Algebraic Graph Theory Seminar - Chris Godsil

Thursday, February 13, 2020 1:00 pm - 1:00 pm EST (GMT -05:00)

Title: Moore Graphs

Speaker: Chris Godsil
Affiliation: University of Waterloo
Room: MC 5417


Moore graphs were introduced by Hoffman and Singleton in a fundamental paper. They can be defined as graphs with diameter $d$ and girth $2d+1$. Hoffman and Singleton proved that there are at most four Moore graphs of diameter two. It was shown later (by Damerell and by Bannai and Ito) that the only Moore graphs of diameter greater than two are the cycles. (Hoffman once lamented to me that is was a pity that there were so few Moore graphs.)

I will discuss the basic theory of Moore graphs and present a summary of Damerell's proof.