Combinatorics Seminar - Georgios Petridis


Speaker: Georgios Petridis

Title: The q-analogue of almost orthogonal sets

Abstract: An almost orthogonal set in R^d is a collection of vectors with the property that among any three distinct elements there is an orthogonal pair. The maximum size of such sets was determined by Rosenfeld, who verified a belief of Erdos. The same question was studied by Ahmadi and Mohammadian in F_q^d. We will present a proof of a conjecture of Ahmadi and Mohammadian and also see how it implies an “almost” analogue of a theorem of Berlekamp on eventowns. Joint work with Ali Mohammadi.