An Erdos-Ko-Rado theorem for the derangement graph of PGL(2,q) acting on the projective plane

Date
2014
Authors
Meagher, Karen
Spiga, Pablo
Journal Title
Journal ISSN
Volume Title
Publisher
SIAM Journal on Discrete Mathematics
Abstract

Let G = PGL(2, q) be the projective general linear group acting on the projec- tive line P_q. A subset S of G is intersecting if for any pair of permutations \pi and \sigma in S, there is a projective point p in P_q such that \pi(p)= \sigma(p). We prove that if S is intersecting, then |S| <= q(q-1). Also, we prove that the only sets S that meet this bound are the cosets of the stabilizer of a point of P_q. Keywords: derangement graph, independent sets, Erdos-Ko-Rado

Description
Keywords
derangement graph, independent sets, Erdos-Ko-Rado theorem
Citation
SIAM Journal on Discrete Mathematics 28(2) 918--941, 2014.
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