.
Of course this does not rule out the idea to use the quantum state reduction as a tool in some calculations, but as presented in some books and lecture notes it seems that the quantum state reduction ist still believed to be an essential, indispensable postulate for quantum mechanics.
(of course I know that there are non-collapse interpretations; to my knowledge they haven’t been ruled out experimentally but agree with observations)
 A: This is a very good question, and I think the answer is yes.  But Mott’s paper on its own doesn’t provide the answer because (at best) it says alpha particles form tracks but it doesn’t say why any one particular track is selected.  I have recently published a paper in Foundations of Physics that offers a new physical analysis of how the selection takes place.  The title is “The first droplet in a cloud chamber track,” and it’s available online.
A: I think the point of Mott's paper is that appear tracks  and not other patterns because there is enough energy just for that. Taking wavefunctions as configurations, you should  study the wave-mechanical configurations in an hypersphere and then translating it in the 3d space.
Collapse is a non-sense   cartoon, just related to measurement, that at the end is where the paradigma of quantas really comes from. If true, all matter should radiate as hell ! (since neither the two momentums and the enegy should be conserved in a collapse)  I think it is the time to admit that we did not get the process. That is clearly a non-linear dynamics where an instability drives the whole system particle+apparatus in a final state with a classical outcomes. I think that quantas are just an illusion of this process. And  this is also the source of the big disconnection we have in physics between the micro and the macro.
Here one can expect the next big thing.
