Notes on explicit special generic maps into Eulidean spaces whose dimensions are greater than 4

Special generic maps are higher dimensional versions of Morse functions with exactly two singular points, characterizing spheres topologically except 4-dimensional cases and 4-dimensional standard spheres. The class of such maps also contains canonical projections of unit spheres. This class is interesting from the viewpoint of algebraic topology and differential topology of manifolds. These maps have been shown to restrict the topologies and the differentiable structures of the manifolds strongly by Calabi, Saeki and Sakuma before 2010s, and later Nishioka, Wrazidlo and the author. So-called exotic spheres admit no special generic map in considerable cases and homology groups and cohomology rings are shown to be strongly restricted. Moreover, special generic maps into Euclidean spaces whose dimensions are smaller than or equal to 4 have been studied well. The present paper mainly concerns cases where the dimensions of targets are greater than or equal to 5.Comment: 21 pages, this is drastically revised based on positive comments after the first submission to a refereed journal, main ingredients are unchanged, expositions including examples and remarks are adde