Tesselation of a triangle by repeated barycentric subdivision

Abstract

Under iterated barycentric subdivision of a triangle, most triangles become flat in the sense that the largest angle tends to $\pi$. By analyzing a random walk on $SL_2(\mathbb{R})$ we give asymptotics with explicit constants for the number of flat triangles and the degree of flatness at a given stage of subdivision. In particular, we prove analytical bounds for the upper Lyapunov constant of the walk.