Diffeomorphisms of the Square
Thursday, December 15, 2016
We prove that the group of diffeomorphisms of the closed square 
Sq = [0,1]2 
has three orbits: the vertices, the edges and the interior. That support the idea that under the formal framework of Diffeology, differential geometry in the geometry of the group of diffeomorphisms, in the sense of Klein.

(Joint post with Serap Gürer) Ref. http://math.huji.ac.il/~piz/documents/DBlog-Rmk-DOTS.pdf