On tight projective designs
arXiv:math/0703526
Abstract
It is shown that among all tight designs in FP^n, where F is R, C, or H (quaternions), other than RP^1, only 5-designs in CP^1 have irrational angle set. This is the only case of equal ranks of the first and the last irreducible idempotent in the corresponding Bose-Mesner algebra.
10 pages, no figures