TETRAHEDRAL GEOMETRY/TOPOLOGY SEMINAR

 

          ANNOUNCEMENT

 

 

DATE:                 Friday, October 2, 2009                      

 

LOCATION:       Hempfield High School, Room 213

(directions at http://www.millersville.edu/~tgts/)              

                          

followed by dinner at a place to be determined.

 

4:30 TALK:  Leigh Cobbs, Lebanon Valley College                          

“Bass-Serre theory: constructing groups as fundamental groups of graphs of groups”

 

Abstract: In this talk, I will give an introduction to Bass-Serre theory.  In particular, this theory allows us to (re)construct groups which act on trees as fundamental groups of graphs of groups.  This is very much analogous to the theory for fundamental groups of graphs, with some added group theoretic data.  A classic example is the presentation for SL_2(Z) as an amalgamated free product of two cyclic groups (order 4 and 6) over the cyclic group of order 2.  The presentation may be obtained from the SL_2 action by Mobius transformations on an infinite tree in the upper half plane.  As time and interest permits, I’ll discuss the use of this theory in my research to construct infinite chains of subgroups of Kac-Moody groups.

 

 

 

 

     EVERYONE WELCOME

 

       PLEASE FORWARD THIS ANNOUNCEMENT TO ANYONE INTERESTED

 

 

           The Tetrahedral Geometry/Topology Seminar is sponsored jointly by

Elizabethtown College, Franklin & Marshall College, Lebanon Valley College and Millersville University.