Speaker: Reza Naserasr
Time and Place: 4 February 2005, 12:00 noon,  KED B015, University of Ottawa
Title: The four colour theorem and graph homomorphisms

Abstract: 

We will start with a short history of the four colour theorem, then we will consider two different conjectures in generalizations of this this theorem/problem. We will show how either one of these problems can be restated in the uniform language of graph homomorphism.

As a corollary we will find that every triangle-free planar graph admits a homomorphism to a well known triangle-free graph on 16 vertices called the Greenwood-Gleason/(or)Clebsch graph.