On evolute cusps and skeleton bifurcations

Consider a 2D smooth closed curve evolving in time, the skeleton (medial axis) of the figure bounded by the curve, and the evolute of the curve. A new branch of the skeleton can appear/disappear when an evolute cusp intersects the skeleton. In this paper, we describe exact conditions of the skeleton bifurcations corresponding to such intersections. Similar results are also obtained for 3D surfaces evolving in time.