Billiards and teichmuller curves

A Teichmuller curve V. M g is an isometrically immersed algebraic curve in the moduli space of Riemann surfaces. These rare, extremal objects are related to billiards in polygons, Hodge theory, algebraic geometry and surface topology. This paper presents the six known families of primitive Teichmuller curves that have been discovered over the past 30 years, and a selection of open problems.