Title: Counting Generalised Proper Colourings
| Speaker: | Ghislain McKay |
| Affiliation: | University of Waterloo |
| Room: | MC 6486 |
Abstract: When colouring a graph, we are often interested in proper colourings. We generalise the notion of proper colouring by requiring that only a subset of the colour classes be stable sets. Counting the number of such colourings yields interesting sequences of numbers. We conjecture that these sequences are logarithmically concave.
Title:The Colin de Verdière Invariant
| Speaker: | Linda Cook |
| Affiliation: | University of Waterloo |
| Room: | MC 6486 |
Abstract: In 1990, Yves Colin de Verdière introduced an interesting graph invariant μ based on matrices that encode a graph’s adjacency. It has been shown that μ is minor monotone and μ < 2, 3, 4 characterizes the outerplanar, planar and linklessly embeddable graphs, respectively. In this talk we will introduce the Colin de Verdière invariant as well as this summer’s work towards determining μ for certain strongly regular graphs.