### Tuesday, July 14

## MS16

Topological Graph Theory

3:30 PM-6:00 PM

*Room: Sidney Smith 1072*

In topological graph theory, one studys the embedding of orientable and nonorientable graphs on surfaces and their properties, such as colorability, facial and noncontractible cycle structure, uniqueness of embeddability, and graph minors. Currently. a focus of research is on the interplay of the properties mentioned above, and their relevance for major research areas in graph theory. The speakers will discuss recent work in the areas mentioned above.

**Organizer: Joan P. Hutchinson**

*Macalester College*
**3:30 Extending Colorings of Embedded Graphs**
- Michael O. Albertson, Smith College
**4:00 Trading Handles or Crosscaps for Crossings**
*Dan Archdeacon*, University of Vermont; C. Paul Bonnington, University of Auckland - Tamaki Campus, New Zealand; and Jozef Siran, Slovak Technical University, Slovakia
**4:30 Some Problems in Topological Graph Theory**
*Nora Hartsfield*, Western Washington University and Alfred W. Hales, Center for Communications Research, San Diego
**5:00 Flexibility of Graph Embeddings**
- Bojan Mohar, University of Ljubljana, Slovenia
**5:30 Vertex Accumulation Points in Locally Finite Planar Graphs**
- C. Paul Bonnington, University of Auckland - Tamaki Campus, New Zealand; and
*Bruce Richter*, Carleton University, Canada

*LMH, 2/23/98; MMD, 7/10/98*