## Discrete Math Seminar: Eric Fusy

- Date: 02/24/2015
- Time: 16:00

*Ecole Polytechnique*

University of British Columbia

Introduction to Maps I: Polygon Gluings and Classification of Surfaces

Maps describe the way a surface can be obtained by gluing polygons together, and as such they provide a handy tool to prove that closed surfaces can be classified by a genus parameter (both in the orientable and non-orientable case). I will review on this and on the equivalence between maps as polygon gluings and maps as graphs endowed with a rotation system. If time allows I will also review on a nice formula due to Harer and Zagier for the number of ways one can obtain the orientable surface of genus g by gluing pairwise the sides of a 2n-polygon.

(This is the first of a series of 3 talks on maps. The next two will occur later in March.)

Location: ESB 4127