##### Department of Mathematics,

University of California San Diego

****************************

### Topology Colloquium

## Daniel Biss

#### University of Chicago

## $K_g$ is not finitely generated

##### Abstract:

In joint work with Benson Farb, we show that $K_g$, a certain subgroup of the mapping class group of a genus $g$ surface, is not finitely generated. $K_g$ is the group generated by Dehn twists about null-homologous (separating) curves; it is also known as the kernel of the Johnson homomorphism out of the Torelli group. No background will be assumed.

Host: Nitya Kitchloo

### December 7, 2005

### 2:00 PM

### AP&M 6218

****************************