##### Speaker

Dr. Thomas Zaslavsky, Professor, Department of Mathematics & Statistics, Binghamton University, SUNY

##### Title

Mathematics Colloquium

##### Subtitle

Why Color a Graph, and What to Do About It?”

##### Physical Location

Allen 14

**Abstract: ** Graphs, or networks, have become a major tool for organizing relationships among objects, organizations, and people. A significant aspect of graph theory is graph coloring, which is valuable for map coloring (its original motivation, back around 1847) and for resolving conflicts such as in scheduling or interpersonal relations. I will explain coloring and the chromatic number (the minimum number of colors), and some of the important questions. Then I will introduce signed graphs, where the graph edges have a sign, either +1 or -1. Signed graphs were motivated by social pyschology (around 1953) and have been reinvented many times because of their greater power in modeling mathematical and applied problems. I will talk about coloring them, which is analogous to ordinary graph coloring but more complicated -- and to some of us, more fascinating.

**Biosketch: **Thomas Zaslavsky received his PhD from MIT in 1974. His research interests include signed graphs, matroid theory, graph theory, and arrangement of hyperplanes. He has published more than 100 papers and has advised 14 PhD students till date. He has been a Full Professor at SUNY Binghamton since 1985. He is credited with the development of signed graph theory as a subdiscipline of combinatorics.