BGU Seminar on Algebraic Combinatorics
 (Note unusual day of meeting ! ) 
Date:    Thursday, April 21, 2011
Time:    12:10 - 14:00
Place:   The Deichmann Building for Mathematics,
          room -101
Speaker: Alexandre Zvonkine
          University of Boredeaux 1, France
          Dept. of Computer Science
Title:   Belyi functions and "dessins d'enfants"
Belyi function is a rational or a meromorphic function having only three
ramification points; traditionally, these points are fixed as
0, 1, and infinity. The preimage of the segment [0,1]
under a Belyi function is a combinatorial map,
i.e., a graph embedded in  (or drawn on) a 2-dimensional surface;
it was Grothendieck who called these maps  "dessins d'enfants",
which means in French "children's drawings".
The above construction  permits to establish profound relations between
combinatorics of maps, Riemann surfaces, Galois  theory,
permutation groups, and various other subjects.
In the talk, we will give a general introduction to the subject,
and then  illustrate it by certain examples.
Dr. Mikhail Klin
Department of Mathematics
Ben-Gurion University of the Negev
P.O.Box 653, Beer Sheva 84105, Israel
Tel: (0)8/6477-811  (office)
      (0)8/641-37-15 (home)
Fax: +972-(0)8/6477-648
e-mail:  <>
Technion Math Net-2 (TECHMATH2)
Editor: Michael Cwikel   <> 
Announcement from: Mikhail Klin   <>