Talk:Wigner function

"Wigner function" as disambiguation page or as redirect
I want to remove the disambiguation page and restore the redirect, if this would not cause any damage. It's a complex topic area, of which I have only a very faint understanding, so I want to lay out my reasoning for review by or others.

Background:
 * The Wigner function article title was used as a redirect to Wigner quasiprobability distribution until recently. It was changed to a disambiguation page by this edit with edit summary noting "Wigner D-matrix" is also sometimes called "Wigner function".
 * The material is technical, and this may not matter anyhow, but it seems to me that the Wigner D-matrix is unrelated to the Wigner quasiprobability distribution except for the fact they are both to be credited to Eugene Wigner.
 * Note there is Wigner Function article title which remains as a redirect to the quasiprobability distribution article. It currently has one usage, from Sadollah Nasiri Gheydari article.
 * Currently the Wigner function title has eight inbound links, from the following articles:
 * Koopman–von Neumann classical mechanics
 * Optical phase space
 * Phase space formulation
 * Quantum tomography
 * Quantum tunnelling
 * Segal–Bargmann space
 * Squeezed coherent state
 * Wolfgang P. Schleich
 * The inbound links to a disambiguation page are targeted to be fixed by wp:DPL editors trying to eliminate links to dab pages.

Reasoning to change back to a redirect:
 * From my review of the usages in those articles, though the topic area is over my head, I think they all would properly link to the "quasiprobability distribution" article, not the D-matrix one. The links are currently "bad", coming to a disambiguation page.  All eight would be fixed by restoring the redirect.  If that is done, then, right away, following the link in those articles would bring one to the quasiprobability distribution article.  Other future usages of "Wigner function" in articles will usually mean the quasiprobability distribution, too, I am surmising.  (Note, either way, the Wigner Function redirect should be updated to go to wherever Wigner function goes.)


 * Also, the Wigner D-matrix article does not mention "Wigner function" much less that it is a synonym. Superficially, it seems to me that referring to a Wigner D-matrix as a Wigner function is technically wrong;  the first is literally a square matrix, not a function.


 * If in some article an editor uses "Wigner function" (and wikilinks it) when they mean "Wigner D-matrix", when they review their changes they would not be surprised to find the wikilink goes to the "Wigner quasiprobability distribution" target. They would have to change their usage to an explicit link or a piped link to "Wigner D-matrix" instead.


 * The purpose of the disambiguation page can be achieved by a hatnote at the quasiprobability distribution article. The hatnote could be something like: "For the irreducible representation of the rotation group SO(3), sometimes called a Wigner function, see Wigner D-matrix."  And I don't think a hatnote at the D-matrix page is needed.  (Drafted, but not being used:  "The term Wigner function, though sometimes referring to Wigner D-matrix, more often means Wigner quasiprobability distribution, a distribution used in quantum physics.")


 * Question: Should the hatnote be revised to mention the SU(2) group? Would wording as follows be correct: "For an irreducible representation of the rotation group SU(2) or of SO(3), sometimes called a Wigner function, see Wigner D-matrix"  Or could this otherwise be improved to mention SU(2)?

For the above reasons, I think I am going to go ahead with the hatnote and with redirecting, even though my knowledge of this topic area is very low. If someone knows better, please do speak up here, explain what is best, and that can be implemented instead. I don't mind being reverted. -- do ncr  am  19:54, 22 August 2015 (UTC)


 * I implemented the hatnote and the redirect, then undid the redirect after seeing others' edits at Wigner distribution. Please see Talk:Wigner distribution.  Maybe this page should be merged to there.  Discuss there. -- do  ncr  am  23:54, 22 August 2015 (UTC)