Special Seminar

Speaker: Ferenc Szollosi (Tohoku U)
Title: EQUIANGULAR LINES IN REAL EUCLIDEAN SPACES AND SEIDEL MATRICES WITH THREE DISTINCT EIGENVALUES
Date (JST): Tue, Oct 29, 2013, 13:45 - 14:45
Place: Seminar Room B
Related File: 1067.pdf
Abstract: Let d > 1 be an integer and let R^d denote the Euclidean d-dimensional space equipped with the usual inner product (.,.). A set of n>1 lines, represented by the unit vectors v1, ..., vn is called equiangular, if there exists a constant A such that |(vi, vj)| = A for all 1 <= i < j <= n. We obtain several new results contributing to the theory of equiangular line systems in Euclidean spaces. Among other things, we present a new general lower bound on the number of equiangular lines; we describe the two-graphs on 12 vertices; and we investigate Seidel matrices with exactly three distinct eigenvalues.