SEMINAR: Groups and Combinatorics Seminar: On the derangement graph of PGL(2,q) acting on the projective line

Groups and Combinatorics Seminar

Pablo Spiga (UWA)

will speak

On the derangement graph of PGL(2,q) acting on the projective line

at 12 noon in MLR1 on Tuesday 3rd of November

Abstract: Given a finite set X and a family S of k-subsets of X, we say that S is intersecting if any two elements in S have non-empty intersection. A classical theorem in extremal combinatorics of Erdos-Ko-Rado classifies the independent sets of maximal size for 2k<|X|. There are many applications and generalizations of this theorem in different areas of mathematics. The extension we are interested in deals with permutation groups. In particular, inspired by a recent paper of Godsil-Meagher, we prove an analogue of the Erdos-Ko-Rado theorem for the derangement graph of PGL(2,q) acting on the projective line.

All welcome