Mediatrices, or Halfway There and Back Again

James Bernhard
Department of Mathematics, Portland State University

Abstract: A mediatrix is defined to be the set of all points equidistant from a given pair of points. Of course, in Rn with its usual notion of distance, any mediatrix is simply an (n-1)-dimensional hyperplane. On the surface of a torus, however, there are multiple possible shapes for mediatrices, depending on the pair of points chosen and on the metric placed on the torus. In more elaborate spaces, the set of possible shapes becomes significantly more complicated.

In this talk, we will show that on a closed surface, mediatrices are certain kinds of graphs (in the sense of vertices connected by edges), and we will discuss restrictions placed on the shape of mediatrices by the topology and geometry of the surrounding space. We will also use related questions as an excuse to explore some introductory Riemannian geometry. This talk is based on joint work with J.J.P. Veerman.