Wikipedia:Reference desk/Archives/Mathematics/2019 July 2

= July 2 =

Why not the Platonic Solid dipyraminds?
I notice that while we have articles on the Polytopes that are the Pyramids and the Prism with the Platonic Solids as "bases", we don't have the equivalent articles for the dipyramids (other than the 16-cell which is the Octahedral dipyramid). Anyone have ideas why we don't? Is there more work done on polytopes whose vertices line in two 3-dimensional spaces?Naraht (talk) 01:48, 2 July 2019 (UTC)
 * Wikipedians are supposed to follow WP's notability guidelines when creating articles, so if there are questions on why some articles exist and some don't you might start there. For math articles notability generally comes down to whether the subject is covered in published textbooks, and for things dealing with regular polytopes that generally means the works of H. S. M. Coxeter. So presumably the Pyramids and Prisms are covered by Coxeter and dipyramids probably aren't; it's possible no one has gotten around to them but it seems unlikely. Imho the article Cubic pyramid I linked to previously would be better combined with other polyhedral pyramids into a single polyhedral pyramid article. In any case, I'm pretty sure most current work on, and practical applications of, polytopes concern the irregular kind; see for example Cyclic polytope, Dehn–Sommerville equations, Simplex algorithm. --RDBury (talk) 11:24, 3 July 2019 (UTC)